JP6363916B2 - Image processing apparatus and method - Google Patents

Description

  The present invention relates to image processing for forming an image suitable for an observation environment.

  Image processing apparatuses such as digital copiers, printers, and facsimiles using various methods such as ink jet, electrophotography, and thermal transfer have become widespread. These image processing apparatuses realize advanced color reproduction by performing color matching processing using an ICC (International Color Consortium) profile describing the color reproduction characteristics of printed matter. In general, the color reproduction characteristics of a printed matter are defined by colorimetric values based on the measurement of spectral reflectance.

  By the way, the place where the printed matter is observed is variously posted even on the wall, posted on the wall, displayed in the center of the room, or hung on the wall. In addition, since the lighting fixtures in the room are also installed in various places, the brightness varies depending on the place. That is, the observation environment light irradiated on the printed matter greatly varies depending on the posting location. For this reason, when the observation environment is different even for the same printed matter, the color of the printed matter perceived by the observer changes to some extent depending on the observer. In other words, there is a problem that a printed matter of a desired color cannot be obtained depending on the observation environment.

  To deal with this problem, Patent Document 1 discloses a technique for switching a color profile used for color matching processing during printing in accordance with an observation environment such as wall brightness or wall color. Patent Document 2 discloses a technique for creating a color profile suitable for an observation environment by separately holding the spectral data of a printed matter and the spectral data of a light source in the observation environment. In addition, it is described that the color profile suitable for the observation environment can be created with a small number of colorimetry work man-hours, and appropriate color management of the printed matter according to the observation environment is possible.

  As described above, the color of the printed matter perceived by the observer changes as the observation environment changes. This is because the diffuse reflection light and the specular reflection light of the printed matter are changed by the reflection properties of the printed matter such as the diffuse reflection characteristic and the specular reflection characteristic of the printed matter and the light source of the observation environment (hereinafter, the observation light source). That is, when the amount of light applied to the printed material from the observation light source is strong, the diffuse reflected light of the printed material becomes relatively strong. In addition, when the amount of light irradiated from the regular reflection direction is strong when observing the printed matter, the specular reflected light of the printed matter becomes strong, and the color of the printed matter with low brightness, particularly the color of the dark portion of the image, is perceived brightly.

  Patent Documents 1 and 2 disclose techniques for applying a color profile corresponding to an observation environment. However, only by changing the color profile, the printing method of the dark part of the image is not changed. Depending on the observation environment, the color of the dark part is perceived brightly, and the color reproduction range of the dark part of the image is narrowed. Of course, not only in the dark portion of the image, but also in the high saturation region of the image, depending on the observation environment, the perceptual saturation in which the color is perceived brightly occurs, and the color reproduction region of the printed material becomes narrow.

JP 2012-044475 A Japanese Unexamined Patent Publication No. 2007-081586

  It is an object of the present invention to control an image output mode when outputting image data of an image arranged in an observation environment according to the observation environment.

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

The image processing according to the present invention acquires an observation condition indicating an observation environment of the image,
For each of multiple image output modes, it retains diffuse reflection and specular reflection characteristics as image reflection characteristics.
As the reflected light of the image under the observation condition, a color value of the diffuse reflected light of the image under the observation condition is calculated based on the diffuse reflection characteristic, and the specular reflection light of the image under the observation condition based on the specular reflection characteristic To calculate the color value of
For each of the plurality of image output modes, the sum of the color value of the diffuse reflection light and the color value of the specular reflection light is calculated, and the image output mode in which the brightness indicated by the sum of the color values is minimum, or the color Select the image output mode with the maximum saturation indicated by the sum of the values ,
Image data for forming an image arranged in the observation environment is output according to the selected image output mode.

  ADVANTAGE OF THE INVENTION According to this invention, the image output mode at the time of outputting the image data of the image arrange | positioned in observation environment can be controlled according to observation environment, for example, the image for forming the image suitable for observation environment Data can be output.

The figure which shows the outline | summary of the colorimeter used for the measurement of an angle-change characteristic. The figure explaining the light which an observer's eyes receive from the printed matter arrange | positioned in a general observation environment. The figure which shows the outline | summary of the general colorimeter which measures a spectral reflectance. 1 is a block diagram illustrating a configuration example of an image processing apparatus according to an embodiment. The block diagram which shows the process structural example of an image processing apparatus. The figure which shows an example of the printed matter reflection characteristic which a reflection characteristic holding part hold | maintains. The block diagram which shows the process structural example of an image data output part. The figure which shows an example of GUI which an observation condition acquisition part provides. 6 is a flowchart for describing image output mode selection processing executed by the image processing apparatus. The figure explaining the relationship between the diffuse reflection special light corresponding to an image output mode, specular reflection light, and a color value. FIG. 3 is a block diagram illustrating a processing configuration example of an image processing apparatus according to a second embodiment.

