JP4369137B2 - Image processing device for printing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus for printing used in an electronic printing apparatus having a print engine, and in particular, is supplied with compressed image data for each color in a predetermined color space, decompresses the compressed image data, and supplies the compressed image data to the print engine. The present invention relates to a printing image processing apparatus to be supplied.
[0002]
[Prior art]
An electronic printing apparatus such as a page printer prints image data in a predetermined color space generated by a host computer or the like with a print engine using a laser beam or the like. Such an electronic printing apparatus generates image data corresponding to a plurality of colors in a color space corresponding to the color of the toner, forms a latent image on the drum according to the image data of each color in the print engine, and applies the toner of the corresponding color. Adhere and transfer to printing paper. Therefore, the electronic printing apparatus has an image memory (or band memory) that stores image data for at least one page, and further processes the image data stored in the image memory to adapt to the print engine. An image processing device that generates image data is included.
[0003]
Usually, the amount of data of image data stored in the image memory becomes enormous, so that the image data is stored in the image memory as image data compressed by a predetermined algorithm. Therefore, the image processing apparatus decompresses at least the compressed image data and supplies the decompressed image data to the print engine.
[0004]
A conventional image processing apparatus decompresses compressed image data for each color and supplies the decompressed image data as it is to a print engine. Accordingly, the image processing apparatus starts decompression of the compressed image data and supplies the decompressed image data to the print engine in accordance with the horizontal synchronization signal or video clock (or dot clock) corresponding to the print timing of the print engine. When decompressing compressed image data, it is necessary to refer to the image data of the preceding raster depending on the compression algorithm. In this case, the image processing apparatus temporarily stores the decompressed image data and starts decompression. In addition, the preceding decompressed image data is referred to.
[0005]
As described above, the conventional image processing apparatus must perform all image processing such as internal decompression processing and reference to the previous decompressed image data for decompression depending on the print timing of the print engine.
[0006]
[Problems to be solved by the invention]
The electronic printing apparatus may be supplied with RGB image data from a host computer, or may be supplied with CMYK image data corresponding to the toner of the print engine. A conventional image processing apparatus in an electronic printing apparatus processes only CMYK image data corresponding to toner used in a print engine. Therefore, when RGB image data is supplied, the color conversion unit in the electronic printing apparatus performs color conversion to CMYK image data. For example, one page of CMYK compressed image data is stored in the image buffer (band memory). Is done. When CMYK image data is supplied, it is compressed as it is and stored in the image buffer. Thereafter, as described above, in accordance with the timing of the print engine, it is decompressed by the image processing apparatus and supplied to the print engine.
[0007]
However, color conversion of RGB image data for one page requires a certain processing time, and the CMYK image data subjected to such color conversion is temporarily compressed and stored in an image buffer, and then rasterized. In the method of performing the decompression process every time, it takes a long time to print. In particular, the color conversion process is an overhead time for the printing process, and causes a long time until the start of printing.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image processing apparatus for printing that solves the above-described conventional problems.
[0009]
It is another object of the present invention to provide an image processing apparatus for printing that can process both image data in a first color space such as RGB and image data in a second color space such as YMCK. is there.
[0010]
Furthermore, an object of the present invention is to process both image data in the first color space and image data in the second color space in an electronic printing apparatus having a print engine that prints in the second color space, An object of the present invention is to provide a printing image processing apparatus capable of supplying image data of a second color space to a printing engine.
[0011]
Furthermore, an object of the present invention is to process both image data in the first color space and image data in the second color space in an electronic printing apparatus having a tandem printing engine that prints in the second color space. Another object of the present invention is to provide an image processing apparatus for printing that can supply image data of the second color space to the print engine.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an image processing apparatus for printing according to the present invention decompresses both image data in a first color space such as RGB and image data in a second color space such as CMYK. And if the decompressed image data is image data in the first color space, the color data is converted into image data in the second color space and supplied to the print engine, and the decompressed image data is in the second color space. In the case of the image data, image data supply means for supplying the image data to the print engine without color conversion is provided.
[0013]
According to the above invention, both when the image data of the first color space is supplied from the host computer and when the image data of the second color space is supplied, the image data is once compressed and stored in the memory. The compressed image data is decompressed as it is by the printing image processing apparatus of the present invention, color-converted only in the case of the image data in the first color space, and supplied to the print engine as decompressed image data in the second color space. Accordingly, the time from the supply from the host computer to the internal decompression and the supply of the image data to the print engine is about the same as the image data in the second color space even in the case of the image data in the first color space. It becomes shorter and enables high-speed printing.
[0014]
To achieve the above object, the present invention is supplied with compressed image data for each color in the first or second color space, decompresses the compressed image data, and prints with toner in the second color space. In the printing image processing apparatus for supplying the decompressed image data to the print engine
The image data in the first color space includes at least four types of data including image data of at least red (R), green (G), and blue (B) and color conversion attribute data (X). The image data in the color space 2 includes at least four types of data of cyan (C), magenta (M), yellow (Y), and black (K).
A decompressor for decompressing the supplied compressed image data of the first or second color space;
A decompressed image data memory having a capacity for retaining decompressed image data of the first or second color space decompressed by the decompressor and retaining at least four types of data of the first color space;
In the case of the decompressed image data in the first color space, the decompressed image data in the first color space is read in parallel from the decompressed image memory, and color-converted into decompressed image data in the second color space, In the case of the decompressed image data of the second color space, the decompressed image data of the second color space corresponding to the color to be printed by the print engine is read from the decompressed image memory, and the second color space is not converted. Image data supply means for supplying decompressed image data in the color space to the print engine.
[0015]
To achieve the above object, the present invention is supplied with compressed image data for each color in the first or second color space, decompresses the compressed image data, and prints with toner in the second color space. In the printing image processing apparatus for supplying the decompressed image data to the print engine
A decompressor for decompressing the supplied compressed image data of the first or second color space;
A decompressed image data memory having a capacity for holding at least decompressed image data for the number of colors in the first color space and retaining decompressed image data in the first or second color space decompressed by the decompressor When,
In the case of the decompressed image data in the first color space, the decompressed image data in the first color space is read in parallel from the decompressed image memory, and color-converted into decompressed image data in the second color space, In the case of the decompressed image data of the second color space, the decompressed image data of the second color space corresponding to the color to be printed by the print engine is read from the decompressed image memory, and the second color space is not converted. Image data supply means for supplying decompressed image data in the color space to the print engine.
