JPH04195268A - Graphic processor - Google Patents

Abstract

PURPOSE:To improve the quality of an image to be formed by providing a subpixel varying means which changes the divisional shape of the subpixel of a graphic processor. CONSTITUTION:The coordinates of the start point and end point of a straight line and the data of inclination calculated from those points are stored in a RAM 204 as table data. Assuming that graphic data D00 in page memory 206 is stored, the Y-coordinate of the start point of the data D00 is read in, and the linear approximation of a curved surface and a graphic edge part are performed. The coordinates of the start point and end point of an approximated straight line and the inclination data calculated from those points are stored as the table data. The subpixel varying means 209 processes each line L. The size of the subpixel is decided, and scan line conversion is performed at every subpixel corresponding to the inclination of the approximated straight line. After that, luminance is calculated from the number of painted out subpixels, and it is written as the luminance data of a picture element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a graphic processing device that removes jaggedness at the edges of vector data, and more specifically, the present invention relates to a graphic processing device that removes jaggedness at the edges of vector data. Adjustment value (
The present invention relates to a graphic processing device that calculates a density value (density value) and outputs the tone value to an output device such as a laser printer.

[Prior Art] In the field of computer graphics, when displaying an image on a CRT, which is an output medium, a technique called anti-aliasing processing is used to make the displayed image more beautiful. This process is performed on the jagged part (called alias) on the stairs as shown in Figure 39(a).
Figure 39(b) visually displays the displayed image by applying brightness modulation to
It is used to smooth the surface as shown in the figure.

In conventional graphic processing apparatuses, (1) uniform averaging method, (2) weighted averaging method, (2) convolution integral method, etc. are generally applied as anti-aliasing processing methods.

■The uniform averaging method calculates each pixel (picture element) to N*M (N,
After decomposing the image into sub-pixels (M is a natural number) and performing rask calculation at high resolution, the brightness of each pixel is determined by taking the average of N*M sub-pixels. Figure 40(a)
, (b), anti-aliasing processing using the uniform averaging method will be specifically explained. If the edge of the image overlaps a certain pixel (here, it is assumed that the image is connected to the bottom right of the diagonal line), and when anti-aliasing processing is not performed, as shown in Figure (a),
The brightness kid of this pixel is assigned the highest brightness of the displayable gradations (for example, kid·255 for 256 gradations). When performing anti-aliasing processing on this pixel using the uniform averaging method with N=M=7, the same figure (
As shown in b), the pixel is decomposed into 7*7 sub-pixels and the number of sub-pixels covered by the image is counted. The count number (28) is divided by the total number of subpixels in one pixel (49 in this case), normalized (averaged), and multiplied by the maximum brightness (255) to calculate the brightness of that pixel. In this way, in the uniform averaging method, the brightness of each pixel is determined by taking into consideration how the image covers each pixel.

■Weighted averaging method The weighted averaging method is a partial modification of the uniform averaging method. In contrast, the weighted averaging method assigns a weight to each subpixel so that the influence on the brightness kid of that subpixel differs depending on which subpixel the image covers. There is. Note that the weight at this time is given using a filter.

Referring to FIGS. 41(a) and 41(a), an example is shown in which the weighted averaging method is applied to the same image data as in FIG. 40(a) using the same division method (N=M=7).

FIG. 41(a) shows a filter (here, conef
i 1 ter ), and the corresponding sub-pixel is given the same weight as this characteristic. For example, the weight of the upper right corner subpixel is 2. When an image is applied to each subpixel, the weight value given by the filter characteristics becomes the count value of that subpixel. FIG. 6B shows the display pattern of the image changed depending on the weight of the sub-pixels. In this case, the number of weighted subpixels in the image is 199. This value is divided by the sum of the filter values (336 in this case) corresponding to uniform averaging, averaged, and multiplied by the maximum brightness to calculate the brightness of this pixel. The filter shown in Fig. 42 (a
), (b), (cl, (a)).

■Convolution integral method The convolution integral method is a method that refers to the appearance of surrounding pixels when determining the brightness of one pixel. That is, the area around one pixel whose brightness is to be determined is N
Consider the ' 2901 indicates the pixel in which the image is displayed.

The image continues below and to the right of the diagonal line, and the subpixels painted black are the subpixels that are counted. Each pixel is divided into 4*4. Therefore, in this case, a 12*12 filter will be used.

This method has the effect of removing high frequency components contained in a vector image.

On the other hand, a publishing system using a personal computer,
With the spread of so-called DTP (desk top publishing), systems for printing vector images, such as those used in computer graphics, have become widely used. A typical example is a system using Adobe's Post Script. PostScript is a page description language (Page Des
criptionLanguage: Hereafter, PDL
It belongs to a language genre called ``Japanese language'', and describes the form of the contents of a single document, including the text (letter part), graphics, and their arrangement and appearance. It is a noflocraming language, and such systems use vector fonts as character fonts. Therefore, even if the characters are scaled, the print quality can be significantly improved compared to systems using bitmap fonts (for example, conventional word processors).
Another advantage is that character fonts, graphics, and images can be mixed and printed.

However, the resolution of the laser printers used in these systems is at most 240dpi to 400dp.
There are many i, computer graphics CR
Similar to the T display, there is a problem in that aliasing occurs due to the low resolution. For this reason, even in printing using a laser printer, there is a need to perform anti-aliasing processing to improve the quality of the printed image.

[Problems to be Solved by the Invention] However, when introducing an anti-aliasing processing method using NXN sub-pixel division in a conventional graphic processing device, for example, if N is made large, calculation takes time; I can't expect much of an effect,
Since an appropriate value of N is determined and used based on specifications for processing time and subjective image quality evaluation, there is a problem in that a sufficient effect cannot necessarily be obtained.

Furthermore, according to a graphic processing device that applies the conventional uniform averaging method, one type of sub-pixel shape (for example, (shape in which a pixel is divided into N*M), depending on the slope of the vector data, the value of the gradation value calculated from the actual area and the value of the gradation value calculated using the sub-pixel shape There was also the problem that sufficient anti-aliasing processing was not performed.

That is, when a sub-pixel shape divided into N*M is used, if the slope of the vector data is close to vertical or horizontal, there is a high possibility that a tone value different from the actual area ratio will be calculated. For example, if a sub-matrix (sub-pixel shape) divided into 3*3 is used, the vector data passes at an almost vertical slope, as shown in Figure 44 (a) and (b). In the case of an edge pixel, the probability that gradation value 1 and gradation value 2 will be calculated among the 10 gradation levels from gradation value 0 to gradation value 9 is small.

On the other hand, since the probability that gradation value 31, gradation value 69, and gradation value 9 will be calculated is high, the gradation value 4) of the gradation value calculated from the actual area (same figure) and this sub-pixel There is a large difference between the gradation value calculated by the division (gradation value 6 in the same figure (a)), and the intended final output cannot be obtained, so the effect of anti-aliasing processing cannot be fully achieved. I can't.

In addition, in a graphic processing device that applies the weighted averaging method and the convolution integral method, compared to the uniform averaging method, the difference between the gradation value calculated from the actual area and the gradation value calculated by subpixel division is Although the difference becomes smaller and the effect of anti-aliasing processing becomes higher, there is a problem in that it takes time to calculate the area ratio and the processing speed decreases.

Furthermore, according to graphic processing devices that apply conventional anti-aliasing processing methods, even though the output device has changed from a CRT to a laser printer that outputs images through an electrophotographic process, the brightness values of the CRT are simply transferred to the laser printer. Since it is used as a density value, there is a problem in that the effect of anti-aliasing processing is not necessarily fully manifested due to the characteristics of the electrophotographic process.

For example, the vector image shown in FIG. 45(a) is subjected to anti-aliasing processing to obtain the gradation values shown in FIG. 45(b) (here represented by 10 gradations from O to 9). When this gradation value is displayed as a brightness value on a CRT, the same figure (C) is obtained.
As shown in the figure, the effect of anti-aliasing processing makes it possible to obtain a smooth image similar to that of a vector image. However, the output of the laser beam is adjusted using the pulse width modulation method using the gradation value of Φ) in the same figure as the density value.
When a latent image is formed, a phenomenon occurs in which the density becomes lighter at the left end (left edge) of the latent image, and conversely, the density becomes darker at the right end (right edge) of the latent image, as shown in Figure (d). An inconvenience occurs in that the effect of anti-aliasing processing is impaired. When forming a latent image using the pulse width modulation method, a predetermined amount (
This is to form a dot by outputting a laser beam only during a predetermined pulse. Therefore, in the pulse width modulation method, at the left end of the latent image, dots with small gradation values are formed far away from the position of the actual image part, so the gradation determined by anti-aliasing processing is Not only is it not possible to faithfully reproduce the image of the value (see the same figure et al.), but it also has the disadvantage of making jagged edges more noticeable.

