JP4973550B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing apparatus.

  2. Description of the Related Art In recent years, image forming apparatuses that acquire image data and can form the acquired image data have become widespread.

The image forming apparatus mainly includes an acquisition unit, an image processing unit, and an output unit.
The acquisition unit acquires image data, and the image processing unit performs various types of image processing on the acquired image data. The output unit forms an image of the image data that has undergone image processing on a sheet and outputs the image.

  Usually, the acquisition unit acquires image data in units of lines. The line unit is a unit in which the main scanning direction (horizontal direction) is one line. The acquisition unit changes the line to be acquired by switching the sub-scanning direction (vertical direction) every time one line is acquired, and acquires all image data by performing this multiple times.

  The output unit also outputs image data line by line, and by performing this a plurality of times, image data for all lines is formed on a sheet and output. Accordingly, an image processing unit that performs intermediate processing in a series of image forming processing is generally configured to perform image processing in units of lines.

  Here, the image processing unit needs to temporarily store a plurality of lines of image data when performing proximity processing, which is one of image processing, and includes a storage unit for that purpose. Examples of the proximity processing include character enhancement processing and moire removal processing.

  In order to perform proximity processing at high speed, it is preferable that the storage unit is capable of high-speed transfer and has a sufficient storage capacity. Specifically, by using a RAM (Random Access Memory, hereinafter referred to as “FIFO / RAM”) having a FIFO (First In First Out) function, it is possible to perform neighborhood processing at high speed. In general, the FIFO / RAM is generally provided in an ASIC (Application Specific Integrated Circuit). In other words, it is preferable from the viewpoint of processing speed that the hardware processing is performed instead of the software processing.

When the FIFO / RAM is arranged in the ASIC, the neighborhood processing can be performed at a high speed as described above, but a great amount of cost is required for the production cost and development cost of the image processing unit. This is because FIFO / RAM is generally expensive because of its good performance.
In order to solve such problems, Patent Documents 1 to 3 disclose image processing units that perform image processing for each rectangular region.

The image processing units described in Patent Documents 1 to 3 perform image processing for each rectangular area.
In the image processing for each rectangular area, the image processing unit first divides the image data for all lines acquired by the acquiring unit into a plurality of m rows and n columns of rectangular regions. Then, image processing is performed for each divided rectangular area. Note that the image processing in the rectangular area is performed for each line in the same manner as in the normal line unit processing.

When the image processing unit performs proximity processing on image data for each rectangular area, it is necessary to store a plurality of lines in the rectangular area, and store a plurality of lines of image data acquired by the acquisition unit. There is no need to keep it. That is, since the volume of image data to be stored in the vicinity processing can be suppressed, the image processing unit does not need to include a large-capacity storage unit.
JP 2000-354168 A JP 2000-351242 A Japanese Patent No. 3510997

  Here, in the image processing apparatuses disclosed in Patent Documents 1 to 3, when performing neighborhood processing on image data in tiles of m rows and n columns, image data outside the rectangular region may be required. For example, it is a case where image data of a boundary portion between one rectangular area and another rectangular area is subjected to proximity processing.

  In such a case, the image data to be stored in the FIFO / RAM is not limited to m rows and n columns, and it is necessary to store, for example, image data for one line of the (m + 1) th row. Further, it is necessary to store the calculation result for one line of the (m + 1) th row calculated by performing the neighborhood processing in the FIFO / RAM.

  Therefore, the image processing unit requires a FIFO / RAM for storing extra image data for one rectangular area or more. As a result, the storage capacity of the FIFO / RAM can be reduced, but the number of FIFO / RAMs used cannot be reduced.

  An object of the present invention is to perform image processing that can reduce the FIFO / RAM by using the calculation result calculated by calculating the image data in one rectangular area for the image data in another rectangular area. Is to provide a device.