[0016]
To achieve the above object, the present invention is supplied with compressed image data for each color in the first or second color space, decompresses the compressed image data, and prints with toner in the second color space. In the printing image processing apparatus for supplying the decompressed image data to the print engine
A decompressor that decompresses the supplied compressed image data of the first or second color space, and a decompressed image data memory that retains the decompressed image data of the first or second color space decompressed by the decompressor And a plurality of decompression units corresponding to at least the number of colors in the first color space,
In the case of the decompressed image data of the first color space, the decompressed image data of the first color space is read in parallel from the decompressed image memory in the plurality of decompression units to decompress the second color space. In the case of color conversion into image data and decompressed image data in the second color space, the decompressed image data in the second color space is read from the decompressed image memory in the plurality of decompression units, and the color And image data supply means for supplying decompressed image data of the second color space to the print engine without conversion.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention. The present invention relates to an image processing apparatus in an electronic printing apparatus. In the following description of embodiments, a page printer using a laser beam will be described as an example. However, the present invention is not limited to such a page printer.
[0018]
[First Embodiment]
FIG. 1 is a diagram illustrating a configuration of an electronic printing apparatus according to the first embodiment. An electronic printing apparatus 2 such as a page printer is connected to the host computer 1 via an input / output buffer 3. The electronic printing apparatus 2 includes a controller that processes image data described in a predetermined printing language supplied from the host computer 1 in addition to the print engine 12 that performs actual printing. The controller is a portion other than the print engine 12 and the host computer 1 in the figure, and includes a CPU 5, a memory 6 for storing an interpretation program for interpreting supplied image data, and a memory 7 for storing a compression / decompression program, for example, one page. An image buffer (band memory) 10 for storing the compressed image data for a portion, a memory 11 for storing a ROP (raster operation) program for performing image composition such as superimposing a plurality of images on the RGB image data, and A setting unit 9 for setting a printing position is provided, and these are connected via the system bus 4. The controller further includes an image processing device 20 that decompresses the compressed image data stored in the image buffer 10 and supplies the decompressed image data adapted to the print engine.
[0019]
Image data described in a predetermined printing language supplied from the host computer 1 is interpreted by the CPU 5 according to an interpretation program. Further, the CPU 5 compresses the image data for each raster, for example, according to a compression / decompression program. The compressed image data is stored in the image buffer 10 in raster units for each color in the color space.
[0020]
In general, image data supplied from the host computer 1 may be image data in an RGB color space or image data in a CMYK color space that is a toner of a print engine. The print engine 12 such as a page printer uses CMYK toner. The electronic printing apparatus 2 in the present embodiment temporarily compresses image data in any color space, stores it in the image buffer 10, and decompresses it with the image processing apparatus 20. The image buffer 10 is composed of, for example, a DRAM that records compressed image data for one page. When RGB image data is supplied, the image data is decompressed in the image processing apparatus 20 and converted into image data in the CMYK color space. Then, the image processing apparatus 20 supplies the CMYK image data in accordance with the printing timing of the print engine 12.
[0021]
The image processing device 20 is an integrated circuit device formed by, for example, an ASIC (Application Specific Integrated Circuit). The image processing device 20 directly reads and decompresses compressed image data in the image buffer 10, and performs color conversion and printing as necessary. Supply the decompressed image data to the engine. The image processing apparatus 20 in the first embodiment includes a controller 30 that controls internal timing, and a direct memory access (DMA) controller that directly reads compressed image data in the image buffer 10 without going through the CPU 5. 21, a decompressor 22 that decompresses the read compressed image data, first and second decompressed image memories 24 and 25 that include high-speed memories such as SRAMs that store the decompressed image data, It has a print readout buffer 27 that reads out the decompressed image data from the first or second decompressed image memory 24, 25, and a converter 33 that performs color conversion from RGB image data to CMYK image data. The printing read buffer 27 and the converter 33 constitute image data supply means for supplying CMYK image data to the print engine 12.
[0022]
Further, the image processing apparatus 20 reads out the decompressed image data from the first or second decompressed image memory 24, 25 and supplies the decompression read buffer 29 to be supplied to the decompressor 22, and prints the image at any position in the raster. It has a print read timing register 32 for storing information on whether to do.
[0023]
For example, image data in the RGB color space is supplied from the host computer 1, compressed by the compression program 7, and stored in the image buffer 10 in color plane units and raster units.
[0024]
The DMA controller 21 continuously reads the compressed image data from the image buffer (band memory) 10 and supplies it to the decompressor 22. The speed of the DMA controller 21 only needs to be guaranteed so that the amount of data required by the decompressor 22 can be continuously supplied. The decompressor 22 normally decompresses compressed image data in units of one raster (print line), and the decompressed image data in units of raster is stored in either one of the first and second decompressed image memories 24 and 25 by the write buffer 23. Is written to. The decompression process performed by the decompressor 22 does not necessarily require decompression of one dot for each dot clock (or image clock) CLK of the print engine, and decompresses compressed image data for one raster within one raster time. do it. The dot clock CLK has a period obtained by dividing the period of the horizontal synchronization signal HSYNC, which is the scanning timing of the laser beam in the print engine 12 in the main scanning direction, by the number of dots in one raster.
[0025]
The decompressed image memories 24 and 25 are high-speed random access memories composed of, for example, SRAMs, etc., each having a capacity capable of storing a plurality of decompressed (for example, four) image data for each one raster, each having an arbitrary address. Can be read out at an arbitrary timing, and includes at least two sets of first and second decompressed image memories 24 and 25. The two sets of decompressed image memories 24 and 25 are physically separate memories, and can be read from the other while writing to either one.
[0026]
The print readout buffer 27 and the decompression readout buffer 29 are connected to the raster unit at a timing independent from the decompression processing timing of the decompressor 22 from the other one of the first or second decompressed image memories 24 and 25. Read the decompressed image data. The printing read buffer 27 reads the decompressed image data from the decompressed image memories 24 and 25 in accordance with the dot clock (HSYNC, CLK) which is the printing timing of the print engine 12, and in the case of CMYK image data, the print engine 12 is used as it is. Convert to that style and supply. In the case of RGB image data, the color is converted into CMYK image data by the converter 33 and supplied to the print engine 12. As will be described in detail later, the print read buffer 27 reads decompressed image data for each raster at each raster timing of the print engine 12 in response to a control signal from the controller 30, and the color conversion converter 33 and the print engine 12. Or the decompressed image data is repeatedly supplied to the color conversion converter 33 and the print engine 12 at each raster timing. The print read buffer 27 may read and supply decompressed image data at an arbitrary position in the raster according to information set in the print read timing register 32. Thereby, it is possible to print the print image by moving it by a predetermined amount in the print paper.
[0027]
The decompression read buffer 29 is used when the decompression algorithm of the decompressor 22 requires reference to the image data of the preceding raster. The decompression read buffer 29 reads decompressed image data in the decompressed image memories 24 and 25 made of SRAM at the timing of the memory and the bus width, converts it into the format of the decompressor 22 and supplies it at the timing of decompression processing. When the decompression read buffer 29 and the print read buffer 27 simultaneously read decompressed image data from the same decompressed image memories 24 and 25, the readout from both buffers is alternately performed, for example, by 8 bytes by time division. Convert to the data width and timing of the supply destination.