The present invention has been made in view of the above, and a first object thereof is to improve the effect of antialiasing processing.

A second object of the present invention is to obtain tone values that are not significantly different from tone values determined from the actual area ratio, without reducing processing speed.

Further, the present invention takes into consideration the characteristics of the electrophotographic process,
The third purpose is to prevent the effect of anti-aliasing processing from being impaired.

Furthermore, the present invention provides a fourth method to avoid low-density dots from impairing the effect of anti-aliasing processing and causing aliasing due to the characteristics of the pulse width modulation method, without reducing the processing speed. The purpose of

Furthermore, a fifth object of the present invention is to be able to avoid the occurrence of aliasing due to low density dots without reducing the accuracy of antialiasing processing.

[Means to solve the problem]

In order to achieve the above first object, the present invention calculates the gradation value (density value) of the edge pixel of vector data by subpixel division, and outputs the gradation value to an output device such as a laser printer. The present invention provides a graphic processing device including subpixel variable means for changing the division shape of subpixels.

In addition, in order to achieve the above-mentioned first object, the present invention calculates the gradation value (density value) of the edge portion pixel of vector data by subpixel division, and sends the gradation value to an output device such as a laser printer. The present invention provides a graphic processing device for outputting data, which is equipped with a subpixel variable means for approximating vector data to a straight line vector and varying the subpixel division size of an edge pixel according to the slope of the straight line vector. be.

Furthermore, in order to achieve the above-mentioned second object, the present invention calculates the gradation value (density value) of the edge pixel of vector data by subpixel division, and sends the gradation value to an output device such as a laser printer. The slope of vector data in the output graphics processing device.

and a graphic processing device equipped with subpixel division means that selects an appropriate subpixel shape from among a plurality of subpixel shapes and executes subpixel division based on the presence or absence of an end point in an edge pixel. It is something.

Furthermore, in order to achieve the third object, the present invention calculates the gradation value (density value) of the edge pixel of vector data by sub-pixel division, and applies the gradation value to a pulse width modulation type laser printer. A graphic processing device for outputting data to a graphics processing device, which is equipped with a gradation value determining means for converting the area of the right side of an edge pixel divided into left and right parts into a gradation value with a higher contribution rate than the area of the left side. It provides:

In addition, in order to achieve the above-mentioned fourth object, the present invention calculates the gradation value (density value) of the pixel at the edge part of vector data by sub-pixel division, and uses the gradation value with a pulse width modulation type laser. In a graphic processing device that outputs to a printer, pixels are divided into a subpixel division area where subpixel division is performed and an area outside the subpixel division area where subpixel division is not performed. The present invention provides a graphic processing device including tone value determining means for determining tone values based on the number of sub-pixels.

In addition, in order to achieve the above-mentioned fifth object, the present invention calculates the gradation value (density value) of the edge pixel of vector data by sub-pixel division, and applies the gradation value to a pulse width modulation type laser printer. In a graphic processing device that outputs to
An image portion determining means that determines whether the image portion to be filled is above, below, left or right of the edge pixel based on the type of edge, and used when the image portion to be filled is located above the edge pixel. soil filter,
The lower filter is used when the image part to be filled is located below the edge pixel, and the Furukawa filter is used when the image part to be filled is located to the right of the edge pixel.

and storage means that stores four weighting filters of filling filters to be used when the image portion to be filled is located to the left of the edge pixel, and the corresponding weighting from the storage means based on the determination result of the image portion determination means. The present invention provides a graphic processing device including tone value determining means for selecting a filter and determining tone values of edge pixels.

[Operation] The graphic processing device of the present invention changes the shape of subpixels in subpixel division, and sets the gradation value of each pixel to an appropriate value.

Furthermore, the graphic processing device of the present invention sets the tone value of each pixel to an appropriate value by using filters with different weights in subpixel division.

[Example] Hereinafter, the graphic processing apparatus of the present invention will be described as Example 1. Implementation, Example 2.
Example 3. Example 4. Embodiment 5 will be described in detail with reference to the drawings.

[Embodiment 1] An image forming system incorporating the graphic processing device of the present invention as a PDL controller will be described as Embodiment 1.

The image forming system of this embodiment uses a page description language output from DTP (desk top publishing).
e: Hereinafter referred to as pDt (three words)) is converted into an image via a PDL controller to form an image of image information.

As shown in FIG. 1, the image forming system includes a host computer 100 that creates a document written in PDL language (Postscript language is used in this embodiment), and P
A PDL controller (the graphical representation of the present invention) that performs anti-aliasing processing on the DL language and develops it into multivalued image data of black (BK), yellow (Y), magenta (M), and cyan (C) necessary for recording. a multi-value color laser printer 300 that prints multi-value image data output from the PDL controller 200, and a PDL controller 200. and a system control section 400 that controls the multivalued color laser printer 300.

FIG. 2 shows the configuration of the PDL controller 200, which includes a receiving device 201 that receives the PDL language sent from the host computer lOO, and a receiving device 201 that controls storage of the PDL language received and executes anti-aliasing processing, etc. CPU 202 and internal system bus 203
, a RAM 204 that stores the PDL language to be transferred from the receiving device 201 via the internal system bus 203, and a ROM 20 that stores an anti-aliasing program and the like.
5 and multivalued YMC with anti-aliasing processing
and page memory 206 for storing BK image data.
, a transmitting device 207 that transfers the YMC and BK image data stored in the page memory 206 to the multilevel color laser printer 300, an I10 device 208 that transmits and receives data to and from the system control unit 400, and a subpixel variable means 209. It consists of

Here, the CPU 202 receives the P received by the receiving device 201.
The DL language is stored in the RAM 204 via the internal system bus 203 according to the program stored in the ROM 205. After that, you will receive one page of PDL language,
Once stored in the RAM 204, the graphic elements in the RAM 204 are subjected to anti-aliasing processing based on the flowchart described later, and the multi-level YMC and BK image data is stored in the plain memory section of the page memory 206 (the page memory 206 is , M.C.

(consists of a BK plane memory section and a feature information memory section).

The data in the page memory 206 is then transferred to the transmitter 2
07 to the multilevel color laser printer 300.

FIGS. 3(a) and 3(b) show a portion of the image information stored in the page memory 206 corresponding to one pixel G. In the same figure (a), pixel G is divided into 4*4 subpixels S
The case where the sub-pixel is divided into 1 is shown, and 4 out of 16 sub-pixels S1 are filled in. In addition, FIGS. 3A and 3B show a case in which a pixel G is divided into eight sub-pixels S2 in the vertical direction and two sub-pixels S2 in the horizontal direction, and three of the 16 sub-pixels S2 are filled in. At this time, the brightness of the pixel in Figure (a) is 2
5%, and the brightness of the pixel in FIG. 5(b) is 18.75%.

In addition, since the actual area of the shaded area is 12.5%, there are cases where the accuracy is higher if different settings are made for the yellow side even if the number of sub-pixels is the same. Therefore, as shown in FIG. 4, the line is divided into areas A, B, and C according to the y-axis and the inclination with respect to the y-axis, and each area is divided into, for example, as shown in FIG. Area A is associated with 4*4 sub-pixels Sl, area B is associated with 2*8 sub-pixels S3, and area C is associated with 8*2 sub-pixels S2.

In this way, the accuracy of anti-aliasing processing is improved.

Next, the PDL controller 200 configured as described above
The operation will be explained in detail with reference to the flowchart of FIG.

First, as shown in FIGS. 4 and 3, data on the coordinates of the start and end points of a straight line and the slope that can be calculated from both points are stored in the RAM 204 as table data.

If the graphic data D0° shown in FIG. 7 is stored in the page memory 206, the position of the start line L=O and the position of the end line L=E of the graphic data D0° are the graphic data I Point eo (X6゜Yo) 1 point e
Equal to the Y coordinate of 2(Xz, Y2). Next, read the Y coordinate of the start L=O of the figure data D0° (5601
), performs linear approximation of the curve/figure edge portion (S602
). Linear approximation refers to processing that allows the curve RL to be represented by a set of straight lines such as the straight line DL, as shown in FIG. In this way, data on the coordinates of the start and end points of the approximate straight line and the slope that can be calculated from both points are stored as table data (5603). When each line L is processed by the sub-pixel variable means 209, the slope of the approximate straight line is obtained from this table data and the table data previously stored in the RAM 204. Next, determine the region to which the obtained slope belongs (560).
4), subpixel SL, S2. The size of S3 is determined (S605). Then, each sub-pixel St, S2 . In S3, scan line conversion processing is performed (S606). After that, calculate the brightness from the number of filled sub-pixels 51, 52, and 53 (5607) and write it as pixel brightness data (56
08). This process is continued from L=O to L=E and ends (5609, 5610).