According to the invention of claim 1,
First storage means;
Second storage means slower than the first storage means;
Compression means for compressing image data in one rectangular area among the plurality of rectangular areas ;
A writing / reading unit that writes the image data compressed by the compression unit to the second storage unit and reads the compressed image data from the second storage unit;
Decompression means for decompressing compressed image data read by the writing and reading means;
A calculation process is performed on the image data expanded by the expansion unit to calculate a calculation result of one rectangular area, a part of the calculation result is stored in the second storage unit, and the remaining calculation result Calculating means for storing the first storage means in the first storage means ,
The calculation means is provided with an image processing apparatus that uses a part of the calculation result of one rectangular area stored in the second storage means for calculation processing of image data in another rectangular area .

According to the invention of claim 2, in the invention of claim 1,
The calculation means calculates the calculation result for m rows by performing calculation processing for each row on the image data in the one rectangular area, and among the calculated calculation results for the m rows, By using the calculation result for the image data of the first row in the other rectangular area, an image processing apparatus that performs the calculation process on the image data of the first line in the other rectangular area is provided.

According to the invention of claim 3, in the invention of claim 1 or 2,
An image processing apparatus is provided in which the first row of image data in the other rectangular area is adjacent to the mth row of image data in the one rectangular area in the sub-scanning direction.

According to the invention described in claim 4, in the invention described in any one of claims 1-3,
The calculation means stores the calculation results from the first line to the (m−1) th line among the calculation results calculated in the rectangular area in the first storage means, and the calculation result in the mth line of the last line. Respectively output to the second storage means,
The first storage unit and the second storage unit are provided with an image processing apparatus that stores the calculation result output from the calculation unit.

According to the invention of claim 5, in the invention of claim 4,
The calculation means calculates the calculation result of the m-th row of the rectangular area after calculating the calculation result of the m-th line of the rectangular area and before calculating the calculation result of the m-th line of the rectangular area to be processed next. Is provided to the second storage means.

According to the invention described in claim 6, in the invention described in any one of claims 4 or 5,
The second storage means calculates the calculation result of the first line of the rectangular area to be processed next after the calculation means calculates the calculation result of the first line of the rectangular area. An image processing apparatus is provided that outputs a calculation result used in the first line of a rectangular area to be processed to the calculation means.

According to the invention described in claim 7, in the invention described in any one of claims 1 to 6,
The calculation means performs an error diffusion process on the image data in the rectangular area to calculate a calculation result, and the image processing apparatus uses the calculated calculation result for the error diffusion process of the image data in the other rectangular area. Provided.

According to the present invention, in the image processing apparatus that performs image processing for each rectangular area, the calculation result of the boundary portion obtained by image processing in one rectangular area can be used for image processing in another rectangular area. That is, it is not necessary to store the calculation result of the boundary portion of another rectangular area in an expensive storage unit. Therefore, it is possible to reduce the production cost and development cost of the image processing unit while maintaining the processing speed.

  Hereinafter, the optimum configuration and operation of the image processing apparatus according to the present embodiment will be described in detail with reference to the drawings.

First, an image forming apparatus 100 according to the present embodiment will be described with reference to FIG.
The image forming apparatus 100 includes an acquisition unit 10, an image processing unit 20, an output unit 30, an operation unit 40, a display unit 50, and a control unit 60.

An external PC (Personal Computer) 200 is connected to the image forming apparatus 100. The external PC 200 outputs data in PDL (Page Description Language) format to the image forming apparatus 100. The image forming apparatus 100 receives data in the PDL format, converts it into image data, performs image processing on this, and prints it.
Hereinafter, each part of the image forming apparatus 100 will be described.

The acquisition unit 10 includes a controller 10a and a scanner unit 10b.
The controller 10a rasterizes the document data converted into the PDL format to generate image data.

The controller 10a outputs the generated image data to the image processing unit 20.
Note that the image data output from the controller 10a is image data for printing composed of a plurality of four colors of C (cyan), M (magenta), Y (yellow), and K (black).

  On the other hand, the scanner unit 10b first reads an original with an optical system provided in the scanner unit 10b, and generates analog image data.

