JP3842650B2 - Image processing apparatus and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and an image processing method having output means for interpreting image data created in a page description language (PDL) or the like, developing it into a raster image, and outputting it to a printer or the like.
[0002]
[Prior art]
Conventionally, in an image processing apparatus that interprets image data including a color image image created in a page description language (PDL) or the like, develops it into a raster image, and outputs it to a printer such as a color printer, the image memory can be saved. For this purpose, run-length encoding and decoding processes are known. For example, the encoding of an image by run-length encoding is performed by encoding the data identification information and the continuation information of the image data as a pair so as to represent the continuous length of the data. If the image is a color image, the data identification information is color identification information, and the continuation information of the image data is continuation information of the color image.
[0003]
When encoding graphic data having high continuity of the same data described in PDL or the like, high encoding efficiency can be obtained by using this run-length encoding method. As a result, the transfer time of image data and While it is possible to reduce the amount of image memory used to temporarily store them and to reproduce the original image data later, this encoding method is useless depending on the target image data. There is a problem that the amount of information increases and the compression rate cannot be improved.
[0004]
As a solution to this problem, for example, Japanese Patent Laid-Open No. 55-21603, which uses a function indicating that the data of one scan line is the same data, such as the same color, is used.
[0005]
In addition, when processing and recording an image signal, an image processing apparatus for that purpose generally has a page memory of a size required for the recording apparatus, interprets the PDL only once, and writes the contents for one page into the memory. This is done by reading the contents of the memory. Therefore, this image processing apparatus requires a large-capacity page memory particularly when outputting to a recording apparatus having high resolution and high gradation.
[0006]
To solve this problem and reduce the memory capacity, there is, for example, Japanese Patent Application Laid-Open No. 1-265579. In this image processing apparatus, PDL input from an external device is temporarily stored, and the recording apparatus is 1 This PDL is interpreted and expanded in a memory for an image that can be printed in a single operation, and the contents of the memory are output to a recording device and printing is repeated.
[0007]
[Problems to be solved by the invention]
However, the conventional image encoding method and image decoding method have the following problems.
(1) In the conventional image encoding method and image decoding method, useless information increases depending on the target image data, and the compression rate cannot be improved.
(2) A method using a function indicating that the image of one scan line is the same data such as the same color can be applied only when the image of one scan line is the same data such as the same color. This is not applicable when another line drawing or graphic image exists in one scan line.
(3) Further, when the conventional run-length encoding method is performed on image data generally called gradation, the encoding efficiency is greatly reduced, and the amount of data after run-length encoding is larger than the amount of data before encoding. The amount of data may increase.
[0008]
Further, the conventional image processing apparatus has the following problems.
(4) Only a recording apparatus capable of intermittent operation can be handled. In order to output image information for one page to the recording device, PDL is output between the output of image information that can be printed in one operation to the recording device and the next output to the recording device. This is because it takes time to interpret and develop the data in the memory, and for this purpose, the recording apparatus needs to repeat driving and stopping.
[0009]
An object of the present invention is to provide an image processing apparatus and an image processing method capable of conserving memory and continuously outputting to a recording apparatus while solving the conventional problems.
[0010]
[Means for Solving the Problems]
Therefore, according to the present invention, in an image processing apparatus and an image processing method for developing and outputting image data described in a page description language, first image expansion data is generated from the image data, and the first data is generated. The expanded data stored in the storage means, stored in the first storage means is encoded, the encoded data is stored in the second storage means, and the encoded data stored in the second storage means is decoded. The encoding step is characterized in that the gradation image data is encoded in a format to which a function indicating a linear function data change is added.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Example 1
First, an embodiment in which the encoding method and decoding method of the present invention are applied to a color image will be described.