[0028]
The print engine 12 performs printing by driving, for example, a laser in accordance with the supplied CMYK decompressed image data. One sheet is printed for each color plane, and when printing of all the CMYK planes is completed, a color image is formed on the printing paper. Alternatively, in the case of the tandem system, printing is performed by supplying CMYK image data in parallel.
[0029]
The image processing device 20 in the first embodiment is an integrated circuit device formed by, for example, an ASIC (Application Specific Integrated Circuit). As described above, the image processing apparatus 20 includes the decompressed image memories 24 and 25 for storing the decompressed image data, the decompression timing by the decompressor 22, and the print engine 12 of the decompressed image data by the print read buffer 27. Can be controlled separately from the supply timing. Thereby, as will be described later, the resolution conversion processing of image data and the movement of the printing position on the printing paper can be performed relatively easily.
[0030]
In the first embodiment, as described above, CMYK image data corresponding to the toner color of the print engine 12 is supplied from the host computer 1 and RGB corresponding to the color of the application program in the host computer. Both the case where image data is supplied can be handled. Therefore, RGB compressed image data may be stored in the image buffer 10, or CMYK compressed image data may be stored.
[0031]
Accordingly, the image processing apparatus 20 has a configuration capable of processing both CMYK compressed image data and RGB compressed image data. That is, the two sets of decompressed image memories 24 and 25 provided in the image processing apparatus 20 can store decompressed image data for four colors, respectively. Accordingly, the write buffer 23 can write the decompressed image data separately for each color of CMYK or RGB in the decompressed image memories 24 and 25. Further, the print readout buffer 27 can read out the RGB decompressed image data from the decompressed image memories 24 and 25 in parallel from an arbitrary position at an arbitrary timing. The decompression read buffer 29 can read and supply decompressed image data for each color in accordance with the processing of the decompressor 22.
[0032]
For example, when image data in a postscript language is supplied, CMYK image data that has already undergone color conversion on the application side is supplied from the host computer 1. In this case, the electronic printing apparatus 2 compresses the CMYK image data corresponding to the supplied toner color as it is and stores it in the image buffer (band memory) 10. In the case of image data in the PostScript language, the color conversion processing is independently performed by the operator specified in the host computer 1 without depending on the color conversion processing by the electronic printing device 2, and the electronic printing device 2 is supplied. CMYK image data is simply printed as it is.
[0033]
On the other hand, when RGB image data is supplied from the host computer 1 as image data by a normal application program, the RGB image data is compressed as it is and stored in the image buffer (band memory) 10. Then, the image processing apparatus 20 decompresses each raster, and the color conversion converter 33 performs color conversion processing on CMYK image data and supplies the image data to the print engine 12.
[0034]
In this embodiment, in the case of RGB image data, attribute data X that specifies conversion processing such as specifying a conversion table used for color conversion processing is accompanied. Therefore, in the present embodiment, in the case of image data in the RGB color space, the image data is RGBX image data (including attribute data).
[0035]
When RGB image data by a normal application program or the like is supplied from the host computer 1, the RGB image data is stored in the image buffer 10, for example, a composite process such as superimposing RGB image data of a plurality of pages is electronically performed. This can be done in the printing device. Such an image composition function may be referred to as a raster operation (ROP), for example.
[0036]
In this way, when RGBX compressed image data is stored in the image buffer 10, if the image processing device 20 is configured to process only CMYK image data, RGBX image data for one page is stored in the image processing device. Before decompression processing in the image data 20, the color conversion unit 8 must convert the image data into CMYK image data. If the image processing apparatus 20 performs decompression processing one raster after the color conversion processing, a relatively long time is required for the color conversion processing before the decompression processing, and the overhead time required for printing becomes long.
[0037]
Therefore, in the first embodiment, the two sets of decompressed image memories 24 and 25 provided in the image processing apparatus 20 can store image data of four colors, respectively. That is, four RGBX compressed image data stored in the image buffer 10 are continuously read out within one raster period by the DMA controller 21 and decompressed by the decompressor 22 to decompress the decompressed image data of four colors. The data is written in one of the image memories 24 and 25 in the writing state. In the next raster period, the written RGBX decompressed image data is read out in parallel from the read-out memories 24 and 25 by the print readout buffer 27, and is converted from the RGBX image data by the color conversion converter 33. The image data is converted into any one of CMYK image data and supplied to the print engine 12. The converter 33 sets a color conversion table (not shown) according to the attribute data X, and converts the image data into one of CMYK image data one dot at a time using the color conversion table.
[0038]
According to the image processing device 20 described above, RGBX image data can be decompressed and color-converted in a raster unit in a pipeline manner, compared to the case where color conversion processing for one page is first performed. Thus, overhead time can be saved and the printing speed can be increased.
[0039]
When CMYK image data is stored in the image buffer 10, the image data is decompressed by the decompressor 22 and stored in the decompressed image memories 24 and 25, and the print readout buffer 27 reads it out without going through the converter 33. Directly to the print engine 12.
[0040]
Hereinafter, when the image processing apparatus 20 in the first embodiment shown in FIG. 1 performs image processing such as decompression on CMYK image data and supplies the image data to a single type print engine, When image data is supplied to a single print engine by performing decompression and color conversion image processing on RGBX image data, and image data is sent to a tandem print engine by performing image processing on CMYK image data. Will be described sequentially.
[0041]
FIG. 2 is a timing chart when image processing is performed on CMYK compressed image data stored in the image buffer (band memory) 10. FIG. 2A shows a horizontal synchronization signal HSYNC indicating the printing timing of the print engine 12 such as the raster periods R0 and R1. FIG. 2B shows a CMYK image memory in the image buffer 10, and in this example, the CMYK compressed image data is stored in one raster unit in the image buffer 10. That is, the image data CIDr0, CIDr1,. . . . In the area with a high address, K plane image data KIDrm-1 and KIDrm are stored. FIG. 2C shows reading by the DMA controller 21, decompression processing by the decompressor 22, and writing processing to the image memories 24 and 25 by the write buffer 23. FIGS. 2D and 2F show image data in the decompressed image memory in the writing state and the decompressed image memory in the reading state, respectively. FIG. 2 (f) shows the read processing of decompressed image data by the print read buffer 27 and the supply processing to the print engine 12.
[0042]
In the example of FIG. 2, it is assumed that the resolution of the image data is not changed. For each raster period R0, R1, the DMA controller 21 reads the compressed image data in the image buffer 10 in units of rasters and supplies the data to the decompressor 22 (process (c)). In the example of FIG. 2, C-plane image processing is shown, and cyan compressed image data CIDr0 is first read. The compressed image data CIDr0 is decompressed by the decompressor 22 in accordance with the decompression algorithm, and written to the decompressed image memory 24 in the written state by the write buffer 23 (process (c)).
