JPH0353768A - Picture data compression and restoration system for print - Google Patents

Abstract

PURPOSE:To improve the transmission efficiency and storage efficiency by providing plural color coordinate conversion sections having a masking matrix and an inverse matrix different from each other and selecting an optimum color coordinate conversion section in response to the hue condition of ink of an original and processing the data. CONSTITUTION:A compression color coordinate conversion section 1 receives Y(yellow), M(magenta), C(cyan) and K(black) data forming a picture data of a print original, separates them into the Y, M, C data and the K data, applies calculation of a masking matrix comprising [A]=[3Xn] matrix to the Y, M, C data to convert them into R, G, B data, which are inputted to a compression device 2 with the K data not converted. A luminance color difference conversion section 21 receives R, G, B data outputted from the compression color coordinate conversion section 1 and converts them into the luminance data Y and color difference data CR, CB and they are outputted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides compression and restoration of print image data that can improve data transmission efficiency and storage efficiency when transmitting and storing print image data. It's about systems.

[Prior Art] With recent advances in digital image processing technology, total scanners have been introduced in the field of printing, for example, which convert images for printing into digital data and perform plate collection and retouching operations. In this case, it is necessary to transmit the image data for printing (for example, between a publisher and a factory, between factories, between a region and a factory), and store it (in a database). Various methods have been tried, but the best method is method has not yet been proposed. This is because the amount of printing image data is enormous compared to normal digital data. For example, in order to express one A4 size printing image with four color components at a resolution of 15 lines/square, 56 Mbytes of data is required as shown by the following equation. Here, one pixel is 4Byte (-8bit (
It is assumed that it is represented by data of IByte)×1 (color).

210mmX297mmX (15 pieces/mm)x4
Byte/point - 56MByte Therefore, when transmitting data for one A4 size printing image, a normal public line (9600b i
t/sec), it would take 13 hours, and even if a high-speed digital line was used, it would take just under two hours. In addition, even when saving print image data to build a database, optical discs (1 to 20B)/
Even if te) is used, the aforementioned A4 size image data can only be stored for 18 to 36 images, which is insufficient for constructing an image database. As mentioned above, handling of printing image data is complicated,
Processing time is required for data transmission and storage.

On the other hand, in the fields of television and facsimile,
In order to improve the transmission efficiency and storage efficiency of monitor image data, compression of monitor image (still image) data is performed. As a compression device for still images of this type for television, there are recent excellent compression devices (for example, A
A compression device based on the DCT method has been proposed. This ADCT compression device compresses image data into 8x8
After performing two-dimensional discrete cosine transformation on a block-by-block basis, and performing threshold processing and quantization processing on the transform coefficients,
The coefficients are variable-length coded to obtain coded data. Therefore, it is possible to reduce the processing time during data transmission and storage by compressing print image data using such a compression device.

[Problem to be solved by the invention] However, in this case, the monitor image data is R, G, B data, while the printing image data is Y, M,
This is data for C and K. Therefore, if such a compression device is directly applied to compress image data for printing, there is a problem in that a difference occurs in color reproduction, that is, image quality deteriorates during color reproduction (colors differ from original colors, etc.).

The present invention has been made to solve the above-mentioned problems, and it compresses and restores print image data without degrading the image quality during color reproduction, and transmits and stores the print image data. The purpose of the present invention is to provide a highly reliable printing image data compression/restoration system that can improve transmission efficiency and storage efficiency.

[Means for Solving the Problems] In order to achieve the above object, the present invention compresses print image data with a compression device and restores the compressed print image data with a decompression device. As a pre-processing means for
, K data is separated into Y, M, C data and K data, and each data of Y, MC is extracted from a [3×n] matrix (n: the number determined by the combination of R, G, and B). R, G, B
and a compression color coordinate conversion unit that converts each data into each data and manually inputs each data to a compression device together with K data,
The restoring device's post-processing means separates the R, G, B, and K data constituting the print image data output from the restoring device into R, G, B data and K data, and processes the R, G, B, and K data. B
A restoration color coordinate conversion unit is provided which calculates the inverse matrix of the masking matrix for each data, converts it into Y, M, and C data, and outputs each data together with K data. ing.