[0012]
FIG. 2 is a schematic diagram showing a color image image, and shows a color image image of a line drawing or figure created by PDL. In a color image image of a line drawing or figure created by PDL as shown in FIG. 2, when a scan line having the same color in one scan line continuously exists, or in a line drawing or figure image in one scan line In many cases, there are consecutive scan lines having the same image of one scan line. In such a case, if the same image is repeatedly run-length encoded as in the prior art, the encoding efficiency decreases. Therefore, in the encoding method of the present invention, when the image of one scan line to be run-length encoded is the same image as the previous one scan line, the function indicating that the image is the same as the previous one scan line is encoded. In the decoding method, only the first image of the same image is run-length decoded, and when the function indicating the same image is decoded, the first run-length decoded scanline image Is to use.
(Format of encoding method of embodiment 1)
The encoding and decoding formats will be described with reference to FIG. 1 illustrating the encoding and decoding formats according to the first embodiment of the present invention. In the figure, CL indicates color data, RL indicates run-length data, REP indicates repeat function data, and END indicates end function data.
[0013]
FIG. 1A shows an encoding format in conventional run-length encoding. In the conventional run-length encoding, a format including color identification information represented by CL, continuation information of a color image represented by RL, a function indicating the end of one line image represented by END, and the like. Encoded. On the other hand, in the first embodiment of the present invention, a function that the same image as the previous line image represented by REP is added to the normal encoding format as shown in FIG. .
(Operation of the encoding method of the first embodiment)
When the format according to the encoding method of the first embodiment is used, the color identification information and the continuation information of the color image are obtained by performing normal run-length encoding on the first part of the continuous image. The subsequent portions are encoded using the run-length encoding performed first by using the REP function as it is, without performing the normal run-length encoding.
(Effect of encoding method of embodiment 1)
By using the format according to the encoding method of the first embodiment, in addition to the run-length encoding of the first image data, the run-length encoding of the same color image can be omitted.
[0014]
Next, the decoding method according to the first embodiment of the present invention will be described.
(Configuration of Decoding Method of Embodiment 1)
First, the configuration of the decoding method according to the first embodiment will be described with reference to FIGS. 3, 4, and 5. FIG. 3 is a block diagram of an entire decoding circuit that decodes image data using the encoding method according to the first embodiment. FIG. 5 illustrates decoding that decodes image data using the encoding method according to the first embodiment. FIG. FIG. 4 shows an encoding format used in the color image encoding method and decoding method of the first embodiment. In FIG. 3, 1 is a decoding circuit, 2 is a FIFO, CLD is color data, RLD is run length data, OD is out data, ID is in data, WE is write enable, WR is write reset, and LE is line. Enable, RE is read enable, RR is read reset, CL in FIG. 4 is color data, RL is run length data, REP is repeat function data, END is end function data, 3 in FIG. 5 is CLD Latch, 4 is a CLD output latch, 5 is an RLD decoder circuit, and 6 is an RL counter / FIFO control.
[0015]
The CLD and RLD input from the encoding means are decoded by the decoding circuit 1, and the decoded image data is temporarily stored in the FIFO 2 and then output.
[0016]
All the encoding formats shown in FIG. 4 have a data length of 8 or 32 bits, the most significant bit of RL is 0, the most significant bit of REP is 1, and END is all 0. (a) CL constitutes the CLD format, and three of RL, REP, and END shown in (b) to (d) constitute the RLD format. The CLD encoded format data is read from the CLD of the decoding circuit 1, and the RLD encoded format data is read from the RLD of the decoding circuit 1 and decoded.
[0017]
In the circuit diagram of the decoding circuit 1 shown in FIG. 5, the decoding circuit 1 includes a CLD latch 3, a CLD output latch 4, an RLD decoder circuit 5, and an RL counter / FIFO control 6. In this configuration, the CLD is input to the CLD latch 3 and the RLD is input to the RLD decoder circuit 5. The CLD latch 3 receives the length data LD of image data from the RLD decoder circuit 5 in addition to the CLD data. The output of the CLD latch 3 becomes an OD through the CLD output latch 4 and a decoded signal is obtained.