  Hereinafter, an image processing apparatus and an image processing method according to embodiments of the present invention will be described in detail with reference to the drawings. In addition, an Example does not limit this invention concerning a claim, and all the combinations of the structure demonstrated in an Example are not necessarily essential for the solution means of this invention.

[Observation of printed matter]
Depending on the viewing environment, the color of the printed matter perceived by the viewer may not match the color value measured by the colorimeter. First, the reason why the color value measured by a general colorimeter is different from the color appearance in the actual observation environment will be described.

  Fig. 1 shows an outline of the colorimeter used for measuring the angle change characteristic. Bidirectional reflectance distribution function (BRDF) is a measurement of the intensity of reflected light with respect to an emission angle (reflection angle) when light is irradiated from a certain angle. As shown in FIG. 1 (a), the variable angle characteristic is measured by irradiating the printed matter 501 with illumination light 502 arranged at the projection angle θ, and the light receiving unit 503 arranged at the acceptance angle θ ′. This is done by measuring the reflection intensity. In the measurement of the variable angle characteristic, the reflection intensity in all directions can be measured by making the projection angle θ and the light reception angle θ ′ variable.

  Fig. 1 (b) shows an example of measurement of the angle-deflection characteristics of general glossy paper, with the projection angle θ fixed at 45 degrees and the reception angle θ 'varied from -90 degrees to +90 degrees. The reflected intensity is shown. The light from the illumination light 502 is reflected by the printed material 501, and shows a large reflection characteristic (hereinafter, specular reflection characteristic) in the regular reflection direction. On the other hand, the printed matter 501 exhibits small reflection characteristics (hereinafter, diffuse reflection characteristics) in directions other than the regular reflection direction.

  The light received by the observer's eyes from a printed material placed in a general observation environment will be described with reference to FIG. In FIG. 2, an observation position 601 corresponds to the regular reflection direction of the illumination 604, and light (specular reflection light) in which the illumination image is reflected on the printed matter 603 reaches the eyes of the observer. The observer cannot recognize the color of the printed matter 603 if the specular reflection light is too strong, and therefore moves from the observation position 601 to the observation position 602 where the specular reflection light does not enter the eyes, and observes the printed matter 603.

  A wall 606 exists in the regular reflection direction corresponding to the positional relationship between the observation position 602 and the printed material 603. The light of the illumination 604 is diffusely reflected on the wall 606 and reaches the printed matter 603. Diffuse reflection light from the wall 606 is received by the observer's eyes as specular reflection light corresponding to the specular reflection characteristic of the printed matter 603. However, the diffusely reflected light from the wall 606 is weaker than the light that directly reaches the printed matter 603 from the illumination 604 and does not have such intensity that the color of the printed matter 603 cannot be recognized at the observation position 602. On the other hand, light from various directions other than the regular reflection direction, for example, light from the illumination 605 also reaches the printed material 603, and the light is received by the observer as diffuse reflected light according to the diffuse reflection characteristics of the printed material 603. .

  That is, the light received by the observer's eyes includes specular reflection light in which the light from the regular reflection direction is reflected according to the specular reflection characteristic of the printed material 603, and diffuse reflection characteristics of the printed material 603 in which the light from other than the regular reflection direction is reflected. It is the diffuse reflection light reflected according to. Accordingly, the color appearance of the printed matter 603 is determined by the diffuse reflection light and specular reflection light received by the observer's eyes, and is greatly influenced by light from the wall in the regular reflection direction and light from other than the regular reflection direction. However, the dark portion of the image has a very small diffuse reflectance compared to the bright region of the image, so the influence of light from the wall in the regular reflection direction becomes very large.

  FIG. 3 shows an outline of a general colorimeter that measures spectral reflectance. As shown in FIG. 3, the colorimeter arranges illumination light 402 in the direction of an incident angle of 45 degrees with respect to the printed matter 401, and reflects the light emitted from the illumination light 402 and reflected by the printed matter 401 at a reflection angle of 0 degree. Light is received by the light receiving unit 403 arranged in the direction.