As mentioned above, in this embodiment, the division size of the sub-pixels that divide each pixel of the approximate straight line is varied according to the slope of the straight line approximated in the image, so that the straight line approximated by The sub-pixel size used to calculate the brightness of one pixel can be changed according to the slope of the image, making anti-aliasing processing more effective than when using a fixed size
Moreover, it can be performed with high precision. Therefore, the quality of the formed image can be improved.

[Example 2] Hereinafter, an image forming system incorporating the graphic processing device of the present invention as a PDL controller will be described as Example 2. ■An outline of anti-aliasing processing.

■Block diagram of image forming system, ■Configuration and operation of PDL controller (graphic processing device of the present invention), ■Configuration and operation of multi-value color laser printer, ■Multi-value drive of driver will be explained in detail in this order. .

■Overview of anti-aliasing processing The graphic processing device (hereinafter referred to as PDL controller) of the second embodiment uses sub-pixel division when performing sub-pixel division based on the slope of vector data that crosses edge pixels and the presence or absence of end points. By changing the shape, the gradation value obtained by subpixel division is prevented from deviating greatly from the gradation value calculated from the actual area.

Hereinafter, with reference to FIGS. 9(a) to 9(g), an outline of the antialiasing process in the graphic processing apparatus of this embodiment will be explained in detail.

FIGS. 9(a), (b), and (C) show three subpixel shapes (hereinafter referred to as submatrices) used in this example, and FIG. 9(a) shows that the slope θ of vector data is tanθ＞9/2 (i.e., 77.47°〈θ＜
102.53°), the 1*9 submatrix used in the same figure (b) shows that the slope θ of the vector data is 2/9>
tanθ>−2/9 (i.e., 12.53°〉θ>−
(C) is a 3*3 submatrix used when the slope θ of the vector data is other than the above. Note that if there is an end point (start point or end point of vector data) in an edge pixel, the slope θ of the vector data cannot be absolutely determined, so in this example, the submatrix shown in FIG. .

For example, if the slope θ of the vector data is tanθ>9/2, in other words, if the slope is close to vertical, then 1*9
When the submatrix is used to perform submatrix division as shown in FIG. 9(d), a tone value of 4 is obtained. On the other hand, the conventional method (
3*3 submatrix), the 9th
As shown in Figure (e), the gradation value is 6. Therefore, 1*
The gradation value obtained using the 9-submatrix becomes a value close to (or the same value as) the actual gradation value.

Also, if there is an end point within the edge pixel, see Figure 9)
The gradation values are determined using a 3*3 submatrix as shown in FIG.

These processes use the value of the slope θ, which can be easily obtained from the vector data of the edge pixel, and the presence or absence of an end point to determine which subpixel in the edge pixel the vector data passes through. Since the same determination processing as the conventional method is performed, the processing speed is almost the same as that of the conventional uniform averaging method. In other words, it can be said that the processing speed is several steps faster than the weighted averaging method or the two-convolution method.

■Block diagram of the image forming system The image forming system of this embodiment uses the Page Description Language output from DTP (Desk Top Publishing).
e: Hereinafter referred to as PDL language) is converted into an image via a PDL controller to form an image of image information. The configuration of the image forming system of this embodiment will be described below with reference to FIG.

The image forming system includes a host computer 100 that creates a document written in PDL language (Postscript language is used in this embodiment);
While anti-aliasing the incoming PDL language sent page by page from
A PDL controller (graphic processing device of the present invention) 200 that develops multi-value image data of BK), yellow (Y), magenta (M), and cyan (C), and multi-value image data output from the PDL controller 200. A multivalued color laser printer 300 that prints
Controller 200. and a system control section 400 that controls the multivalued color laser printer 300.

■Configuration and operation of the PDL controller (graphic processing device of the present invention) FIG. 11 shows the configuration of the PDL controller 200,
A receiving device 201 that receives the PDL language sent from the host computer 100, a CPU 202 that performs storage control and anti-aliasing processing, etc. of the PDL language received by the receiving device 201, and an internal system bus 20.
3 and the receiving device 201 via the internal system bus 203.
A RAM 204 for storing PDL language to be transferred from the
ROM2 that stores anti-aliasing programs, etc.
05 and multivalued YM with anti-aliasing processing
Page memory 20 for storing C and BK image data
6 and the YMC and BK image data stored in the page memory 206 to the multilevel color laser printer 300.
and an I10 device 208 that performs transmission and reception with the system control unit 400.

Here, the CPU 202 receives the P received by the receiving device 201.
The DL language is stored in the RAM 204 via the internal system bus 203 according to the program stored in the ROM 205. After that, you will receive one page of PDL language,
Once stored in the RAM 204, the graphic elements in the RAM 204 are subjected to anti-aliasing processing based on the flowchart described later, and the multi-level YMC and BK image data is stored in the plain memory section of the page memory 206 (the page memory 206 is , M.C.

(consists of a BK plane memory section and a feature information memory section).

The data in the page memory 206 is then transferred to the transmitter 2
07 to the multilevel color laser printer 300.

The operation of the PDL controller 200 will be described below with reference to FIGS. 12(a) and 12(b).

1211m(a) shows a flowchart of processing performed by the CPU 202. As described above, the PDL controller 200 performs anti-aliasing processing on the PDL language sent page by page from the host computer 100, and processes black (BK), yellow (Y), magenta (M), and cyan (C). ) is developed into a four-color image.

In the PDL language, graphics and characters are all described using vector data, and as the name "page description language" indicates, image information is processed in units of pages. Furthermore, one page is made up of at least one path, with each path being made up of one or more elements (graphic elements and character elements).

First, when PDL language is input, it is determined whether the element is a curved vector, and if it is a curved vector, it is approximated to a straight line vector and registered as a straight line element (line) in the work area. This is performed for all graphic and character elements within one path, and linear elements are registered in the work area for each path (processing 1).

Then, the linear elements of the work area registered in this path unit are sorted by the starting X coordinate of the straight line (Processing 2
).

Next, in process 3, while updating the X coordinate one by one,
Performs filling processing using scanning lines. For example, when performing the path filling process shown in FIG. (If a straight line is not shown, it is written as a scanning line) and the real value of the X coordinate (the 12th
XI, X2. X3. X4) and A
ET (Active Edge Table: a table that records the X coordinates of edge portions appearing on the scanning line). Here, the order of the elements registered in the work area is the order in which they were registered in process 1, so they are not necessarily registered in order of decreasing X coordinate across the scanning line yc. For example, in process 1, if a straight line element passing through scanning lines yc and X3 in FIG. be registered. Therefore, after the AET is registered, the elements on each side within the AET are sorted in descending order of X coordinate. Then, pair the first two elements of AET and fill in the space between them (specifically, for example, fill processing with scan lines formed by scan line yc and scan line y (-1-1))
.

Anti-aliasing processing is achieved by adjusting the density of edge pixels in accordance with the area ratio in this filling processing. Then remove the processed edge from the AET, update the scanline (update the Repeat the process.

The above processing 1, processing 2. The work in process 3 is executed pass by pass and repeated until all passes for one page are completed.

Next, the anti-aliasing process executed during the scan line filling process of process 3 described above will be described in detail with reference to the flowchart in FIG. 12(C).

For example, if a rectangle ABCD as shown in FIG. 13(a) is input in process 1 of FIG. 12(a), this figure has the following elements.

(b) Four line vectors AB, BC, CD, and DA (represented by real numbers) (a) Color and brightness values inside the figure As shown in Figure 13 (b), this figure is mainly It is divided into five linear vectors (expressed as real numbers) extending in the scanning direction. At this time, in this embodiment, the following information is added to the starting points and ending points of the five straight line vectors.

That is, (c) Starting point coordinate values (real number expression) of the vector elements ((a) above) forming the starting point and ending point of the straight line vector (d) Slope information (near ) Characteristic information of the start point and end point of a straight line vector (right edge, left edge, vertices of two figures, line of 1 dot or less, intersection of straight lines, etc.) When an edge pixel is detected in the scan line filling process, the Antialiasing processing shown in the flowchart of FIG. 12(C) is executed.