[0018]
The RLD decoder circuit 5 is connected to the RL counter / FIFO control 6 and outputs RL, REP, END and RLDD constituting the RLD encoded format data. RL, REP, and END are signals indicating whether the input data is run-length data, repeat function data, or end function data, and RLDD represents data related to the length length of the run-length data. The RL counter / FIFO control 6 counts run lengths and controls a FIFO (not shown in FIG. 5), outputs the LD to the CLD latch 3 and the RLD decoder circuit 5, and outputs OE (output). Enable) and RES (reset) are output to the CLD output latch 4. The RL counter / FIFO control 6 outputs WR, WE, and LE for controlling the FIFO to the FIFO.
(Operation of the decoding method of the first embodiment)
In the block diagram of the decoding circuit shown in FIG. 3, CL is converted from the encoding means to the CLD encoding format and read from the CLD terminal of the decoding circuit 1. The other RL, REP, and END are converted into the RLD encoding format and read from the RLD terminal of the decoding circuit 1. In the decoding circuit 1, LE is processed for each line corresponding to the line enable input, and the decoded OD is input to the input terminal ID of the FIFO 2. Also, the decoding circuit 1 outputs signals WE and WR for controlling writing and resetting of OD to the input terminals WE and WR of the FIFO 2.
[0019]
The FIFO 2 outputs the OD input from the decoding circuit 1 based on the RE and RR signals that control reading and resetting.
[0020]
In the circuit diagram of the decoding circuit shown in FIG. 5, the RLD decoder circuit 5 first reads run length data from the RLD, and the data is run length data RL, repeat function data REP, and end function data END. Decode it.
[0021]
When the RLD data is the run length data RL, the run length value is set in the RL counter, the color data is read from the CLD, and the color data read by the count value is output to OD (out data).
[0022]
If the RLD data is repeat function data, the color data is not read, and even if the new line becomes LE (line enable) becomes active, FIFO WR (write enable) and WR (write reset) are enabled. Therefore, the image of the previous line is read from the FIFO.
[0023]
If it is end function data, the CLD output latch 4 is reset and 0 is output until the next line.
(Effect of Example 1)
For the same data, encoding and decoding processes can be reduced, the encoding efficiency of run-length encoding is increased, and the run-length encoded color image image is temporarily stored, In an image processing apparatus that outputs to a color printer or the like, the amount of image memory required for one page can be greatly reduced.
(Example 2)
Next, an embodiment in which the encoding method and decoding method of the present invention are applied to an image having gradation data will be described.
[0024]
FIG. 6 is a schematic diagram showing an image image having gradation data, and shows a line image or graphic image image created by PDL. As shown in FIG. 2, in a line image or graphic image created with PDL and having gradation data, a line image or graphic image exists in one scan line, and the data is continuous in one scan line. In general, the data increases or decreases by a predetermined value n (n = 1 or more integer) having a certain equal interval m (m = 1 or more) during the period l (l = 1 or more). In some cases, image data called gradation is created.
[0025]
The gradation shown in FIG. 6 can represent data by the data diagram shown in FIG. In FIG. 7, the gradation data is a predetermined value n (n = 1 or greater integer) having a certain equal interval m (m = 1 or greater integer) for a certain continuous length 1 (1 = 1 or greater integer). ) This is a data change in which the data increases or decreases one by one, and is expressed by a data function that is discontinuous but linear.
[0026]
When conventional run-length encoding is applied to such gradation image data, the encoding efficiency is reduced, and the amount of data after run-length encoding is greater than the amount of data before encoding. There is. In the encoding method and decoding method of the present invention, such gradation image data is encoded using a function indicating that the data is a linear function change. Interprets the function and decodes it.
(Format of encoding method of embodiment 2)
Next, the encoding and decoding format of the second embodiment will be described with reference to FIG. In the figure, CL indicates color data, RL indicates run-length data, REP indicates repeat function data, and END indicates end function data.
[0027]
FIG. 8A shows an encoding and decoding format in conventional run-length encoding. In conventional run-length encoding, a format comprising image data identification information represented by CL, continuation information of image data represented by RL, a function indicating the end of one line image represented by END, and the like. Is encoded by On the other hand, in the second embodiment of the present invention, as shown in FIG. 8B, the normal encoding format is a change in linear function data such as gradation represented by GRA. Add the function shown. (Operation of the encoding method of the second embodiment)
When the format according to the encoding method of the second embodiment is used, the gradation image data is encoded by a function indicating that the data change is a linear function.