[0043]
In the next raster period R1, the compressed image data CIDr1 of the next raster is read by the DMA controller 21, supplied to the decompressor 22, and written to the decompressed image memory 25 in a write state by the write buffer 23. At the same time, the printing read buffer 27 reads the stored decompressed image data CIDr0 for one raster from the decompressed image memory 24 in the read state, and supplies it directly to the print engine 12. The readout timing at this time is controlled by a control signal from the controller 30, and the decompressed image data area in the raster to be read out is set in the print readout timing register 32. The frequency of reading, the number of repetitions, and the like are controlled by a control signal from the controller 30, and the resolution can be changed as described above. Further, by setting a reading area according to the setting value of the print reading timing register 32 and controlling the reading timing, it is possible to move the print image in the printing paper. In any case, the read timing and supply timing of the print read buffer 27 are controlled at a timing independent of the decompression process.
[0044]
In the raster period R1, when the decompressor 22 needs to reference the image data of the preceding raster, the decompressed read buffer 29 causes the decompressed image data CIDr0 in the decompressed image memory 24 in the read state to be decompressed. And is supplied to the decompressor 22. The read timing of the decompression read buffer 29 is independent of the print read buffer 27. However, when both the buffers 27 and 29 need to read the same decompressed image data CIDr0 at the same time, they are read in a time division manner in a predetermined data unit (for example, 8 byte unit).
[0045]
Similar image processing is performed by the image processing apparatus 20 in the next raster. When image processing for one page of the C plane is completed, image processing for one page of the next M plane is performed, and image processing for one page of the Y plane and K plane is further performed. As a result, in the print engine 12, the CMYK toners are overprinted on the printing paper according to the latent images, and a color image is generated.
[0046]
FIG. 3 is a timing chart illustrating a case where image data is supplied to a single-type print engine by performing decompression and color conversion image processing on RGBX image data. (A)-(f) in the figure is the same as FIG. In the case of FIG. 3, in the image buffer 10, RGBX image data (where X is attribute data) are sequentially stored in raster units from a low address area to a high address area. That is, for the raster r0, R image data RIDr0, G image data GIDr0, B image data BIDr0, and X attribute data Xr0 are stored. These data lengths differ depending on each. Similarly, for the next raster r1, RGBX data is stored for one raster, and RGBX data for the last raster rm is stored in the final area.
[0047]
In the case of FIG. 3, all the RGBX image data is decompressed and supplied to the color conversion converter 27 within one raster period, so that, for example, image data CID for one raster of the C plane is supplied to the print engine 12. To do. Accordingly, the DMA controller 21, the decompressor 22, the write buffer 23, and the decompression read buffer 29 have a processing speed four times that of CMYK in FIG. 2, and have four types of image data within one raster period. Are processed respectively.
[0048]
In the raster period R0, the DMA controller 21 reads the RGBX image data (including the attribute data X) of the first raster r0 from the image buffer 10 and supplies it to the decompressor 22 (process (c)). The decompressor 22 decompresses each image data RIDr0, GIDr0, BIDr0, and Xr0 at a speed four times the video clock CLK determined from the horizontal synchronization signal HSYNC. Then, the write buffer 23 writes the decompressed image data RIDr0, GIDr0, BIDr0, and Xr0 to the corresponding areas in the decompressed image memory 24 in the writing state (process (c)).
[0049]
Similarly, in the next raster period R1, the DMA controller 21 reads the RGBX image data of the next raster r1 from the image buffer 10 and supplies it to the decompressor 22, which decompresses the video clock CLK by four times. The image data RIDr1, GIDr1, BIDr1, and Xr1 are decompressed at a speed. At this time, if the decompressor 22 needs to refer to the preceding image data of the previous raster, the decompressed read buffer 29 reads the decompressed image in the read state corresponding to the decompression processing timing of the decompressor 22. The image data RIDr0, GIDr0, BIDr0, and Xr0 are sequentially read from the memory 24 and supplied to the decompressor 22.
[0050]
The decompressed image data RIDr0, GIDr0, BIDr0, and Xr0 in the decompressed image memory 24 in the readout state are read out in parallel by the print readout buffer 27 and supplied to the converter 33 for color conversion. The color conversion converter 33 refers to the attribute data X and uses the corresponding color conversion table to convert the RGB image data into C plane image data CIDr0. This color conversion process is performed in units of dots in synchronization with the image clock CLK of the print engine. The color-converted image data CIDr0 is supplied to the print engine 12 and printed. At this time, the processing delay of the color conversion converter 33 occurs in the image data CIDr0 supplied to the print engine 12. Compared with the time required for the color conversion processing for one page before the decompression processing, The delay time is short.
[0051]
In the above example, the decompressed image memories 24 and 25 are configured to be able to store image data of four colors at the same time. Therefore, the print readout buffer 27 reads out RGBX data in parallel, and converts the color conversion converter 33. Can be supplied to. The color conversion converter 33 performs color conversion from RGB image data to any one of CMYK image data in units of dots corresponding to the printing speed of the print engine 12. Therefore, it is possible to increase the printing speed as compared with the case where the RGBX image data for one page is subjected to color conversion processing to CMYK in the previous stage of the image processing apparatus 20.
[0052]
FIG. 4 is a timing chart when image processing is performed on CMYK image data and image data is supplied to a tandem print engine. In the first embodiment shown in FIG. 1, the DMA controller 21, decompressor 22 and the like have the ability to process four image data within one raster period. However, when CMYK image data is stored in the image buffer 10 as shown in FIG. 2, the image data is decompressed and supplied to the print engine for each color plane. Therefore, in the case of CMYK image data, the capacity of the decompressor 22 or the like is not fully utilized.
[0053]
In the example of FIG. 4, the print engine 12 is of a tandem type that can perform printing for four colors in parallel, and the CMYK image data is decompressed within each raster period and the decompressed image memory 24. , 25, read in parallel, and supplied to the print engine 12.
[0054]
In the image buffer 10, color-converted CMYK compressed image data is continuously stored for each raster. That is, CMYK image data CIDr0, MIDr0, YIDr0, and KIDr0 are stored in that order for the raster r0, and the same applies to the next raster r1.
[0055]
In the raster period R0, the DMA controller 21 reads out the CMYK compressed image data CIDr0, MIDr0, YIDr0, and KIDr0 from the image buffer 10 in time series and supplies them to the decompressor 22 (process (c)). Therefore, the decompressor 22 decompresses the four compressed image data within one raster period. Then, the write buffer 23 writes the decompressed image data in one decompressed image memory 24 in the writing state (processing (c)).
[0056]
Similarly, in the next raster period R1, the DMA controller 21 reads CMYK compressed image data CIDr1, MIDr1, YIDr1, and KIDr1 of the next raster from the image buffer 10 in time series, and the decompressor 22 compresses these four compressions. Decompress the image data. Then, the write buffer 23 writes the decompressed image data in the decompressed image memory 25 that has been converted to the write state (processing (c)). At this time, if the decompressor 22 needs to refer to the image data of the previous raster, the decompression read buffer 29 has the image data CIDr0, MIDr0, decompressed from the decompressed image memory 24 in the read state. YIDr0 and KIDr0 are read and supplied according to the timing of the decompression process.
