JP2009105765A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor and image processing method for reproducing conventional stored colors while effectively utilizing a color reproduction area that an image output device such as a printer can present originally, and for providing an excellent image even after saturation correction. <P>SOLUTION: The image processor converts a color image signal input by an image input device 401 into an image signal suitable for an image output device 402. A gamut converting section 705 performs color compression on an image signal IMG1, and a first color converting section 706 converts the color-compressed image signal IMG1 into a color space different from the color space of the image signal. Meanwhile, a second color converting section 707 converts an image signal IMG2 that is not color-compressed, into the different color space. A synthesis section 708 synthesizes the color-converted two image signals in a predetermined synthesis ratio to produce a new image signal IMG3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method for improving the image quality of image data such as a digital photographic image.

  Conventionally, when color matching is performed on a monitor, color reproduction is performed within a range that does not exceed the color reproduction area of the monitor, and color reproduction that can be originally produced by a printer has not been used to the maximum extent. For this reason, depending on the printer and media, the main memory colors in landscapes and portraits have not been reproduced sufficiently.

  With respect to this problem, a method has been proposed in which when color matching is performed, correction for extending the saturation in a uniform color space is performed to widen the reproduction region.

  In the invention described in Patent Document 1, the amount of change in hue differs according to the value of the hue angle with respect to the hue, and the amount of change in saturation differs according to the value of the hue angle and the value of saturation with respect to the hue, With regard to lightness, the invention is characterized in that the amount of change in lightness varies depending on the hue angle.

  That is, in Patent Document 1, hue conversion is performed so that each hue is independently converted to a target hue, instead of shifting all hue angles uniformly. Then, with respect to the saturation, different saturation conversion is performed for each hue by using the saturation conversion curves prepared for the respective hues having different shift directions and hue shift amounts. The brightness is also converted by a brightness conversion curve that associates the brightness conversion amount for each hue.

  Therefore, in Patent Document 1, by controlling the hue, saturation, and brightness as described above, it is possible to reproduce a more preferable color that is close to a human memory color in any image. Accordingly, it is possible to expect the effect that the color desired to be vivid is reproduced more vividly and the color desired to suppress the color change is reproduced as it is.

JP 2003-110868 A

  As is clear from the above, in color matching technology, a method that independently controls the values of components relating to hue, saturation, and brightness is influential, but even with this method, image processing such as printing can be performed better. In order to do this, there are still issues that must be improved. In particular, it is necessary to consider the characteristics of the color material used for image formation.

  However, the method of Patent Document 1 does not consider the characteristics of the color material required for printing. For this reason, even if the hue is originally reproduced in pure color, other color materials may be mixed in the area expanded by the effect of saturation correction. This is not so much a problem with an inkjet printer, but in an electrophotographic process, when other color materials are mixed into a pure color, the graininess on the paper surface increases, which may be a cause of image quality degradation.

This will be specifically described below.
1, 2, and 3 represent “input device color gamut”, “output device color gamut”, and “input device color gamut” in Lab space, respectively. In general, the uniform color space is a space in which the color can be expressed as a three-dimensional positional relationship. Here, for convenience, the L value, which is a lightness component, is mapped onto the ab plane to express the color space two-dimensionally. To do.

  Here, the “color gamut of the input device” is a color gamut of a color space that can be expressed on a monitor device such as a CRT or a liquid crystal display, and examples thereof include sRGB and AdobeRGB. In general, the “color gamut of the input device” is wider than the “color gamut of the output device” and the number of gradations that can be expressed is large.

  The “color gamut of the output device” is the maximum color gamut that can be expressed on a recording material such as paper by a color material (for example, ink or toner) used in an ink jet printer or an electrophotographic printer. Specifically, it is composed of four colors CMYK. Since the “color gamut of the output device” is strongly influenced by the characteristics of the color material and the performance of the output device itself, in recent years, it has been proposed to add colors other than CMYK as a method for improving this. Yes. For example, a six-color system in which light cyan and light magenta are added to the above four colors, and a printing system with more colors are proposed. Therefore, in the present invention, the color space of the output device is not limited to four colors.

  Further, the “color gamut obtained by compressing the color gamut of the input device” is a color reproduction gamut when the image is actually expressed on a recording material such as paper within the range of the “color gamut of the output device”. Usually, this color gamut varies in size, hue, and gradation depending on the type and purpose of image data to be expressed. For example, since natural images such as landscapes and portraits emphasize the overall gradation, the color gamut is smaller than the “color gamut of the output device”. Also, in graphic images and characters in electronic materials for presentation, vividness is more important than gradation, so the reproduction range is close to the “color gamut of the output device”.

FIG. 1 is a diagram for explaining saturation correction in Patent Document 1. In FIG.
PL indicates a point on the L axis where a = 0 and b = 0. PA indicates that the signal value of (R, G, B) = (0, 255, 255) is converted into the Lab color space in the color space of the input device. PB indicates a point on the Lab space in which PA is color-gamut-compressed in accordance with the printing purpose. Further, when the PC outputs a signal value of (C, M, Y, K) = (255, 0, 0, 0) in the color space of the output device, the color material is a recording material such as paper. Shows the color to be reproduced.

  Furthermore, the arrow HA indicates a red component from (R, G, B) = (255, 255, 255) to (R, G, B) = (0, 255, 255) in the color space of the input device. Represents the hue on the Lab color space when is gradually subtracted. An arrow HC indicates a hue when the color gamut is compressed according to the purpose of printing.