(Effect of encoding method of embodiment 2)
By using the format according to the encoding method of the embodiment 2 and encoding into a function indicating a linear function data change with respect to the gradation image data, the encoding efficiency in the run-length encoding is improved. In an image processing apparatus that temporarily stores run-length encoded image image data and outputs it to a printer or the like, the amount of image memory required for one page can be greatly reduced. be able to.
[0028]
Next, the decoding method according to the second embodiment of the present invention will be described.
(Configuration of Decoding Method of Embodiment 2)
The configuration of the decoding method according to the second embodiment will be described with reference to FIGS. 9, 10, and 11. FIG. FIG. 9 is a block diagram of a decoding circuit that decodes image data using the encoding method of the second embodiment, and FIG. 10 shows a color image encoding method and a coding format used for the decoding method of the first embodiment. FIG. 11 is a block diagram of a gradation generation circuit in the encoding method and decoding method of the second embodiment.
[0029]
In FIG. 9, 11 is an RLD decoder and MUX, and 12 is an RL counter, gradation generation circuit, and output MUX. 13 is a run length counter, 14 is an m counter, 15 is an n register, 16 is a CLD selector and latch, and 17 is an ALU.
[0030]
The CLD and RLD input from the encoding means are decoded by the RLD decoder and MUX1, and the decoded image data is output after the gradation is generated by the gradation generation circuit and the output MUX12.
[0031]
In the encoding format shown in FIG. 10, CL is color data, RL is run-length data, GRA is gradation function data, END is end function data, and all encoding formats have a data length of 8 or 32 bits. The most significant bit of RL is 0, the most significant bit of GRA is 1, and END is all 0.
[0032]
In FIG. 9, from the RLD decoder and MUX1, the output of RL and GRA, the output of RLDD and GRA 1 (continuous length of data in one scan line), the GRA m (gradation change interval), and the GRA n (Gradation change interval) is output to the gradation generation circuit and the output MUX 12. Further, CLD data is also input to the gradation generation circuit and the output MUX 12.
[0033]
The gradation generation circuit shown in FIG. 11 includes a run length counter 13, an m counter 14, an n register 15, a CLD selector and latch 16, and an ALU 17.
(Operation of the encoding method of the second embodiment)
In the decoding circuit shown in FIG. 9, the color data is read from the CLD (color data) of the encoding circuit into the gradation generation circuit and the output MUX 12, and the other RL, GRA, and END are RLD (run length) of the encoding circuit. Data) is read by the RLD decoder and the MUX 11 and is run-length decoded.
[0034]
Further, a gradation generation circuit in the decoding method of the present invention shown in FIG. 11 is shown. The run-length decoding circuit 11 first reads run-length data from the RLD, and the RLD decoding circuit decodes whether the data is run-length data, gradation function data, or end function data.
[0035]
If it is run-length data, the run-length value is set in the run-length counter, color data is read from the CLD, and the color data read by the count value is output to OD (out data). In this case, the ADD / SUB processing by the ALU (arithmetic logic unit) 17 is not performed, and the color data read from the CLD is output as OD as it is.
[0036]
In the case of gradation function data, the color data is read once as an initial value at the beginning of the gradation function. At the same time as reading the color data, RLD decoding and 1 (gradation block length), m (number of repetitions of the same data), and n (increase / decrease when the data changes) output from the MUX 11 are read. The n data is sign-extended. When the most significant bit is 0, it indicates ADD (increase), and when it is 1, it indicates SUB (decrease). The 1, m, and n data read by the gradation generation circuit 12 are stored in a run length counter 13, an m counter 14, and an n register 15, respectively. When the color data read as the initial value is output to the OD for m pixels, the CAL signal becomes active, the ALU 17 performs addition / subtraction processing of the initial value color data and n, and the output result is output to the OD. Is output. In this case, the run-length counter 13 performs a count-down process based on the CRR (carry) output of the m counter, and repeats the series of processes until the value of the run-length counter becomes 0, and the value of the run-length counter becomes 0. Then, the series of gradation function processing ends, and when the LD (load) signal becomes active, the next new CLD and RLD are read and the continuation processing is performed.
