JPH1117971A - Image processor, its method, data processing method and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processor, its method and a data processing method capable of compressing a table of a profile to be used for a color matching processing at high compression rate. SOLUTION: An order of scanning data in the table as shown in the Fig. is defined that a G component is made incremental when an R component is increased and it reaches the maximum value, the G component is made incremental again when the R component is reduced and it reaches the minimum value and the R component is increased again by the succeeding repetition by defining a starting point of scanning to be GRB=(0, 0, 0). And when both of the R component and the G component reach the maximum value, the R, G components are reduced by making a B component incremental and when all components of RGB reach the maximum value (4, 4, 4), the scanning is completed. A data column consisting of data of the starting point of the scanning and difference data after the starting point of the scanning is obtained by performing the scanning in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method, a data processing method, and a recording medium.
For example, the present invention relates to an image processing apparatus and method relating to color matching processing of a digital image, a data processing method, and a recording medium.

[0002]

2. Description of the Related Art In a multimedia system mainly including a host computer, a color matching system (CMS) for performing color matching processing of image data between an input device and an output device has been actively developed.

[0003] Apple's ColorS, a typical CMS framework
ync (TM) is a color space (Device Depende
(nt Color Space) image signal to a device-independent color space (Device Independent Color Space), and further, image signal in a device-independent color space to an output device-dependent color space. , Common on the system
CMS is realized.

Data representing conversion characteristics used in the process of converting a color space is called a profile, and is prepared in the host computer for each device. And
The color space of the image signal is converted according to the conversion characteristics of the profile automatically or manually selected when converting the color space.

As shown in the industry standard InteColor profile format (storage format), in a device having a complicated nonlinear characteristic such as a printer or a scanner, an input value is used as an address and a value corresponding to the address is output. Look Up Tab
le) method is used.

In this case, it is not practical to store output signals for all input signals in a look-up table in view of the storage capacity of the table. For example, RGB
When converting an image signal of 8 bits for each color, a table for inputting a total of 24 bits of signals as an address and outputting an image signal for one color is required for three colors, so 2 ^ 24 × 3 = 48M
A bit, a table with a storage capacity of about 6 Mbytes is required. Note that a ^ b represents a raised to the power of b.

Therefore, the storage capacity is reduced by dividing the input signal into upper bits and lower bits and creating a table that is addressed only by the upper bits (refer to address data). For example, if addressing is performed using the upper 4 bits of an image signal of 8 bits for each color of RGB, a table for inputting a signal of 12 bits in total as an address and outputting an image signal for one color is required for three colors. A table having a storage capacity of 2 ^ 12 × 3 = 12 k bits and 1.5 k bytes is sufficient.

However, since the precision of expressing the gradation of the image is reduced by ignoring the lower bits, at the time of conversion, interpolation is performed according to the values stored in the table and the lower bits, for example. The gradation accuracy (hereinafter, referred to as “conversion accuracy”) of an image represented by the converted image signal is improved.

In the case of using color space conversion based on a look-up table combining addressing and interpolation, conversion accuracy is sacrificed to some extent, but in order to obtain practical conversion accuracy, at least 4 to 5 bits are required for addressing. Will be needed. On the other hand, the output value stored in the table currently requires 8 bits or more in consideration of the correction by the lower bits.

[0010]

Even if the same device is used, the conversion characteristics change depending on conditions such as the recording medium and user settings, that is, the color represented by the image signal (hereinafter referred to as "input color"). The color output by the image signal (hereinafter referred to as “output color”) may be different. For example, in the case of a printer, the output color changes depending on settings such as a recording medium, a recording material, an image forming method, a printing resolution, and a color space compression method for each application (Rendering Intent in the InterColor profile format).

To predict such a change in input color or output color requires extremely complicated calculations. Therefore, the conversion characteristics of the device are measured in advance for each combination of material and setting, and the measured conversion characteristics are measured. Each characteristic as a profile,
When the material or the setting is changed, a profile corresponding to the material and the setting is automatically or manually selected, and color space conversion, that is, color matching processing is performed.