  The saturation correction method in Patent Document 1 extends HC linearly to GB (color gamut of the output device), and the result of saturation correction corresponds to the arrow HB. According to this method, since the color gamut is extended to the limit of the color gamut of the output device, the maximum saturation is improved, and vivid color reproduction is possible as compared with the conventional color gamut. In addition, the conventional hue (arrow HC) is not changed at all, and the memory color is expected to be sufficiently reproduced.

However, depending on the printing purpose, it may be preferable to reproduce the hue HC after color gamut compression with a pure color. In particular, in the electrophotographic process, preserving pure colors is an important factor in image quality.
Furthermore, although there are some differences in the characteristics of toners that are generally widely used in electrophotographic processes, the hue of a pure color draws a trajectory of a curve rather than a straight line, although there are some differences depending on the components.
Accordingly, the hue HC obtained by color-compressing the HA is not always reproduced linearly in consideration of the characteristics of the color material when trying to preserve the pure color.

FIG. 2 represents a pure color hue in the electrophotographic process.
An arrow HC2 indicates a pure color hue within the color gamut GC, and an arrow HB2 indicates a pure color hue outside the color gamut GC and inside the color gamut GB. That is, when only the amount of cyan toner is gradually increased from C = M = Y = K = 0% to C = 100% and M = Y = K = 0% in this electrophotographic process. The hue in the Lab color space is represented by a trajectory of a curve obtained by connecting HC2 and HB2.

  Therefore, when the hue of HA is reproduced as a pure color after gamut compression, it must be assumed that the hue after gamut compression is HC2. In addition, the point having the maximum saturation after color gamut compression corresponding to PA is indicated by PC2, not PC, and if the correction is performed to preserve the pure color and extend the saturation, the expanded hue is It is assumed to be HB2.

FIG. 3 shows a diagram in which saturation correction is performed by the method of Patent Document 1 after the color gamut compression of HA while preserving pure colors in the electrophotographic process. As described above, the maximum saturation point after color gamut compression that preserves the pure color is PC2.
According to the method of Patent Document 1, since the hue is corrected linearly, the hue expanded after the correction is indicated not by HB2 in FIG. 2 but by HB3 obtained by extending HC3. Further, the maximum saturation point at that time is not PB but PB3.
As a result, in the case of the method of Patent Document 1, even if the hue is originally reproduced in pure color depending on the printing purpose, the pure color is not stored in the region where the color gamut is expanded by the effect of saturation correction.

  In view of these circumstances, the present invention aims to reproduce a conventional memory color while utilizing a color reproduction region that an image output apparatus such as a printer can originally output, and to obtain a good image after saturation correction. An object is to provide an image processing apparatus and an image processing method that can be obtained.

  In order to achieve such an object, the present invention provides an image processing apparatus capable of converting a color image signal input by an input device into an image signal suitable for the output device, wherein the first input image signal is color-coded. Color compression means for compression, first color conversion means for converting the image signal color-compressed by the color compression means into a color space different from the color space of the image signal, and the same as the first input image signal A second color conversion means for converting the second input image signal, which is a signal, into the different color space without color compression; and two images that have been color-converted by the first color conversion means and the second color conversion means Synthesizing means for synthesizing signals and generating new image signals.

  Further, the present invention is an image processing method capable of converting a color image signal input by an input device into an image signal suitable for an output device, the color compression step of color-compressing the first input image signal, A first color conversion step of converting the image signal color-compressed by the color compression step into a color space different from the color space of the image signal; and a second input image which is the same signal as the first input image signal A second color conversion step of converting the signal into the different color space without color compression, and the two image signals color-converted by the first color conversion step and the second color conversion step, and a new image And a synthesis step for generating a signal.

  In the image processing apparatus and the image processing method according to the present invention, saturation correction for more vividly outputting an input image can be realized by reproducing a conventional memory color while utilizing a color reproduction region that can be originally output by a printer. .

  Furthermore, in the image processing apparatus and the image processing method according to the present invention, the characteristics of the color material used for printing are taken into consideration. Therefore, a hue that has been reproduced with a pure color for printing purposes is preserved even after the saturation correction processing according to the present invention, so that a more vivid image without graininess or with reduced graininess is obtained. Obtainable.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings described below, components having the same function are denoted by the same reference numerals, and repeated description thereof is omitted.
(First embodiment)
FIG. 4 shows a configuration diagram of the entire system of this embodiment. FIG. 4 is a block diagram showing the overall configuration of the image processing system according to the present embodiment.

  Reference numeral 401 denotes an image input device applied to the present invention, such as a PC. Reference numeral 402 denotes an image output device that forms and outputs an image based on the image data input from the image input device 401. Reference numeral 403 denotes a network system for connecting the image input device 401 and the image output device 402. In this embodiment, the network system 403 is described as a network such as a wired LAN, a wireless LAN, or a WAN such as the Internet. However, the network system 403 is a communication mode in which the image output apparatus 402 and the image input apparatus 401 are connected by a dedicated line. May be. That is, any communication means of these devices may be used.

  In the present embodiment, any method may be used as the image forming method of the image output apparatus 402. For example, it is possible to form an image on a recording medium such as an electrophotographic system that uses toner as a color material to form an image on a photosensitive drum or a photosensitive belt, or an ink jet system that ejects ink from a minute nozzle array to print on paper. Any method may be used. However, as described above, when toner is used as the color material, the hue of the pure color is not a straight line but a curved orbit, so that the effect of the present invention is further exhibited when the image output device 402 is an electrophotographic system. Is done.

