JP2003134335A - Color picture processor and composite color picture printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color picture processor which reduces data areas in a cache area to improve the memory efficiency. SOLUTION: The processor retrieves a cache table in the event of reference of dither (S10). If data exist in the cache table (S11; Y), it replaces the data to the head of the cache table (S12) as reference data. If the data do not exist in the cache table (S11; N), requested data must be prepared. But prior to preparation, it calculates the size of data created thereafter, and decides whether free areas of the calculated size exist in the cache area (S13). If the free areas exist (S13; Y), it creates data (S14) and adds the formed data to the head of the cache table (S15). If the free areas do not exist (S13; N), it deletes the data (S16) to make free areas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image processing apparatus for processing a digital image signal of a copying machine, a printer or the like for converting CMYK color information into a color image for printing using matrix arrangement information of dither patterns. .

[0002]

2. Description of the Related Art In recent years, printing apparatuses such as color digital copying machines and color laser printers capable of processing not only black and white images but also color images have become widespread. In order to perform full-color printing with a printing apparatus such as a color laser printer or a color digital copying machine, R (red), G (green), and B which are color modes for image processing are used.
C, which is the color mode for printing (blue) color data
(Cyan), M (magenta), Y (yellow), K
It is necessary to convert to (black) color data. When expressing the converted halftone of each color by a binary value, an area gradation method in which the number of ON (ON) dots included in a unit area is changed to express an intermediate density is widely used.

The dither method, which is an example of the area gradation method, includes a conditional decision method such as an error diffusion method which decides a threshold matrix in consideration of the peripheral density of a pixel of interest, and a systematic decision method. There is an independent determination method such as a dither method or a sub-matrix method that determines a threshold level only with a pixel of interest. The systematic dither method prepares an N × N threshold matrix with N × N pixels as one unit for gradation reproduction,
This threshold value matrix is superposed on the original image as a kind of mask pattern, and the density of each pixel of the original image, for example, f
The threshold value Txy calculated by (x, y) and a certain rule
Is a method of comparing and binarizing. In addition, the sub-matrix method uses an N × N mother matrix (density matrix).
Is set to perform gradation reproduction, and an m × m submatrix of an appropriate size is regularly cut out from this mother matrix (density matrix) to obtain output pixels corresponding to the original image. .

Generally, there are various matrices in the dither table of the independent decision method. In addition, depending on the type of the original image, there are also print engines such as a binary engine that represents one color with one dot, a four-value engine that represents one color with two dots, and a sixteen-value engine that represents one color with four dots. Engines that can be switched in page units in settings are becoming mainstream. When the resolution and the multi-tone setting are changed on a page basis, the matrix of the dither table is also changed to a dedicated one. The same resolution,
And even with the same gradation, a plurality of matrices are used on a case-by-case basis in an actual printing device.
The size of the dither matrix used is 24
X24, 32x32, 40x40, 48x48, 64x
There are 64 etc. Usually these dither matrices are R
It is supplied from OM (Read Only Memory). However, if the CPU (Central Processing Unit) is 32 bits and a matrix that is not a multiple of 32 is to be pasted to the image, it must be pasted to the image while converting the source data, resulting in extreme processing performance. Will decrease. Therefore, for a matrix that is not a multiple of 32, data converted to have a multiple of 32 is prepared in a cache area on a RAM (random access memory), and the data is pasted. FIG. 6 shows an example of this matrix conversion.

Generally, the above-mentioned independent decision method is easier to process than the conditional decision method, but it requires a dither matrix corresponding to the number of gradations to be expressed, and requires a large memory. As means for avoiding such a memory capacity problem at the time of color printing, Japanese Patent Laid-Open No. 10-16666.
Japanese Patent Laid-Open No. 4 (1994) discloses a method of registering pattern information of a dither matrix into a plurality of patterns such as a basic pattern and pattern arrangement information, thereby registering pattern information of a relatively large capacity in a memory of a smaller capacity. Is disclosed. Further, in Japanese Patent Laid-Open No. 11-34400, there is no reduction in the expressiveness of colors represented by gradation from low-resolution color image information having a resolution of 1 / n (n = integer) of a color printer. Color printing,
A method for reducing the amount of color image information and reducing the memory capacity is disclosed.