[0057]
During the raster period R0, the decompressed image data CIDr0, MIDr0, YIDr0, and KIDr0 of the four colors CMYK are stored in the image memory 24 so that they can be accessed in parallel. The buffer 27 can read image data of four colors from an arbitrary area at an arbitrary timing and supply it to the print engine 12. When the print engine 12 is a tandem engine capable of printing in parallel with respect to four colors, as shown in FIG. 4 (f1), the print read buffer 27 has four image data CIDr0, for example. , MIDr0, YIDr0, and KIDr0 are simultaneously supplied in parallel to enable high-speed printing.
[0058]
Also, depending on the operation timing of the four engines in the print engine 12, if it is necessary to gradually shift the supply of the four image data CIDr0, MIDr0, YIDr0, and KIDr0, printing is performed as shown in FIG. The read-out buffer 27 reads out the respective image data from the read-out image memory 24 at different times, and supplies the read image data to the print engine 12.
[0059]
By providing two sets of decompressed image memories for storing the decompressed image data, the readout timing for supplying the image data to the print engine 12 can be arbitrarily set independently of the decompression process, Image data can be supplied corresponding to various printing engines 12.
[0060]
In the first embodiment, it is also possible to process RGBX image data and supply the CMYK image data to the tandem engine in parallel. In that case, the color conversion converter 33 needs to be configured to convert the image data into four colors. For example, by providing four color conversion converters 33, it is possible to perform color conversion from RGBX image data in parallel to CMYK four-color image data. In this case, the processing in the image processing apparatus 20 is the same as the example in FIG. 3, and only the last color conversion processing is performed in parallel for four colors, and CMYK image data is simultaneously supplied to the print engine. Is done.
[0061]
In the first embodiment, one of the two sets of decompressed image memories 24 and 25 is used as a write memory after decompression, and the other is used as a read memory for printing. The read area, read frequency, etc. can be controlled independently of the decompression process. Therefore, as in the second embodiment described later, it is possible to freely change the resolution and print. Furthermore, by appropriately controlling the timing of reading by the print readout buffer 27 and the readout area, it is possible to appropriately move the print image on the printing paper for printing.
[0062]
FIG. 5 is a diagram illustrating processing of the image processing apparatus when there is no change in resolution. In this example, the image processing apparatus 20 processes compressed image data corresponding to a resolution of 600 dpi, generates image data corresponding to 600 dpi that is the resolution of the print engine 12, and supplies the image data to the print engine 12. In FIG. 2, (a) to (f) correspond to (a) to (f) in FIGS. Further, (g) shows image data to be printed by the print engine 12.
[0063]
The compressed image data IDr0 to IDr5 in units of raster stored in the image buffer (band memory) 10 is read by the DMA controller 21 at the timing of each raster, supplied to the decompressor 22, and compressed image data IDr0 to IDr0 to IDr0. IDr5 is decompressed (process (c)). The write buffer 23 alternately writes the decompressed image data into the decompressed image memories 24 and 25 (process (c)). The decompressed image memory 24 is indicated by SRAM # 0, and the decompressed image memory 25 is indicated by SRAM # 1. Next, the decompressed image memories 24 and 25 are switched between the writing state and the reading state in the next raster period, and the decompressed image data is alternately read from the decompressed image memories 24 and 25 by the print readout buffer 27 (processing). (F)). The print read buffer 27 supplies the read decompressed image data to the print engine 12 in synchronization with the print timing HSYNC (or dot clock CLK) (process (f)). When the decompressor 22 uses a decompression algorithm that requires reference to the image data of the preceding raster, the decompressed image memory reads the decompressed image data in a time-sharing manner together with the print readout buffer 27 by the decompression read buffer 29. 24 and 25.
[0064]
As shown in FIG. 5, while writing is being performed on one of the decompressed image memories 24 and 25, reading is performed from the other of the decompressed image memories 24 and 25. The frequency of both processes is the same.
[0065]
FIG. 6 is a diagram illustrating processing of the image processing apparatus when converting to a high resolution. In this example, the image processing apparatus 20 processes compressed image data corresponding to a resolution of 300 dpi, generates image data corresponding to 600 dpi, which is the resolution of the print engine 12, and supplies the image data to the print engine 12.
[0066]
In order to perform printing with a 600 dpi print engine, the image data IDr0 to IDr5 corresponding to the 300 dpi resolution is read from the image buffer 10 every other raster period, decompressed, and stored in the decompressed image memories 24 and 25 in the written state. Write. On the other hand, from the decompressed image memories 24 and 25 in a read state, the decompressed image data is read out for each raster period by the print readout buffer 27 and supplied to the print engine 12. The decompression read buffer 29 reads the decompressed image data in the decompressed image memories 24 and 25 in the read state and supplies the decompressed image data to the decompressor 22 only when the decompressor 22 performs the decompression process. When the printing read buffer 27 has a memory of one raster capacity, it is not necessary to read the decompressed image data twice.
[0067]
In addition, while the image data IDr1 is being decompressed, depending on the decompression algorithm, the decompressed image memory 24 (SRAM # 0) may be simultaneously read in a time-sharing manner by the print readout buffer 27 and the decompression readout buffer 29. .
[0068]
When the image data supplied from the host computer 1 has a higher resolution, in contrast to the above, reading from the decompressed image memories 24 and 25 in the read state and the print engine are compared with the frequency of decompression by the decompressor 22. The frequency of supply of image data to 12 is low. As a result, dot image data thinned out at a predetermined ratio from high-resolution image data is supplied to the print engine 12 to enable printing of low-resolution images.
[0069]
The controller 30 appropriately controls the DMA controller 21 and the print read buffer 27 when the resolution is changed.
[0070]
As shown in FIG. 6, the image processing apparatus 20 in the first embodiment is provided with at least two sets of decompressed image memories 24 and 25 for temporarily storing the decompressed image data, and writes in one of the memories. In the meantime, reading from the other memory is performed independently of the writing. With this configuration, the frequency of reading from the decompressed image memory in the read state and the frequency of writing to the decompressed image memory in the write state from the decompressor 22 can be controlled separately, and the resolution of the image data can be controlled. Changes can be made freely.
[0071]
FIG. 7 is a diagram for explaining a print image moving process in the printing paper. (A)-(f) in FIG. 7 respond | corresponds to 2-6 (a)-(f). In the image buffer (band memory) 10, image data IDr0, IDr1, and IDr2 compressed in raster units are stored for each color of CMYK. Since the raster unit image data is compressed image data, the data length is variable.