[Function] Therefore, in the printing image data compression/restoration system of the present invention, [3×n
] Matrix, each of R, G, B . The data is input to the compression device together with the K data, and the R, G data from the decompression device is
, B, the inverse matrix of the above-mentioned masking matrix is calculated, and each data of Y, M, and C is output together with the K data. This makes it possible to compress and restore print image data while preventing image quality from deteriorating during color reproduction.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an example of the configuration of a printing image data compression system according to the present invention. As shown in FIG. 1, the print image data compression system of this embodiment includes a compression color coordinate conversion section 1 as a preprocessing means of the compression device, and an ADCT
It is composed of a compression device 2 according to the method.

Here, the compression color coordinate conversion unit 1 inputs Y (yellow), M (magenta), C (cyan), and K (black) data constituting the image data of the print document, and converts these into Y , M, C data and K data, Y, M, C
/7A1 of the masking matrix consisting of [A] − [3×n] matrix only for each data of
5 to convert the data into R, G, and B data, and manually input the data to the compression device 2 together with the unconverted K data. In this case, n is a number determined by the combination of R, G, and B, and in this example, for example, a masking matrix consisting of a [3×3] matrix as shown below is used as the primary color.

On the other hand, as a detailed example of the configuration is shown in the block diagram of FIG.
CT section 24, quantization section 25, and zigzag scanning section 2
6 and an unequal length encoding section 27. here,
The luminance/chrominance conversion section 21 receives the R, G, and B data output from the compression color coordinate conversion section 1, converts them into luminance data Y, and chrominance data CR, CB, and outputs the converted data. be. Further, the sub-sampling section 22 receives the luminance data Y and the chrominance data CR + from the luminance/chrominance conversion section 21 .
CBs and K output from the compression color coordinate conversion unit 1
The data is manually input and its resolution is changed (corrected) so that the resolution of the color difference data CR and CB is lower than that of the luminance data Y. Furthermore, the 8×8 blocking unit 23
H-Sassa? Enter the data from Bling #22 and D
The amount of data is optimized (formed into 8×8 blocks) so that the amount of calculations when performing CT does not increase.

On the other hand, the DCT unit 24 has an orthogonal transform function,
The Y, CR, and Ca data on the X and Y coordinate axes are
This converts the data on the frequency axes (horizontal and vertical directions) Fx and FY to Y'', CR'' and cB-. Also,
The quantization section 25 receives data Y-, CR from the DCT section 24.
−． CB is input, and data is allocated to these data such that a large bit is allocated to the low frequency portion and a small bit is allocated to the high frequency portion.

Further, the zigzag scanning section 26 inputs the data from the quantization section 25 and rearranges the data from the low frequency data side to the high frequency data side. Furthermore, the unequal-length encoding unit 27 encodes the rearranged data from the zigzag scanning unit 26 with unequal-length encoding to generate encoded data, that is, compressed data y'', cR'',
It outputs c8°.

Next, the operation of the printing image data compression system configured as above will be explained.

In the figure, each data of Y (yellow), M (magenta), C (cyan), and K (black) constituting the image data of the print document is processed by the compression color coordinate conversion unit 1 before being input to the compression device 2. is input.

In the compression color coordinate conversion unit 1, these data Y, M, C
, K are separated into Y, M, C data and K data. Of these, each of the Y, M, and C data is converted into R, G, and B data by performing masking ◆ matrix operations consisting of a [3 x 3] matrix as described above, and the K data is is input to the compression device 2 as is without any conversion.

On the other hand, in the compression device 2, the R, G, and B data from the compression color coordinate conversion section 1 are converted into luminance data Y and color difference data C R +Ca by the luminance/color difference conversion section 21, and then sent to the subsampling section. It will be man-powered on the 22nd. The sub-sampling section 22 compares the resolution of the luminance data Y from the luminance/color difference conversion section 21, the color difference data CR*CB %, and the K data from the compression color coordinate conversion section 1 with the color difference data CR, The CB resolution is changed so as to be lowered and inputted to the 8×8 blocking unit 23. Then, in the 8×8 blocking unit 23, the data amount is optimized (8×8 blocking) is performed on the data from the sub-sampling unit 22 so that the amount of calculation when performing DCT is not increased. 24.

On the other hand, in the DCT unit 24, Y and C on the X and Y coordinate axes are
R.C. Each data is frequency axis (horizontal and vertical direction) FX
, FY are converted into respective data Y'CR, CB and manually inputted to the quantization section 25. In the quantization section 25, DC
Data is assigned to the data Y", CR+.cB- from the T section 24 in such a way that a large bit is assigned to the low frequency component and a small bit is assigned to the high frequency component. In the zigzag scanning unit 26, the data from the quantization unit 25 is rearranged from the low frequency data side to the high frequency data side, and then in the unequal length encoding unit 27, the data is zigzag scanned. The data from the unit 26 is unequal length encoded, and the encoded data is compressed data Y゜cR'',c. ” is output.