  Next, the scanner unit 10b performs A / D conversion on the generated analog image data to convert it into image data composed of three colors of R (red), G (green), and B (blue). Then, this is output to the image processing unit 20. The image data composed of R, G, and B output from the scanner unit 10b is used for display. Therefore, the image processing unit 20 converts R, G, and B into image data including Y, M, C, and K as necessary.

  The image processing unit 20 performs various image processing on the image data output from the acquisition unit 10. Various image processing includes, for example, neighborhood processing such as character enhancement processing and moire removal processing. The error diffusion process is also one of the neighborhood processes, and in the present embodiment, this error diffusion process will be described in detail later together with the image processing unit 20.

The output unit 30 receives the image data that has been subjected to image processing from the image processing unit 20, and performs print processing in accordance with a control signal from the control unit 60.
Hereinafter, the printing process will be described.

  The output unit 30 performs electrophotographic printing processing, and includes, for example, a paper feed unit that stores print paper, an exposure unit that includes a photosensitive drum, a developing unit that attaches toner, and a fixing unit that fixes toner (not illustrated). ).

Based on the image data to be printed, the output unit 30 irradiates the photosensitive drum with laser light or the like at the exposure unit to form an electrostatic latent image, and the developing unit attaches toner. Then, the toner image formed on the photosensitive drum is transferred to the printing paper fed from the paper feeding unit, and the transferred toner image is fixed in the fixing unit. After fixing, the print paper is discharged to a paper discharge tray or the like.
The above is a series of printing processes.

The control unit 60 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.
The CPU reads the system program and various control programs stored in the ROM and expands them in the RAM. Then, the respective units of the image forming apparatus 100 are centrally controlled in cooperation with the developed various programs.

  The operation unit 40 is for inputting user operation instructions, and includes various keys, a touch panel configured integrally with the display unit 50, and the like. The operation unit 40 generates an operation signal corresponding to the operation, and outputs the generated operation signal to the control unit 60.

The display unit 50 includes an LCD (Liquid Crystal Display) or the like.
The display unit 50 receives the control signal output from the control unit 60, and displays various setting information, operation status, and the like on the LCD according to the received control signal.

Next, the image processing unit 20 will be described with reference to FIG.
The image processing unit 20 includes a line / tile conversion unit 20a, a compression unit 20b, a writing / reading unit 20c, an expansion unit 20d, a calculation unit 20e, a tile / line conversion unit 20f, a first storage unit 20g, and a second storage unit 20h. It is configured with.

  The line / tile conversion unit 20a performs a process of dividing the image data acquired by the acquisition unit 10 in units of lines into a plurality of rectangular regions (hereinafter referred to as “tiles”). The size of the tile, that is, the number of pixels constituting the tile is determined in advance, and the line / tile conversion unit 20a divides the tile into a plurality of tiles according to the predetermined size. In the present embodiment, description will be made assuming that the tile is divided into tiles of 8 × 8 pixels.

The compression unit 20b performs tile compression processing.
The compression unit 20b outputs the compressed plurality of tiles to the writing / reading unit 20c.

The writing / reading unit 20c performs a process of writing the image data output in units of tiles from the compression unit 20b to the second storage unit 20h.
In addition, the writing / reading unit 20c reads image data to be subjected to image processing from the second storage unit 20h in units of tiles, and outputs the read image data to the expansion unit 20d in units of tiles.

  Note that writing image data in units of tiles means writing image data of 8 × 8 pixels in the second storage unit 20h as one unit. Similarly, reading out image data in units of tiles means reading out image data of 8 × 8 pixels as one unit.

  The decompressing unit 20d decompresses the tile-unit image data output from the writing / reading unit 20c for use in image processing, and outputs the decompressed image data to the arithmetic unit 20e.

  The calculation unit 20e performs predetermined image processing on the image data output in units of tiles from the expansion unit 20d. The predetermined image processing includes, for example, character enhancement processing, moire removal processing, and the like, and the calculation unit 20e includes an arithmetic circuit corresponding to each processing.

