JP2008312264A - Image processing device - Google Patents

Abstract

The present invention reduces image quality degradation due to compression processing and inking processing, realizes high compression ratio especially for images containing many achromatic colors, and further improves the quality of both compressed and uncompressed images when performing signal conversion. A high quality image is generated by reducing the difference.
A control circuit controls the whole, reads an original image with a scanner, converts a RGB signal into a CMY signal by a color conversion unit, and converts a CMY signal from a CMY signal to a C′M′Y′K by an inking processing unit. A signal is generated, and after this inking process, the compression unit 1004 compresses the C′M′Y′K signal by the frequency conversion method and stores it in the memory 1005. The compressed data stored in the memory 1005 is decoded by the decoding unit 1006 Then, printing is performed by the printer engine 1007.
[Selection] Figure 1

Description

  The present invention relates to an image processing apparatus for improving the image quality of an electronic image by sharpening or smoothing.

  Conventional systems such as color printers, color copying machines, and printing fields that print on paper or the like using toner or ink output C, M, Y, and K signals in combination. However, the original document to be output is an R, G, B signal because an optical reading means such as a scanner is used, and processing for converting from 3 signals to 4 signals is required. As the conversion process, there are a method of directly converting an RGB signal into a CMYK signal, and an inking process for generating a CMYK signal after conversion from an RGB signal into a CMY signal.

  On the other hand, the data amount of the input / output image becomes 100 MB (RGB) or 133 MB (CMYK) at 600 dpi / A4 (8 bits), so it is necessary to reduce the memory capacity by performing compression processing. In addition, when irreversible compression is used, the image quality is different from that of a non-compressed image. Therefore, it is necessary to suppress deterioration in image quality when compression is used. As a technique for meeting these requirements, for example, there are those disclosed in the following documents.

Literature 1: Takashi Yabe, JP-A-8-18807 Literature 2: Takahiro Yamauchi, “Image Processing by Processing of Compressed Information” PCSJ91, 2-4, pp37-40, 19991-10
The method disclosed in the above-mentioned document 1 prevents the image quality deterioration due to noise of an input device such as a scanner from being emphasized by the compression process by providing a smoothing process before the compression process.

  The method disclosed in the above-mentioned document 2 performs enlargement / reduction and filtering processing with the code compressed using the DCT method which is one of frequency conversions used in compression processing.

  However, although the method disclosed in the above-mentioned document 1 can reduce the deterioration of image quality due to the compression process, the UCR (Under Color Reduction) process is performed as the inking process after compression to convert the 3-color signal into the 4-color signal. It has not been done to reduce image quality degradation due to quantization. Also, the UCR or lower processing is always performed on an image that has been subjected to compression processing, but it is not considered to handle both uncompressed images and compressed images. From three-color signals according to the properties of images such as characters and photographs, Conversion processing to four-color signals is not performed.

  Moreover, although the method disclosed in the above-mentioned document 2 performs a filtering process or the like with a compressed bear, the consistency between the compression process and other image processes is not mentioned.

  As described above, image quality deterioration due to compression processing can be reduced. However, image quality by quantization when converting a three-color signal into a four-color signal by performing UCR (Under Color Reduction) processing as an inking process after compression. Deterioration is not reduced, and images that have undergone compression processing are always processed below the UCR, but are not considered to handle both uncompressed images and compressed images. Conversion processing from 3 color signals to 4 color signals according to the nature of the image is not performed, and further, filtering processing is performed with the compressed bear and the consistency between the compression processing and other image processing is touched. There was a problem that not.

  Therefore, the present invention reduces image quality degradation due to compression processing and inking processing, realizes high compression ratio compression especially for images containing many achromatic colors, and further, both compressed images and non-compressed images when performing signal conversion An object of the present invention is to provide an image processing apparatus that generates a high-quality image by reducing the difference in image quality.

  An image processing apparatus according to the present invention includes a color conversion unit that converts a color of an input color image signal according to a condition for outputting, and a processing unit that performs an inking process on the image signal converted by the color conversion unit. And a compression means for compressing the image signal subjected to the inking process by the processing means by the frequency conversion method, and a decoding means for decoding the image signal compressed by the compression means by the frequency conversion method.