[0072]
The compressed image data in the image buffer 10 is read by the DMA controller 21 in the order of low address to high address in raster units, and supplied to the decompressor 22. The decompressor 22 decompresses the compressed image data for one raster within the raster period R0 defined by the horizontal synchronization signal HSYNC, and the write buffer 23 writes the decompressed image data to the decompressed image memory 24 in the written state. (Process (c)). During the decompression process of the decompressor 22, if necessary, decompressed image data of the preceding previous raster is read from the other readout memory 25 by the decompression read buffer 29, and the decompression process is performed. It is supplied to the decompressor 22 in the form of a decompression process according to the timing. The decompressor 22 decompresses image data compressed by a predetermined decompression algorithm while referring to the preceding raster image data.
[0073]
In the next raster period R1, the writing state and reading state of the decompressed image memories 24 and 25 are switched, and the decompressed image data IDr1 of the next raster is written in the decompressed image memory 25 in the writing state. The raster decompressed image data IDr0 is read from the decompressed image memory 24 in the read state by the print read buffer 27, and in a data format suitable for the print engine 12, corresponding to the print timing of the print engine 12, the print engine 12 To be supplied. This process is performed in synchronization with the timing of the dot clock CLK of the print engine 12. At the same time, the image data IDr0 is read from the decompressed image memory 24 by the decompression read buffer 29 if necessary for decompression processing.
[0074]
The print read buffer 27 refers to the print read timing register 32 that stores the print start position and end information supplied by the print position setting unit 9, and arbitrarily reads the decompressed image data in the decompressed image memory 24 in the read state. Are read from the position to an arbitrary position and supplied in accordance with the print timing of the print engine 12. The readout area of the image data in the raster and the supply timing of the image data to the print engine 12 are controlled independently of the decompression target image data and the decompression timing of the decompressor 22 by the information set in the register 32. The
[0075]
Therefore, in the case of normal printing (f1), all the image data IDr0 for one raster is read from the read-out memory 24 in the raster period determined by the horizontal synchronization signal HSYNC and supplied to the print engine 12 at normal timing. Is done.
[0076]
Further, when it is desired to move the print image to the left side of the print paper PP (f2), the print read buffer 27 uses the image data in the decompressed image memory 24 in the read state in the raster according to the set value of the register 32. From the middle region, image data on the back side in the raster is read out in synchronization with the first timing of the raster period R1. As a result, as shown in the drawing, the image on the right side of the raster is printed in the printing paper PP, and the image moves leftward in the printing paper PP. However, during the raster period R1, the next raster image data IDr1 is all decompressed within the raster period R1. The timing of the decompression process is independent of the read timing of the print read buffer 27 and the like. When it is necessary to refer to the image data of the previous raster in the decompression process, the decompression read buffer 29 reads the image data for one raster from the memory 24 in the readout state, and supplies it to the decompressor 22. That is, in the period of raster R1, the decompressor 22 decompresses the image data IDr1 for the next one raster, and the decompression read buffer 29 reads the previous one raster image data IRr0 and supplies it to the decompressor. The printing read buffer 27 reads the image data IDr0 of the latter half of one raster and supplies it to the print engine 12 in synchronization with the dot clock CLK.
[0077]
Further, when it is desired to move the print image to the right side of the print paper PP (f3), the print read buffer 27 sets the image data IDr0 in the decompressed image memory 24 in the read state in the raster according to the set value of the register 32. Is read out from the first area in synchronization with the first timing of the raster period R1, and image data up to the middle of the raster is read out. Then, a part of the image data IDr0 is supplied to the print engine 12. As a result, an image on the left side of the raster is printed in the printing paper PP as shown in the figure, and the image moves rightward in the printing paper PP. The operation of the decompression read buffer 29 in this case is the same as in the case of (f2) above.
[0078]
As described above, the two sets of decompressed image memories 24 and 25 that hold the decompressed image data are provided and controlled alternately in the writing state and the reading state, so that the printing read buffer 27 is independent of the decompression process. The image data in the independent raster area can be read out from the memories 24 and 25 in the read state and supplied to the print engine 12 at this timing. Accordingly, as shown in FIG. 7, image data in an arbitrary region can be supplied to the print engine 12 at an arbitrary timing for image data in the raster and printed. That is, a print image in an arbitrary area can be moved to an arbitrary position in the printing paper and printed without adversely affecting the decompression process.
[0079]
When RGBX image data is stored in the image buffer 10, any color data from RGBX image data to CMYK image data is converted by the color conversion converter 33 between the print buffer 27 and the print engine 12. Is converted to Accordingly, the printing read buffer 27 is controlled for the read timing in consideration of the time required for the color conversion.
[0080]
[Second Embodiment]
FIG. 8 is a view showing a part of the electrophotographic apparatus in the second embodiment. In the first embodiment, the decompressor 22 requires the ability to decompress four types of compressed image data within one raster period. Even when the attribute data X is not provided, the decompressor 22 must decompress the compressed image data of three colors of RGB. Therefore, in the second embodiment, two sets of decompressed image memories 24 and 25 are set, and at the same time, two sets of compressed image memories 34 and 35 for temporarily storing compressed image data, and four sets of decompression units 220 to 226. Have Similar to the decompressed image memories 24 and 25, the two sets of compressed image memories 34 and 35 are alternately controlled in a writing state and a reading state.
[0081]
As shown in FIG. 8, the decompression unit 220 includes a decompressor 22 for one color image data and decompressed image data 24 and 25, unlike the first embodiment. However, since the compressed image memories 34 and 35 are SRAM # 0, 1, the decompressed image memories 24 and 25 are SRAM # 2 and SRAM # 3. The other thawing units 222, 224, and 226 have the same configuration as the thawing unit 220 shown in the lower half of FIG. The decompression unit has a read buffer 38 for reading compressed image data from the compressed image memories 34 and 35 and supplying the compressed image data to the decompressor 22.
[0082]
Along with the provision of four sets of decompression units, compressed image memories 34 and 35 and a write buffer 39 are provided between the DMA controller 22 and those decompression units, one of which is in a writing state and the other is in a reading state. . Each of these compressed image memories 34 and 35 has at least a capacity for holding four sets of compressed image data for one raster. Similarly to the decompressed image memories 24 and 25, the compressed image memories 34 and 35 are alternately controlled in a writing state and a reading state.
[0083]
Also in the case of FIG. 8, the controller 30 is provided in the image processing apparatus 20 and controls the timing in the DMA controller 21, the DMA write buffer 39, and the decompression unit. The controller 30 is supplied with a horizontal synchronization signal HSYNC or a dot clock CLK corresponding to the timing of the print engine.
[0084]
When RGBX image data is stored in the image buffer 10, RGBX data is decompressed by the four decompression units 220 to 226, supplied to the color conversion converter 33, and color converted according to the attribute data X. Image data is supplied to the print engine 12. Also in the present embodiment, the print read buffer 27 and the converter 33 constitute image data supply means for supplying CMYK image data to the print engine 12.
[0085]
FIG. 9 is a diagram illustrating processing of the image processing apparatus when there is no change in resolution in the second embodiment. In this example, RGBX image data (or attribute data) is stored in the image buffer 10, and C-plane image data is supplied to the print engine 12.