FIG. 5 is a block diagram showing the configuration of the main controller 501 of the image input apparatus 401 of the present invention.
Reference numeral 501 is a block diagram of the controller hardware of the image input apparatus 401. Reference numeral 502 denotes a CPU that operates a program for controlling the entire image input apparatus 401, and executes various processing operations such as calculation, control, and determination. Reference numeral 503 denotes a ROM that stores each program executed by the CPU 502 and a program for starting the image input apparatus 401. Reference numeral 504 denotes a RAM for temporarily storing data during the processing operation of the CPU 502, input data, and the like, and for operating a program for controlling the image input apparatus 401. Reference numeral 505 denotes a hard disk, which is a secondary storage device for storing program data to be developed and operated in the RAM 504, application software programs, and data required by the application software.

  Reference numeral 506 denotes a network communication device that performs data input / output processing with the image input device 402. Reference numeral 507 denotes a video data transmission unit for transmitting image data to an image display device for displaying an image or the like formed on the image input device 401. Reference numeral 508 denotes a cable for transmitting image data from the video data transmission unit to an external image display device. Reference numeral 509 denotes an operation unit that also serves as an image display device for displaying image data received from the video data transmission unit 508.

  Reference numeral 510 denotes an image processing unit for performing various kinds of image processing on the bitmap image data received from the network communication apparatus 506. The image processing unit 510 has a function of synthesizing two pages of bitmap image data with one page of bitmap image data and a function of removing illegal drawing portions existing in the bitmap image data. Further, the image processing unit 510 has a function of digitally correcting the bitmap image data such as a function of correcting the printing position when it is determined that the bitmap image data is skewed.

  Reference numeral 511 denotes a network cable for receiving image data from an external device and transmitting print data to the external device. The network cable 511 is connected to the network device 506. An external device I / F 512 serves as an interface with an external input / output device. A keyboard 513 and a mouse 514 are connected to the external device I / F 512.

Next, the configuration of the main controller 601 of the image output apparatus 402 will be described. FIG. 6 is a block diagram showing the configuration of the main controller 601 of the image output apparatus 402 of this embodiment.
Reference numeral 602 denotes an operation unit for operating the device. Reference numeral 603 denotes a network cable for connecting to an external device via a network. Reference numeral 604 denotes a line cable for connecting to an external device via a telephone line.

  Reference numeral 605 denotes a CPU that operates a program for controlling the entire controller 601 and executes various processing operations such as calculation, control, and determination. Reference numeral 606 denotes a RAM managed by a program operating on the CPU 605. The RAM 606 is used for purposes such as a reception buffer for temporarily storing data received from the outside and an image data buffer for temporarily storing image data rasterized by the RIP.

  Reference numeral 607 denotes an interface for connecting the operation unit 602 and the controller 601. Reference numeral 608 denotes an interface for connecting the controller 601 and the network. Reference numeral 609 denotes a modem as an interface for connecting the controller 601 and a telephone line.

  Reference numeral 610 denotes a ROM for storing programs, data, and the like that operate on the CPU 605. Reference numeral 611 denotes a hard disk that is a nonvolatile storage device capable of storing various data for a long period of time. Reference numeral 612 denotes a CPU bus for connecting the above components to each other and connecting to the CPU 605.

  Reference numeral 624 denotes an image bus connected to a hardware group for performing image processing. Reference numeral 613 denotes an interface for connecting the CPU bus 612 and the image bus 624. Reference numeral 621 denotes a rasterize board (RIP) having a function of converting image data input from the outside into bitmap image data. Reference numeral 614 denotes an interface for connecting the RIP 621 and the image bus 624 via the image transfer bus 618. Reference numeral 615 denotes a data compression device for compressing data.

  Reference numeral 616 denotes a device interface for connecting the scanner and the printer to the image bus 624 via the data buses 619 and 620. Reference numeral 617 denotes an image processing unit for performing various types of image processing on the bitmap image data generated by the scanner 622 and the RIP 621.

  The image processing unit 617 has a function of synthesizing two pages of bitmap image data into one page of bitmap image data, and a function of removing an illegal drawing portion caused by mixing of dust or the like when a document is read by the scanner 622. Prepare. In addition, the image processing unit 617 has a function of digitally correcting bitmap image data, such as a function for correcting a printing position when the scanner 622 scans an original and skews the document. Prepare.

Next, the flow of image processing in this embodiment will be described.
FIG. 7 is a block diagram showing the flow of image processing in this embodiment. 7 according to the present embodiment may be performed by the image input device 401 or the image output device 402. That is, the image input device 401 or the image output device 402 includes the OS 701, the driver unit 702, and the controller unit 703, thereby functioning as an image processing device that executes the processing illustrated in FIG. The OS 701, the driver unit 702, and the controller unit 703 are integrated by the CPU of the image processing apparatus (CPU 502 when the image processing apparatus is the image input apparatus 401, and CPU 605 when the image processing apparatus 402 is the image output apparatus 402). Controlled.

  The image processing apparatus only needs to be able to convert a color image signal input by the image input apparatus 401 (input apparatus) into an image signal suitable for the image output apparatus 402 (output apparatus). The image output device 402 may be provided separately.

