JPH0433075A - Graphic processor - Google Patents

Abstract

PURPOSE:To execute an anti-aliasing processing at high speed by deciding the ratio of an area to be painted-out in an edge part picture element based on the position of an end point and the direction of painting-out when the end point exists in the edge part picture element. CONSTITUTION:The anti-aliasing processing is executed to adjust an output from the edge part picture element of a vector data based on the ratio of the area to be painted-out, and to smoothly express the edge part of an output picture. Then, it is decided whether the end point of the vector data exists in the edge part picture element or not, and when the end point does not exist, the ratio of the area to be painted-out in the edge part picture element is decided based on input / output coordinates when the vector data crosses the edge part picture element. On the other hand, when the end point exists, the ratio of the area to be painted-out in the edge part picture element is decided based on positions P1-P9 of the end points and directions D1-D4 of painting-out. Thus, without executing sub pixel division and counting the number of areas to be painted-out, the area ratio can be calculated at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a graphic processing device that performs anti-aliasing processing to remove jagged edges of an output image.
More specifically, the present invention relates to a graphic processing device that can perform anti-aliasing processing at high speed.

[Conventional technology]

In the field of computer graphics, when displaying a color 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 Fig. 25(a).
The visually displayed image is shown in Figure 25 ('b
) 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 used as anti-aliasing processing methods.

■In the uniform averaging method, each pixel (iii! ii element) is
*After decomposing into M (N, M is a natural number) sub-vixels and performing rask calculation at high resolution, the brightness of each pixel is calculated as N*
It is determined by taking the average of M subpixels. Second
Anti-aliasing processing using the uniform averaging method will be specifically explained with reference to FIGS. 6(a) and (5). 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 the highest brightness of the gradation that can be displayed (for example, kid・255 for 256 gradations)
is assigned. When performing anti-aliasing processing on this pixel using the uniform averaging method of N-M=7, as shown in the same figure (b), the pixel is decomposed into 7 sub-vixels, and the sub-vixels covered by the image are Count the numbers. The count number (28) is divided by the total number of sub-vixels 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.

■Weighting is an averaging method The weighting and averaging method is a partial modification of the uniform averaging method. In contrast to the weighting method, which simply counts the number of sub-vixels in the image, the averaging method assigns a weight to each sub-vixel, so that the influence on the brightness kid of that sub-vixel differs depending on which sub-vixel the image falls on. I have to. Note that the weight at this time is given using a filter.

With reference to FIGS. 27(a) and (b), FIG. 26(a)
An example is shown in which the same image data is weighted using the same dividing method (N-M-7) and the averaging method is applied.

FIG. 27(a) shows a filter (here, conef
For example, the sub-vixel in the upper right corner has a weight of 2. When an image is applied to each sub-vixel, the weight value given by the filter characteristics becomes the count value of that sub-vixel. FIG. 6B shows the display pattern of the image changed depending on the weight of the sub-vixels. In this case, counting the weighted sub-vixels of the image results in 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. In addition, the filter shown in Fig. 28 (a
), et al.), (C), and (d) are known.

■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 'xN' pixels to correspond to pixels in the equal-averaging or weighted averaging method. FIG. 29 shows a 3×3 pixel reference convolution method, in which the pixel whose brightness is to be determined is indicated by 2901.

The image continues to the lower right of the diagonal line, and the sub-vixels painted in black are the sub-vixels that are counted, and each hixel is divided into 4*4. Therefore, in this case, 12 filters are 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 programming language for systems such as this, and vector fonts are used as character fonts in such systems. 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 7 display, there is a problem 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.

[Problem to be solved by the invention]

However, according to a graphic processing device that applies a conventional anti-aliasing processing method, one pixel is divided into a plurality of sub-vixels (for example, 49 sub-pixels), and the area ratio is calculated by counting the number of sub-vixels that are filled. (m1 degrees), it takes time to calculate the area ratio, which hinders the improvement of display speed or printing speed. In particular, the convolution method is
The problem is that it is difficult to improve processing speed because the amount of calculation is large and multiple pixels are affected.

The present invention has been made in view of the above, and an object of the present invention is to quickly obtain an area ratio without dividing subpixels or counting the number of filled pixels.

[Means to solve the problem]

In order to achieve the above object, the present invention adjusts the output of edge pixels of vector data based on the area ratio to be filled, and performs anti-aliasing processing to smoothly express jagged edges (aliases) of the output surface image. In a graphic processing device that executes, an end point determining means for determining whether or not an end point of vector data exists within an edge pixel, and a means for determining whether or not an end point of vector data exists within an edge pixel; The first step is to determine the area ratio to be filled in for edge pixels based on the input/output coordinates of
and a second area for determining the area ratio to be filled in for the edge pixel based on the position of the end point in the edge pixel and the filling direction when an end point exists in the edge pixel. The present invention provides a graphic processing device equipped with rate determining means.