For example, in the case of a printer in which seven types of recording media can be selected, two types of image forming methods and three types of color space compression methods for each application can be selected, the printer has a maximum of 42 types of conversion characteristics, and 42 types of conversion characteristics. A profile is required for each conversion characteristic.

When considering distributing the above-described device profile from a device maker to a user, distribution via a computer network can be used. However, the connection rate to the computer network is lower than the spread rate of the image input / output device, and the distribution using the floppy disk depends on the reliable distribution of the device profile. However, due to the limitation of the storage capacity, only about 10 conversion tables can be stored per floppy disk, so that a large number of floppy disks are required to distribute a set of profiles. Therefore, regardless of whether the profile is distributed on a floppy disk or a computer network, it is desirable that the profile size be smaller in order to reduce media cost and communication cost.

Data compression is conceivable in order to reduce the size of the profile. However, lossless compression is preferred as the compression method because it is necessary to completely restore the same data as before compression upon decompression. Commonly used lossless compression methods include the run-length method, Huffman method, and LZ (Lempel-Ziv) method. It can be converted to a data string with a low algorithm, and can be realized with a simple algorithm.

However, even if these compression methods are applied to a profile, the effect of compression is small. This is because color space conversion is usually represented by a smooth function due to color continuity, and the value of a data string obtained by scanning a profile conversion table also changes smoothly. That is, in binary data such as text data and programs, the same characters or words appear repeatedly or the same data are repeated frequently, but in the case of a profile conversion table, the frequency is low.

The present invention has been made to solve the above-mentioned problem, and provides an image processing apparatus, a method thereof, and a data processing method capable of compressing a profile table used for color matching processing at a high compression ratio. The purpose is to do.

It is another object of the present invention to provide an image processing apparatus and method capable of using a compressed profile, and a data processing method.

[0018]

The present invention has the following configuration as one means for achieving the above object.

An image processing apparatus according to the present invention is an image processing apparatus for transferring color image information between an input or output device and performing color matching processing. Compression means for compressing data of profile information used for the color matching processing;
Output means for outputting profile information compressed by the compression means.

An image processing apparatus for inputting a color image from an input device, applying a color matching process to the input color image, and outputting the color image to an output device, wherein the input image is obtained from a plurality of profiles stored in a storage means. Or a selection unit corresponding to an output device for selecting a profile to be used for the color matching process, and a processing unit for expanding a compression table stored in the profile selected by the selection unit and performing the color matching process And characterized in that:

An image processing method according to the present invention is an image processing method for transferring color image information between an input or output device and performing a color matching process. The profile information used for the color matching processing is data-compressed, and the profile information compressed by the compression unit is output.

An image processing method for inputting a color image from an input device, applying a color matching process to the input color image, and outputting the color image to an output device, wherein the input image is obtained from a plurality of profiles stored in a storage means. And a profile to be used for the color matching process is selected, and a compression table stored in the selected profile is expanded to perform the color matching process.

Further, the data processing method according to the present invention comprises:
Scan the data in the compressed table by a predetermined scanning method,
It is characterized in that a data string consisting of data of a scanning start point and difference data after the scanning start point is obtained.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Configuration] FIG. 1 is a block diagram showing the system configuration of the present embodiment.

This system uses a camera 11 as an input device.
And a host computer 10 that performs image processing including color matching processing and editing processing on image data, and a monitor 12 and a printer 13 that are output devices. Note that the host computer 10 may be a personal computer that executes software having the functions described below, or dedicated hardware having the same functions.

An image such as a digital camera or a video camera, a camera 111 serving as a video input device, and a scanner 112 serving as an image input device such as a flatbed scanner or a film scanner read an image of a document or a subject and read the read image. Is supplied to the host computer 10 as image data.