First, in the sub-pixel filling process, it is determined whether there is an end point of vector data in the edge pixel, and if there is an end point, the 3*3 sub pixel shown in FIG. 9(C) is Using a matrix, one pixel is divided into subpixels, and a filled area for each subpixel is calculated. Also, if there is no endpoint, determine the slope θ of the vector data, and if θ is tanθ>9/2, 1*9
Using the submatrix (see Figure 9(a)), θ is 2.
/9 > tan θ > -2/9, use 9*1 submatrix (see Figure 9(b)); otherwise, use 3*3 submatrix to divide one pixel into subpixels. Then, a filled area for each subpixel is calculated (51201). This process is repeated for all vectors that cross the scanning line (S1202).

Next, in the density determination process, the gradation value (density) of each pixel is calculated in order from the first pixel of the scanning line (51203
').

Next, the details are omitted, but each color of the shape (
The gradation values (densities) of the four colors BK, R, G, and B are calculated (51204).

Thereafter, the gradation values of each color are written into the page memory in page memory drawing processing (51205).

Furthermore, the processes from 51203 to 51205 described above are repeatedly executed for all pixels for one line (S120
6).

The CPU 202 repeats the above processing up to the last pixel of the scanning line (y coordinate), and at the same time updates the contents of (c) above with the information of (d) above. The gradation values of the figure shown in FIG. 13(a) obtained by the anti-aliasing process in this way have values as shown in FIG. 14.

The gradation values obtained in this way are processed by predetermined YMC and BK conversion processing (details are omitted, but in this embodiment, a YMC and BK conversion program is provided as software). Color and brightness values ((
(2) information), the image is developed into four-color images of black (BK), yellow (Y), magenta (M), and cyan (C), and the corresponding plain memory section of the page memory 206 is expanded. is stored as image data. In Fig. 15 (a), (b), (C), and (d), the color and luminance value information is C: M: Y= 1:
This shows the state when OCR is applied at 100% in the case of 0.5:0.3.

(2) Structure and operation of multi-value color laser printer First, the general structure of multi-value color laser printer 300 will be explained with reference to the control block diagram shown in FIG.

A photoreceptor development processing unit 301 uniformly charges the surface of a photoreceptor drum (described later), exposes the charged surface to a laser beam to form a latent image, develops the latent image with toner, and transfers it to recording paper. The details will be explained later, but the development and development of BK data is
Black developing/transfer section 30 l bk and C
Cyan development/transfer section 301c that develops and transfers data
and a cyan developing/transfer section 3 that develops/transfers M data.
01m, and a cyan developing/transfer section 301y that develops and transfers Y data.

The laser drive processing unit 302 receives Y, M, and C signals output from the PDL controller 200 described above.

Buffer memories 303)', 303m input 5-bit BK data (here image density data) and output a laser beam, and input 5-bit Y, M, and C data.

303c, and laser diodes 304y and 3 that output laser beams corresponding to Y, M, C, and BK, respectively.
Drivers 305y, 305m, 305c, and 30 drive the laser diodes 304y, 304m, 304C, and 304bk, respectively.
It consists of 5bk.

In addition, the black developing/transfer section 3 of the photoreceptor development processing section 301
01bk, the laser drive processing unit 302, the laser diode 304bk, and the driver 305bk are called a black recording unit BKU (see FIG. 17). Similarly, the combination of the cyan developing/transfer section 301c, laser diode 304 (driver 305c, and buffer memory 303c) is connected to the cyan recording unit CU (
(see Figure 17), magenta developing/transfer section 301m,
Laser diode 304m, driver 305m,
The combination of the buffer memory 303m is a magenta recording unit I-MU (see Figure 17), a yellow developing/transfer section 301y, a laser diode 304y,
Driver 305y, and.

The combination of buffer memories 303y is called a yellow recording unit (YU) (see FIG. 17). As shown in the figure, each of these recording units is connected to a conveyor belt 30 that conveys the recording paper.
A black recording unit BKU, a cyan recording unit CU, a magenta recording unit MU, and a yellow recording unit YU are arranged around the recording paper 6 in this order from the recording paper conveyance direction.

Due to this arrangement of each recording unit, the laser diode 3 for black exposure starts exposure first.
04bk, and the laser diode 304y for yellow exposure starts exposure last. Therefore,
There is a time difference in the order of exposure start between each laser diode,
In order to hold the recording data (output of the PDL controller 200) during the time difference, the laser drive processing unit 302 includes the three sets of buffer memories 303y described above.

303m and 303c are provided.

Next, the configuration of the multilevel color laser printer 300 will be specifically explained with reference to FIG. 17.

The multilevel color laser printer 300 includes a conveyor belt 306 that conveys recording paper, and seven recording units YU and Mu disposed around the conveyor heald 306 as described above.
, ',C1,', BKU, paper feed cassettes 307a, 307b storing recording paper, and paper feed cassettes 307a, 3.
Paper feed rollers 308a that feed recording paper from 07b
, 308b, and a registration roller 3 that aligns the recording paper sent out from the paper feed cassettes 307a and 307b.
09 and the recording unit BKU by the transport heald 306.
, CU, MU, and YU are sequentially conveyed and the transferred images are fixed on the recording paper by a fixing roller 310, and a paper discharge roller 311 that discharges the recording paper to a predetermined discharge section (not shown). Ru. Here, each recording unit YU, MU, CU
, BKU is the photosensitive drum 312)', 312m, 31
2c, 312bk, and photoreceptor drum 312y, respectively.
312m.

Charger 313y that uniformly charges 312c and 312bk
, 313m, 313c, 313bk, and photosensitive drum 3
12y, 312m, 312c.

Polygon mirrors 314y, 314m, 314c, 314bk and motors 3tsy, 315m, 315c for guiding the laser beam to 312bk.

315bk, photosensitive drum 312y, 312m.

Toj-developing devices 316)', 316m, and 316c that develop the electrostatic latent images formed on the latent images 312c and 312bk using toners of corresponding colors, respectively.

316bk, and transfer chargers 317y, 317m, and 317c that transfer the developed toner image onto recording paper.

317bk and a photosensitive drum 312y after transfer.

Cleaning devices 318y, 318m, 318 for removing toner remaining on 312m, 312c, 312bk
c, 318bk.

Note that 319y, 319m, 319c, and 319bk are photosensitive drums 312y and 312m, respectively.

A CCD line sensor for reading a predetermined pattern provided on 312c and 312bk is shown, and although the details are omitted, the process status of the multilevel color laser printer 300 is detected by this.

In the above configuration, the operations of the yellow recording unit YU will be explained using exposure, development, and transfer as examples.

Figures 18(a) and 18(b) show the yellow recording unit YU.
The configuration of the exposure system is shown. In the figure, a laser beam emitted from a laser diode 304y is reflected by a polygon mirror 314y, passes through an f-theta lens 302y, and then passes through a mirror 321y.

322y and is irradiated onto the photoreceptor drum 312y through the dustproof glass 323y. At this time, since the polygon mirror 314y is rotated at a constant speed by the motor 315y, the laser beam moves in the direction along the axis of the photosensitive drum 312y (main scanning direction). Further, in this embodiment, a photosensor 324y is provided to detect the base point for tracking the scanning position of the main scan, so that the laser beam at the non-exposed position is detected. The laser diode 304y outputs recording data (
Since the photosensitive drum 304y is activated to emit light based on the 5-bit data from the PDL controller 200, multivalue exposure corresponding to the recording data is performed on the surface of the photosensitive drum 304y. As described above, the surface of the photoreceptor drum 304y is charged in advance in the negative direction by the charger 313y, and an electrostatic latent image corresponding to the original image is formed by the exposure. The electrostatic latent image is developed by a yellow developing device 316y to become a yellow toner image. This toner image is fed out from a cassette 307a (or 307b) by a paper feed roller 308a (or 308b) as shown in FIG. and transport belt 30.
The image is transferred onto the recording paper conveyed by 6.

Other recording units) BKU, CU, and MU have similar configurations and perform similar operations, but the blank recording unit BKU is equipped with a black toner developing device 316bk and forms and transfers a black toner image, and the cyan recording unit C
U is equipped with a cyan toner developing device 316c, which forms and transfers a cyan toner image, and a magenta recording unit) M
Lt includes a magenta toner developing device 316m, and forms and transfers a magenta toner image.

■ Multi-value drive drivers 305y, 305m, 305c, and 305bk drive Y, M, C, and B signals sent from the image processing device 400.
Based on the 5-bit data of K, the corresponding laser diodes 304y and 304m.