[Effect]

In the graphic processing apparatus of the present invention, the end point determining means determines whether an end point of vector data exists within an edge pixel. If there is no end point within the edge pixel, the first area ratio determining means determines the area ratio to be filled in for the edge pixel based on the input/output coordinates when the vector data crosses the edge pixel. On the other hand, if there is an end point in the edge pixel, the second area ratio determining means determines the area ratio to be filled in for the edge pixel based on the position of the end point in the edge pixel and the filling direction. do.

〔Example〕

Hereinafter, as an example of an image forming system incorporating the graphic processing device of the present invention as a PDL controller, 1) Overview of anti-aliasing processing (main part of the present invention), and 2) A block diagram of the image forming system.

A detailed explanation will be given in the following order: 1) the configuration and operation of the PDL controller (graphic processing device of the present invention), 2) the configuration of the image processing device, 2) the configuration and operation of the multi-valued color laser printer, and 2) the multi-valued drive of the driver.

■Overview of anti-aliasing processing
0), if there is no end point within the edge pixel, the area ratio is determined based on the input/output coordinates when the vector data crosses the edge pixel, and the end point exists within the edge pixel. In this case, anti-aliasing processing can be executed at high speed by setting a predetermined constant as the area ratio of edge pixels.

Hereinafter, the principle of anti-aliasing processing, which is the main part of the present invention, will be explained in detail with reference to FIG. 1 (6).

The details will be described later, but when vector data is input, the PDL controller 200 determines whether the element is a curved vector, and if it is a curved vector, it is proximal to a straight line vector and used as a straight line element (line) for a predetermined operation. area, and sort the linear elements in this work area by the starting X coordinate of the straight line (in other words, rearrange them in the order of the scan lines), then perform the filling process for each scan line while performing anti-aliasing processing. do. When performing this filling process, first, in order to identify the edge pixels on the scan line to be processed and the image portion within the edge pixels, the X coordinate and edge information (left and right of the edge) of the edge pixels appearing on the scan line are identified.
to a predetermined table (so-called AET: Activ
In this embodiment, information on whether an end point exists in an edge pixel and input/output information when a straight line element (vector data) crosses an edge pixel are stored in this AET. The coordinates (relative coordinates within the edge pixel), the edge pixel self-position information of the end point, and the filling direction information for the end point are registered together with the aforementioned X coordinate of the edge pixel.

Specifically, the coordinates of the intersection between the linear element (vector data) and the target scan line are calculated, and the pixel where the intersection exists is defined as the edge pixel.

Next, check whether there is an end point within the edge pixel, in other words, 1
Check whether two straight line elements (vector data) intersect within one edge pixel. If an end point exists, the specified end point flag information is turned on, and the coordinates of the end point within the edge pixel are set to the relative coordinates within the edge pixel based on the Xsye coordinate system as shown in FIG. 1(a). Calculated as If there is no end point, the input/output coordinates of the linear element for that edge pixel are calculated as relative coordinates within the edge pixel, similarly based on the Xs'10 coordinate system. Thereafter, the coordinates (X coordinates) of the intersection, end point flag information, edge pixel coordinates, input/output coordinates, etc. are registered in the AET. still,
To register the filling direction information for the endpoints, the filling direction for the endpoints is detected during sorting by the X coordinate in the AET, and is added to the AET.

Based on the AET information registered in this way, the end point flag information is turned OFF during antialiasing processing.
In this case, it is determined that there is no end point within the edge pixel, input and output coordinates of vector data are input from the AET, and the area ratio is determined by the following method.

The coordinates of the edge pixels are set in advance as al, a2, . a3. a4. ...al2 no 12
Based on the combination of these 12 input and output canilia, create a LUT as shown in Figure 1 (C).
(Look Lip Table) 1 is created.Next, the input and output coordinates of the vector data are converted to input and output canilia using the conversion table shown in Figure 1(d), and the combination of the input and output canilia and the edge Read the corresponding area ratio from the above-mentioned LUTI using the type of 0 as a key.
For example, when vector data passes through an edge pixel from input/output canilia a1 to input/output canilia a4, LU
From T, the area ratio is determined to be r3/9J for the left edge and r9/9j for the right edge. Note that this area ratio corresponds to the area ratio determined by 3*3 subpixel division (uniform averaging method).

On the other hand, if the end point flag information is ON, it is determined that the end point exists within the edge pixel, the coordinates of the end point within the edge pixel and the filling direction are input from the AET, and the area ratio is determined by the following method. .

As shown in FIG. 1(e), the coordinates of the edge pixels are set in advance as Pl, P2, . P3. P4. ...... P9 is divided into nine edge pixel positions, and these nine edge pixel positions and four fill directions (01, 0
2. Based on the combination of D3゜D4), the first figure)
Create LUT2 as shown in FIG. 1. Next, convert the coordinates in the edge pixel input from the AET to the position in the edge pixel using the conversion table shown in FIG. Using the white value and filling direction as keys, read the corresponding area ratio from LUT2 described above.0For example, if the edge pixel position is P2 and the filling direction is D2, the area ratio is determined from LUT2 to be 11/9 J. Ru. Note that the area ratio set in LUT2 is just an example, and is not particularly limited to this value.