The monitor 12 is composed of a display such as a CRT or a liquid crystal panel, and is an image display device that displays images, displays information necessary for a user to make an input to the system, and confirms operation of the system. is there. Also a printer
Reference numeral 13 denotes a printing machine, which is an image output device that forms a visible image on a recording medium such as recording paper using a recording material such as ink or toner.

The external storage device 14 includes a storage medium such as a hard disk, a magneto-optical disk or a floppy disk,
And a drive which is a device for reading and writing these recording media. The host computer 10 stores the image data supplied from the camera 111 or the scanner 112 in the external storage device 14, performs image processing on the stored image data, and further stores the stored unprocessed or processed By supplying the image data to the monitor 12 and the printer 13, an image corresponding to the image data can be displayed and printed.

The external storage device 14 also stores profiles required for color matching processing. The host computer 10 reads the profile stored in the external storage device 14 as necessary, and performs a color matching process. The profiles stored in the external storage device 14 include those whose data has been compressed by a predetermined compression method as necessary.

Normally, the image processing program and the control program for the apparatus according to the present invention
However, these programs can be stored in the external storage device 14. That is, the host computer 10 can read the program stored in the external storage device 14 and execute the image processing and the control of the apparatus according to the present invention in accordance with the user's instruction.

The keyboard 15 and the mouse 16 are operated by the user as needed, and are used to input instructions, data, and the like to the host computer 10.

[Host Computer] FIG. 2 is a block diagram showing an example of the configuration of the host computer 10. The figure
2, a console 21 including a keyboard 15, a mouse 16, a monitor 12, and the like includes an input / output interface 22 and
It is connected to the CPU 17 via the CPU bus 25. Further, the external storage device 14 includes an external storage device interface 26 and a CPU.
A bus 25 is connected to the CPU 17.

The CPU 17 has a system control section 171 for controlling the entire system, an arithmetic processing section 172 for executing various arithmetic operations, and a working memory 173 for storing necessary data at the time of arithmetic operations. The CPU 17 executes the host computer 10 based on a program stored in the ROM 18 or the RAM 19.
Then, the image data stored in the RAM 19 is subjected to image processing such as color matching processing and output to an output device.

The video RAM 23 stores a screen to be displayed on the monitor 12.

[Color matching processing] In this system,
The following combinations are available as combinations of input devices and output devices. Note that the combination (4) is a combination for performing a so-called “preview”, and is used for displaying an image output from the printer 13 on the monitor 12 and confirming the image.

(1) Image input device → Monitor 12 (2) Image input device → Printer 13 (3) Monitor 12 → Printer 13 (4) Printer 13 → Monitor 12 Color matching processing corresponding to the above combination is performed. At this time, the CPU 17 reads, from the external storage device 14, an input profile corresponding to the input device and an output profile corresponding to the output device. The profile stores data representing the relationship between a device-dependent color space and a device-independent color space. Therefore, the input profile contains
Data for converting an image signal in a color space dependent on the input device into an image signal in a color space independent of the device is stored. On the other hand, the output profile stores data for converting an image signal in a color space independent of the device into an image signal in a color space independent of the output device. Further, the output profile data may include not only color space conversion but also color space compression for compressing input image data into the color reproduction range of the output device.

That is, the CPU 17 first reads an input profile from the external storage device 14 based on the combination of the input device and the output device, and uses the input profile to generate an image signal depending on the color space of the input device. Into an image signal in a color space that does not depend on

Next, the CPU 17 reads an output profile corresponding to the output device from the external storage device 14 and uses the output profile to convert an image signal in a device-independent color space into a color space in an output device-dependent color space. Convert to image signal.

[Compression of Profile] As described above, the profile used in the color matching process is data based on the characteristics of the apparatus, and is indispensable for the color matching process of an image. However, as described above, the size of the profile must be increased to some extent in order to obtain a predetermined conversion accuracy, which is a hindrance in distributing the profile.