  The light received by the light receiving unit 403 of a general colorimeter is only the diffuse reflection light of the printed matter 401, and the specular reflection light corresponding to the specular reflection characteristic of the printed matter 401 is not measured. As a result, there may occur a case where the color value of a general colorimeter does not match the color of the printed material 401 that is actually perceived by the observer. On the other hand, according to the measurement of the angle change characteristic shown in FIG. 1, it is possible to predict the color of the printed matter perceived by the observer from the specular reflection characteristic and diffuse reflection characteristic of the printed matter, and the light source characteristic of the observation environment. .

  The following is a method for predicting the color of a printed material perceived by an observer from the specular reflection characteristics and diffuse reflection characteristics of the printed material, and the light source characteristics of the observation environment, and image processing for forming a printed material suitable for the observation environment. explain.

[Device configuration]
A block diagram of FIG. 4 shows a configuration example of an information processing apparatus that functions as the image processing apparatus 100 of the embodiment. The CPU 104 uses the RAM 106 as a work memory, executes an OS and various programs stored in the ROM 105 and the storage unit 103, and controls a configuration to be described later via the system bus 109.

  The input unit 101 is a serial bus interface such as a USB, and is connected to an input device such as a keyboard or mouse, a memory card reader, an image input device such as a digital camera or a scanner. The CPU 104 inputs user instructions, image data, and the like via the input unit 101, and displays a graphic user interface (GUI), images, processing progress, results, and the like on a display unit 102 that is a monitor.

  The storage unit 103 is a recording medium such as a hard disk drive (HDD) or a solid state drive (SSD) in which various programs and various data are stored. The program stored in the storage unit 103 includes a program for realizing image processing to be described later.

  The communication unit 107 is a network interface for connecting to a wired or wireless network 110 such as Ethernet (registered trademark), Bluetooth (registered trademark), Wi-Fi, or P2P. The output unit 108 is a serial bus interface such as a USB, and outputs image data and the like to the image output device 111 and the memory card writer connected to the serial bus.

  The CPU 104 communicates with a server device and other computer devices on the network 110 via the communication unit 107. The CPU 104 receives various programs and data from server devices and other computer devices on the network 110, executes processing, and provides processing result data to the server devices and other computer devices on the network 110. can do. Note that the computer device with which the CPU 104 can communicate via the communication unit 107 includes the image output device 111, and image data can also be output to the image output device 111 via the communication unit 107.

  The image processing apparatus 100 is realized by supplying a program for realizing image processing described later to a computer device such as a personal computer, a tablet, or a smartphone. When a tablet or a smartphone is used as the image processing apparatus 100, the input unit 101 and the display unit 102 may be stacked and configured as a touch panel.

  FIG. 4 shows an example in which the image processing apparatus 100 and the image output apparatus 111 are configured separately, but the present invention includes an image forming apparatus in which the image processing apparatus 100 and the image output apparatus 111 are integrated, Further, it can be applied to an image copying apparatus provided with an image reading apparatus.

[Processing configuration]
An example of the processing configuration of the image processing apparatus 100 is shown in the block diagram of FIG. Note that the processing configuration shown in FIG. 5 is realized by supplying the information processing apparatus shown in FIG. 4 with a program for realizing the processing configuration and its function, and the information processing apparatus executing the program.

  The diffuse reflection characteristic acquisition unit 203 acquires the diffuse reflection characteristic of the image output from the image output device 111 from, for example, a colorimeter or a gonometric measuring instrument. The specular reflection characteristic acquisition unit 204 acquires the specular reflection characteristic of the image from, for example, an angle change measuring device. These diffuse reflection characteristics and specular reflection characteristics are acquired in advance for all image output modes included in the image processing apparatus 100, and are stored in the reflection characteristic holding unit 205 as printed matter reflection characteristics. The reflection characteristic holding unit 205 is assigned to the storage unit 103 and the like.

  In order to simplify the explanation, it is assumed that the print reflection characteristic is acquired from the darkest part of the image (that is, the black patch formed from the image data having the maximum density). However, the present invention is not limited to this, and for example, the printed material reflection characteristics are obtained from a patch formed from image data corresponding to the maximum applied amount (or the maximum amount of ink applied) when recording recording materials of all colors. May be.