[0006]

However, since the dither cache table is secured as data attached to page data for each print page, it is necessary to secure a large cache area on the memory for printing. . Therefore, a first object of the present invention is to make it possible to change the printer engine resolution and the multi-gradation setting in page units without having a conversion table for dither in page units, so that a single cache area can be changed. It is an object of the present invention to provide a color image processing apparatus capable of reducing the data area in the printer and increasing the memory efficiency of the printing apparatus. A second object of the present invention is to provide a composite color image printing apparatus which controls color image processing using the above-mentioned color image processing apparatus and functions such as copying and FAX with a single controller.

[0007]

According to a first aspect of the present invention, a dither table storing dithers and dither cache data created by converting the dithers stored in the dither table. Is stored in the memory of the device, and a dither method that expresses the gradation of color by referring to the dither cache data in this dither cache table is used. In a color image processing apparatus that performs color image processing using this, if a reference to new dither cache data occurs when changing the printer engine resolution and multi-tone setting of the print image, this dither
Retrieval means for retrieving whether cache data exists in the dither cache table, and if the dither cache data exists in the dither cache table by the retrieval by the retrieving means, The dither cache data of the request was not found in the dither cache table by the replacing unit that replaces the searched dither cache data with the first data of the dither cache table and the search by the searching unit. If the dither in the reference dither table is
There is a creating means for creating the data, a calculating means for calculating the size of the dither cache data created by the creating means, and an empty area for storing the size of the dither cache data calculated by the calculating means. A determination unit that determines whether the cache region in the memory exists, and if the determination unit determines that the cache region in the memory does not have the free space, the oldest in order to secure the free space. The present invention is characterized by including deleting means for deleting the reference dither cache data, and adding means for adding the dither cache data created by the creating means to the top data of the dither cache table. This achieves the first object.

According to the second aspect of the invention, the second object is achieved by performing color image processing using the color image processing apparatus of the first aspect.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to FIGS.
FIG. 1 is a block diagram showing the configuration of a color printing apparatus according to an embodiment of the present invention. This color printing device
CPU (Central Processing Unit) 1, ROM (Read Only Memory) 2, RAM (Random Access Memory) 3, VIDEO I / F (Video Interface) 5, SIF (Serial Interface) 6, and external I / Fs (interfaces) 7 are connected to each other via a bus 4. And VIDEO I /
The color print engine 8 is connected to F5. This color printing apparatus may be a composite color image printing apparatus in which functions such as copying and FAX are controlled by a single controller.

The CPU 1 controls the entire control device,
The ROM 2 stores programs necessary for the execution of the CPU 1, fonts, resolutions, multivalued conditions, and dither tables required for printing conditions. The RAM 3 holds a frame buffer that stores a color image for printing and various data. There are two types of data in the RAM 3; page-specific information and page-independent information. The page-specific information includes a display list in which drawing data is intermediately coded and dither information obtained by converting dither table information.・ There is a cache table, etc. The VIDEO I / F 5 has a function of transferring the image of the frame buffer created in the RAM 3 to the color print engine 8. The SIF 6 controls the operation of the color printing apparatus with a command and fetches the status of the color printing engine as a status. The external I / F 7 transmits / receives print information to / from the outside via the line 9.

FIG. 2 shows a dither table and a dither cache table A, which has a conventional configuration of 600 dpi2.
Dither table for values and dither to be converted from
It shows the contents of the cache table. In addition, FIG. 3 shows a dither table and a dither cache.
Table B is a table showing the contents of a conventional dither table for 600 dpi 4-value and a dither cache table converted from the dither table. The color printing apparatus allocates the necessary maximum size as a dither cache table at the beginning of each page as information for each page.