In this way, if there is no end point in the edge pixel, the area ratio can be easily calculated from LUTI using the input/output coordinates, and if there is an end point, the area ratio can be easily calculated from LUT2 based on the edge part pixel coordinates and the filling direction. can be asked for,
Anti-aliasing processing can be performed at high speed.

■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)) and image information read by an image reading device. 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);
A PDL controller (graphic processing device of the present invention) that applies anti-aliasing processing to the PDL language sent page by page from ) 200, an image reading device 300 that reads image information via an optical system unit, and a PDL controller 200. Or.

An image processing device 400 that inputs the image output from the image reading device 300 and performs image processing (details will be described later); and a multi-value color printer that prints the multi-value image data output from the image processing device 400. 4-.7'lJ printer 500 and PDL controller 200. i! i-image reading device 3001 image processing device 400. And multi-value color/
System control unit 6 that controls the laser printer 500
00.

■Configuration and operation of PDL controller FIG. 3 shows the configuration of the PDL controller 200, which includes a receiving device 201 that receives the PDL language sent from the host computer 100, and storage control and control of the PDL language received by the receiving device f201. A CPU 202 that executes anti-aliasing processing and an internal system bus 203
, a RAM 204 that stores the PDL language 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 RGB with anti-aliasing processing
It is composed of a page memo I 7206 that stores image data, a transmitting device 207 that transfers the RGB image data stored in the page memory 206 to the image processing device 400, and an I10 device 208 that performs transmission and reception with the system control unit 600.

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 multivalued RGB image data is stored in the plain memory section of the page memory 206 (the page memory 206 has R, G, B (7) Consists of a 7'' layer 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 image processing device 400.

PDL)
:/) The operation of the roller 200 will be explained.

FIG. 4(a) shows a flowchart of the processing performed by the CPU 202. The PDL controller 200 performs anti-aliasing processing on the PDL language sent page by page from the host combinator 100 as described above. R).

It is developed into three-color images: green (C) and blue (B).

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 text 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 (process 1).

Then, the linear elements of the work area registered in this bus 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,
For example, 0, which performs filling processing using scanning lines. Figure 4 (
When performing the path filling process shown in b), the element on the side across which the scanning line yc to be processed and the real value of the X coordinate across the scanning line yc (XI X!
3 X4) and AET (Active Edge
ble: Register in the table (table for recording the X coordinate of the edge portion 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 l, so they are not necessarily registered in ascending order of the X coordinates that cross the scanning line yc. For example, process 1, scan Figure 5 & 9! When a straight line element passing through yc and X3 is processed first, X is first registered in the AET as the X coordinate of the edge portion appearing on the scanning line yc. Therefore, after the AET is registered, the elements on each side within the AET are sorted in descending order of X coordinate. And A.E.
Pair the first two elements of T and fill in the space between them (for example, scan line yc and scan lip
y c + l).

Anti-aliasing processing is achieved by adjusting the density and brightness of pixels in the edge portion in accordance with the area ratio in this filling processing. After that, move the processed side to A
Remove from ET, update scan line (update X coordinate), A
Similar processing is repeated until all edges in ET are processed, in other words, until all elements in one path are processed.

Above processing 1. Processing 2. The work in process 3 is executed for each bus and repeated until all passes for one page are completed.

Next, FIG. 4(C) shows the AET registration and anti-aliasing processing executed during the scan line filling process of Process 3 described above.

This will be explained in detail with reference to the flowchart in (d).

Here, for example, in process 1 of FIG. 4(a),
), this figure has the following elements.

(A') Five line vectors AB, BC, CD, DE, and EA (represented by real numbers) (El) Color and brightness values inside the figure This figure is shown in Figure 5 (b) by the above-mentioned operation. It is divided 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) the starting point coordinate value (
Real number expression) (d) Slope information of vector elements that constitute the starting point and ending point (edge part pixels) of the straight line vector (d) Feature information of the starting point and ending point (edge part pixel) of the straight line vector (right edge,
(Left edge, end point flag information, line of 1 dot or less, etc.) (f) Input/output coordinates (relative coordinates within edge pixels) when a vector element crosses the start and end points (edge pixels) of a straight line vector.

(G) Coordinates of the end points within the edge pixel (relative coordinates within the edge/2nd pixel) (f): Filling direction for 4 points FIG. 4 (C) is a flowchart showing the registration of AET in Process 3. .