When compressing the profile conversion table including the InterColor profile format described above, the scanning order of the data is as follows. First, the initial values of a plurality of elements of the input signal are set to zero, and the first element is set from zero. Increase, when the first element reaches the maximum value, increment the second element, again increase the first element from zero,
In that order. That is, a data sequence in the combination order of the values of the plurality of elements is obtained, and the data sequence is subjected to processing such as compression.

In the present embodiment, the conversion table is scanned in a predetermined order based on the characteristic that the value of the data string obtained by scanning the profile conversion table changes smoothly, and the address of the address corresponding to the scan start point is scanned. For data, the absolute value is used, and for data at subsequent addresses, the difference from the immediately preceding data is used (hereinafter, referred to as “difference data sequence”). The “difference” here does not indicate a difference in the square distance, but means a difference between numerical values of respective color components of the image signal.

The configuration of the data string in this embodiment is such that adjacent signals are continuous in the input color space. Such a scanning order of the conversion table is called "one-stroke scanning". To When scanning with one stroke, the absolute value of the difference constituting the obtained difference data sequence is obtained when the conversion table is 4-bit addressing and 8-bit output.
At most, it is about "18", and even if negative values are considered, 6 bits per element is sufficient. Therefore, the size of the profile conversion table can be compressed to at least 6/8 = 0.75.

Furthermore, since the range of the data string obtained from the profile conversion table of the present embodiment is compressed to about "18", the frequency of repeating the same data increases. Therefore, when the conversion table is compressed by the run-length method, the Huffman method, the LZ (Lempel-Ziv) method, or the like after performing such processing, a higher compression ratio can be obtained. For example, according to a compression method combining the LZ method and the Huffman method, the compression ratio of a data string read out from a conversion table by normal scanning is about 54%. On the other hand, the one-stroke writing scan and the difference data
When the compression method and the Huffman method are used, the compression ratio becomes about 24%, and the conversion table can be compressed to about 1/4 of the size.

FIG. 3 is a diagram for explaining single-stroke scanning, showing the scanning order of data in a conversion table for inputting image signals of five gradations of RGB and outputting image signals of three color components. . With RGB = (0,0,0) as the scanning start point, when the R component increases and reaches the maximum value, the G component is incremented.When the R component decreases and reaches the minimum value, the G component is changed again. The scanning is performed in the order of incrementing, increasing the R component, and so on. When both the R and G components reach the maximum value, the B component is incremented to reduce the R and G components, and when all the RGB components reach the maximum value (4, 4, 4), the scanning end point is reached. Become. Note that in FIG. 3, RGB = (4,4,4) is the starting point, RG
B = (0,0,0) may be the end point.

[Processing Procedure] FIG. 4 is a flowchart showing an example of the procedure of the color matching processing in this embodiment.
This is the process executed by 7.

First, in step S31, image data is received from the image input device and stored in the external storage device 14. In step S32, the input profile used for the color matching process, that is, the image profile corresponding to the image input device and its image input conditions. Select the input profile to be used. In step S33, it is determined whether or not the conversion table of the selected input profile is compressed. If it is compressed, in step S34, the compressed data of the conversion table is expanded and the original conversion table is reproduced.

Next, in step S35, an output profile to be used for color matching processing, that is, an output profile corresponding to the image output device and its image output conditions is selected.
In step S36, it is determined whether or not the conversion table of the selected output profile is compressed. If the conversion table is compressed, in step S37, the compressed data of the conversion table is expanded and the original conversion table is reproduced.

Then, in step S38, the image data stored in the external storage device 14 is subjected to color matching processing using the input profile and the output profile.
9, the image data subjected to the color matching process is output to the output device,
That is, the data is transmitted to the monitor 12 or the printer 13.