  The input image is appropriately corrected by the image processing unit 510. The corrected input image (color image signal) is converted into an image signal IMG1 (first input image signal) and an image signal IMG2 (second input image signal) by the OS 701 via the network device 506 and the network cable 511. It is transmitted to the driver unit 702. That is, the OS 701 distributes the corrected color image signal to at least two image signals, and acquires the image signal IMG1 that is the first input image signal and the image signal IMG2 that is the second input image signal.

  Note that two systems of signals for the same image data are transmitted to the driver unit 702, but this is not limited to two systems, and the processing for distributing the image data to a plurality of systems is also realized by the OS 701. It is not limited to. For example, the driver unit 702 and other modules may be used.

  In this embodiment, as will be described later, color gamut compression is performed so that the image signal for color gamut compression for reproducing the original memory color and the color gamut of the output device can be used to the maximum. There is no need to prepare an image signal. Therefore, in the present embodiment, it is only necessary that the image processing apparatus can acquire at least two image data (image signals) that are the same as each other from the input image.

  The image signal IMG1 transmitted to the driver unit 702 is output from the color gamut compressing unit 705 in an appropriate color gamut that can reproduce the memory color in accordance with the printing purpose designated by the user in the operation unit 509 or the specified printing purpose. Is compressed. That is, the color gamut compression unit 705 performs color gamut compression on the image signal IMG1 that is the first input image signal to an appropriate color gamut. The color gamut compression unit 705 transmits the image signal IMG1 to the controller unit 703 after color gamut compression.

On the other hand, the image signal IMG2 that is the second input image signal is transmitted to the controller unit 703 without performing color gamut compression processing. Since the image signal IMG2 does not perform color gamut compression processing, the image signal IMG2 is an image signal that can use all the color gamuts of the printer to the maximum extent.
Further, the color gamut compression process does not necessarily need to be realized by the driver unit 702, and it can be considered to be realized by the controller unit 703 or other devices.

  The image signal IMG1 and the image signal IMG2 transmitted to the controller unit 703 are converted from RGB signals into CMYK signals that are the color space of the output device (printer unit 623) by the first color conversion unit 706 and the second color conversion unit 707, respectively. Is converted to That is, the first color conversion unit 706 converts the image signal IMG1 subjected to color gamut compression by the color gamut compression unit 705 into a color space (CMYK) different from the color space (RGB) of the image signal IMG1. The second color conversion unit 707 converts the image signal IMG2 that has not been color gamut-compressed into the different color space (CMYK).

  Each image signal converted into the CMYK signal is further transmitted to the synthesis unit 708. That is, the first color conversion unit 706 transmits the first color-converted image signal, which has been color-converted as a CMYK signal that is the color space of the printer unit 623, to the synthesis unit 708. Similarly, the second color conversion unit 707 also transmits a second color converted image signal that has been color-converted as a CMYK signal, which is the color space of the printer unit 623, to the synthesis unit 708.

  Here, since the second color-converted image signal is generated based on a signal that has not been subjected to color gamut compression, it is a signal that can make maximum use of the color gamut of the printer unit 623. As described above, according to the present embodiment, at least one of the color-converted image signals subjected to the color conversion can be a signal that can use all the color gamuts that can be reproduced by the printer unit 623.

  Note that the first color conversion unit 706 and the second color conversion unit 707 do not have to prepare different tables when converting the color space, and may be the same table.

  The synthesis unit 708 holds a synthesis rate conversion table (709 (for cyan), 710 (for magenta), 711 (for yellow), 712 (for black)) corresponding to each component of the CMYK signal. The combining unit 708 combines the first color conversion image signal generated based on the input image signal IMG1 and the second color conversion image signal generated based on the image signal IMG2 in accordance with each signal value. Both image signals are synthesized based on a predetermined synthesis rate such as a rate. The synthesis unit 708 generates a new image signal IMG3 by the synthesis. The image signal IMG3 is further subjected to appropriate image processing such as halftone processing, and finally transmitted to the printer unit 623 for output.

Next, the synthesis process in the synthesis unit 708 will be described below.
FIG. 8 shows a synthesis of the first color conversion image signal and the second color conversion image signal that are transmitted from the first color conversion unit 706 and the second color conversion unit 707 in the synthesis unit 708 regarding only the cyan component image signal. It is a block diagram explaining processing. In the figure, C1 indicates the cyan component of the first color conversion image signal that is a CMYK signal, and C2 indicates the cyan component of the second color conversion image signal that is a CMYK signal. Here, the configuration of only the cyan component will be described, but the composition processing regarding other color components (MYK) also has the same configuration.

  First, the image signal C1 and the image signal C2 transmitted to the synthesis unit 708 are transmitted to the calculation unit 801. That is, the synthesis unit 708 acquires the image signal C1, acquires the image signal C2, and passes the acquired image signal C1 and image signal C2 to the calculation unit 801.

  Next, the synthesis unit 708 inputs the image signal C2 to the synthesis rate conversion table LUTC 708a in which values are set for the cyan component, and generates a synthesis rate NC corresponding to the image signal C2. Here, a value that can be taken by the synthesis rate NC is set to a value in the range of 0 to 1 in consideration of the synthesis operation in the calculation unit 801. Next, the synthesis unit 708 transmits the synthesis rate NC generated by the synthesis rate conversion table LUTC 708a to the calculation unit 801.

The calculation unit 801 receives the image signal C1, the image signal C2, and the combination rate NC as input, and generates a new image signal C3 by a combination calculation represented by the following Expression 1.
C3 = NC * C1 + (1-NC) * C2 (Formula 1)
The combining unit 708 performs the above processing on each component of the CMYK signal. Note that Equation 1 is a simple example of an arithmetic expression used for the composition operation, but image signal composition is not limited to Equation 1. Here, it is only necessary to combine two or more input signals and adjust the ratio of the respective input signals. In other words, any arithmetic expression that can adjust the rate of change in hue according to a change in saturation may be used.