  The image processing apparatus according to the present invention includes a compression unit that compresses an input color image signal, a decoding unit that decodes the image signal compressed by the compression unit, and an output of the image signal decoded by the decoding unit. First color conversion means for converting into color separation signals in accordance with the above conditions, second color conversion means for converting into color separation signals in accordance with the conditions for outputting the input color image signal, and It comprises switching means for switching between the color separation signal from the first color conversion means and the color separation signal from the second color conversion means, and control means for controlling switching by this switching means.

  The image processing apparatus according to the present invention includes a first color conversion unit that converts an input color image signal into a color separation signal, and the input color image signal that is different from the first color conversion unit. Second color conversion means for converting to color, switching means for switching between the color separation signal from the first color conversion means and the color separation signal from the second color conversion means, and switching by this switching means And control means for controlling according to the nature of the input color image signal.

  An image processing apparatus according to the present invention includes a switching unit that switches input of an input color image signal, a compression unit that compresses the input color image signal when switched to one by the switching unit, and the compression unit Decoding means for decoding the image signal compressed in step 1, and the image signal decoded by the decoding means when switched to one by the switching means, and the input color when switched to the other by the switching means. Controls color conversion means for converting an image signal into a color separation signal, processing means for performing inking processing on the color separation signal converted by the color conversion means at a set black rate, and switching of the switching means. The control means is configured to set different black ratios in the processing means depending on whether the switching means is switched to one or the other.

  An image processing apparatus according to the present invention includes a switching unit that switches input of an input color image signal, a compression unit that compresses the input color image signal when switched to one by the switching unit, and the compression unit Decoding means for decoding the image signal compressed in step 1, and the image signal decoded by the decoding means when switched to one by the switching means, and the input color when switched to the other by the switching means. Color conversion means for converting an image signal into a color separation signal, processing means for performing an inking process on the color separation signal converted by the color conversion means, switching of the switching means and controlling the switching means to one side The control means is configured to set different inking processes in the processing means depending on whether switching is performed or switching to the other.

  The image processing apparatus according to the present invention includes a first color conversion means for converting an input color image signal into a color separation signal using a first inking method, and the input color image signal as a second black ink. Second color conversion means for converting into a color separation signal using an insertion method; switching means for switching between the color separation signal from the first color conversion means and the color separation signal from the second color conversion means; And control means for controlling switching by the switching means.

  The image processing apparatus according to the present invention performs a blacking process at a set black rate on a color conversion unit that converts an input color image signal into a color separation signal and the color separation signal converted by the color conversion unit. It comprises processing means, identification means for identifying images such as characters and photographs of the input color image signal, and setting means for setting different black rates in the processing means according to the identification result of the identification means. ing.

  The image processing apparatus according to the present invention includes a first color conversion means for converting an input color image signal into a color separation signal using a first inking method, and the input color image signal as a second black ink. Second color conversion means for converting into a color separation signal using an insertion method; switching means for switching between the color separation signal from the first color conversion means and the color separation signal from the second color conversion means; And an identification unit for identifying an image such as a character or a photograph of the input color image signal, and a control unit for controlling switching by the switching unit in accordance with the identification result of the identification unit.

  As described above in detail, according to the present invention, the image quality deterioration due to the compression process and the inking process is reduced, and a compression with a high compression rate is realized particularly for an image containing a large number of achromatic colors. It is possible to provide an image processing apparatus that generates a high-quality image by reducing a difference in image quality between both an image and an uncompressed image.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of a digital color copying machine to which the image processing apparatus according to the first embodiment of the present invention is applied. This digital color copying machine includes a scanner 1001 that reads a document as image data, a color conversion unit 1002 that converts an input image into an ink signal CMY, an inking process unit 1003 that generates a C′M′Y′K signal from the CMY signal, A compression unit 1004 that compresses the C′M′Y′K signal, a memory 1005 that stores the compressed data, a decoding unit 1006 that decodes the compressed data, a printer engine 1007 that prints the decoded data, and a control circuit that controls the entire copying operation 1100.

  Next, an outline of processing of this digital color copying machine will be described.