When the conversion table of the selected profile is compressed, the original conversion table obtained by expanding the compressed data is stored in the external storage device 14 or the RAM 19. Then, after the color matching processing is completed, the original conversion table may be deleted or may be left as it is in the corresponding profile of the external storage device 14.

FIG. 5 is a flowchart showing an example of the decompression processing in steps S34 and S37. The variable Asrc stores a value indicating the address of the decompressed differential data string, and the variable Ades
In t, the address of the conversion table is stored. The variable X stores data corresponding to the scan start point of the conversion table, and the variable a stores data read from the difference data string.

In step S41, compressed data of the conversion table is extracted from the selected profile and decompressed. That is, the data sequence compressed by the LZ method or the Huffman method is decompressed, and the one-stroke scanning differential data sequence is reproduced.

Next, in step S42, the address to be referred to first in the differential data string (usually the address of the first data) is substituted for the variable Asrc, and in step S43, the scanning start point of the conversion table is set to the variable Adest. Substitute the address shown.
Then, in step S44, the data of the difference data sequence indicated by the variable Asrc is stored in the variable X, and in step S45, the variable X
Is stored in the address indicated by the variable Adest in the conversion table.

Next, in step S46, it is determined whether or not the scanning of the conversion table has been completed, and if it has been completed, the processing is terminated, or in step S51, the data corresponding to the conversion table with the expanded profile is read. After updating, the process ends.

If the scanning has not been completed, the process proceeds to the next step. In steps S47 and S48, the address to be referred next is substituted into variables Asrc and Adest.
The data of the difference data sequence indicated by src is stored in variable a,
After substituting X + a for the variable X in step S50, the process returns to step S45. Therefore, in step S45, the address indicated by the variable Adest in the conversion table stores data obtained by adding the data indicated by the variable Asrc in the data string to the data at the address indicated by the immediately preceding variable Adest. Become.

By repeating the above processing from the scan start point to the scan end point of the conversion table, the original conversion table can be reproduced from the compressed data.

As described above, according to the present embodiment, the conversion table of the profile is scanned by one-stroke and converted into a differential data string, so that the data range can be reduced and the conversion table can be compressed. Furthermore, conversion table data consisting of one-stroke scanning and a difference data sequence
Since the data sequence is suitable for lossless compression such as the run-length method, the Huffman method, and the LZ (Lempel-Ziv) method, a high compression rate can be obtained by performing compression using such a method. Therefore, for example, when distributing a profile via a floppy disk or a computer network, it is possible to reduce media cost and communication cost.

The compression method is not limited to the above-listed methods, but may be another method as long as it is a so-called entropy coding method.

In the above-described embodiment, an example in which the present invention is applied to a profile conversion table used for color matching processing has been described. However, the present invention is not limited to this, and a gamma conversion table, a masking processing table, This can be effectively used when compressing an arbitrary table for performing image processing on color image data such as a luminance-density conversion table.

[0060]

[Other Embodiments] Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (for example, a copying machine) Machine, facsimile machine, etc.).

Further, an object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU or MPU) of the system or apparatus.
Needless to say, this can also be achieved by the PU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the OS running on the computer based on the instructions of the program code.
It goes without saying that an (operating system) performs a part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

In the above-described embodiment, an example in which a profile is selected and then decompressed has been described. However, the present invention is not limited to this, and a profile to be used is selected after decompressing all compressed profiles. You can also do so.

[0064]

As described above, according to the present invention,
An image processing apparatus, a method thereof, and a data processing method for compressing a table of a profile used for color matching processing at a high compression ratio can be provided.

Further, it is possible to provide an image processing apparatus, a method thereof, and a data processing method which can use a compressed profile.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment;

FIG. 2 is a block diagram showing a configuration example of a host computer;

FIG. 3 is a diagram for explaining one-stroke scanning according to the present invention;

FIG. 4 is a flowchart illustrating an example of a procedure of a color matching process according to the embodiment;

FIG. 5 is a flowchart illustrating an example of a decompression process.