  9A to 9D show examples of the synthesis rate conversion table LUTC 708a. The synthesis rate conversion table LUTC 708a is a table showing the relationship of the synthesis rate NC to the input of the image signal C2. Here, since the image signal C2 is an image signal that is not subjected to color gamut compression, by using the image signal C2 as an input, it is possible to generate a composition ratio that makes maximum use of all the color gamuts of the printer.

  FIG. 9A is a simple example in which the relationship between input and output is linear. In FIG. 9A, the composition rate NC is 1 when the image signal C2 is the minimum value, and the composition rate NC is 0 when C2 is the maximum value. That is, the newly generated image signal C3 reflects the value of the color gamut-compressed image signal C1 when the value of the input signal is low, that is, regarding the color tone of the low saturation region. On the other hand, when the value of the input signal is high, that is, the color of the high saturation region, the value of the image signal C2 that is not subjected to color gamut compression is reflected.

  In the present embodiment, the image signal C2 is generated from a signal not subjected to color gamut compression, and therefore corresponds to the input signal. Therefore, the synthesis unit 708 can determine that the value of the input signal is low when the value of the acquired image signal C2 is low, and that the value of the input signal is high when the value is high. Accordingly, when generating the synthesis rate, the image signal C2 is used as an input, and the synthesis rate conversion table LUTC708a that defines the synthesis rate when the signal is synthesized is referred to, so that an appropriate synthesis according to the signal value of the input signal is performed. The rate can be obtained. That is, the synthesis rate can be changed so as to obtain a good output result in accordance with the change in the saturation of the input color image signal.

  Here, the image signal C1 is a color that reproduces a conventional memory color, and the image signal C2 is a color gamut that can utilize the color gamut of the printer to the maximum extent. Therefore, by inputting the NC calculated from FIG. 9A into Equation 1, the synthesized image signal C3 reproduces the hue of the memory color in the low saturation region, and the high saturation region has a higher saturation than in the conventional case. Can be reproduced. That is, the image signal C1 that has been subjected to color gamut compression and the image signal C2 that has not been subjected to color gamut compression are combined and the two signals are combined at different combining rates depending on the signal value of the input signal. Good output according to the saturation of the image can be performed.

  In FIG. 9B, the output composition ratio NC is set so as to draw an upwardly convex curve with respect to the input of the image signal C2. When this table is used, the value of the image signal C1 subjected to color gamut compression is strongly reflected from the low saturation region to the high saturation region. That is, it is the same as FIG. 9A that reproduces higher saturation than in the conventional art in the high saturation region, but in the process of transition from the low saturation region to the high saturation region, the effect of reproducing the memory color more is achieved. I can expect.

  On the other hand, FIG. 9C shows the case where the output synthesis rate NC is set to draw a downwardly convex curve with respect to the input of the image signal C2. When this table is used, contrary to FIG. 9B, the value of the image signal C2 is strongly reflected from the low saturation region.

  Further, the synthesis rate conversion table is not limited to the above-mentioned format. For example, it may be an inverted S shape as shown in FIG. As yet another example, it may be possible to determine the hue of the input signal and use different tables depending on the hue.

  Furthermore, as another example of the synthesis rate conversion table, the setting value may be changed for each image data or object transmitted from the driver unit 702, instead of using a predetermined table. For example, a method of appropriately changing the synthesis rate conversion table by accepting an input from the user in the operation unit 509 in the image input device 401 or in the operation unit 602 in the image output device 402 can be considered.

  As described above, in this embodiment, in order to make the color gamut of the first color conversion image signal that has been subjected to the color gamut compression to reproduce the original memory color and the output device the color gamut available to the maximum, It is important to use the second color-converted image signal that has not undergone area compression. Then, based on the signal value of the second color-converted image signal corresponding to the input signal, the combination rate of the first and second color-converted image signals is determined, and the first and second color conversion image signals are determined based on the combination rate. The color conversion image signal is synthesized. Therefore, even if the synthesized signal has a color tone outside the color gamut that has been color gamut-compressed with the input signal before synthesis, due to the presence of the appropriately synthesized second color-converted image signal, high saturation is achieved. Can be reproduced in degrees.

  That is, according to the present embodiment, the saturation is not linearly corrected when the color gamut is expanded as in the prior art, and the first color conversion image signal and the second color conversion image signal are input. Since synthesize by changing the synthesis ratio according to the signal, HC2 and HB2 in FIG. 2 can be realized. Therefore, it is possible to suppress the state in which the pure color is not preserved in the area where the color gamut is expanded by the effect of saturation correction as in the conventional case, and the characteristics of the color material in which the hue of the pure color such as toner becomes a curve. Considering this, a good image can be obtained even after saturation correction.

A method for changing the synthesis rate conversion table by the above method will be described below.
FIGS. 10A to 10C show a synthesis rate conversion table input screen 1001 when the operation unit 509 or the operation unit 602 displays on a monitor device such as a CRT or a liquid crystal display.

  The user changes the values of the CMYK component synthesis rate conversion table by changing each slider of the slider unit 1002a assigned to each CMYK component to the left or right via a pointing device such as a mouse or a touch panel as necessary. Can be made. The state of this change can be confirmed on the table display unit 1003a.