[0086]
In the raster period R0, RGBX compressed image data IDr0 for one raster stored in the image buffer 10 is read by the DMA controller 21 and stored in the compressed image memory 34 in the written state by the DMA write buffer 39. (Process (c1)). Each of the compressed image memories 34 and 35 can store at least one raster of four types of data.
[0087]
Next, in the raster period R1, similarly, the compressed image data IDr1 of RGBX for one raster stored in the image buffer 10 is read by the DMA controller 21, and the writing state is compressed by the DMA write buffer 39. It stores in the image memory 35 (process (c1)). At the same time, the read buffer 38 in the decompression units 220 to 226 reads the compressed image data corresponding to RGBX from the compressed image memory 34 in the read state, and supplies it to the decompressor 22 in each decompression unit. Accordingly, the compressed image data IDr0 (RGBX) is decompressed in parallel by the decompressors 22 in the four decompression units, and written into the decompressed image memory 24 in the written state by the write buffer 23 in each unit. (Process (c4)).
[0088]
In the next raster period R2, the next compressed image data IDr2 is read by the DMA controller 21 and written to the compressed image memory 34 in the written state by the DMA write buffer 39 (process (c1)). Concurrently, RGBX compressed image data IDr1 is read out from the compressed image memory 35 in the read state by the read buffer 38, decompressed by the respective decompressors 22, and stored in the decompressed image memory 25 in the written state. Written (process (c4)). The RGBX decompressed data IDr0 stored in the decompressed decompressed image memory 24 is read out by the print readout buffer 27 and supplied in parallel to the color conversion converter 33 (process (f)). Similar to the first embodiment, the read and supply timings are controlled to an arbitrary timing independently of the decompression timing, and an arbitrary area is read and supplied. The color conversion converter 33 performs color conversion processing according to the attribute data X from the RGBX decompressed data, generates C (cyan) image data IDr0 (C), and supplies the image data IDr0 (C) to the print engine 12.
[0089]
In the raster period R2, the decompressor 22 decompresses the RGBX compressed image data IDr1, but when it is necessary to refer to the previous image data, the decompression read buffer 29 in the decompression unit is in the read state. The decompressed image data IDr0 is read in parallel from the decompressed image memory 24 (SRAM # 2) in accordance with the timing of the decompression process, and is supplied to the corresponding decompressor 22 respectively.
[0090]
As shown in FIG. 9, decompression of compressed image data and writing to decompressed image memories 24 and 25, reading from decompressed image memories 24 and 25, and supply to the print engine after color conversion are performed for each raster period. Each is done each time. Therefore, 600 dpi image data is supplied to the print engine 12 and printed with respect to RGBX image data having a resolution of 600 dpi.
[0091]
FIG. 10 is a diagram illustrating processing of the image processing apparatus when changing to a high resolution in the second embodiment. In this example, 600 dpi C-plane decompressed image data IDr0 (C) is generated from 300 dpi RGBX compressed image data IDr0 (RGBX). Therefore, the reading process of the DMA controller 21 and the decompressing process of the decompressing unit 22 in the decompressing unit are performed once every two raster periods, and the reading process of the print readout buffer 27 in the decompressing unit is performed every raster period. Done. Therefore, the printing read buffer 27 has a processing frequency twice that of the decompressor. When the resolution is lowered, the frequency of the above process is reversed. By providing two sets of the decompressed image memories 24 and 25 and setting one to the writing state and the other to the reading state, the above frequency can be easily changed.
[0092]
First, in the raster period R0, the compressed data IDr0 (RGBX) of RGBX is read by the DMA controller 21 and written into one compressed image memory 34 (processing (c1)). In the next raster period R1, the read buffer 38 in the decompression unit is supplied with the compressed data IDr0 from the corresponding compressed image memory 34 to the decompressor 22, decompressed, and written in the decompressed image memory 24 (processing ( c4)).
[0093]
In the next raster period R2, each decompressed image data (or attribute data X) is read from the decompressed image memory 24 (SRAM # 2) in the read state by the print readout buffer 27 and supplied to the color conversion converter 33. (Process (f)). Then, the color-converted image data IDr0 (C) is supplied to the print engine 12. In parallel, the compressed image data IDr1 (RGBX) of the next raster is read by the DMA controller 21 and written to the compressed image memory 35 in the written state.
[0094]
In the next raster period R3, the corresponding data IDr1 (RGBX) is read from the compressed image memory 35 (SRAM # 1) in the read state by the read buffer 38, supplied to each decompressor 22, and decompressed. At this time, if necessary, the previous decompressed image data IDr0 (RGBX) is read from the decompressed image memory 24 in the read state by the decompression read buffer 29 and supplied to the decompressor 22 in accordance with the decompression process. Is done. In the raster period R3, the printing read buffer 27 again reads the decompressed RGBX image data IDr0 (RGBX) from the decompressed image memory 24 in the readout state, and the color conversion converter 33 converts the image data into C plane image data. And supplied to the print engine 12. As a result, 600 dpi image data having a double resolution is supplied to the print engine 12.
[0095]
The compressed image data IDr2 (RGBX) of the next raster is also read out and decompressed in the same manner, and then color-converted twice and supplied to the print engine.
[0096]
Although not shown, also in the second embodiment, the printing paper as shown in FIG. 7 in the first embodiment is controlled by controlling the reading area and the reading timing by the print reading buffer 27. It is possible to print by moving the print image to any position.
[0097]
Next, in contrast to the first embodiment, image processing such as decompression is performed on the CMYK image data in the second embodiment, and the image data is supplied to a single-type print engine. A case where image data is supplied to a single print engine by performing decompression and color conversion image processing on RGBX image data, and a tandem print engine performing image processing on CMYK image data The case where image data is supplied to will be sequentially described.
[0098]
FIG. 11 is a timing chart in the case of performing image processing such as decompression on CMYK image data and supplying the image data to a single-type print engine. In this case, only the decompression unit corresponding to CMYK among the four decompression units 220 to 226 performs the decompression process. In this case, the compressed image data in the image buffer 10 is the same as in FIG.
[0099]
In the raster period R0, the DMA controller 21 reads compressed image data CIDr0 for one raster of the C plane from the image buffer 10 and writes it to the compressed image memory 34 (c1). Next, during the raster period R1, while the DMA controller 21 reads the next compressed image data CIDr1 and writes it into the compressed image memory 35 (c1), the read buffer 38 reads the image data CIDr0 from the compressed image memory 34 in the read state. And supplied to the decompressor 22. The decompressor 22 decompresses the compressed image data CIDr0 while referring to the image data of the previous raster as necessary, and writes it in the decompressed image memory 24 in the written state. In this decompression process, the decompression process is performed at the same speed as the video clock (or dot clock) CLK synchronized with the horizontal synchronization signal HSYNC.
[0100]
In the raster period R2, the print readout buffer 27 reads the decompressed image data CIDr0 from the decompressed image memory 24 in the readout state, and supplies the decompressed image data CIDr0 to the print engine 12. This reading and supplying are also performed at a constant speed with respect to the video clock (or dot clock).