The controller 304c and 304bk are controlled to perform multi-value driving, and a pulse width modulation method is used as the driving method.

Hereinafter, multi-level driving using the pulse width modulation method applied in this embodiment will be explained as shown in FIGS.
This will be explained in detail with reference to . In addition, the driver 305y.

305m, 305c, 305bk and laser diodes 304y, 304m, 304c, 304bk have the same configuration, so here
5y and the laser diode 304y will be explained as examples.

As shown in FIG. 19(a), the driver 305y controls the pulse of the LD drive clock based on a laser diode on10ff circuit 350 that turns on and off the laser diode 304y and 5-bit image density data (here, Y data). The pulse width modulation circuit 351 that modulates the width and the current (LD drive current) Id that drives the laser diode 304y are connected to the laser diode on10f.
It is composed of a constant current circuit 352 that supplies an f circuit 350.

FIG. 19(b) shows the configuration of the pulse width modulation circuit 351, and FIG. 19(C) shows its timing chart. In this circuit, DolD 1. D
2. D3. Input the 5 focus data of D4 and select 0(o
ff) is selected by the D latch 351a. DO is the laser beam onl
When it is 0, the laser beam is off, and when it is 1, it is on.

Furthermore, only when the laser beam is on, DLD2°D3.
Nine different pulse widths can be selected using the four focus points of D4. Nine ways of adjusting the pulse width will be described below.

First, the LD drive clock is connected to the delay element 351b,
Pass through 351c, 351d, 351e Tel, C2, C
3. Order four types of signals, C4.

Next, LD drive clock and 01 NAND351i
The A1 signal is obtained, and by passing this and the LD drive clock through an AND 351m, a Pl of about 1/9 duty is obtained. In the same way, connect the LD drive clock and C.
Approximately 279.2 from the signals of 2, C3, and C4. Approximately 379. Approximately 47
9 duty signal P2. Obtain P3°R4. Further LD
Approximately 11/by OR351q of drive clock and C1
A signal P6 of 18 duty is obtained. In the same way, from the LD drive clock and C2, C3, C4 signals, approximately 13/
1B, signal P of approximately 15/18° and approximately 17/18 duty.
7. P8. Get P9. On the other hand, R3 with a duty of approximately 90% is obtained using the LD drive clock and 0R351f of C2.

On the other hand, the LD drive clock itself is R5 with a duty of about 50%. P1. R2, R3, R4, R5, R
6°R7, R8, R9 are input to the data selector 351g, and image density data DI, D2 . D3. One of them is selected based on D4. Then, AND351
Pn only when DO is on due to h (n is 0 to 3)
is output as the LD drive clock ■ after pulse width modulation.

Next, referring to FIG. 19(d), the laser diode on10ff circuit 350. A specific circuit configuration of the constant current circuit 352 is also shown. laser diode on10f
The f circuit 350 includes TTL inverters 353 and 354,
Differential switching circuits 355 and 356 perform an onloff toggle operation, and when VGI>VC2, the differential switching circuit 355 is on, and the differential switching circuit 3
56 is off, and when VGI<VC2, the differential switching circuit 355 is off, and the differential switching circuit 356 is off.
It is composed of resistors R2 and R3 forming a voltage dividing circuit that generates VC2 that satisfies the condition that VC2 is turned on. Therefore,
When the LD drive clock is on, the output of the inverter 354 generates VGI, the above conditions (VC1>VC2) are satisfied, the differential switching circuit 355 is on, the differential switching circuit 356 is off, and the laser is turned off. Turn on the diode 304y. Conversely, when the LD drive clock is off, there is no output from the inverter 354, so the condition (VC, 1 < VC, 2) l! Add f,
The differential switching circuit 355 is turned off, the differential switching circuit 356 is turned on, and the laser diode 30
Turn off 4y.

The constant current circuit 352 includes the laser diode 304 in the laser diode ON10ff circuit 350 as described above.
y current, and the transistor 360
and resistors R4 and Rs.

The laser beam from the laser diode 304y is
Based on levels 0 to 9 (corresponding to gradation values O to 9),
A latent image as shown in FIG. 20 is formed on the photosensitive drum 312y (however, level O indicates no dots and is therefore not shown).

In the graphic processing apparatus of the second embodiment, the toner image shown in FIG. 21 is finally formed on the recording paper for the rectangle ABCD shown in FIG. 13(a) by the configuration and operation described above.

[Embodiment 3] Hereinafter, an outline of anti-aliasing processing will be explained using an image forming system incorporating the graphic processing device of the present invention as a PDL controller as Embodiment 3. Note that the other configurations are the same as those of the second embodiment, so explanations of the configuration and operation will be omitted.

The graphic processing device (hereinafter referred to as PD, L controller) of Embodiment 3 forms artificial edge pixels thinly and right edge pixels darkly in the edge pixels of the final image output from the laser printer. When determining the gradation value (1 degree value) in advance, taking into account the characteristics of the electrophotographic process that It converts into gradation values with a high contribution rate.

Hereinafter, with reference to FIGS. 22(a) to 22(C), an outline of the antialiasing process in the graphic processing apparatus of the third embodiment will be explained in detail.

In Embodiment 3, in order to convert the area of the right side when an edge pixel is divided into left and right sides into gradation values with a higher contribution rate than the area of the left side, when comparing adjacent subpixels, the area of the right side is always Sub-pixels divided by a predetermined sub-pixel division ratio set so that the sub-pixels become smaller are used. Specifically, as shown in FIG. 22(a), the horizontal division ratio when dividing a pixel into subpixels is
The pixels are divided in a ratio of 3:2:1 from the left side. In this embodiment, 3*3 subpixel division will be explained as an example, but it is not limited to this.
Of course, it is applicable to all subpixel divisions.

Furthermore, the horizontal division ratio of subpixels is not particularly limited.

FIG. 22(a) shows the case of performing 3*3 subpixel division, in other words, the area to be filled when the number of gradations of the output device (here, a laser printer) is 1olli scale (o to 9). The case where (area of an image part) is converted into a gradation value is shown. The weights of these subpixels are uniform, and rl is assigned to all of them, regardless of the size of the subpixel, as shown in (■) in the same figure. Therefore, when the left side of the vector image is drawn (that is, when the edge pixel is the left edge), there is an increased possibility that the subpixel intersects with the image part on the right side of the pixel, so the edge part of the left edge The density of pixels tends to increase.

On the other hand, when the right side of the vector image is drawn (that is, when the edge pixel is on the right edge), the possibility that a subpixel intersects with the image part on the left side of the pixel decreases, so the edge part on the right edge The density of pixels tends to decrease.

For example, as shown in Fig. 22(b), when a vector image covers an edge pixel, there are 3 subpixels that intersect with the image area, resulting in 379 gradations (gradation value 3). . On the other hand, the conventional 3
*Using 3-subpixel division to find the gradation of the edge pixel in the vector image in the same way, there are 2 subpixels that intersect with the image part, so it is 279 gradations (gradation value 2). Become.

Although the explanation will be omitted, if the image part is to the left of the edge pixel, on the contrary, the gradation value will be lower in the sub-pixel division in the same figure (bl) than in the sub-pixel division in the same figure (C). become a trend.

Therefore, by using the subpixel division shown in FIG. 22(a), when an edge pixel is divided into left and right parts, the area of the right part is converted into a gradation value with a higher contribution rate than the area of the left part. be able to.

In addition, by subpixel division with different horizontal division ratio,
Even though weighting is performed to convert the area of the right side into gradation values with a higher contribution rate than the area of the left side when the edge pixel is divided into left and right parts, the gradation values are determined using the conventional uniform averaging method. It can be done as fast as the method.

As a method for converting the area of the right side of an edge pixel into left and right parts into gradation values with a higher contribution rate than the area of the left side, we use a weighting filter that increases the weight of the subpixel on the right side of the edge pixel. It is also possible to use the weighted averaging method to determine tone values. For example, as shown in FIG. 22(d), pixels are divided horizontally into 6.
The image is divided into subpixels by the number of divisions @i, and as shown in the figure, the gradation value is determined using a weighted filter. The same figure (b
) can obtain the same effect as (3) 9 gradations (gradation value 3)). However, in this case, since weighted multiplication processing is performed, the processing speed is slower than the method shown in FIG. 22(a) in which subpixel division is performed by changing the horizontal division ratio.

Here, for example, a pentagon A as shown in FIG.
If BCDE is input, this figure has the following elements.