(Effect of Example 2)
Gradient image data with low continuity of the same data and low run-length encoding efficiency can be obtained by encoding and decoding the gradation image data using a function indicating that the data changes linearly. Encoding can be performed efficiently, and encoding efficiency in run-length encoding can be greatly increased.
Example 3
Next, an image processing apparatus using the encoding method and decoding method of the present invention will be described.
(Configuration of Example 3)
FIG. 12 is a block diagram of an image processing apparatus using the encoding method and decoding method of the present invention, and FIG. 13 is a diagram for explaining a band buffer.
[0037]
In FIG. 12, the image processing apparatus 20 includes a PDL memory 21, a PDL processing apparatus 22, a band buffer 23, an encoding apparatus 24, an encoded page memory 25, and a decoding apparatus 26. Then, an image signal is input to the image processing apparatus 20 from the external device 41 through the communication apparatus 42, and the image-processed signal is output to the recording apparatus 29 through the decoding apparatus 26.
[0038]
The PDL memory 21 is a memory for storing a page description language (PDL) input from the external device 41 such as a computer through the communication device 42, and can store one page of PDL. Has capacity.
[0039]
The PDL processing device 22 reads and interprets a part of the PDL stored in the PDL memory 21 and develops it in the band buffer 23.
[0040]
The band buffer 23 is a memory for storing the image information interpreted and expanded by the PDL processing device 22 as it is, and has a capacity smaller than the capacity required for one page. FIG. 13 shows the relationship on one page of the band buffer. The band buffer region 31 on the one-page region 30 corresponding to the memory of the band buffer 23 is composed of pixels arranged in the main scanning direction and the sub-scanning direction, and the length in the sub-scanning direction is one page. The length of the region 30 is divided into an arbitrary number. The adjacent band buffer regions 31 are formed so as not to overlap or fall out. In FIG. 13, the position of the band buffer area 31 at a certain time is indicated by a solid line, and the position of the band buffer area at the next time is indicated by a broken line.
[0041]
Then, by moving the position of the band buffer area 31 in the direction of the arrow 32, the entire area 30 of one page can be covered.
[0042]
The encoding device 24 encodes the image information stored in the band buffer 23 according to the encoding method of the present invention. In this encoding, when encoding is performed on n × n pixels collectively, the width and the height of the band buffer 23 are set to an integer multiple of n.
[0043]
The encoded page memory 25 is a memory for storing image information encoded by the encoding device 24, and has a capacity sufficient to store image information for one page. Since this storage capacity stores the encoded information, it is possible to store one page of image information with a smaller capacity compared to the case where the image information is stored as it is. The encoded page memory 25 can be configured by a single memory, or can be configured by using a partial area of the PDL memory 21.
[0044]
The decoding device 26 decodes one page of image information encoded and stored in the encoded page memory 25 and converts the image information into image information that can be processed by the recording device 43.
[0045]
The recording device 43 performs printing based on image information output from the decoding device 26, and is not limited to a recording device capable of intermittent operation but may be a recording device capable of only continuous operation.
(Operation of Example 3)
Next, the operation of the third embodiment of the present invention will be described using the flowchart of FIG. In the following description, description will be made using the reference numerals in step S.
Step S1:
When a request for PDL processing is made from the external device 41 to the image processing apparatus 20, the PDL is once stored in the PDL memory 21 through the communication apparatus 42. The signal form in the PDL memory 21 remains PDL, and for example, information for one page is stored.
Step S2:
The PDL corresponding to the band buffer area 31 is read from the PDL memory 21 to the PDL processing device 22, and the read PDL is interpreted and expanded in the band buffer 23.
Step S3:
The content of the band buffer 23 is encoded by the encoding device 24 by the encoding method of the present invention and stored in the encoded page memory 27. The storage capacity of the encoded page memory 27 requires a capacity capable of storing information for one page, but the encoded page memory 27 stores encoded information, and thus image information is not subjected to encoding processing. It is possible to store information for one page with a smaller capacity than the storage capacity required to store the data as it is.