[0101]
FIG. 12 is a timing chart when image data is supplied to a single-type print engine by performing decompression and color conversion image processing on RGBX image data. The RGBX compressed image data in the image buffer 10 is the same as in FIG.
[0102]
In the raster period R0, the DMA controller 21 reads the RGBX compressed image data RIDr0, GIDr0, BIDr0, and Xr0 of the raster r0 from the image buffer, and the DMA write buffer 39 stores the compressed image data in the written state. Write to each area of the memory 34 (c1).
[0103]
In the next raster period R1, the four decompression units read the corresponding compressed image data from the compressed image memory 34 in the read state, perform decompression processing, and write it into the decompressed image memory 24 (c4). In the third embodiment, unlike the second embodiment, four decompression units are provided in parallel, so that the decompressor 22 in each decompression unit is equal in speed to the video clock (dot clock) CLK. The decompression process can be performed. At this time, if necessary, the decompression read buffer 29 reads the image data from the decompressed image memory 25 and supplies it to each decompressor.
[0104]
In the next raster period R2, RGBX decompressed data is read from the decompressed image memory 24 in the four decompressing units and supplied to the color conversion converter 33 (f). Then, it is color-converted into C plane image data CIDr0 according to the attribute data X and supplied to the print engine 12. Supply to the print engine is also performed at a constant speed using a video clock (dot clock).
[0105]
FIG. 13 is a timing chart when image processing is performed on CMYK image data and image data is supplied to a tandem print engine. The compressed image data in the image buffer 10 in this case is the same as that in FIG.
[0106]
In the raster period R0, the DMA controller 21 reads CMYK compressed image data CIDr0, MIDr0, YIDr0, and KIDr0 for one raster from the image buffer 10, and the DMA write buffer 39 stores the image data in the compressed image memory 34. Are written in the corresponding areas (c1).
[0107]
In the next raster period R1, the read buffer 38 in each decompression unit reads the corresponding image data, and the decompressor 22 performs decompression processing. Then, the write buffer 23 writes the decompressed image data into the decompressed image memory 24 in the written state. These decompression processes are performed at a constant speed on the image clock (or dot clock) CLK in parallel by the four decompression units.
[0108]
In the next raster period R2, the printing read buffer 27 in each decompression unit reads the decompressed CMYK image data from the decompressed image memory 24 and supplies it to the print engine 12 at a predetermined timing (f). The read and supply timings by the print read buffer 27 are appropriately controlled according to the operation of the tandem print engine. The timing is controlled by the controller 30 as in the second embodiment.
[0109]
Although not shown, RGBX compressed image data can be decompressed and CMYK image data can be supplied to a tandem printing engine. In this case, as shown in FIG. 12, RGBX data is read from the image buffer 10, decompressed in parallel by the decompression unit, converted into CMYK image data by the color conversion converter 33, and the tandem printing engine 12. Are supplied at a predetermined timing.
[0110]
【The invention's effect】
As described above, according to the image processing apparatus of the present invention, the compression processing is performed on both the compressed image data in the first color space such as RGB and the compressed image data in the second color space such as CMYK. For image data in one color space, color conversion is performed to image data in the second color space after decompression processing. Therefore, even if image data of the first or second color space is supplied from the host computer, the decompression process can be performed in the same manner and supplied to the print engine, and the printing speed can be increased.
[0111]
According to the image processing apparatus of the present invention, by providing an image memory having a capacity for recording the decompressed image data for at least the colors of the first color space, the first color space such as RGB is provided. Image data can be read in parallel and color-converted into image data in a second color space such as CMYK. Therefore, the time required for color conversion is a speed synchronized with the dot clock, and the printing delay due to color conversion is small.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an electronic printing apparatus according to a first embodiment.
FIG. 2 is a timing chart when image processing is performed on CMYK compressed image data.
FIG. 3 is a timing chart illustrating a case where image data is supplied to a single-type print engine by performing decompression and color conversion image processing on RGBX image data.
FIG. 4 is a timing chart when image processing is performed on CMYK image data and image data is supplied to a tandem print engine.
FIG. 5 is a diagram illustrating processing of the image processing apparatus when there is no change in resolution.
FIG. 6 is a diagram illustrating processing of the image processing apparatus when converting to high resolution.
FIG. 7 is a diagram for explaining a print image movement process in a print sheet;
FIG. 8 is a diagram illustrating a configuration of an electronic printing apparatus according to a second embodiment.
FIG. 9 is a diagram illustrating processing of the image processing apparatus when there is no change in resolution in the second embodiment.
FIG. 10 is a diagram illustrating processing of the image processing apparatus when changing to a high resolution in the second embodiment.
FIG. 11 is a timing chart in the case where image processing such as decompression is performed on CMYK image data and image data is supplied to a single-type print engine.
FIG. 12 is a timing chart when image data is supplied to a single-type print engine by performing image processing for decompression and color conversion on RGBX image data.
FIG. 13 is a timing chart when image processing is performed on CMYK image data and image data is supplied to a tandem print engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Host computer, 2 Electronic printing apparatus, 10 Image data, 12 Print engine, 20 Image processing apparatus, 21 DMA controller, 22 Decompression machine, 24, 25 Decompression image memory, 27 Printing read buffer, 29 Decompression reading buffer, 33 Color conversion converter, 34, 35 Compressed image memory

Claims (3)

In a printing image processing apparatus that decompresses compressed image data for each color in a first color space and supplies the decompressed image data in the second color space to a print engine that prints with toner in the second color space.
The compressed image data of the first color space, and the compressed color data of each raster having different data lengths, the plurality of color data of each raster is converted to a cycle of a print timing synchronization signal of the print engine. A decompressor that decompresses at a speed that is twice the number of colors of the sync signal in sequence ,
A decompressed image data memory for storing decompressed image data of the first color space decompressed by the decompressor;
At the printing timing of the print engine, the decompressed image data in the first color space is read from the decompressed image data memory, converted into decompressed image data in the second color space, and the decompressed image in the second color space. Image data supply means for supplying data to the print engine;
The decompressor decompresses the compressed image data of all the colors in the first color space for each cycle of the synchronization signal of the printing timing, and stores the decompressed image data in the decompressed image data memory. The decompressed image data of each color in the second color space is supplied to the print engine in synchronization with a print timing synchronization signal ,
The image processing apparatus for printing , wherein the decompressor decompresses the compressed image data of the current raster while referring to the decompressed image data of the previous raster stored in the decompressed image data memory .   The printing image processing apparatus according to claim 1, wherein the decompressed image data memory holds decompressed image data of the first color space for at least one raster.   2. The printing method according to claim 1, wherein the decompressed image data memory stores at least decompressed image data corresponding to the number of colors in the first color space, and reads decompressed image data corresponding to the number of colors. Image processing device.

Images