(B) Five line vectors AB, BC, CD, DE, and EA (represented by real numbers) (El) Color and brightness values inside the figure This figure is created as shown in Figure 23 (b) by the above-mentioned operation. , into seven straight line vectors (expressed as real numbers) extending in the main scanning direction. At this time, in this embodiment, the following information is added to the starting points and ending points of the seven straight line vectors.

That is, (c) Starting point coordinate values (real number expression) of the vector elements ((a) above) forming the starting point and ending point of the straight line vector (d) Slope information (near ) Characteristic information of the start point and end point of the straight line vector (right edge, left edge, apex of figure, line of 1 dot or less, intersection of straight lines, etc.) Next, referring to the flowchart in Figure 24, calculate the line vector. Anti-aliasing processing in fill processing will be explained. As shown in FIGS. 22(a) to (C), in the present invention, when an edge pixel is divided into left and right parts, the area of the right part is converted into a gradation value with a higher contribution rate than the area of the left part. .

First, in the sub-pixel filling process, one pixel is divided into 3*3 sub-pixels at the horizontal division ratio shown in FIG. 22(a), and a filling area for each sub-pixel is calculated (52401). This process is repeated for all vectors that cross the scanning line (S2402).

Next, the gradation value (density) of each pixel is calculated in order from the first pixel of the target scanning line using a uniform averaging method (anti-aliasing processing method) (S2
403).

Next, the details are omitted, but each color of the shape (
The gradation values (densities) of the four colors BK, R, G, and B are calculated (52404).

Thereafter, the gradation value of each color is written into the page memory in page memory drawing processing (S2405).

Furthermore, the processes from 52403 to 52405 described above are repeatedly executed for all pixels for one line (S240
6).

The CPU 202 repeats the above processing up to the last pixel of the scanning line (y coordinate), and at the same time updates the contents of (c) above with the information of (d) above. The gradation values of the figure shown in FIG. 23(a) obtained by the anti-aliasing process in this way have values as shown in FIG. 25.

The gradation values obtained in this way are processed by predetermined YMC and BK conversion processing (details are omitted, but in this embodiment, a YMC and BK conversion program is provided as software). Color and brightness values ((
0) information), black (BK), yellow (Y), magenta (M), and cyan (C).
The image is expanded into a color image and stored as image data in the corresponding plain memory section of the page memory 206. Figure 26 (a), (b), (C1, (d)
The color and brightness value information is C: M: Y= 1
:0.5:0.3 and the UCR is multiplied by 100%.

In the graphic processing apparatus of the third embodiment, the toner image shown in FIG. 27 is finally formed on the recording paper for the pentagon ABCDE shown in FIG. 23(a) by the configuration and operation described above. FIG. 28 shows toner images of pentagon ABCDH when sub-pixel division is performed with a horizontal division ratio of 1:1:1.
As is clear from a comparison with the figure, a toner image can be formed without impairing the effect of anti-aliasing processing. In fact, the characteristics (disadvantages) of the electrophotographic process
Therefore, the effect of Example 3 becomes even more apparent in the image after development and transfer, since the low density edge portions of the toner image cannot be reliably reproduced.

In addition, in Example 3, when an edge pixel is divided into left and right by subpixel division with a horizontal division ratio of 3:2:1, the area of the right side has a higher contribution rate to the gradation value than the area of the left side. Although the conversion is performed, it goes without saying that the same effect can be obtained by using a weighting filter as shown in FIG. 22(d).

[Embodiment 4] Hereinafter, an outline of anti-aliasing processing will be explained using an image forming system incorporating the graphic processing device of the present invention as a PDL controller as Embodiment 4. Note that the other configurations are the same as those of the second embodiment, so explanations of the configuration and operation will be omitted.

The graphic processing device (hereinafter referred to as PDL controller) of the fourth embodiment divides one pixel into a sub-pixel division area where sub-pixel division is performed and an area outside the sub-pixel division area where sub-pixel division is not performed. By determining the gradation value based on the number of subpixels covered by the image part of the subpixel division area, the characteristics of the pulse width modulation method may impair the effectiveness of antialiasing processing and cause aliasing. The gradation value of a certain edge pixel can be set to "0".

Hereinafter, with reference to FIGS. 29(a) to 29(e), an overview of the antialiasing process in the graphic processing apparatus of the fourth embodiment will be explained in detail.

In the fourth embodiment, as shown in FIG. 29(a), the left side of a pixel (pixel to be subjected to anti-aliasing processing) is set as a sub-pixel division area, and the right side is set as outside the sub-pixel division area.

Further, the sub-pixel division area is divided into 3*3 sub-pixels.

Next, with reference to FIGS. 29 et al.) to (e), the method of determining gradation values according to the present invention will be described in comparison with the conventional method (method using 3*3 subpixel division). As shown in FIG. 6(b), if the image part covers only the outside of the subpixel division HNi of the pixel, in other words, if the image part does not cover the subpixel, the number of subpixels to be filled is 079. Therefore, the tone value is "0". on the other hand,
In the conventional 3*3 subpixel division, the number of subpixels to be filled in is 179, as shown in FIG. 3C, so the gradation value is "1". In this case, since the image portion barely touches the edge of the pixel, if a dot is formed using the pulse width modulation method, the dot will be separated from the image portion and the effect of anti-aliasing processing will be impaired.

Furthermore, as shown in Figure (d), when the image part covers the subpixel divided area, the number of subpixels to be filled is 2/9, so the gradation value is "2". . On the other hand, in the conventional 3*3 subpixel division, the number of subpixels to be filled is 379, as shown in FIG. becomes. In this case, the gradation value is determined to be smaller compared to the conventional method, but when looking at the pixels at the left edge in the sub-scanning direction, all pixels are similarly assigned smaller gradation values. Therefore, the effectiveness of anti-aliasing processing is not impaired.

Furthermore, as is clear from the above description, since no weighting filter is used, there is no need to perform weighted multiplication processing, and gradation values can be obtained at the same processing speed as the normal uniform averaging method.

Next, antialiasing processing in scan line filling processing will be described with reference to the flowchart in FIG. 30. As shown in FIGS. 29(a) to (e), in the present invention, when an edge pixel is divided into left and right parts, the area of the right part is converted into a gradation value with a higher contribution rate than the area of the left part. .

First, in the subpixel filling process, as shown in FIG. 29(a), one pixel is divided into a subpixel division area and an outside subpixel division area, and the subpixel division area is further divided into 3 * 3 subpixels. Then, a filled area for each subpixel is calculated (S3001). This process is repeated for all vectors that cross the scanning line (S3002).

Next, the gradation value (density) of each pixel is calculated in order from the first pixel of the target scanning line using a uniform averaging method (anti-aliasing processing method) (S3
003).

Next, the details are omitted, but each color of the shape (
The gradation values (densities) of the four colors BK, R, G, and B are calculated (S3004).

Thereafter, the gradation values of each color are written into the page memory in page memory drawing processing (53005).

Furthermore, the above processes 53003 to 53005 are repeatedly executed for all pixels for one line (S300
6).

The CPU 202 repeats the above processing up to the last pixel of the scanning line (y coordinate), and at the same time updates the contents of (c) (see Example 3) with the information of (d) (see Example 3). In this way, the anti-aliasing process
For example, the gradation values of the figure in FIG. 23(a) have values as shown in FIG. 31.

The gradation values obtained in this way are processed by predetermined YMC and BK conversion processing (details are omitted, but in this embodiment, a YMC and BK conversion program is provided as software). Color and brightness values ((
tr) information), the image is developed into four-color images of black (BK), yellow (Y), magenta (M), and cyan (C), and is stored in the corresponding plain memory section of the page memory 206. is stored as image data. In FIG. 32 (a), (bL (C), (d), the color and luminance value information is C: M: Y= 1:
This shows the state when UCR is multiplied by 100% in the case of 0.5:0.3.

In the graphic processing apparatus of the fourth embodiment, the toner image shown in FIG. 33 is finally formed on the recording paper for the pentagon ABCDH shown in FIG. 23(a) by the above-described configuration and operation. As is clear from a comparison with the conventional 3*3 subpixel division shown in FIG. 28, a toner image can be formed without impairing the effect of anti-aliasing processing.

Further, in the fourth embodiment, the sub-pixel division area is divided into 3*3 sub-pixels υI, but the invention is not particularly limited to this. Furthermore, the ratio outside the sub-pixel division area may be increased.

(Embodiment 5) Hereinafter, an outline of anti-aliasing processing will be explained using an image forming system incorporating the graphic processing device of the present invention as a PDL controller as Embodiment 5. Note that the other configurations are the same as those of the second embodiment, so explanations of the configuration and operation will be omitted.