Step S4:
For the image information for one page, the end of the processing in steps S2 and S3 is monitored.
Step S5:
If the image information for one page is not completed in the step S4, the process returns to step S2, and the steps S2 and S3 are repeated.
[0046]
By repeating the steps S2 and S3, the encoding of all the image information for one page is completed, and the information is stored in the encoded page memory 27 in an encoded state.
Step S6:
Next, the information stored in the encoded page memory 27 is decoded by the decoding device 26 and output to the recording device 43. The recording device 43 records image information by printing or the like.
[0047]
In this recording, the image information for one page stored in the encoded page memory 27 is printed by a single process, and therefore this one page can be continuously processed.
(Effect of Example 3)
According to the third embodiment, PDL processing can be performed with a small amount of memory, recording by a recording apparatus that requires continuous operation is possible, and image output can be performed.
[0048]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and they are not excluded from the scope of the present invention.
[0049]
【The invention's effect】
As described above, according to the present invention, PDL processing is possible with a small amount of memory, recording by a recording apparatus that requires continuous operation is possible, and image output can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining encoding and decoding formats according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a color image image.
FIG. 3 is a block diagram of a decoding circuit according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating a configuration of an encoding format used for a color image encoding method and a decoding method according to Embodiment 1 of the present invention.
FIG. 5 is a circuit diagram of a decoding circuit according to the first embodiment of the present invention.
FIG. 6 is a schematic view of an image explaining gradation.
FIG. 7 is a gradation data diagram.
FIG. 8 is a diagram for explaining the encoding and decoding formats according to the second embodiment of the present invention.
FIG. 9 is a circuit diagram of a decoding circuit according to the second embodiment of the present invention.
FIG. 10 is a diagram illustrating a configuration of an encoding format used for a color image encoding method and a decoding method according to Embodiment 2 of the present invention.
FIG. 11 is a gradation generation circuit diagram in the decoding method of the present invention.
FIG. 12 is a block diagram of an image processing apparatus using the encoding method and decoding method of the present invention.
FIG. 13 is a diagram illustrating a band buffer according to the present invention.
FIG. 14 is a flowchart of the image processing apparatus of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Decoding circuit, 2 ... FIFO, 3 ... CLD latch, 4 ... CLD output latch, 5, 11 ... RLD decoding circuit, 6 ... RL counter / FIFO control circuit, 12 ... RL counter / gradation generation circuit / output MUX, DESCRIPTION OF SYMBOLS 13 ... Run length counter, 14 ... m counter, 15 ... n register, 16 ... CLD selector / latch, 17 ... ALU, 20 ... Image processing device, 21 ... Memory for PDL, 22 ... PDL processing device, 23 ... Band buffer, 24: Encoding device, 25: Encoded page memory, 26: Decoding device, 31: External device, 32: Communication device, 33: Recording device.

Claims (2)

In an image processing apparatus that expands and outputs image data described in a page description language,
A description language processing means for generating, from the image data, expanded data of a partial area of the image data area;
First storage means for storing the expanded data generated by the description language processing means;
Encoding means for encoding the decompressed data stored in the first storage means;
Second storage means for storing the encoded data encoded by the encoding means;
Decoding means for decoding the encoded data stored in the second storage means;
With
The image processing apparatus characterized in that the encoding means encodes gradation image data in a format to which a function indicating a change in data of a linear function is added. In an image processing method for developing and outputting image data described in a page description language,
A description language processing step of generating, from the image data, expanded data of a partial area of the image data area;
A first storage step of storing in the first storage means for storing the expanded data generated in the description language processing step;
An encoding step of encoding the decompressed data stored in the first storage means;
A second storage step of storing the encoded data encoded by the encoding step in a second storage means;
A decoding step of decoding the encoded data stored in the second storage means;
With
The image processing method characterized in that the encoding step encodes the gradation image data in a format to which a function indicating a change in linear function data is added.

Images