  The basic operation of the digital color copying machine is to read an original image to be copied from a scanner 1001 and convert it into an RGB signal 1008, convert it to a CMY signal 1009 by a color conversion unit 1002, and further convert C'M 'by an inking process unit 1003. The Y′K signal 1010 is converted and compressed by the compression unit 1004, and the compressed signal 1011 is stored in the memory 1005. The compressed signal 1011 is read from the memory 1005 at any time, and a decoded signal 1012 is generated by the decoding unit 1006 and output by the printer engine 1007 to obtain a copy of the original image.

  Next, the operation of the inking unit 1003 will be described using the configuration example shown in FIG. The inking process unit 1003 includes a minimum value circuit 1003-1, a multiplication circuit 1003-2, and difference circuits 1003-4, 1003-5, and 1003-6.

  The inking process generates a C'M'Y'K signal from the CMY signal by performing the process shown in the following equation.

K = k × min (C, M, Y) (min: minimum value in C, M, Y)
(K: black rate, 100% → 1, 0% → 0)
C ′ = C−KM ′ = M−KY ′ = Y−K Now, the operation will be described assuming that the black rate is 100%. The minimum value is obtained from the CMY signal using the minimum value circuit 1003-1, and the multiplication circuit 1003-2 is obtained. Is multiplied by the black rate k1003-3 to generate a K signal 1010-4, and C′1010-1, M′1010-2, and Y are generated using the difference circuits 1003-4, 1003-5, and 1003-6. '1010-3 is generated.

  FIG. 3 shows the conversion result with specific numerical values. As shown in FIG. 3 (a), the difference in signal due to noise or the like is C or M where the difference from the adjacent pixel is 5, but as shown in FIG. 3 (b), C ′ after inking. In M and M ', it can be seen that the maximum is 15.

  Next, the compression unit 1004 will be described using the configuration example of FIG. The compression unit 1004 includes a line memory 1004-1, a DCT 1004-2, and an encoder 1004-3.

The line memory 1004-1 holds values so that signals sent in raster units can be handled in block units of 4 × 4 pixels by the DCT 1004-2. The DCT 1004-2 performs the following DCT operation in the known 4 × 4 unit.

  N is the number of blocks = 4, x [m, n] is a pixel value, and X [u, v] is a DCT coefficient.

  Next, DCT operation result 1004-4 (C is 1004-4-1, M is 1004-4-2, Y is 1004-4-3, and K is 1004-4-4) is encoded by encoder 1004-3. The encoded signal is output as a compressed signal 1011 and stored in the memory 1005.

  In general, in an image signal, when frequency conversion is performed, a spectrum is collected in a low-frequency component rather than a high-frequency component. Therefore, by encoding only the low-frequency component, compression with irreversible compression efficiency can be performed.

  FIG. 5 shows an example of a 4 × 4 DCT calculation result for one signal and a compressed signal. The code amount can be reduced by about 20% by simply DCT-converting an 8-bit image signal and removing 10 high-frequency components by the encoder 1004-3 and allocating 10 bits to the remaining frequency components (black frames). As in this example, encoding of low-frequency components using frequency conversion is generally performed, and thus only an outline description will be given, but similar processing is performed on each CMYK signal.

  Next, the operation of the decoding unit 1006 will be described with reference to FIG.

The compressed signal 1011 is read from the memory 1005, and the inverse DCT operation of the following formula 2 is performed to decode the image signal.

  N is the number of blocks = 4, X [u, v] is a DCT coefficient, and x [m, n] is a decoded pixel value.

  In the decoded image signal shown in (b) of FIG. 6, the variation in pixel values is less than that of the original image shown in FIG. 5. This is because a compression method using frequency conversion generally performs encoding by removing high frequency components, and therefore compression processing is performed in combination with low-pass processing. Further, in the compression using frequency conversion after inking as in this embodiment, the variation in the value of a certain color component is locally reduced after inking as shown by Y ′ in FIG. Since values other than K are close to 0, the compression efficiency can be increased by using a frequency conversion method for compression after inking.

  FIG. 7 shows an example in which 4 × 4 CMY signals are inked, compressed and decoded. In the present embodiment, the encoder 1004-3 has been described with fixed-length coding, but it is configured with only a small value such as a signal with many 0s such as Y 'and Y' and M 'signals shown in FIG. A further compression rate can be achieved by performing variable length coding on the signal to be processed.