First, calculate the X coordinate (intersection point) of a straight line element (hector data) that crosses the current scanning line (for example, scanning line yc).
5401), Next, check whether an end point exists within the edge pixel that includes the X coordinate (5402), and if the end point exists, turn on the end point flag information 5403), and then check the coordinates of the end point within the edge pixel. Calculate the relative coordinates within the edge pixel (5404). On the other hand, if there is no end point, calculate the input/output coordinates for the corresponding edge pixel of the straight line element as the relative coordinates within the edge pixel (540
5) Write the information in (a) to (g) above into the AET (5406), perform the processing in steps 5401-5406 above for all linear elements (340'l),
Although the explanation is omitted, the information on the filling direction for the end point in (H) is
When sorting by coordinates, the filling direction for the end point is detected and additionally registered in the AET.

FIG. 4(b) is a flowchart showing the filling process using scan lines in process 3, in which anti-aliasing processing is performed based on AET information and pixels are filled.

First, refer to the end point flag information of the edge pixel (54
08), when the end point flag information is ON, the LUT is
The corresponding area ratio is read from 2 and set as the area ratio of the edge pixel (5409).If the end point flag information is not ON, the LUTI is read based on the input/output coordinates of the edge pixel.
The corresponding area ratio is read from , and is set as the area ratio of the edge portion pixel (5410).

The above processes 5408 to 5410 are repeated until all edge pixels are completed (5411), and then the area ratio is set to 1 for non-edge pixels (pixels in the image area other than edge pixels). 5412), the anti-aliasing process is finished, and then the overwrite process (5413) is performed and lfi! is stored in the page memory. Perform i (5414).

The area ratio of the figure in FIG. 5(a) obtained by the anti-aliasing process in this way has a value as shown in FIG.

Here, if the figure in FIG. 5(a) has a white background color (
The figure color is red (maximum brightness: 25) on top of (maximum brightness: 255)
5), from the area ratio k (see Figure 6), the brightness values for each color of the figure are (red), (green),
, (blue) is calculated based on the following formula.

K, −K□Xk 10K. X(1-k)K, = Kit
xk + KggX(1k)Kb ”K□Xk
10 K0×(1-k) However, Kll, KGI, K,
I is the color of the given figure (Ill), respectively.
K * z +
K c z + K * t indicates the luminance value of each previously painted color. Note that Kit, Keg, and Kmz refer to data in each plane memory section corresponding to ROB of the page memory 206.

The brightness value Kr+Kl+ obtained in this way is stored as ROB image data in the corresponding brain memory section of the page memory 206, as shown in FIGS. 7(a), (b), and (C). Stored. Here, for comparison, RGB image data without antialiasing processing is shown in Figures 8 (a), (b),
Shown in (c).

(2) Configuration of Image Processing Apparatus The configuration of the image processing apparatus f400 will be explained with reference to FIG.

The image processing device 400 is a CC in the image reading device 300.
Blank (BK) necessary for recording three color image signals read by D7r, 7g, and 7b.

Yellow (Y), magenta (M), and cyan (C)
Convert to each recording signal. In addition, the RGB image data given from the PDL controller 200 described above is similarly applied to black (BK), yellow (Y), magenta (M
) and cyan (C) recording signals. Here, the mode for inputting image signals from the image reading device 300 is set to copy machine mode, and the mode for inputting image signals from the PDL controller 200 is set to RO mode.
The mode in which B image data is input is called a graphics mode.

The image processing device 400 includes CCDs 7r, 7g, and 7b.
The color gradation data obtained by A/D converting the output signal of
a shading correction circuit 401 that performs correction for variations in anger level of internal terminal elements of 7r, 7g, and 7b;
a multiplexer 402 that selectively outputs either the color gradation data output from the shading correction circuit 401 or the color gradation data (RGB image data) output from the PDL controller 200 according to the above-described mode;
A T correction circuit 40 that inputs the 8-bit data (color gradation data) output from the multiplexer 402, changes the gradation according to the characteristics of the photoreceptor, and outputs it as 6-bit data.
3, and the (R) and green (G) output from the T correction circuit 403.
), 6-bit gradation data indicating 11111 of blue (B) is converted into complementary colors cyan (C) and magenta (M).
.

A complementary color generation circuit 405 converts into yellow (Y) gradation data (6 bits), and a masking processing circuit 406 performs predetermined masking processing on each Y, M, and C gradation data output from the complementary color generation circuit 405. , a UCR processing/black generation circuit 407 that inputs Y, M, and C gradation data after masking processing and executes UCR processing and black generation processing;
Y and M output from the UCR processing/black generation circuit 407
.

The 6-bit gradation data of C9 and BK are converted into 3-bit gradation data Yl, M1 . Convert to C1 and BKI,
It is comprised of a gradation processing circuit 408 that outputs output to the laser drive processing section 502 inside the multivalued color laser printer 50o, and a synchronization control circuit 409 for synchronizing each circuit of the image processing apparatus 400.

Although details will be omitted, the T correction circuit 403 has a configuration in which the illumination property can be changed arbitrarily using an operation button on the console 700.