  In addition, the print reflection characteristics are a combination of diffuse reflection characteristics measured at a projection angle of 45 degrees and a reception angle of 0 degrees, and regular reflection characteristics measured at a projection angle of 45 degrees and a reception angle of 45 degrees (variation characteristics). Get as. The diffuse reflection characteristic and the specular reflection characteristic are not limited to the measured value of the angle change characteristic, but may be a measured value measured according to JIS standards.

  FIG. 6 shows an example of the printed material reflection characteristic held by the reflection characteristic holding unit 205. FIG. 6 shows an example in which the CIEXYZ value of the diffuse reflection characteristic and the CIEXYZ value of the specular reflection characteristic are held as a table in two image output modes. Note that the CIELAB value may be used instead of the CIEXYZ value, or only the luminance value Y may be used.

  FIG. 6 illustrates the diffuse reflection characteristic and the specular reflection characteristic when the black patch is formed in the image output modes A and B. In either characteristic, the smaller the luminance value Y is, the more difficult the light is reflected. In the diffuse reflection characteristic, it can be said that the luminance value Y of the image output mode A is smaller than that of the image output mode B, and the image output mode A has a characteristic of low diffuse reflectance.

  On the other hand, in the specular reflection characteristic, it can be said that the luminance value Y of the image output mode A is larger than that of the image output mode B, and the image output mode A has a high specular reflectance. In other words, the image processing apparatus 100 includes a plurality of image output modes having different printed material reflection characteristics.

  Although the details will be described later, the observation condition acquisition unit 202 provides a GUI for acquiring, for example, the type of light source and the observation position of the observer as a condition when the printed matter is observed (hereinafter referred to as an observation condition), User instruction for the GUI is acquired as an observation condition.

  Although the details will be described later, the reflected light calculation unit 206, based on the observation conditions acquired by the observation condition acquisition unit 202, and the printed material reflection characteristics for each image output mode held by the reflection characteristic holding unit 205, the black patch of the printed material in the observation environment The intensity of the diffuse reflection light and the intensity of the specular reflection light are calculated. Based on the calculation result of the reflected light calculation unit 206, the output mode selection unit 207 selects an image output mode suitable for the observation condition from a plurality of image output modes of the image processing apparatus 100.

  The image data input unit 201 inputs image data in accordance with a user instruction, and stores the image data in a buffer assigned to the RAM 106 or the like. The image processing unit 208 performs image processing on the image data stored in the buffer based on the image output mode selected by the output mode selection unit 207, and outputs the image data after the image processing. The image data after the image processing is supplied to the image output device 111 via the output unit 108 and the like, and image formation is performed.

Image Processing Unit A processing configuration example of the image processing unit 208 is shown in the block diagram of FIG. A color management system (CMS) processing unit 301 refers to a color profile designed in advance and performs color matching processing on image data stored in the buffer.

  The color separation processing unit 302 performs color separation processing on the image data on which color matching processing has been performed with reference to a color separation table designed in advance. For example, when the image output device 111 is equipped with six color recording materials of CMYKLcLm, RGB image data is color-separated into recording material data representing the amount of each recording material of CMYKLcLm.

  The density correction processing unit 303 uses a correction table, which is a one-dimensional lookup table (1DLUT), for example, from the paper white to the maximum density of each recording material, the output characteristics of the image formed by each recording material is density linear or brightness Each recording material data is subjected to density correction processing so as to be linear. The halftone processing unit 304 binarizes each recording material data that has been subjected to density correction processing, using binarization processing such as an error diffusion method.

  When the image output device 111 is an ink jet printer, when the halftone image data obtained by the binarization process is input, the image output device 111 controls the ejection of the corresponding ink according to each recording material data, and prints An image is formed on the medium.

  The color profile used by the CMS processing unit 301, the color separation table used by the color separation processing unit 302, the correction table used by the density correction processing unit 303, and the halftone table used by the halftone processing unit 304 for binarization processing are output to each image. Prepared for each mode. Then, according to the selection of the image output mode, at least one of the color profile, the color separation table, the correction table, and the halftone table is changed, so that reflection characteristics of different printed materials can be obtained.

  For example, the image output mode B uses six color materials, the image output mode A uses a high transparency material (for example, clear material CL) in addition to the six color materials, and the image output mode C uses CMYK four colors. Different printed material reflection characteristics can be obtained due to differences such as the use of only the color material. In other words, the image data output from the image processing unit 208 varies depending on the image output mode, and thereby, different reflection characteristics of the printed matter can be obtained. The halftone table is, for example, an error diffusion matrix that defines a diffusion coefficient for controlling error diffusion or a dither matrix that holds a threshold value.