  In this embodiment, the value of the CMYK component synthesis rate conversion table for each color component of the image signal is changed independently for each color component. However, the present invention is not limited to this, and is linked to each color component. And may be changed. That is, by changing each color component (CMYK component) of the image signal after color conversion independently or in conjunction with each other, it is possible to determine the value of the synthesis rate conversion table and to determine the synthesis rate.

  In FIG. 10A, the slider value of each CMYK component is set at the center. This state is a reference state in the setting of the slider portion 1002a. At this time, the color component is linear as shown in the table display portion 1003a in the synthesis rate conversion table.

  On the other hand, in FIG. 10B, relative setting is made such that the cyan component is +4 and the magenta component is −4 in the slider portion 1002b. At this time, as shown in the table display part 1003b, the cyan component and the magenta component draw a curve in the synthesis rate conversion table.

  Further, in FIG. 10C, the relative setting of cyan component +8, magenta component +6, and yellow component +2 is made. At this time, as shown in the table display unit 1003c, the cyan component, the magenta component, and the yellow component draw a curve in the synthesis rate conversion table.

  Note that the composition rate conversion table changing method does not necessarily satisfy the configuration shown in the input screen 1001. Any display method or input method may be used as long as the composite rate conversion table can be changed by the user.

FIG. 11 is a flowchart illustrating a processing procedure in the synthesis unit 708.
In the combining unit 708, processing of the cyan component image signal C (1106), processing of the magenta component image signal M (1107), processing of the yellow component image signal Y (1108), and processing of the black component image signal K ( Each process of 1109) is executed sequentially. These processes may be executed in parallel. Since the content of the processing of each component is the same, the internal processing of the processing of the image signal C (1106) will be described here, but each processing may be changed as necessary. And Further, the content of the processing may be changed by the mutual interaction of the respective processing.

  Hereinafter, internal processing in the processing (1106) of the image signal C will be described.

  First, the synthesis unit 708 functions as a first image signal acquisition unit, and acquires the value of the image signal C1 that is the cyan component of the image signal IMG1 (1101). Subsequently, the synthesizing unit 708 functions as a second image signal acquisition unit, and acquires the value of the image signal C2 that is the cyan component of the image signal IMG2 (1102).

  Further, the synthesizing unit 708 refers to the synthesis rate conversion table LUTC in which a value is set for the cyan component from the value of the image signal C2 (1103), and generates a synthesis rate NC of the cyan component (synthesis rate generation) ( 1104).

  Finally, the synthesis unit 708 receives the image signal C1 acquired in the process 1101, the image signal C2 acquired in the process 1102, and the synthesis rate NC generated in the process 1104, and performs the calculation shown in Expression 1. A new image signal C3 is generated (1105).

  FIGS. 12A to 12C are graphs showing signal values before and after the synthesis process in the present embodiment. The signals input in FIGS. 12A to 12C are changed from (R, G, B) = (255, 255, 255) to (R, G, B) = (0, 255, 255). And an image obtained by gradually subtracting the red component, which corresponds to the hue HA in FIG. 1 when expressed in the Lab space. Each graph in FIG. 12 is a graph with the red signal to be subtracted as the horizontal axis and the CMYK components before and after the synthesis processing as the vertical axis.

  FIG. 12A corresponds to the image signal IMG1 in FIG. 7. The color compression unit 705 performs color gamut compression processing on the input signal, and the first color conversion unit 706 performs color conversion processing. The respective CMYK component values are shown. (1) is a graph in which cyan and yellow are mixed due to the influence of color compression and the characteristics of the first color conversion unit 706. In the figure, C1 represents a cyan component and Y1 represents a yellow component.

  FIG. 12B corresponds to the image signal IMG2 in FIG. 7, and the second color conversion unit 707 performs color conversion on the same input signal as in the case of the above (a) without performing color gamut compression processing. CMYK component values when the conversion process is performed are shown. (2) is a cyan pure color linear graph in which R = 0 and C2 = 100% due to the fact that color compression is not performed and the characteristics of the second color conversion unit 707.

  Further, FIG. 12C shows a combination unit 708 when FIGS. 12A and 12B are used as input signals and FIG. 9A is used as the combination rate conversion table (709, 710, 711, 712). It is a graph of the result of a synthetic | combination process. C3 and Y3 in the figure represent the cyan component and the yellow component after synthesis, respectively, and the broken line represents C2.

  As shown in FIG. 12C, both the cyan component and the yellow component reflect the influence of the signal value of FIG. 12A in the first half of the graph corresponding to the low saturation region. However, the latter half of the graph which is the high saturation region reflects the influence of FIG. 12B, and the maximum saturation portion is a cyan pure color.

FIG. 13 is a diagram showing saturation correction in the present embodiment. FIG. 13 shows changes in saturation and hue on the Lab space.
In FIG. 13, PL indicates a point on the L axis, and H (1) indicates a hue that the color material reproduces on a recording material such as paper when the signal value of FIG. P (1) indicates a point having the maximum saturation at that time.
H (2) indicates the hue that the color material reproduces on the recording material such as paper when the signal value of FIG. 12B is output by the output device, and P (2) is the maximum at that time. Indicates the saturation point.
Further, H (3) indicates the hue that the color material reproduces on the recording material such as paper when the signal value of FIG. 12C is output by the output device, and the maximum saturation at that time is P (2 ).