Further, as the algorithm used in the gradation processing circuit 408, a multi-value dither method, a multi-value error diffusion method, etc. can be used. For example, a dither matrix of the multi-value dither method can be
x3, multilevel color laser printer 500
The number of gradations is the product of 3×3 area gradations and 3-bit (that is, 8 steps) multivalue level, and is 3×3×8−72 (floor!It).

Next, the processing of the masking processing circuit 406 and the UCR processing/black generation circuit B4O7 will be explained.

Generally, the arithmetic expression for the masking process of the masking process circuit 406 is as follows: Y, , M, , C: Data before masking process Y・1M
. . , C@: data after masking processing Also, the arithmetic expression for UCR processing of the UCR processing/black generation circuit 407 is generally expressed as follows.

Therefore, in this embodiment, new coefficients are obtained from these equations using the product of both coefficients.

In this embodiment, a new coefficient (such as "all") that performs this masking processing and UCR processing at the same time is calculated in advance, and
Furthermore, the masking processing circuit 40
6 scheduled input values Y,,M,.

Output value (Y, °, etc.: U) corresponding to C, (6 bits each)
A value that is the calculation result of the CR processing/black generation circuit 407 is obtained and stored in a predetermined memory in advance.

Therefore, in this embodiment, the masking processing circuit 4.6 and O
The CR processing/black generation circuit 407 is composed of a set of ROMs, and the data at the address specified by the inputs Y, M, and C of the masking processing circuit 406 is given as the output of the OCR processing/black generation circuit 407.

In addition, for boat fishing, the masking processing circuit 406 performs Y and M according to the characteristics of the spectral reflection wavelength of the toner for forming a recorded image.
, C signals, and the UCR processing/black generation circuit 407 performs correction for color balance in overlapping toners of each color. UCR processing/black generation circuit 4
07, black component data BK is generated by combining the input three color data of Y, M, and C, and the output Y,
The M and C color component data are corrected to values obtained by subtracting the black component data BK.

In the above configuration, the T correction circuit 403 executes the process based on the T correction conversion graph shown in FIG. 10, and the complementary color generation circuit 405 executes the process as shown in FIG. 11(a).

Suppose that processing is executed based on the conversion graphs for complementary color generation shown in (b) and (C), and then the masking processing circuit 406 and the UCR processing/black generation circuit 407 execute processing based on the following equation. Figure 7(a).

The RGB image data shown in (b) and (C) is T
Correction circuit 403. Complementary color forming circuit 405. Masking processing circuit 406. Then, through the UCR processing/black generation circuit 407, it is converted as shown in FIGS. 12(a), (b), (C), and (c).

Furthermore, if the gradation processing circuit 408 uses a Bayer-type 3×3 multilevel dither matrix shown in FIG. 13, Y in FIGS. ,M.

The data for C and BK are shown in Figure 14 (a) and (b), respectively.
, (C).

It is converted into the data shown in (d).

For comparison, when data without anti-aliasing processing (data in FIGS. 8(a), (b), and (C)) is processed by the image processing device 400, the first
The images are converted as shown in Figures 5 (a], et al.), (C), and (d).

■Configuration of multilevel color laser printer First, the 16th
The schematic configuration of the multivalued color laser printer 500 will be described with reference to the control block diagram shown in the figure.

A photoreceptor development processing unit 501 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
A black developing/transfer section 501bk that performs transfer, a cyan developing/transfer section 501c that develops and transfers C data,
Cyan development/transfer section 501 that develops/transfers M data
m, and a cyan developing/transfer section 501y that develops and transfers Y data.

The laser drive processing unit 502 includes the image processing device 4 described above.
It outputs a laser beam by inputting the 3-bit data of Y, M, C, and BK output from 00 (in this case, image density data). Input buffer memory 503y, 503m
, 503c, and a laser diode 504y that outputs laser beams corresponding to Y, M, C, and BK, respectively.
Drivers 505y, 505m, 505c, and 5 drive the laser diodes 504y, 504m, 504c, and 504bk, respectively.
05b.

Note that the blank developing/transfer section 5 of the photoreceptor development processing section 501
0 l bk, the laser drive processing unit 502, the laser diode 504bk, and the driver 505bk are called a black recording unit BKLJ (see FIG. 17).Similarly, the cyan developing/transfer unit 501c,
Laser diode 504c, driver 505c,
The combination of the buffer memory 503c and the cyan recording unit CU (see FIG. 17) and the magenta developing/transfer section 5
01m, laser diode 504m, driver 505m, and buffer memory 503m are combined into magenta recording unit MU (see figure M17), yellow developing/transfer section 501y, and laser diode 504.
y, driver 5osy, and.

The combination of the buffer memories 503y is called a yellow recording unit YU (see FIG. 17). Each of these recording units is connected to a conveyor belt 506 that conveys the recording paper as shown in the figure.
Black recording unit B from the recording paper conveyance direction
KU, cyan recording unit CU, magenta recording unit MU, and yellow recording unit Yυ are arranged in this order.