  As described above, according to the first embodiment, by using frequency conversion compression after inking, noise due to inking processing can be suppressed by the low-pass effect and compression efficiency can be improved due to the characteristics of inking processing. it can.

  In this embodiment, UCR is used as the inking method, but other inking methods such as GCR (Gray Component Removal) can also be used.

  Next, a second embodiment will be described.

  FIG. 8 shows the overall configuration of a digital color copying machine to which the image processing apparatus according to the second embodiment of the present invention is applied.

  This digital color copying machine includes a scanner 2001 that reads an original as an RGB image signal, a selector 2002 that sends the image signal to the compression unit 2003 or the color conversion unit (2) 2007, a compression unit 2003 that compresses, stores, and decodes the image signal, Memory 2004, decoding unit 2005, color conversion unit (1) 2006 for converting compressed / decoded signals into CMYK signals for printers, color conversion unit (2) 2007 for converting uncompressed signals into CMYK signals for printers, color conversion unit 2006 Alternatively, it includes a selector 2008 that selects a signal from the color converter 2007 and sends it to the printer engine 2009, a printer engine 2009 that prints out an image, and a control circuit 2100 that controls the entire copying operation.

  An outline of processing of this digital color copying machine will be described. During normal copying, the control circuit 2100 sends the RGB image signal 2010 from the scanner 2001 to the color conversion unit 2007 by the selector 2002 in response to the switching signal 2016, and the color conversion unit 2007 converts it into a CMYK signal that can be printed out by the printer engine 2009. The selector 2008 sends the data to the printer engine 2009 for printing.

  When a function called electronic sort as shown in FIG. 9 is operated, the RGB image signal 2010 is sent to the compression unit 2003 by the selector 2002, and irreversible compression processing is performed to store the compressed data 2011 in the memory 2004. Arbitrary compressed data is read from the memory 2004, decoded by the decoding unit 2005, converted into a CMYK signal by the color conversion unit 2006, sent to the printer engine 2009 by the selector 2008, and printed out.

  Next, operations of the compression unit 2003 and the decoding unit 2005 will be described with reference to FIGS. As shown in FIG. 10, the compression process performs a known four-value one-dimensional error diffusion process using the threshold value and the quantization value shown in FIG. 11. A total of 24 bits for each 8 bits of the RGB signal is compressed to a total of 6 bits and a data amount of 25% of the representative value of each 2 bits of the RGB signal. The compressed data 2011 is stored in the memory 2004 and then decoded by the decoding unit 2005.

  Next, the color conversion unit (1) 2006 and the color conversion unit (2) 2007 will be described. The color conversion process is a process of converting RGB3 signals into CMYK4 signals to be printed by the printer engine 2009. FIG. 12 shows an example of a color conversion table. If all values of an 8-bit RGB3 signal are stored in a lookup table (LUT), 256 × 256 × 256 (input RGB) × 4 × 8 bits (output CMYK) = 64 Mbytes. In addition, as shown in FIG. 12, the input RGB does not have all cases, and has a table that is thinned at a constant interval, and performs a known interpolation output. In this example, since it has 15 steps, the LUT is only 23 KB.

  However, if the non-compressed data and the compressed data are color-converted by the same method, the conversion error between them becomes large even when viewed in units of several pixels. Therefore, the color conversion unit 2007 is configured using the same interpolation LUT 2007-1 as illustrated in FIG. 13 and the color conversion unit 2006 is illustrated in FIG.

  As shown in FIG. 14, the color conversion unit 2006 includes D-FFs 1006-1 to 1006-9, averaging circuits 2006-11 to 1006-13, and an interpolation LUT 2007-1, and before input of the interpolation LUT 2007-1. By taking the average of several pixels, the conversion error between them is reduced.

  FIG. 15 shows a conversion example. A case where the compressed image signal (decoded signal) 2012 shown in FIG. 15B of the original image 2010 shown in FIG. 15A is converted using the color conversion unit (2) 2007 at the time of compression is shown in FIG. 15 (c) and 15 (e) show a case where the conversion is performed using the color conversion unit 2006 during compression, and a case where the conversion is performed using the color conversion unit (2) 2007 during non-compression. (F). It can be seen that the conversion using the color conversion unit 2006 has fewer conversion errors and the difference between the compressed and non-compressed images is smaller than the conversion using the color conversion unit (2) 2007 during compression.