  As shown in FIG. 13, the combined image signal reflects the influence of H (1), which is a memory color, in the low saturation region, but H (2), which has higher saturation in the high saturation region. Reflects the impact of. In the maximum saturation portion, P (2) is obtained, and a cyan pure color is obtained.

  As described above, by performing the synthesis processing according to the present embodiment, the color reproduction area that can be originally output by the printer is effectively used, and the conventional memory color is reproduced, thereby suppressing deterioration in the quality of the input image, Correction processing that outputs more vividly can be realized.

  Furthermore, according to the synthesis process of the present embodiment, since the synthesis process is performed in the color space of the color material, if both the synthesized image signals are pure colors and have the same color components, the synthesized image signal is also the same. The pure color in the color component is preserved.

  For example, even if color reproduction with a pure color is realized in the image signal after the color compression unit 705 and the first color conversion unit 706, the pure color is stored according to the composition processing of the present embodiment. As a result, a more vivid image with reduced graininess can be obtained.

  Furthermore, according to the synthesis processing of the present embodiment, saturation correction is performed so as to reproduce the conventional memory color more in the low saturation region, so that there is no influence on the skin color reproduction in the portrait, Only high-saturation areas in landscapes can be made vivid.

(Second Embodiment)
Next, another embodiment of the present invention will be described.
The present embodiment applies the image processing apparatus and the image processing method according to the present invention when encoded image data such as JPEG is transmitted from the digital camera or the memory card to the image output apparatus 402 via the USB interface. This is an embodiment.

  FIG. 14 is a block diagram showing the flow of image processing in this embodiment.

  The JPEG image data transmitted from the digital camera 1401 is expanded in the YCC image processing unit 1403, and YCbCr color image data corresponding to each pixel is generated. The YCC image processing unit 1403 further performs appropriate image processing in the YCrCb color space, converts it to the RGB color space, and transmits it to the color gamut compression processing unit. That is, the YCC image processing unit 1403 distributes at least two image signals from the color image signal converted into the RGB color space, and uses the image signal IMG1 that is the first input image signal and the second input image signal. A certain image signal IMG2 is acquired. Next, the acquired image signal IMG1 is transmitted to the first color gamut compression unit 1410, and the acquired image signal IMG2 is transmitted to the second color gamut compression unit 1411.

  That is, the YCC image processing unit 1403 transmits the two types of image signals (the image signal IMG1 and the image signal IMG2) to the first color gamut compression unit 1410 and the second color gamut compression unit 1411, respectively. The

  Similar to the color gamut compression unit 705 (FIG. 7) in the first embodiment, the first color gamut compression unit 1410 performs compression to an appropriate color gamut capable of reproducing the memory color in accordance with the printing purpose. The transmitted signal is transmitted to the first color conversion unit 1412. In the color gamut compression, considering that the color gamut of the digital camera is wider than the color gamut of the monitor, the Adobe RGB color space or the sRGB color space which is the monitor color space is expanded to enable encoding. It is also conceivable to use an extended sRGB color space.

In the second color gamut compression unit 1411, a linear table may be provided so that the process is passed through in the same manner as in the first embodiment, and the signal is transmitted as it is to the second color conversion unit 1413 as a signal in the printer color gamut. .
It is also conceivable to control the effect of subsequent synthesis processing by performing color gamut compression different from that of the first color gamut compression unit 1410.

  Further, in the first color gamut compression unit 1410 and the second color gamut compression unit 1412, it is determined whether the color space of the input image data is AdobeRGB or extended sRGB, and a color space table corresponding to the determination result is displayed. refer. It is also conceivable to always realize color gamut compression in an appropriate color space by the reference. This makes it possible to output an image corresponding to input of image data in various color spaces.

  The respective image signals converted into the printer color space by the first color gamut compression unit 1410 and the second color gamut compression unit 1412 are sent to the synthesis unit 708 via the first color conversion unit 706 and the second color conversion unit 707. Thus, a new image signal is generated and printed by the printer unit 623.

  As described above, in the image processing apparatus according to the present embodiment, even if the input image data is encoded using JPEG or the like, the composition process can be performed as in the case of the first embodiment. That is, even if the color space differs depending on the input image data, the color gamut compression unit can refer to an appropriate table to perform the synthesis process without causing the image to fail.

(Other embodiments)
The present invention can be applied to a system constituted by a plurality of devices (for example, a computer, an interface device, a reader, a printer, etc.), or can be applied to an apparatus (multifunction device, printer, facsimile machine, etc.) comprising a single device. Is also possible.

  The processing method for storing the program for operating the configuration of the above-described embodiment so as to realize the function of the above-described embodiment in a storage medium, reading the program stored in the storage medium as a code, and executing the program on the computer is also described above. It is included in the category of the embodiment. That is, a computer-readable storage medium is also included in the scope of the embodiments. In addition to the storage medium storing the computer program, the computer program itself is included in the above-described embodiment.

  As such a storage medium, for example, a floppy (registered trademark) disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, and a ROM can be used.

  In addition, the processing is not limited to the single program stored in the above-described storage medium, but operates on the OS in cooperation with other software and expansion board functions to execute the operations of the above-described embodiments. This is also included in the category of the embodiment described above.