  The arithmetic unit 20e includes an arithmetic circuit that performs error diffusion processing in addition to the character enhancement processing described above. The arithmetic circuit that performs error diffusion processing includes the first storage unit 20g and the like. In the present embodiment, error diffusion processing performed by the arithmetic unit 20e will be described in detail later with reference to FIG.

  The arithmetic unit 20e performs various image processing on the image data, and then outputs the image data to the tile / line conversion unit 20f in units of tiles.

  The tile / line conversion unit 20f converts the image data output in units of tiles from the calculation unit 20e into units of lines, and outputs the converted image data in units of lines to the output unit 30.

  The first storage unit 20g is a storage unit arranged on the ASIC in the arithmetic circuit provided in the arithmetic unit 20e. The first storage unit 20g is composed of a RAM capable of high-speed transfer. The RAM writes and reads image data by a FIFO operation.

The second storage unit 20h includes an external DRAM (Dynamic RAM).
The second storage unit 20h stores tile-converted image data in units of tiles, and stores calculation results calculated by the calculation unit 20e. Furthermore, the 2nd memory | storage part 20h outputs a calculation result required for the calculating part 20e.

Next, the calculation unit 20e that performs error diffusion processing will be described with reference to FIG.
The arithmetic unit 20e that performs error diffusion processing includes an adding unit 201, an output processing unit 202, a DRAM writing / reading unit 203, and a first storage unit 20g on an arithmetic circuit. The DRAM writing / reading unit 203 is connected to the second storage unit 20h. Note that the arithmetic unit 20e may include the above-described units other than the first storage unit 20g. In this case, the first storage unit 20g is externally connected to the adding unit 201 and the output processing unit 202.

  The addition unit 201 performs addition processing for adding the calculation result (error data) for each line to the image data output in units of tiles from the expansion unit 20d.

In the addition process, each error data is added to all the pixels in one line in the tile. The error data is output from the first storage unit 20g or output from the second storage unit 20h via the DRAM writing / reading unit 203. The adding unit 201 acquires these error data. The error data will be described later.
The adding unit 201 outputs the image data subjected to the adding process to the output processing unit 202.

  The output processing unit 202 performs a conversion process in which a plurality of predetermined pixel values are used as reference values, and the pixel values of input image data are converted into any of the reference values.

The above conversion process will be described in detail.
First, the output processing unit 202 acquires the image data output in units of tiles from the addition unit 201 for each line. Then, the pixel value of each pixel in the acquired image data of one line is compared with a plurality of predetermined reference values. As a result of the comparison, the output processing unit 202 determines the closest reference value among the plurality of reference values. Then, the determined reference value is replaced with a pixel value.
The above is a series of conversion processes.

  The conversion process will be further described using specific numerical values. The reference value is “0, 85, 170, 255”, and each pixel value in the input image data is “0, 40, 80, 120,. The output processing unit 202 converts the input pixel value to “0, 0, 85, 85,...”.

  In addition, the output processing unit 202 compares the image data before the conversion process and the image data after the conversion process for each pixel, and calculates a difference between the two pixel values. In the present embodiment, the difference calculated here is referred to as error data.

  To explain using the above-described specific example, the output processing unit 202 performs image data “0, 40, 80, 120,...” Before conversion processing and image data “0, 0, 85, 85,. And error data “0, 40, −5, 35,...” Is calculated.

  The output processing unit 202 stores the calculated error data in the first storage unit 20g, or outputs and stores it in the second storage unit 20h via the DRAM writing / reading unit 203.

  The first storage unit 20g acquires and stores error data output from the output processing unit 202. The error data stored in the first storage unit 20g is the error data from the first line to the (m-1) th line in the image data in the tile.

  The second storage unit 20 h acquires and stores error data output from the output processing unit 202 via the DRAM writing / reading unit 203. Note that the error data stored in the second storage unit 20h is the error data of the m-th row among the image data in the tile.

The DRAM writing / reading unit 203 writes the mth row error data output from the output processing unit 202 to the second storage unit 20h. The DRAM writing / reading unit 203 reads the error data of the mth row from the second storage unit 20 h and outputs the read error data of the mth row to the adding unit 201.
The above is a series of flow of error diffusion processing performed by the arithmetic unit 20e.