  Further, when the image output device 111 is an ink jet printer, it is possible to change the pass separation method in multi-pass printing according to a print job instruction corresponding to the image output mode. For example, by switching the pass mask used for the pass separation to the dot concentration type or the dot dispersion type, different printed matter reflection characteristics can be obtained. Further, when the image output device 111 is an electrophotographic printer, the reflection characteristics of different printed materials can be obtained by changing the toner fixing conditions (fixing temperature, fixing speed) and the like according to the instruction of the print job corresponding to the image output mode. . That is, the image processing unit 208 obtains different printed material reflection characteristics by changing the image forming conditions for the output image data.

Observation condition acquisition unit Fig. 8 shows an example of a GUI provided by the observation condition acquisition unit 202. The user sets observation conditions using the GUI shown in FIG. “Light source type setting” selects the type of illumination such as a fluorescent lamp, an incandescent lamp, and an LED lamp. According to the “color temperature setting”, the color temperature of the light source is input, or an indicator representing the color temperature or spectral distribution of illumination such as a light bulb color, daylight white, or a three-wavelength type is selected. By “illuminance setting”, for example, the total luminous flux of the illumination (if there are a plurality of lumens and light sources, the total of the total luminous flux of each light source) is input or the number of light sources is designated. For example, “whiteness”, “slightly dark color”, “dark color”, “dark”, or the like is selected as the wall brightness index by “wall brightness setting”.

  The center of the circle of “observation position setting” is the position of the printed material, and the user sets the observation position (□ in the circle) for the printed material. The horizontal axis of the circle corresponds to the horizontal angle of the observation position viewed from the printed material, and the vertical axis corresponds to the depth direction angle of the observation position viewed from the printed material. “Open” in “observation position setting” is a button for designating a data file of an observation environment image.

  Fig. 8 (b) is an example of an observation environment image. An omnidirectional image was taken with a camera installed at a position on the printed matter (center of the circle in Fig. 8 (a)) and the fisheye lens of the camera facing the ceiling of the room. It is an image. In the omnidirectional image shown in FIG. 8 (b), a plurality of light sources arranged on the black ceiling are shown, and the surrounding walls are shown in gray. The center of the omnidirectional image coincides with the position of the printed material (the center of the circle in FIG. 8 (a)), and the direction of the axis shown in the omnidirectional image coincides with the direction of the axis of the circle in FIG. 8 (a). Such an omnidirectional image is designated as the observation environment image.

  The brightness of the light irradiated on the printed material from the specular direction (hereinafter referred to as the normal light) from the observation conditions (light source type setting, color temperature setting, illuminance setting, wall brightness setting, positional relationship between the observation position and the printed material, observation environment image). The reflection direction light source characteristic) can be calculated. Similarly, it is possible to calculate the brightness of light irradiated on the printed matter from a direction other than the regular reflection direction (hereinafter, light source characteristics other than the regular reflection direction).

  Further, as described above, the color appearance of the printed material is important for the light irradiated to the printed material from the regular reflection direction with respect to the observation position and the light irradiated to the printed material from other than the regular reflection direction. Accordingly, the observation condition acquisition unit 202 determines the brightness level of the user from several levels such as “bright”, “slightly bright”, “medium”, “slightly dark”, or “dark” for each of these two light brightness levels. The structure which selects may be sufficient. Of course, the result of measuring the light from the regular reflection direction with respect to the observation position at the position of the printed matter and measuring the light from other than the regular reflection direction may be input.

[Image processing]
The image output mode selection process executed by the image processing apparatus 100 will be described with reference to the flowchart of FIG. When selection of the image output mode is instructed by the user, the observation condition acquisition unit 202 acquires the observation conditions (S801). The reflected light calculation unit 206 calculates the regular reflection direction light source characteristic Ls (XYZ value) and the light source characteristic Ld (XYZ value) other than the regular reflection direction from the observation conditions (S802).

  Note that the direct reflection direction light source characteristics Ls and the light source characteristics Ld other than the regular reflection direction are directly used, such as when the brightness level of the light emitted to the printed material is specified or when the number of light sources is specified instead of the total luminous flux. Cannot be calculated. In such a case, the reflected light calculation unit 206 calculates the regular reflection direction light source characteristics Ls and the light source characteristics Ld other than the regular reflection direction using representative numerical values.