It is a figure for demonstrating the conventional saturation correction | amendment. It is a figure showing the hue of the pure color in the conventional electrophotographic process. It is a figure at the time of carrying out the saturation correction | amendment by the method of patent document 1, after carrying out color compression of HA, preserving a pure color in the conventional electrophotographic process. It is a block diagram of the whole system which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the main controller of the image input device based on one Embodiment of this invention. It is a block diagram which shows the structure of the main controller of the image output device which concerns on one Embodiment of this invention. It is a block diagram which shows the flow of the image processing in one Embodiment of this invention. It is the block diagram explaining the synthetic | combination process in the synthetic | combination part based on one Embodiment of this invention. (A)-(d) is a figure which shows the example of the synthetic | combination rate conversion table LUT about cyan, for example based on one Embodiment of this invention. It is a figure which shows the example of the synthetic | combination rate conversion table input screen in the case of making it display on an operation part based on one Embodiment of this invention. It is the flowchart explaining the procedure of the process in the synthetic | combination part based on one Embodiment of this invention. (A)-(c) is a figure which shows the signal value before and behind the synthetic | combination process in one Embodiment of this invention. It is the figure which showed the saturation correction | amendment in one Embodiment of this invention. It is a block diagram which shows the flow of the image processing in one Embodiment of this invention.

Explanation of symbols

401 Image input device 402 Image output device 403 Network 701 OS
702 Driver unit 703 Controller unit 705 Color gamut compression unit 706 First color conversion unit 707 Second color conversion unit 708 Composition unit 709 Synthesis rate conversion table LUT for cyan
710 Composite rate conversion table LUT for magenta
711 Composite rate conversion table LUT for yellow
712 Composite rate conversion table LUT for black

Claims (16)

An image processing device capable of converting a color image signal input by an input device into an image signal suitable for the output device,
Color compression means for color-compressing the first input image signal;
First color conversion means for converting the image signal color-compressed by the color compression means into a color space different from the color space of the image signal;
Second color conversion means for converting the second input image signal, which is the same signal as the first input image signal, into the different color space without color compression;
An image processing apparatus comprising: combining means for combining two image signals color-converted by the first color conversion means and the second color conversion means to generate a new image signal. The color space of the two image signals input to the combining means is the color space of the output device,
The image processing apparatus according to claim 1, wherein at least one of the two image signals is a signal that can use all color gamuts that can be reproduced by the output device.   The image processing apparatus according to claim 1, wherein the synthesizing unit changes a synthesis rate of two input signals input to the synthesizing unit in accordance with a change in saturation.   The image processing apparatus according to claim 3, wherein the synthesis rate is a synthesis rate determined according to a signal value of an image signal color-converted by the second color conversion unit.   The image processing apparatus according to claim 4, wherein the synthesis rate is determined by changing each color component of the image signal after conversion independently or in conjunction with the image signal. The synthesis means includes
First image signal acquisition means for acquiring an image signal color-converted by the first color conversion unit;
Second image signal acquisition means for acquiring the image signal color-converted by the second color conversion unit;
The second image signal acquisition unit refers to a combination rate conversion table that defines a combination rate when combining the two image signals color-converted by the first color conversion unit and the second color conversion unit. From the acquired image signal and the synthesis rate conversion table, a synthesis rate generation means for generating the synthesis rate,
Means for synthesizing the image signal acquired by the first image signal acquiring means and the image signal acquired by the second image signal acquiring means in accordance with the combining rate to generate the new image signal; The image processing apparatus according to claim 1, comprising:   2. The apparatus according to claim 1, further comprising means for acquiring the first input image signal and the second input image signal by distributing the input color image signal into at least two image signals. 7. The image processing device according to any one of 1 to 6. An image processing method capable of converting a color image signal input by an input device into an image signal suitable for the output device,
A color compression step for color-compressing the first input image signal;
A first color conversion step of converting the image signal color-compressed by the color compression step into a color space different from the color space of the image signal;
A second color conversion step of converting the second input image signal, which is the same signal as the first input image signal, into the different color space without color compression;
An image processing method comprising: a combining step of combining the two image signals color-converted by the first color conversion step and the second color conversion step to generate a new image signal. The color space of the two image signals input to the synthesis step is the color space of the output device,
9. The image processing method according to claim 8, wherein at least one of the two image signals is a signal that can use all the color gamuts that can be reproduced by the output device.   The image processing method according to claim 8 or 9, wherein the synthesis step changes a synthesis rate of the two input signals input in the synthesis step according to a change in saturation.   The image processing method according to claim 10, wherein the synthesis rate is a synthesis rate determined according to a signal value of the image signal color-converted in the second color conversion step.   The image processing method according to claim 11, wherein the synthesis rate is determined by changing each color component of the converted image signal independently or in conjunction with each other. The synthesis step includes
A first image signal acquisition step of acquiring the image signal color-converted by the first color conversion step;
A second image signal acquisition step of acquiring the image signal color-converted by the second color conversion step;
With reference to the synthesis rate conversion table that defines the synthesis rate when synthesizing the two image signals color-converted by the first color conversion step and the second color conversion step, the second image signal acquisition step From the acquired image signal and the synthesis rate conversion table, a synthesis rate generation step of generating the synthesis rate,
Synthesizing the image signal acquired by the first image signal acquisition step and the image signal acquired by the second image signal acquisition step according to the synthesis rate, and generating the new image signal; The image processing method according to claim 8, further comprising:   9. The method according to claim 8, further comprising the step of distributing the input color image signal into at least two image signals to obtain the first input image signal and the second input image signal. 14. The image processing method according to any one of items 13 to 13.   A computer program for causing a computer to execute the image processing method according to claim 8.   A storage medium storing a computer-readable program, wherein the computer program according to claim 15 is stored.

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