  As described above, according to the second embodiment, the color difference between the two can be reduced by changing the color conversion between compression and non-compression. In this embodiment, the color conversion table is shared, but it may be provided separately for compression and non-compression.

  Next, a modification of the second embodiment will be described.

  FIG. 16 shows the overall configuration of a digital color copying machine to which an image processing apparatus according to a modification of the second embodiment is applied.

  In FIG. 16, only the color conversion unit (3) 2017 and the inking processing unit 2018 are different, and the other processes are the same as those in the second embodiment, so the same reference numerals are given and description thereof is omitted. The inking processing unit 2018 will be described.

  FIG. 17 shows a table of the color conversion unit 2017, which is a table for outputting CMY signals in response to RGB signal inputs, and is composed of 15 steps as in the second embodiment, and performs known interpolation output for input values. .

  FIG. 18 shows a configuration example of the inking processing unit 2018. The inking processing unit 2018 includes a minimum value circuit 2018-1, a multiplying circuit 2018-2, difference circuits 2018-4 to 2018-6, and an inking rate memory 2018-7.

  This is the same as in the first embodiment except that the black rate k 2018-3 is switched between compression and non-compression from the black rate memory 2018-7 by the switching signal 2016 from the control circuit 2100.

  FIG. 19 shows a comparison of color conversion and inking processing for a compressed image and an uncompressed image. When compressed images and uncompressed images are processed with the same black rate, the signal varies greatly. By switching the black rate of 100% when uncompressed to 50% when compressed, the variation of the compressed image is suppressed. I understand.

  As described above, according to the modification of the second embodiment, the degree of variation in the value due to the compression process can be suppressed by changing the black rate of the inking process during compression and non-compression. It can improve the feeling of interference.

  In this embodiment, the black rate is switched by the same blacking method, but the image quality can be improved in the same manner even if the blacking method itself is switched.

  Next, a third embodiment will be described.

  FIG. 20 shows the overall configuration of a digital color copying machine to which an image processing apparatus according to the third embodiment of the present invention is applied.

  This digital color copying machine includes a scanner 3001 that reads a document, an identification device 3002 that generates a character / photo identification signal 3007 for an image signal 3006, a color conversion 3003 that converts the image signal 3006 into a CMY signal for a printer, and an inking process. And an inking process unit 3004 for generating a C′M′Y′K signal from the CMY signal and a printer engine 3005 for printing an image.

  An outline of processing of this digital color copying machine will be described. The identification device 3002 generates an identification signal 3007 for identifying whether the RGB image signal 3006 is a character or a photograph, and converts the RGB image signal 3006 into a CMY signal 3008 by color conversion 3003. From the CMY signal 3008, the black rate of the inking unit 3004 is changed in accordance with the identification signal 3007 to output a C'M'Y'K signal 3009, and the printer engine 3005 prints it out.

  FIG. 21 shows a configuration example of the identification device 3002. The identification device 3002 includes a line memory 3002-1, average processing circuits 3002-2-1 to 3002-2-4, a selector 3002-3, D-FFs 3002-12-1 to 3002-12-12, and a maximum value comparator 3002. -7, a minimum value comparator 3002-8, a difference unit 3002-9, and a comparator 3002-11.

  As shown in FIG. 22, the identification device 3002 displays text as a pixel having a large change if (maximum value−minimum value) in the 3 × 3 matrix of the average value of RGB signals is larger than the difference threshold 3002-10, and photographs if it is small. judge. In operation, data in units of lines is stored in the line memory 3002-1, and the average of the RGB3 signals is obtained by the average processing circuit 3002-2. The result of average processing by the selector 3002-3 and the average unprocessed data are selectively output so that three lines out of four lines are extracted.