Claims (20)

[Claims] 1. An image processing apparatus for transferring color image information between an input or output device and performing color matching processing, wherein the image processing apparatus is used in the color matching processing corresponding to the input or output device. An image processing apparatus comprising: compression means for compressing profile information, and output means for outputting profile information compressed by the compression means. 2. The image processing apparatus according to claim 1, wherein the compression unit entropy-encodes the data constituting the profile into a one-dimensional data sequence. 3. The image processing apparatus according to claim 2, wherein the compression unit performs the entropy coding after performing differential coding on a data sequence forming the profile. 4. The image processing apparatus according to claim 2, wherein the entropy coding includes at least one of a run length method, a Huffman method, and an LZ method. 5. An image processing method for transferring color image information between an input or output device and performing a color matching process, wherein the image processing method is used for the color matching process corresponding to the input or output device. An image processing method, comprising compressing profile information and outputting profile information compressed by the compression unit. 6. A recording medium storing a program code for image processing for transferring color image information to and from an input or output device and performing color matching processing, the recording medium corresponding to the input or output device. A recording medium comprising: a code for compressing profile information used for the color matching processing; and a code for outputting profile information compressed by the compression unit. 7. A color image is input from an input device,
An image processing apparatus that performs color matching processing on the input color image and outputs the input color image to an output device. The image processing apparatus corresponds to the input or output device from a plurality of profiles stored in a storage unit and is used for the color matching processing. An image processing apparatus comprising: a selection unit for selecting a profile to be selected; and a processing unit for expanding a compression table stored in the profile selected by the selection unit and performing the color matching processing. 8. The image processing apparatus according to claim 7, wherein the compression table is obtained by compressing a table describing a conversion characteristic of a color space by a predetermined compression method. 9. The image processing apparatus according to claim 7, wherein the compression table is obtained by compressing a table in which gamma conversion characteristics are described by a predetermined compression method. 10. A compression table for compressing a conversion table for outputting a second image signal representing a plurality of color components corresponding to a first image signal representing a plurality of input color components by a predetermined compression method. Claims characterized by the following
7. The image processing device according to 7. 11. The predetermined compression method scans data in a table to be compressed by a predetermined scanning method to obtain a data string consisting of data at a scan start point and difference data after the scan start point. 11. The image processing device according to claim 8, wherein the image processing device is an image processing device. 12. The image processing apparatus according to claim 11, wherein the predetermined compression method further performs lossless compression on the data sequence. 13. The image processing apparatus according to claim 11, wherein in the predetermined scanning method, adjacent data on an input color space is continuously scanned. 14. An image processing method for inputting a color image from an input device, performing a color matching process on the input color image, and outputting the color image to an output device, wherein the input image is obtained from a plurality of profiles stored in a storage unit. Alternatively, an image processing method which selects a profile corresponding to an output device and is used for the color matching process, decompresses a compression table stored in the selected profile, and performs the color matching process. 15. A recording medium which stores a program code for image processing for inputting a color image from an input device, performing color matching processing on the input color image, and outputting the color image to an output device, wherein the program code is stored in storage means. From a plurality of profiles, a code for a step of selecting a profile corresponding to the input or output device and used in the color matching process, and expanding a compression table stored in the selected profile, And a code for performing a process. 16. A data processing method, wherein data in a table to be compressed is scanned by a predetermined scanning method, and a data sequence including data at a scanning start point and difference data after the scanning start point is obtained. . 17. The data processing method according to claim 16, further comprising: losslessly compressing the data sequence. 18. The data processing method according to claim 17, wherein in the predetermined scanning method, adjacent data on the input color space is continuously scanned. 19. A recording medium on which a table processed by the data processing method according to claim 16 is recorded. 20. A recording medium recording a color matching profile including a table processed by the data processing method according to any one of claims 16 to 18.