The graphic processing device (hereinafter referred to as PDL controller) of the fifth embodiment determines whether the image portion to be filled is above, below, to the left or right of the edge pixel, based on the slope of vector data that crosses the edge pixel and the type of edge. determine which part it is in, and select a corresponding weighting filter from predetermined weighting filters based on this determination result,
Determine the gradation value of the edge pixel. In other words, by selecting the weighting filter to be used based on the slope of the vector data and the direction of the filled area, and determining the gradation value using the most appropriate weighting filter for each of the upper, lower, left, and right edge pixels, It is designed to obtain a printed image with appropriate density at the final output, and in particular, it is possible to avoid problems caused by the characteristics of the pulse width modulation method in left edge pixels (edge pixels where the image part to be filled is located on the right side of the pixel). This makes it possible to avoid the occurrence of aliasing due to low density dots.

Hereinafter, with reference to FIGS. 34(a) to 34(f), an outline of the antialiasing process in the graphic processing apparatus of the fifth embodiment will be explained in detail.

In Example 5, the gradation value of the edge pixel is determined using four weighting filters with a 4*4 filter shape and different weight values of the weighted averaging method, and this gradation value is set to 10.
Multi-level color laser with pulse modulation method with gradation.
In order to output to the printer 300, the final gradation value is converted into 10 gradations.

Figures 34 (a), (b), (C), and (d) show four weighting filters used in this example, and in Figure 34 (a), the image portion to be filled is located to the left of the edge pixel. The right edge filter is used when the image part to be filled is located to the right of the edge pixel, and (C) is the left edge filter used when the image part to be filled is located to the right of the edge pixel. This is an upper edge filter used when the image part is located below the edge pixel, and (d) in the same figure shows a lower edge filter used when the image part to be filled is located above the edge pixel. It is. Note that the weighting values of these filters are not particularly limited to these values, and should be determined to reduce jaggedness in the final printed image, taking into account the number of gradations and dot shape of the laser printer that is the output device. You can set it like this.

FIG. 34(e) shows an image section that determines whether the image portion to be filled is above, below, to the left, or to the right of the edge pixel, based on the slope of vector data that crosses the edge pixel and the type of edge. This shows an example of determination.

Here, for example, if the slope α of the vector data is π/2,
For an edge pixel whose type is right edge, it is determined that the left side of the edge pixel is filled in, and as shown in the figure, the right edge filter is selected as the filter to be used.

In the fifth embodiment, the image portion to be filled is determined from the top and bottom or from the left and right based on whether the slope α of the vector data is greater than or equal to π/4 (or -π/4) or less. π/4 (or -
π/4)L is not limited to this.

Next, a specific example of how the filter is used will be explained with reference to FIG.

As is clear from the diagram, pixel G has a slope α of O≦α.
Since the edge type is a left edge in <π/4, it can be determined that the lower side of the edge pixel is to be filled.

Therefore, when the gradation value is determined using the upper edge filter, the gradation value is 4 (4/19).

Since the slope α of pixel G2 is greater than π/4 and the edge type is a left edge, it can be determined that the right side of the edge pixel is to be filled. Therefore, when the gradation value is determined using the left edge filter, the gradation value is 0 (0/1
9).

Since the slope α of pixel G3 is smaller than 1π/4 and the type of edge is a right edge, it can be determined that the left side of the edge pixel is to be filled. Therefore, when the gradation value is determined using the right edge filter, the gradation value is 6 (6/
16).

Since the slope α of pixel G4 is O≦α<π/4 and the edge type is a right edge, it can be determined that the upper side of the edge pixel is to be filled. Therefore, when determining the gradation value using the lower edge filter, the gradation value is O(0/20
).

Next, anti-aliasing processing in scan line filling processing will be described with reference to the flowchart of FIG. 35.

First, in subpixel filling processing, one pixel is divided into 4*4 subpixels, and a filling area for each subpixel is calculated (S3501). This process is repeated for all vectors that cross the scan line (53
502).

Next, in the density determination process, as shown in FIG. 34(e), the slope of vector data crossing the edge pixel,
Then, based on the type of edge, it is determined whether the image part to be filled is above, below, left or right of the edge pixel, the appropriate filter is selected, and the weighted averaging method is used to fill in the target scanning line. The gradation value (density) of each pixel is calculated in order from the first pixel (S3503).

Next, the details are omitted, but each color of the shape (
The gradation (!! (density)) of the four colors BK, R, G, and B is calculated (S3504).

Thereafter, the gradation value of each color is written into the page memory in page memory drawing processing (S3505).

Furthermore, the above processes 53503 to 53505 are repeatedly executed for all pixels for one line (S350
6).

The CPU 202 repeats the above processing up to the last pixel of the scanning line (y coordinate), and at the same time updates the contents of (c) (see Example 3) with the information of (d) (see Example 3). The gradation values of the figure shown in FIG. 23(a) obtained by the anti-aliasing process in this way have values as shown in FIG. 36.

The gradation values obtained in this way are processed by predetermined YMC and BK conversion processing (details are omitted, but in this embodiment, a YMC and BK conversion program is provided as software). Color and brightness values ((
Based on the information in (B)), the image is developed into four-color images of black (BK), yellow (Y), magenta (M), and cyan (C), and is stored in the corresponding plain memory section of the page memory 206. is stored as image data. In FIG. 37 (al) (b), (c), and (a), the color and luminance value information is C: M: Y= 1:
This shows the state when UCR is multiplied by 100% in the case of 0.5:0.3.

In the graphic processing apparatus of the fifth embodiment, the toner image shown in FIG. 38 is finally formed on the recording paper for the pentagon ABCDH shown in FIG. 23(a) by the configuration and operation described above. As shown in the figure, a toner image can be formed without impairing the effect of anti-aliasing processing.

[Effects of the Invention] As explained above, the graphic processing device of the present invention calculates the gradation value (density value) of the edge pixel of vector data by subpixel division, and prints the gradation value on a laser printer or the like. Since the graphics processing device that outputs to the output device includes a subpixel variable means that changes the division shape of the subpixels, the effect of antialiasing processing can be improved.

Further, the graphic processing device of the present invention calculates the gradation value (density value) of the edge portion pixel of vector data by subpixel division, and outputs the gradation value to an output device such as a laser printer. In this case, the effect of anti-aliasing processing is improved by providing a sub-pixel variable means for approximating vector data to a straight-line vector and varying the sub-pixel division size of edge pixels according to the slope of the straight-line vector. I can do it.

Further, the graphic processing device of the present invention is a graphic processing device that calculates the gradation value (density value) of an edge pixel of vector data by subpixel division and outputs the gradation value to an output device such as a laser printer. , a subpixel division means is provided for selecting an appropriate subpixel shape from among a plurality of subpixel shapes and performing subpixel division based on the slope of the vector data and the presence or absence of an end point in an edge pixel. , without reducing the processing speed (I of a value that is not significantly different from the gradation value obtained from the actual area ratio)
ll tone value can be obtained.

Further, the graphic processing device of the present invention calculates the gradation value (density value) of the edge portion pixel of vector data by sub-pixel division, and outputs the gradation value to a pulse width modulation type laser printer. In the present invention, the present invention is equipped with a tone value determining means that converts the area of the right side of an edge pixel into left and right parts into tone values with a higher contribution rate than the area of the left side, taking into consideration the characteristics of the electrophotographic process. This can prevent the effects of anti-aliasing processing from being impaired.

The graphic processing device of the present invention also performs graphic processing that calculates the gradation value (density value) of a pixel at an edge portion of vector data by subpixel division, and outputs the gradation value to a pulse width modulation type laser printer. The device divides pixels into a sub-pixel division area where sub-pixel division is performed and an area outside the sub-pixel division area where sub-pixel division is not performed, based on the number of sub-pixels covered by the image part of the sub-pixel division area. Since it is equipped with a gradation value determining means for determining gradation values, it does not reduce processing speed, and due to the characteristics of the pulse width modulation method, low density dots can impair the effect of anti-aliasing processing and cause aliasing. This can be avoided.