  With this configuration, raster data is processed without stopping the scanner 3001. Then, each line is output to the maximum value comparator 3002-7 and the minimum value comparator 3002-8, the difference between them is obtained by the differencer 3002-9, and compared with the difference threshold 3002-10 by the comparator 3002-11. If it is larger, “1” is output to the identification signal 3007 as a character, and if it is smaller, “0” is output to the identification signal 3007 as a photograph.

  FIG. 23 shows a configuration example of the inking process unit 3004. The inking processing unit 3004 includes a minimum value circuit 3008-1, a multiplying circuit 3008-2, difference circuits 3008-4 to 3008-6, and an inking rate memory 3008-7.

  This is the same as the first embodiment except that the black rate memory 3008-7 switches the black rate k3008-3 between text and photo by the identification signal 3007 from the identification device 3002.

  The color conversion unit 3003 is the same as that of the modification of the second embodiment, and the operation shown in FIG. 24 will be described based on the values shown in FIG.

  FIG. 24 shows an example in which the black rate is switched between characters and photos. As shown in FIG. 24A, black characters and the like are easily printed in K1 color, so that a black output is obtained. As shown in (b) of FIG. 24, since the amount of K can be kept small in a photograph or the like, it is possible to obtain an output image retaining color.

  As described above, according to the third embodiment, since the black rate is changed between characters and photos, color reproduction suitable for characters and photos can be realized.

  In this embodiment, the black rate is changed by the same blacking method, but the image quality can be improved similarly by changing the blacking method.

  As described above, according to the embodiment of the present invention, the compression using the frequency conversion method is performed after the inking process, so that noise during the inking process can be reduced by the filter effect of the compression, and the compression efficiency is further increased. I can do it.

  In addition, the color difference between compression and non-compression can be reduced by switching the color conversion method and the black rate / inking method between compression and non-compression.

  Furthermore, by changing the black rate and the inking method according to the characteristics of the character and the photograph by the identification process, the character and the like can be printed black and the printing cost can be reduced, and the photograph can be reproduced vividly.

  In this embodiment, the case where the 3 → 4 signal inking method is used has been described. However, as described in the second embodiment, the conversion of the 3 → 4 signal is performed using a plurality of lookup tables (LUTs). It is also possible to do so.

1 is a block diagram showing the overall configuration of a digital color copying machine to which an image processing apparatus according to a first embodiment of the present invention is applied. The figure which shows the structure of the inking process part of 1st Example. The figure for demonstrating the inking process part of 1st Example. The figure which shows the structure of the compression part of 1st Example. The figure for demonstrating the compression by DCT conversion of 1st Example. The figure for demonstrating decoding by the inverse DCT transformation of 1st Example. The figure for demonstrating from the inking process of 1st Example to compression and decoding. FIG. 3 is a block diagram showing the overall configuration of a digital color copying machine to which an image processing apparatus according to a second embodiment of the invention is applied. The figure for demonstrating the operation | movement of the electronic sort of 2nd Example. The figure for demonstrating the compression by the one-dimensional four-value error diffusion of 2nd Example. The figure for demonstrating the threshold value and quantization value of 4 value error diffusion of 2nd Example. The figure for demonstrating the color conversion of 2nd Example. The figure which shows the structure of the color conversion part of 2nd Example. The figure which shows the structure of the color conversion part of 2nd Example. The figure for demonstrating to compression and decoding of 2nd Example, and color conversion. FIG. 9 is a block diagram showing the overall configuration of a digital color copying machine to which an image processing apparatus according to a modification of the second embodiment according to the present invention is applied. The figure for demonstrating the color conversion of the modification of 2nd Example. The figure which shows the structure of the inking process part of the modification of 2nd Example. The figure for demonstrating the compression and decoding of the modification of 2nd Example, color conversion, and inking. FIG. 9 is a block diagram showing the overall configuration of a digital color copying machine to which an image processing apparatus according to a third embodiment of the invention is applied. The figure which shows the structure of the identification device of 3rd Example. The figure for demonstrating the identification apparatus of 3rd Example. The figure which shows the structure of the inking process part of 3rd Example. The figure for demonstrating identification, color conversion, and inking of a 3rd Example.