Due to this arrangement of each recording unit, the laser diode 5 for black exposure starts exposure first.
04bk, and the laser diode 504y for yellow exposure starts exposure last. Therefore,
There is a time difference in the order of exposure start between each laser diode,
Data recorded during the time difference (output of the image processing device 400)
, the laser drive processing unit 502 includes the aforementioned 3 & l buffer memories 503y, 503m, 503.
c is provided.

Next, the configuration of the multivalued color laser printer 500 will be specifically explained with reference to FIG.

The multilevel color laser printer 500 includes a conveyor belt 506 that conveys eight recording sheets, and recording units YU and MU arranged around the conveyor belt 506 as described above.
, CU, BKU, and a paper feed cassette 50 containing recording paper.
7a, 507b, and paper feed rollers 508a, 508 that feed recording paper from paper feed cassettes 507a, 507b, respectively.
b, and a registration roller 509 that aligns the recording paper sent out from the paper feed cassettes 507a and 507b.
The recording units) BKU, CU,
It is composed of a fixing roller 510 that sequentially transports MU and YU and fixes the transferred image on the recording paper, and a paper discharge roller 511 that discharges the recording paper to a predetermined discharge section (not shown). Here, each recording unit YU, MU, CU, BKU
are photosensitive drums 5t2y, 512m, 512c, 51
2bk, and photoreceptor drums 512y and 512m, respectively.

Charger 513y that uniformly charges 512c and 512bk
, 513m, 513c, 513bk, and photosensitive drum 5
Polygon mirrors 514y, 514m for guiding the laser beam to 12y, 512m, 512c, 512bk,
514c, 514bk and motor 515y, 515m,
515c, 515bk, and photosensitive drums 512y, 51
2m, 1ft of static formed on 512c, 512bk?
! Toner developing devices 51631, 516m, 516c, 516 for developing images using toners of respective colors;
bk, transfer chargers 517y, 517m, 517c, 517bk that transfer the developed toner image onto recording paper, and photosensitive drums 512y, 512m, 512c, 51 after transfer.
Cleaning devices 518y and 518m remove toner remaining on 2bk.

It consists of 518c and 518bk. In addition, 519y
, 519m, 519c, and 519bk indicate CCD line sensors for reading predetermined patterns provided on the photoreceptor drums 512)', 512m, 512C, and 512bk, respectively. Although details are omitted, this allows multi-value color - Detecting the process status of the laser printer 500.

In the above configuration, the operation will be explained using exposure, development, and transfer of the yellow recording unit 7) YU as an example.

Figure 18 (a) and (b) are yellow record units/)
In the figure showing the configuration of the exposure system of YU, a laser beam emitted from a laser diode 504y is reflected by a polygon mirror 514y, and is reflected by an f-theta lens 5.
Pass through 02y and then mirror 521y.

522y and is irradiated onto the photosensitive drum 512y through the dustproof glass 523y. At this time, since the polygon mirror 514y is rotated at a constant speed by the motor 515°y, the laser beam moves in the direction along the axis of the photoreceptor drum 512y (main scanning direction). Furthermore, in this example,
In order to detect the base point for main scanning scanning position tracking, a photosensor 524y is provided to detect the laser beam at the non-exposed position. Since the laser diode 504y is activated to emit light based on the recording data (3-bit data from the image processing device 400), multilevel exposure corresponding to the recording data is performed on the surface of the photoreceptor drum 504y. As described above, the surface of the photosensitive drum 504y is uniformly charged in advance by the charger 513)', and an electrostatic latent image corresponding to the original image is formed by the exposure. The static latent image is developed by a yellow developing device 516y to become a yellow toner image. This toner image, as shown in FIG.
Recording paper is fed out from a cassette 507a (or 507b) by a paper feed roller 508a (or 508b) and is conveyed by a conveyor belt 506 by a registration roller 509 in synchronization with the formation of a toner image in a black recording unit (BKU). transcribed into.

Other recording units (BKU, CU, MU) have similar configurations and perform similar operations, but the black recording unit (BKU) is equipped with a black toner developing device 516bk, forms and transfers black toner images, and performs cyan toner image formation and transfer. Recording unit C
U includes a cyan toner developing device 516C, which forms and transfers a cyan toner image, and a magenta recording unit M.
U includes a magenta toner developing device 516m, which forms and transfers a magenta toner image.

■The multi-value drive drivers 505y, 505m, 505c, and 505b are as follows:
(Y) sent from the image processing device 400.

Based on the 3-bit data of M, C, and BK, the corresponding laser diodes 504y, 504m, 504c, and 50
It performs control for multi-value driving of 4bk, and power modulation, pulse width modulation, etc. are generally used as the driving method.

Hereinafter, the multivalue drive by power modulation applied in this embodiment will be explained in detail with reference to FIGS. 19(a), (b), (c), and (d). In addition, drivers 505y, 505m
.