Next, with reference to FIG. 4, a conceptual diagram of the error diffusion processing described above is shown.
Note that the image data shown in FIG. 4 is image data for one line in the tile.

  The adding unit 201 includes input image data D1 and error data D2. The image data D3 calculated by adding the two is output to the output processing unit 202.

The output processing unit 202 compares the pixel value in the added image data D3 with the reference value S1. As a result of the comparison, binary data D4 and error data D5 are calculated.
The output processing unit 202 outputs the binary data D4 to the tile / line conversion unit 20f, and outputs the error data D5 to the first storage unit 20g or the second storage unit 20h.

  Here, the output processing unit 202 outputs error data from the first line to the m−1th line among the error data from the first line to the m-th line in the tile to the first storage unit 20g. Further, the output processing unit 202 outputs the error data of the m-th row to the second storage unit 20h.

The error data from the first line to the (m−1) th line is stored in the first storage unit 20 g and then output to the adding unit 201 until the next input image data is input to the adding unit 201. As described above, the adding unit 201 performs a process of adding the input image data D1 and the error data D2.
That is, the error data calculated for one line in the same tile is used in the next line process.

On the other hand, the error data of the m-th row is stored in the second storage unit 20h and then used in the processing of the first row of another tile adjacent in the sub-scanning direction.
Hereinafter, processing using error data in the m-th row will be described with reference to FIGS.

First, the relationship between all image data and tiles will be described with reference to FIG.
As described above, the image processing unit 20 divides all the image data D10 acquired by the acquisition unit 10 into a plurality of m rows and n columns of tiles D11, and performs image processing for each of the divided tiles D11.

  In the present embodiment, it is assumed that the entire image data D10 is composed of 8000 × 8000 pixels, and the tile D11 is composed of 8 rows and 8 columns (8 × 8 pixels).

  The image processing unit 20 processes “tile 1” and “tile 2” in the main scanning direction, performs image processing up to “tile 1000”, and then increments by +1 in the sub-scanning direction. Then, image processing is performed again from the “tile 1001” in the main scanning direction. By repeating this, the image processing unit 20 performs image processing of all the image data D10.

Next, with reference to FIG. 6, processing of error data in the m-th row will be described.
The number in the tile indicates the tile number and the row number. For example, “T1-1 line” indicates that the tile number is the first line.

  The arithmetic unit 20e performs arithmetic processing on image data input in units of tiles in units of lines. For example, when the image data of the T1-1 line is arithmetically processed, binary data D4 and error data D5 are calculated. Of these, the arithmetic unit 20e uses the error data D5 for the arithmetic processing of the image data on the T1-2 line.

The process of the error data D5 calculated by the m-th row calculation process will be described.
The calculation unit 20e stores the error data D5 calculated by the calculation process of the m-th row, for example, the calculation process of the T1-8th row, in the second storage unit 20h. In the process of storing the error data D in the T1-8th row, the arithmetic unit 20e stores the error data D5 in the mth row of the tile to be processed next, that is, the T2-8th row in the second storage unit 20h. You can go to

  When the arithmetic unit 20e performs arithmetic processing on the image data of the T1001-1 line, the arithmetic unit 20e reads the error data D5 calculated by the arithmetic processing of the T1-8 line from the second storage unit 20h. The reading process may be performed before the calculation process is started on the image data on the T1001-1 line.

  The arithmetic unit 20e adds the read error data D5 in the T1-8th row to the image data in the T1001-1 row, compares the added image data with the reference value, and outputs the binary data as described above. Data D4 and error data D5 are calculated.