Explanation of symbols

1001, 2001, 3001 ... Scanners 1002, 2006, 2007, 2017, 3003 ... Color conversion units 1003, 2018, 3004 ... Inking processing units 1004, 2003 ... Compression units 1005, 2004 ... Memory 1006, 2005 ... Decoding units 1007, 2009 , 3005... Printer engine 1100, 2100... Control circuit 2002, 2008.

Claims (6)

Processing means for performing an inking process on the image signal to generate a C′M′Y ′ image signal and a K image signal;
Compression means for compressing by a frequency conversion method to encode a low-frequency component that is a component having a frequency lower than that of the high-frequency component except for the high-frequency component of the C′M′Y ′ image signal and the K image signal;
Storage means for storing the C′M′Y ′ image signal and the K image signal compressed by the compression means;
Decoding means for decoding the C′M′Y ′ image signal and the K image signal stored in the storage means by the frequency conversion method;
An image processing apparatus comprising: Color conversion means for converting an input RGB image signal into a CMY image signal;
Processing means for performing inking processing on the CMY image signal to generate a C′M′Y ′ image signal and a K image signal;
Compression means for compressing by a frequency conversion method to encode a low-frequency component that is a component having a frequency lower than that of the high-frequency component except for the high-frequency component of the C′M′Y ′ image signal and the K image signal;
Storage means for storing the C′M′Y ′ image signal and the K image signal compressed by the compression means;
Decoding means for decoding the C′M′Y ′ image signal and the K image signal stored in the storage means by the frequency conversion method;
An image processing apparatus comprising: Processing means for performing an inking process on the image signal to generate a C′M′Y ′ image signal and a K image signal;
Compression means for compressing by a frequency conversion method to encode a low-frequency component that is a component having a frequency lower than that of the high-frequency component except for the high-frequency component of the C′M′Y ′ image signal and the K image signal;
Storage means for storing the C′M′Y ′ image signal and the K image signal compressed by the compression means;
Decoding means for decoding the C′M′Y ′ image signal and the K image signal stored in the storage means by the frequency conversion method;
A print engine that performs output based on the C′M′Y ′ image signal and the K image signal decoded by the decoding unit;
An image processing apparatus comprising: Color conversion means for converting an input RGB image signal into a CMY image signal;
Processing means for performing inking processing on the CMY image signal to generate a C′M′Y ′ image signal and a K image signal;
Compression means for compressing by a frequency conversion method to encode a low-frequency component that is a component having a frequency lower than that of the high-frequency component except for the high-frequency component of the C′M′Y ′ image signal and the K image signal;
Storage means for storing the C′M′Y ′ image signal and the K image signal compressed by the compression means;
Decoding means for decoding the C′M′Y ′ image signal and the K image signal stored in the storage means by the frequency conversion method;
A print engine that performs output based on the C′M′Y ′ image signal and the K image signal decoded by the decoding unit;
An image forming apparatus comprising: A scanner that reads a document image and generates an image signal;
Processing means for performing an inking process on the image signal to generate a C′M′Y ′ image signal and a K image signal;
Compression means for compressing by a frequency conversion method to encode a low-frequency component that is a component having a frequency lower than that of the high-frequency component except for the high-frequency component of the C′M′Y ′ image signal and the K image signal;
Storage means for storing the C′M′Y ′ image signal and the K image signal compressed by the compression means;
Decoding means for decoding the C′M′Y ′ image signal and the K image signal stored in the storage means by the frequency conversion method;
A print engine that performs output based on the C′M′Y ′ image signal and the K image signal decoded by the decoding unit;
An image forming apparatus comprising: A scanner that reads an original image and generates an RGB image signal;
Color conversion means for converting the RGB image signal into a CMY image signal;
Processing means for performing inking processing on the CMY image signal to generate a C′M′Y ′ image signal and a K image signal;
Compression means for compressing by a frequency conversion method to encode a low-frequency component that is a component having a frequency lower than that of the high-frequency component except for the high-frequency component of the C′M′Y ′ image signal and the K image signal;
Storage means for storing the C′M′Y ′ image signal and the K image signal compressed by the compression means;
Decoding means for decoding the C′M′Y ′ image signal and the K image signal stored in the storage means by the frequency conversion method;
A print engine that performs output based on the C′M′Y ′ image signal and the K image signal decoded by the decoding unit;
An image forming apparatus comprising:

Images