Next, the reflected light calculation unit 206 selects one of a plurality of image output modes (S803), and acquires the diffuse reflection characteristic Pd and the specular reflection characteristic Ps corresponding to the selected image output mode from the reflection characteristic holding unit 205. (S804). Then, the diffuse reflection light Od of the printed material under the observation condition is calculated by the following equation (S805).
Od _X m = Ld _X × Pd _X m;
Od _Y m = Ld _Y × Pd _Y m;… (1)
Od _Z m = Ld _Z × Pd _Z m;
Here, Ld _X Ld _Y Ld _Z is a light source characteristic other than the regular reflection direction,
Pd _X mPd _Y mPd _Z m is the diffuse reflection characteristic of the image output mode m,
Od _X mOd _Y mOd _Z m is the diffuse reflected light in the observation condition and image output mode m.

Next, the reflected light calculation unit 206 calculates the specular reflected light Os of the printed material under the observation conditions by the following equation (S806).
Os _X m = Ls _X × Ps _X m;
Os _Y m = Ls _Y × Ps _Y m;… (2)
Os _Z m = Ls _Z × Ps _Z m;
Where Ls _X Ls _Y Ls _Z is the light source characteristic of specular reflection direction,
Ps _X mPs _Y mPs _Z m is the specular reflection characteristic of image output mode m,
Os _X mOs _Y mOs _Z m is the specular reflection light under the observation conditions and image output mode m.

  Next, the reflected light calculation unit 206 determines whether or not the diffuse reflected light Od and the specular reflected light Os have been calculated for all image output modes (S807). If there is an image output mode that has not been calculated, the process returns to step S803 to calculate diffuse reflection light Od and specular reflection light Os for all image output modes.

When the calculation of the diffuse reflection light Od and the specular reflection light Os is completed for all image output modes, the output mode selection unit 207 calculates the color value Ot (diffuse reflection light Od and specular reflection light Os in each image output mode by the following equation. Is calculated (S808).
Ot _X m = Od _X m + Os _X m;
Ot _Y m = Od _Y m + Os _Y m;
Ot _Z m = Od _Z m + Os _Z m;… (3)
Here, Ot _X mOt _Y mOt _Z m is a color value in the image output mode m.

Next, the output mode selection unit 207 selects an image output mode based on the color value Ot of each image output mode (S809). Here, an image output mode in which the black patch appears to have lower luminance under the obtained observation conditions is selected. In other words, the image output mode in which the black patch looks the darkest and the color value Ot _Y is the smallest is selected.

  The relationship among the diffuse reflection special light Od, the specular reflection light Os, and the color value Ot corresponding to the image output mode will be described with reference to FIG. For example, FIG. 10A shows the case of the image output mode A, and FIG. 10B shows the case of the image output mode B.

  When the regular reflection direction light source characteristic Ls (XYZ value) is relatively bright, the specular reflection light Os becomes strong, and the color value Ot of the image output mode A having a high specular reflectivity characteristic increases. Since the black patch is recognized brightly when the color value Ot is large, the image output mode B is selected in this case. On the other hand, when the regular reflection direction light source characteristic Ls (XYZ value) is dark, the specular reflection light Os decreases, and the color value Ot of the image output mode A decreases. Therefore, the image output mode A having the characteristic of low diffuse reflectance is selected.

  In this way, the diffuse reflection light and specular reflection light of the printed material in the observation environment are predicted for each image output mode, and an image output mode suitable for the observation environment is selected. As a result, the printing method is changed to form a printed matter that perceives the dark color as dark as possible in the observation environment, and the dark color reproduction range of the image can be solved.

  In the above description, an example in which the black patch corresponding to the image data of the maximum density is perceived darker has been described. However, the present invention can be applied to patches corresponding to other image data. For example, it is possible to form a printed matter in which a patch of a specific color looks like the color with the highest saturation in the observation environment.

For example, for the yellow patch corresponding to the image data of CMYK = (0, 0, 255, 0) or RGB = (255, 255, 0), acquisition of the printed material reflection characteristics shown in FIG. 6 and the image output mode shown in FIG. Make a selection. However, the image output mode with the maximum saturation Ot _C = √ (Ot _X ² + Ot _Z ² ) is selected. Note that the saturation Ot _C of the color value is calculated as follows. A CIEXYZ value (Xn, Yn, Zn) of a black polishing glass plate or the like is previously held. Then, from Ot _X Ot _Y Ot _Z and XnYnZn, by converting the CIEXYZ value (Xn, Yn, Zn) into CIELAB value Ot _L LOt _a Ot _b , the saturation Ot _C = √ (Ot _a ² + Ot _b ² ) is calculated. In this way, an image output mode is selected in which the yellow patch looks the most saturated color in the observation environment.