  As described above, according to the present embodiment, the calculation result calculated by performing the calculation process on the image data in one tile is output separately to the first storage unit 20g and the second storage unit 20h. Can do. That is, the number of first storage units 20g can be reduced, and the necessary calculation results to be stored can be stored in the second storage unit 20h. The first storage unit 20g is a storage unit configured by a FIFO / RAM capable of high-speed transfer, and the second storage unit 20h is a storage unit configured by a DRAM that transfers at a lower speed than the first storage unit 20g. Therefore, the production cost and development cost of the image processing unit 20 can be reduced. Furthermore, the calculation results stored in the second storage unit 20h can be used for image data in other tiles.

  The calculation result used for the image data in the other tile is the calculation result of the mth row in the tile. According to the present embodiment, the calculation results of the T1-8th row, the T2-8th row, the T1001-8th row, and the like can be used for the calculation processing of other tiles.

  Further, the image data of other tiles using the calculation result of the m-th row in the tile is the image data of the first row of the tile adjacent to the m-th row image data in the sub-scanning direction. According to this embodiment, the calculation result of the T1-8th line can be used for the calculation process of the image data of the T1001-1 line.

  In addition, among the calculation results calculated within one tile, the calculation results from the first row to the (m−1) th row and the calculation result of the m-th row can be stored in different storage units. According to the present embodiment, the calculation results from the T1-1 line to the T1-7 line are stored in the first storage unit 20g, and the calculation result of the T1-8 line is stored in the second storage unit 20h. Can do.

  Further, the writing speed of the second storage unit 20h is such that the calculation result of the m-th row of the tile processed immediately before the calculation processing from the first row to the (m-1) -th row in the tile can be written. I just need it. According to the present embodiment, the second storage unit 20h stores the calculation result of the T1-8 line until the calculation unit 20e finishes the calculation process from the T2-1 line to the T2-7 line. Just keep it.

  The output speed of the second storage unit 20h is the first row of the tile to be processed next after the calculation processing from the second row to the m-th row is completed after the calculation processing of the first row is completed. It is sufficient if the calculation result can be output. According to this embodiment, the second storage unit 20h outputs the calculation result of the T2-1 line until the calculation unit 20e finishes the calculation process from the T1-2 line to the T1-8 line. Just keep it.

  Further, the arithmetic unit 20e can perform error diffusion processing as in the present embodiment, and can use error data calculated in one tile for error diffusion processing of other tiles.

In this embodiment, the image processing unit 20 includes the calculation unit 20e, and the calculation unit 20e performs error diffusion processing. However, the present invention is not limited to this, and for example, line adjustment is simply performed without performing calculation processing. It is also possible to provide an image processing unit that enables
Hereinafter, an image processing unit according to another embodiment will be described.

FIG. 7 shows an image processing unit 21 in another embodiment.
The image processing unit 21 shown in FIG. 7 is configured by further including three peripheral circuits in the image processing unit 20 of FIG. Further, the image processing unit 21 in FIG. 7 is configured without the calculation unit 20e.

The three peripheral circuits are a character image processing circuit 21a, a photo image processing circuit 21b, and a photo / character discrimination circuit 21c.
Hereinafter, processing of the image processing unit 21 including these peripheral circuits will be described.

  The character image processing circuit 21a performs processing for enhancing the outline of the character. A filter size of 7 × 7 (pixels) is used as the filter size, and processing for delaying the input pixels by three lines is performed in order to output the target pixel.

FIG. 8 is a conceptual diagram of character image processing using a 7 × 7 filter size.
As shown in FIG. 8, the character image processing circuit 21a performs a process of delaying image data (for three lines) after the line of the target pixel P1 in order to output the target pixel P1.

  The photographic image processing circuit 21b performs an averaging process. A filter size of 9 × 9 is used as a filter size, and processing for delaying input pixels by four lines is performed in order to output a target pixel.

FIG. 9 shows a conceptual diagram of photographic image processing using a 9 × 9 filter size.
As shown in FIG. 9, the photographic image processing circuit 21b performs a process of delaying image data (for four lines) after the line of the target pixel P2 in order to output the target pixel P2.

The photo / character discrimination circuit 21c performs a process of counting the number of pixels at the halftone level. A filter size of 9 × 9 is used as a filter size, and processing for delaying input pixels by four lines is performed in order to output a target pixel.
The conceptual diagram of the photo / character discrimination process when the line is delayed by 4 lines is the same as FIG.