505c, 505b, and laser diode 504
y, 504m, 504c, and 504bk each have the same configuration, so here, the driver 505y and laser diode 504y will be explained as an example.

As shown in FIG. 19(a), the driver 505y turns on and off the laser diode 504y based on a predetermined LD drive clock.
n10ff circuit 550 and 3-bit image density data (
Here, the D/A converts Y data) into an analog signal.
From a converter 551 and a constant current circuit 552 that inputs an analog signal based on the image density value from the D/A converter 551 and supplies a current (LD drive current) Id for driving the laser diode 504y to the laser diode on10ff circuit 550. configured.

Here, the LD drive clock is “1” and on “0”.
As shown in FIG. 19(b), the laser diode on10ff circuit 550 turns off the laser diode 504y accordingly. Furthermore, since there is a proportional relationship between the LD drive current 1d and the laser beam power, by generating <LD drive current 1d based on the color image density data value, the laser beam power output corresponding to the image density data value can be obtained. For example, as shown in FIG. 19(b), when the image density data value is "4" (data N-1 in the same figure), the constant is set by the current circuit 552 to output the corresponding LD drive current. Id is supplied, and the laser beam power of the laser diode 504y becomes level 4. Also, the color image density data value is “7”
(Data N in the figure), the corresponding LD drive current 1d is supplied by the constant current circuit 552, and the laser beam power of the laser diode 504y is level 7.
becomes.

Next, referring to FIG. 19(C), laser diode on10ff circuit 550. The laser diode on10ff circuit 550, which shows the specific circuit configuration of the D/A converter 551 and the constant current circuit 552, includes TTL inverters 553 and 554, and differential switching circuits 555 and 556 that perform an onloff toggle operation. ,VC,
When 1>VC2, the differential switching circuit 555 is on.
, the differential switching circuit 556 is of f%VGI
<When VC20, differential switching circuit 555 is off
.

Resistors R and R form a voltage dividing circuit that generates VC2 that satisfies the conditions for the differential switching circuit 556 to be turned on.
It consists of 3. Therefore, when the LD drive clock is 1", the output of the inverter 554 generates VGI,
The above condition (VGI>VO2) is satisfied, the differential switching circuit 555 is on, and the differential switching circuit 556 is turned on.
turns off and turns on the laser diode 504y.

Conversely, when the LD drive clock is '0''',
Since there is no output from the inverter 554, the above condition (VGI
<VO2), the differential switching circuit 555 is off, the differential switching circuit 556 is onL, and the laser diode 504y is turned off.

The D/A converter 551 includes a latch 557 that latches the input image density data while the LD drive clock is ``1'', and a latch 557 that latches the input image density data while the LD drive clock is ``1'', and the maximum output value v1. ．． 2.1 generator 558 that provides the image density data and the 3-bit D/A that outputs analog data Vd based on the maximum output value V ref
converter 559. Note that the relationship between Vd, image density data, and maximum output value V, . . . is expressed by the following equation.

The constant current circuit 552 includes the laser diode 504 in the laser diode ON10ff circuit 550 as described above.
y current, and the transistor 560
and resistors R- and Rs. The output Vd from D/A converter 551 is applied to the base of transistor 560 to determine the voltage applied to resistor R4.

In other words, the current flowing through the resistor R4 is the current flowing through the transistor 5.
60, the current 1d flowing through the laser diode 504y is controlled by Vd.

FIG. 19(d) shows the output of the latch 557 mentioned above.

5 is a timing chart showing the relationship between VGI, Vd, and Id. Here, Vd is determined based on the image density data (3 bit data: 8 gradation data from 0 to 7).
X takes values in 8 stages from O/7 to 7/7, and 1d is based on this VdO value.・The laser diode 504y shows 8 levels of 11, 8 levels of this Id (Is-level 0° It-t' belt . . . , I,
- Level 7), a latent image as shown in FIG. 20 is formed on the photosensitive drum 512F.

In the image forming system using the anti-aliasing processing and the device of the present invention, the toner image shown in FIG. 21 is finally created for the pentagon ABCDH shown in FIG. 5(a) by the above-described configuration and operation. Formed on recording paper. -Resolution of laser printer for boat fishing is 240~
Considering that it is 400 dpi, the density of the edge portion of the figure becomes visually lighter due to the anti-aliasing process. FIG. 22 shows a toner image of pentagon ABCDH when anti-aliasing processing is not performed.
As is clear from a comparison between the figure (toner image of the present invention) and FIG.
becomes visually smoother.

Further, in this embodiment, multi-value drive using power modulation is used, but it goes without saying that the same effect can be obtained by using multi-value drive using pulse width modulation.

For reference, FIG. 23 shows changes in the latent image form depending on the level of pulse width modulation, and furthermore, the toner when pulse width modulation is applied to the pentagonal ABCDH shown in FIG. 5(a). The image is shown in Figure 24.