Further, the graphic processing device of the present invention calculates the gradation value (i! degree value) of the edge portion pixel of vector data by sub-pixel division, and outputs the gradation value to a pulse width modulation type laser printer. In the processing device, an image portion determining means for determining whether an image portion to be filled is above, below, to the left, or to the right of the edge portion pixel, based on the slope of vector data that crosses the edge portion pixel and the type of edge; The upper filter is used when the image part to be filled is located above the edge pixel, the lower filter is used when the image part to be filled is located below the edge pixel, and the image part to be filled is the edge part. Right filter used when located on the right side of the pixel,
and storage means that stores four weighting filters of filling filters to be used when the image portion to be filled is located to the left of the edge pixel, and the corresponding weighting from the storage means based on the determination result of the image portion determination means. Since the present invention includes a gradation value determining means that selects a filter and determines the gradation value of the edge pixel, the occurrence of aliasing due to low density dots can be avoided without reducing the accuracy of antialiasing processing.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of an image forming system according to the first embodiment, FIG. 2 is an explanatory diagram showing the configuration of a PDL controller according to the first embodiment, FIGS. 3(a) and 3(b), and FIG. 4. 5(a), (b), and (C) are explanatory diagrams each showing the principle of the first embodiment, FIG. 6 is a flowchart showing the operation of the first embodiment, and FIGS. 7 and 8 are respectively An explanatory diagram showing the operation of the first embodiment, FIGS. 9(a) to (f) are explanatory diagrams showing an outline of anti-aliasing processing in the graphic processing apparatus of the second embodiment, and FIG. 10 is an image forming system of the second embodiment. FIG. 11 is an explanatory diagram showing the configuration of the PDL controller (graphic processing device of the second embodiment), FIG. 12(a) is a flowchart showing the operation of the PDL controller, and FIG. 12(b) is an explanatory diagram showing the configuration of the PDL controller. 12(C) is a flowchart showing anti-aliasing processing, FIGS. 13(a) and 13(b) are illustrations showing linear vector division of a figure, and FIG. Explanatory diagrams showing gradation values after performing aliasing processing, FIGS. 15(a) and 15(b). (C) and (d) are explanatory diagrams showing YMC and BK image data stored in the brain memory section of the page memory, Fig. 16 is a control block diagram showing a multi-value color laser printer, and Fig. 17 is a multi-value color laser printer. 18(a) and (b) are explanatory diagrams showing the configuration of the exposure system of the yellow recording unit, and FIGS. 19(a), (b), (cl. , (d) is an explanatory diagram showing multi-value driving by pulse width modulation, FIG. 20 is an explanatory diagram showing the state of a latent image depending on the level of pulse width modulation, and FIG.
The figures are explanatory diagrams showing the final toner image of rectangle ABCD shown in FIG. 13(a), FIGS. 22(a), (b),
(C1, (d) is an explanatory diagram showing an overview of anti-aliasing processing in the graphic processing device of Example 30, and FIG. 23 (
a), Φ) are explanatory diagrams showing linear vector division of a figure, FIG. 24 is a flowchart showing anti-aliasing processing in Example 3, and FIG. 25 is a diagram showing tone values after performing anti-aliasing processing in Example 3. Explanatory diagram showing, No. 26
Figures (a), (b), (C), and (d) show Y stored in the brain memory section of the page memory in the third embodiment.
An explanatory diagram showing MC and BK image data, Fig. 27 is an explanatory diagram showing the final toner image of the pentagon ABCDE shown in Fig. 23 (a), and Fig. 28 is an explanatory diagram showing the toner image of the pentagon ABCDE by conventional subpixel division An explanatory diagram showing the image, FIG. 29(a). (b), (c), (d), and (e) are explanatory diagrams showing an overview of the antialiasing process in the graphic processing device of the fourth embodiment, and FIG. 30 is a flowchart showing the antialiasing process of the fourth embodiment. Fig. 31 is an explanatory diagram showing the gradation values after performing anti-aliasing processing in Example 4, and Fig. 32 (a), [with]), (C), (d
) is an explanatory diagram showing YMC and BK image data stored in the brain memory section of the page memory in Example 4, and FIG. 33 is an explanatory diagram showing the pentagon ABCD shown in FIG. 23(a).
Explanatory diagram showing the final toner image of E, FIG. 34(a),
(b), (c), (d), (e), and (f) are explanatory diagrams showing an overview of the antialiasing process in the graphic processing device of the fifth embodiment, and FIG. 35 shows the antialiasing process of the fifth embodiment. FIG. 36 is an explanatory diagram showing gradation values after performing anti-aliasing processing in Example 5, and FIG. 37 (a), (b), (
C). (d) is an explanatory diagram showing YMC and BK image data stored in the brain memory section of the page memory in Example 5, and FIG. 38 is a diagram showing the pentagon AB shown in FIG. 23(a).
Explanatory diagram showing the final toner image of CDH, FIG. 39 (a
), (b) are explanatory diagrams showing conventional anti-aliasing processing, Figures 40 (a) and (b) are explanatory diagrams showing anti-aliasing processing using the uniform averaging method, and Figure 41 (
a), (b) are explanatory diagrams showing anti-aliasing processing using the weighted averaging method; FIGS. 42(a), (b),
(C), (d) are explanatory diagrams showing examples of filters used in the weighted averaging method, Fig. 43 is an explanatory diagram showing the convolution method with 3 x 3 pixel reference, Fig. 44 (a), etc.)
, and FIGS. 45(a), (b), (C), (d
) is an explanatory diagram showing problems with conventional antialiasing processing. Explanation of symbols 100 ------- Host computer 200 -
Go to PDL controller 201, Go to receiving device 202, Go to CPU2
To 03...-Internal system 204--To RAM 205--To ROM
To 206 - Page memory To 207 - Transmitting device 20
8--I10 device 209--Sub pixel variable means 300--
------One-value color laser printer 400・
・-m-- System control section

Claims (9)

[Claims] (1) In a graphic processing device that calculates the gradation value (density value) of an edge pixel of vector data by subpixel division and outputs the gradation value to an output device such as a laser printer, the subpixel division shape A graphics processing device characterized by comprising subpixel variable means for changing subpixel. (2) In a graphic processing device that calculates the gradation value (density value) of an edge pixel of vector data by subpixel division and outputs the gradation value to an output device such as a laser printer, the vector data is converted into a straight line vector. 1. A graphic processing apparatus, comprising: a sub-pixel variable means for approximating , and varying the sub-pixel division size of the edge pixel according to the slope of the straight line vector. (3) In a graphic processing device that calculates the gradation value (density value) of an edge pixel of vector data by subpixel division and outputs the gradation value to an output device such as a laser printer, the slope of the vector data; and subpixel dividing means for selecting an appropriate subpixel shape from among a plurality of subpixel shapes based on the presence or absence of an end point in the edge pixel and performing subpixel division. Graphic processing device. (4) In claim 3, the shape of the plurality of sub-pixels is a quadrilateral obtained by dividing an edge pixel into 1*N, and a quadrilateral obtained by dividing an edge pixel into N*1.
A graphic processing device comprising three types of sub-pixel shapes: a divided quadrilateral and a quadrilateral divided into N*M edge pixels. (5) In a graphic processing device that calculates the gradation value (density value) of an edge pixel of vector data by subpixel division and outputs the gradation value to a laser printer using a pulse width modulation method, the edge pixel is 1. A graphic processing device characterized by comprising tone value determining means for converting the area of the right side portion into a tone value with a higher contribution rate than the area of the left side when divided into left and right parts. (6) In claim 5, the gradation value determining means uses a predetermined sub-pixel division ratio set such that when adjacent sub-pixels are compared, the sub-pixel on the right side is always smaller, and uniformly. A graphic processing device characterized in that tone values are determined by an averaging method. (7) In claim 5, the gradation value determining means determines the gradation value by a weighted averaging method using a weighting filter that increases the weight of a sub-pixel on the right side of the edge pixel. Characteristic graphic processing device. (8) In a graphic processing device that calculates the gradation value (density value) of a pixel at an edge portion of vector data by sub-pixel division and outputs the gradation value to a pulse width modulation laser printer, the pixel is The gradation value is divided into a subpixel division area where subpixel division is performed and an area outside the subpixel division area where subpixel division is not performed, based on the number of subpixels covered by the image part of the subpixel division area. A graphic processing device characterized by comprising a tone value determining means for determining a gradation value. (9) In a graphic processing device that calculates the gradation value (density value) of an edge pixel of vector data by subpixel division and outputs the gradation value to a laser printer using a pulse width modulation method, the edge pixel is an image portion determining means for determining whether an image portion to be filled in is above, below or to the left or right of the edge portion pixel, based on the slope of the transverse vector data and the type of edge; an upper filter used when the image portion to be filled is located above the edge pixel; a lower filter used when the image portion to be filled is located below the edge pixel; A right-hand filter to be used when located on the right side of the
a storage means that stores four weighting filters of a left filter to be used when the image portion to be filled is located to the left of the edge pixel; 1. A graphic processing device comprising: tone value determining means for selecting a weighting filter to determine a tone value of the edge pixel.