FIG. 4 shows a dither cache table according to the present embodiment, in which a required size is secured in the cache area as data independent of pages. Each cache data is linked in a chain structure, starting with the header, and then sequentially from the most recently referenced to the oldest. In each of this cache data,
"Data for 600-dpi binary characters and the matrix is 9
6 × 48 ”is added with identification information that enables determination.

FIG. 5 is a flow chart showing the procedure of the dither cache data reference method in this embodiment. Whenever a new dither cache data reference occurs, no matter what page you print, follow the chain structure from the header to get the dither cache for the request.
A search is made to see if the data is in the dither cache table (step 10). If the dither cache data of the request is in the dither cache table (step 11; Y), the found dither cache data is replaced with the head of the chain (step 12), and the dither at the head is replaced. -Use cached data as reference data.

On the other hand, if the dither cache data of the request is not in the dither cache table (step 11; N), the dither in the dither table is converted and the dither cache data of the request is obtained. Must be created. However, before that, the size of the dither cache data after the dither conversion is calculated, and it is judged whether or not there is an empty area of the calculated size of the dither cache data in the cache area (step 13). If there is an empty area of the size of the calculated dither cache data in the cache area (step 1
3; Y) converts the dither in the reference dither table to the empty area and creates dither data (step 1).
4) Then, the created dither data is added to the beginning (step 15). On the other hand, if there is no empty area of the size of the calculated dither data in the cache area (step 13; N), the last-referenced dither data is deleted (step 16) to create an empty area.

[0015]

According to the first aspect of the present invention, it is not necessary to secure the maximum size cache area as in the past, and even in the case where a plurality of page data is created in the RAM, it corresponds to the page. Since it is not necessary to secure the required number of cache areas, the memory efficiency of the color image processing apparatus can be improved by reducing the memory area. According to the invention of claim 2, by performing color image processing using the color image processing apparatus of the invention of claim 1, it is possible to increase the memory efficiency of the composite color image printing apparatus.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a color printing apparatus according to this embodiment.

FIG. 2 is a dither table and a dither cache table A, and is a dither table for a 600 dpi binary value of the conventional configuration and a dither cache converted from the dither table.
It shows the contents of the table.

FIG. 3 is a dither table and a dither cache table B, which are a dither table for 600 dpi 4-value having a conventional configuration and a dither cache converted from the dither table.
It shows the contents of the table.

FIG. 4 is a dither cache table according to the present embodiment.

FIG. 5 is a flowchart showing a procedure of a dither data reference method according to the present embodiment.

FIG. 6 is a diagram showing an example of dither table matrix conversion.

[Explanation of symbols]

1 CPU (Central Processing Unit) 2 ROM (Read Only Memory) 3 RAM (Random Access Memory) 4 Bus 5 VIDEO I / F (Video Interface)
Part 6 SIF (serial interface) 7 External I / F (interface) 8 Color print engine 9 lines

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Claims (2)

[Claims] 1. A dither table storing dither and a dither cache table storing dither cache data created by converting the dither stored in the dither table. In a color image processing device that performs color image processing by using a dither method that is stored in the memory of the device and refers to the dither cache data in this dither cache table to express the gradation of the color. If a new dither cache data reference occurs when changing the printer engine resolution and multi-tone setting of the print image, search whether this dither cache data exists in the dither cache table. And a dither cache data by the search by the search unit. If present in the I The cache table, and replacing means for replacing the dither cache data the search to the head data of the dither cache table, the search by the searching means, dither of the request
Creating means for creating the dither cache data by converting the dither in the reference dither table when cache data does not exist in the dither cache table; Dither cache
Calculating means for calculating the size of the data, and the dither cache calculated by the calculating means
Determination means for determining whether or not there is a free area enough to store the size of data in the cache area in the memory; and when the determination means determines that the free area does not exist in the cache area in the memory, In order to secure the area, the deleting unit that deletes the oldest reference dither cache data, and the dither cache created by the creating unit.
A color image processing apparatus comprising: an addition unit that adds data to the head data of the dither cache table. 2. A composite color image printing apparatus, wherein color image processing is performed by using the color image processing apparatus according to claim 1.