〔Effect of the invention〕

As explained above, the graphic processing device of the present invention adjusts the output of some pixels at the edge of vector data based on the area ratio to be filled, and smoothly expresses jaggedness (alias) at the edge of the output image. In a graphic processing device that performs anti-aliasing processing, there is provided an end point determining means for determining whether an end point of vector data exists within an edge pixel, and if an end point does not exist within an edge pixel, the vector data a first area ratio determination means that determines the area ratio to be filled in for the edge pixel based on the input/output coordinates when crossing the edge pixel; and a second area ratio determination means that determines the area ratio to be filled in for the edge pixel based on the filling direction and the filling direction. You can find the rate.

[Brief explanation of drawings]

FIGS. 1(a) to (6) are explanatory diagrams showing the principle of anti-aliasing processing in the graphic processing apparatus of the present invention, FIG. 2 is an explanatory diagram showing the configuration of the image forming system of this embodiment, and FIG. FIG. 4(a) is a flowchart showing the operation of the PDL controller; FIG. 4(b) is an explanatory diagram showing the bus filling process; FIG. Figure (C) is a flowchart showing AET registration, Figure 4 (b) is a flowchart showing anti-aliasing processing in fill processing using scan lines, and Figures 5 (a) and (b) show linear vector division of a figure. Explanatory diagram, Figure 6 is an explanatory diagram showing the area ratio after anti-aliasing processing, Figure 7
Figures (a), (b), and (C) are explanatory diagrams showing RGB image data stored in the plain memory section of the page memory. FIG. 9 is an explanatory diagram showing the configuration of the image processing device;
FIG. 1O is an explanatory diagram showing a conversion graph for T correction of the T correction circuit, and FIGS. Figures 12 (a), (b), (C), and (d) are similar to Figure 7 (a).
, (b), (c) An explanatory diagram showing the state in which the RGB image data shown in (d) is output from the OCR processing/black generation circuit, and Fig. 13 is an explanation showing a Bayer type 3 × 3 multilevel dither matrix. Figure 14 (a), (b), (C
), ' (d) are shown in Figure 12 (a), (b), (C)
, (d) An explanatory diagram showing the state in which the Y, M, C, BK data is converted by the gradation processing circuit, FIG. 15 (a),
(b), (C), (d) are I! Figure 8 (a), (
An explanatory diagram showing the state in which the data in b) and (c) are processed by an image processing device. Fig. 16 is a control block diagram showing a multi-value color laser printer. Fig. 17 is a control block diagram showing a multi-value color laser printer. Explanatory diagrams showing the configuration; FIGS. 18(a) and 18(Cb) are explanatory diagrams showing the configuration of the exposure system of the yellow recording unit; FIGS. 19(a), (b), (C)
, (d) is an explanatory diagram showing multi-value drive by power modulation,
Fig. 20 is an explanatory diagram showing the state of the latent image depending on the level of power modulation, and Fig. 21 shows the pentagon ABC shown in Fig. 5(a).
An explanatory diagram showing the final toner image of DH, Fig. 22 is a pentagon ABCD when anti-aliasing processing is not performed.
FIG. 23 is an explanatory diagram showing the state of the latent image depending on the level of pulse width modulation, and FIG. 24 is an explanatory diagram showing the toner image of H.
FIG. 25(a) is an explanatory diagram showing a toner image when pulse width modulation is applied to the pentagonal ABCDH shown in FIG. 25(a),
26(b) is an explanatory diagram showing conventional anti-aliasing processing, and FIG. 26(a). (b) is an explanatory diagram showing antialiasing processing using the uniform averaging method; FIGS. 27(a) and (b) are explanatory diagrams showing antialiasing processing using the weighted averaging method; FIG. 28(a), (b), (C), and (d) are explanatory diagrams showing examples of filters used in the weighting averaging method;
FIG. 9 is an explanatory diagram showing a convolution method with reference to 3×3 pixels. Explanation of symbols --- Host computer --- PDL controller --- Receiving device 202 --- CPU
−・−・−・−Internal system bus 1=−RAM 205−−−−−=ROM・・・・
...Page memory 207...--Transmitting device...
...I10 device...--Image reading device...Image processing device...Multi-value color laser printer...System control unit

Claims (1)

[Claims] A graphic processing device that adjusts the output of edge pixels of vector data based on the area ratio to be filled, and executes anti-aliasing processing to smoothly express jagged edges (aliases) of an output image. An end point determining means for determining whether or not an end point of vector data exists within the edge pixel, and an input point when the vector data crosses the edge pixel if the end point does not exist within the edge pixel. a first area ratio determination unit that determines the area ratio to be filled in the edge pixel based on the output coordinates; if an end point exists within the edge pixel, the position of the end point within the edge pixel; and second area ratio determining means for determining an area ratio to be filled in for the edge pixel based on the filling direction.