As described above, when the filter size is different in each circuit, the number of lines of image data to be delayed is also different.
Therefore, the image processing unit 21 performs a delay process for delaying the image data output from the character image processing circuit 21a by one line. The delay process is the same as the process of the image processing unit 20 illustrated in FIG. 2 except that the calculation process by the calculation unit 20e is not performed.

  As described above, according to another embodiment, in order to achieve consistency in the number of lines of image data to be delayed, the delay process is performed to delay the image data output from the character image processing circuit 21a by one line. Can do. That is, the present invention is not limited to arithmetic processing (error diffusion processing) but can be applied as a delay adjustment circuit.

2 is a functional block diagram of the image forming apparatus. FIG. It is a functional block diagram of an image processing part. It is a functional block diagram of a calculating part. It is a conceptual diagram of an error diffusion process. It is a conceptual diagram of a tile. It is a conceptual diagram of a tile and an error diffusion process. It is a functional block diagram of the image processing part in other embodiments. It is a conceptual diagram of the image processing using a 7x7 filter size. It is a conceptual diagram of the image processing using a 9x9 filter size.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 10 Acquisition part 20 Image processing part 30 Output part 40 Operation part 50 Display part 60 Control part 20a Line / tile conversion part 20b Compression part 20c Writing / reading part 20d Expansion part 20e Calculation part 20f Tile / line conversion part 20g First storage unit 20h Second storage unit 201 Addition unit 202 Output processing unit 203 DRAM writing / reading unit

Claims (7)

In an image processing apparatus that divides image data for all lines into a plurality of m rows and n columns of rectangular regions and performs image processing for each of the divided rectangular regions,
First storage means;
Second storage means slower than the first storage means;
Compression means for compressing image data in one rectangular area among the plurality of rectangular areas ;
A writing / reading unit that writes the image data compressed by the compression unit to the second storage unit and reads the compressed image data from the second storage unit;
Decompression means for decompressing compressed image data read by the writing and reading means;
A calculation process is performed on the image data expanded by the expansion unit to calculate a calculation result of one rectangular area, a part of the calculation result is stored in the second storage unit, and the remaining calculation result Calculating means for storing the first storage means in the first storage means ,
The said calculating means is an image processing apparatus which uses a part of calculation result of one rectangular area memorize | stored in the said 2nd memory | storage part for the calculation process of the image data in another rectangular area .   The calculation means calculates the calculation result for m rows by performing calculation processing for each row on the image data in the one rectangular area, and among the calculated calculation results for the m rows, The image processing apparatus according to claim 1, wherein the calculation result is used for the first row of image data in the other rectangular area by using the calculation result for the first row of image data in the other rectangular area. .   The image processing apparatus according to claim 1, wherein the first row of image data in the other rectangular area is adjacent to the mth row of image data in the one rectangular area in the sub-scanning direction. The calculation means stores the calculation results from the first line to the (m−1) th line among the calculation results calculated in the rectangular area in the first storage means, and the calculation result in the mth line of the last line. Respectively output to the second storage means,
The image processing apparatus according to claim 1, wherein the first storage unit and the second storage unit store the calculation result output from the calculation unit.   The calculation means calculates the calculation result of the m-th row of the rectangular area after calculating the calculation result of the m-th line of the rectangular area and before calculating the calculation result of the m-th line of the rectangular area to be processed next. The image processing apparatus according to claim 4, wherein:   The second storage means calculates the calculation result of the first line of the rectangular area to be processed next after the calculation means calculates the calculation result of the first line of the rectangular area. The image processing apparatus according to claim 4 or 5, wherein a calculation result used for a first line of a rectangular area to be processed is output to the calculation means.   The calculation means performs error diffusion processing on image data in the rectangular area to calculate a calculation result, and uses the calculated calculation result for error diffusion processing of image data in the other rectangular area. The image processing device according to claim 6.

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