As described above, the printing image data compression system of this embodiment uses Y, M, C, K, which constitutes the image data of the printing original, as a preprocessing means of the compression device 2 using the ADCT method.
Separate each data into Y, M, C' data and K data, perform a masking matrix operation consisting of a [3X3] matrix on each data of Y, M, C, and calculate R.
, G, and B data, and manually inputs each data to the compression device 2 together with the K data.

Therefore, Y. which constitutes the image data of the printed manuscript. Each data of M and C is converted into each data of R, G, and B by calculating a masking matrix consisting of a [3X] matrix, and this data is compressed by the ADCT method in the compression device 2, so the compression process While increasing the calculation speed when
It becomes possible to compress the image data of a printed original while ensuring an acceptable range of image quality when reproducing brown color (without causing problems such as colors differing from the original color of the printed original).

Thereby, it is possible to significantly improve the transmission efficiency and storage efficiency when transmitting and storing print image data.

In the above embodiment, a case has been described in which the present invention is applied to a print image data compression system, but the present invention is not limited to this, and the present invention can be similarly applied to a print image data restoration system.

In this case, the printing image data restoration system is A.
As a post-processing means of the restoration device using the DCT method, R, G,
Separate each data of B and K into R, G, B data and K data, and perform the above-mentioned masking ◆ Inverse matrix [A-'] of matrix [A] for each data of R, G, B. It may be configured to include a restoring color coordinate conversion unit that performs wide calculations, converts into Y, M, and C data, and outputs each data together with K data. Further, a restoring device using the ADCT method may be constructed from the same elements as those shown in FIG. 3 described above, and may perform inverse transformation processing by manually inputting data in the direction completely opposite to the arrow.

Further, in the above embodiment, a case has been described in which only one compression color coordinate conversion section is provided, but the present invention is not limited to this. Each is equipped with a coordinate conversion section,
The optimum compression color coordinate conversion section may be selected and processed according to the ink hue conditions of the printing document, and even higher accuracy can be obtained. Further, it is possible to do exactly the same with the restoration color coordinate conversion section.

Furthermore, in the above embodiment, a case has been described in which a masking matrix consisting of a [3×3] matrix is operated, but the operation is not limited to this in any way; for example, a [3×9] matrix (in the case of secondary colors) or [3X6] matrix (for secondary color simple type)
Alternatively, a masking matrix composed of a [3×11] matrix (in the case of a simple tertiary color type) may be calculated.

[Effects of the Invention] As explained above, according to the present invention, printing image data can be compressed and restored without deteriorating image quality during color reproduction, and transmission when printing image data is transmitted and stored. It is possible to provide an extremely reliable print image data compression/restoration system that can improve efficiency and storage efficiency.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a printing image data compression system according to the present invention, and FIG. 2 is a block diagram showing an example of the configuration of a compression device in the same embodiment. 1... Compression color coordinate conversion unit, 2... Compression device, 21
... Luminance/color difference conversion section, 22... Subsampling section, 23... 8x8 blocking section, 24... DCT
section, 25... quantization section, 26... zigzag scanning section, 27... unequal length encoding section.

Claims (3)

[Claims] (1) In a device in which print image data is compressed by a compression device and this compressed print image data is restored by a decompression device, Y, M, which constitutes the print image data, is used as a preprocessing means of the compression device. , C, K data is separated into Y, M, C data and K data, and a [3×n] matrix (n: combination of R, G, B a compression color coordinate conversion unit that calculates a masking matrix consisting of a number determined by the above data, converts it into R, G, and B data, and inputs the data to the compression device together with the K data; As post-processing means of the restoring device, R, G, B,
Separate each K data into R, G, B data and K data, and apply the masking and masking to each of the R, G, and B data.
Y, M by calculating the inverse matrix of the matrix
, C, and outputs each data together with the K data. (2) As the masking matrix, [3×
3] The printing image data compression/restoration system according to claim (1), wherein the printing image data compression/restoration system is a masking matrix consisting of a matrix. (3) As the color coordinate conversion unit for compression and restoration,
A plurality of color coordinate conversion sections each having a masking matrix and an inverse matrix different from each other are provided, and the optimum color coordinate conversion section is selected and processed according to the hue condition of the ink of the document. Claim (1
) Printing image data compression/restoration system described in section 2.