  Hereinafter, an image processing apparatus and an image processing method according to a second embodiment of the present invention will be described. Note that the same reference numerals in the second embodiment denote the same parts as in the first embodiment, and a detailed description thereof may be omitted. In the second embodiment, a method for forming a printed matter in which a color desired by a user is perceived in an observation environment will be described.

  An example of the processing configuration of the image processing apparatus 100 according to the second embodiment is shown in the block diagram of FIG. The image processing apparatus 100 according to the second embodiment includes a target color value input unit 211. The target color value input unit 211 inputs a user instruction indicating the target color value of the image, and outputs the target color value to the reflected light calculation unit 206 and the output mode selection unit 207.

  The target color value input unit 211 inputs, for example, an 8-bit RGB value for each color as the first target color value. For example, when RGB = (0, 0, 0) is input as the target color value, a black patch is processed as in the first embodiment. The reflected light calculation unit 206 acquires the printed material reflection characteristic corresponding to the target color value (RGB value) from the reflection characteristic holding unit 205. Based on the observation condition acquired by the observation condition acquisition unit 202, the diffuse reflection light, specular reflection light, and color value of the color corresponding to the target color value (RGB value) are predicted.

  The reflection characteristic holding unit 205 of Example 2 holds printed matter reflection characteristics corresponding to a plurality of color values (RGB values). However, when the printed material reflection characteristic corresponding to the target color value (RGB value) is not held, the reflected light calculation unit 206 calculates the printed material reflection characteristic corresponding to the target color value (RGB value) by interpolation.

  Further, the target color value input unit 211 inputs, for example, an XYZ value corresponding to the target color value (RGB value) as the second target color value used for determining the image output mode. The output mode selection unit 207 selects an image output mode that minimizes the color difference with respect to the target color value (XYZ value). That is, the color difference is calculated from the target color value (XYZ value) and the color value of each image output mode predicted by the reflected light calculation unit 206, and the image output mode in which the color difference from the target color value (XYZ value) is minimized. select.

  In this way, it is possible to generate image data for forming a printed matter that allows the user to perceive the color value desired by the user in the viewing environment.

[Modification]
Since glossy paper is relatively strong in specular reflection light compared to other recording media and has a large variation in color appearance with respect to the observation environment, the processing of each of the above embodiments is particularly effective for glossy paper.

  In each of the above-described embodiments, the example in which the XYZ values are used as the color values has been described. However, Lab values or Luv values may be used as the color values. Further, spectral reflectance, spectral radiance, and the like may be used instead of the reflection characteristics and color values.

[Other Examples]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program It can also be realized by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  202… Observation condition acquisition unit, 205… Reflection characteristic holding unit, 206… Reflected light calculation unit, 208… Image processing unit

Claims (12)

An acquisition means for acquiring an observation condition indicating an observation environment of the image;
For each of the plurality of image output modes, holding means for holding the diffuse reflection characteristic and the specular reflection characteristic as the reflection characteristic of the image,
As the reflected light of the image under the observation condition, a color value of the diffuse reflected light of the image under the observation condition is calculated based on the diffuse reflection characteristic, and the specular reflection light of the image under the observation condition based on the specular reflection characteristic Calculating means for calculating the color value of
For each of the plurality of image output modes, the sum of the color value of the diffuse reflection light and the color value of the specular reflection light is calculated, and the image output mode in which the brightness indicated by the sum of the color values is minimum, or the color Selection means for selecting an image output mode in which the saturation indicated by the sum of values is maximum ;
An image processing apparatus comprising: output means for outputting image data for forming an image arranged in the observation environment according to the selected image output mode. An input means for inputting a target color value;
An acquisition means for acquiring an observation condition indicating an observation environment of the image;
For each of the plurality of image output modes, holding means for holding the reflection characteristics of the image corresponding to each of the plurality of color values;
Calculation means for calculating reflected light of an image corresponding to the target color value in the observation condition based on reflection characteristics of the image corresponding to the target color value;
Calculating means for calculating a color difference between the reflected light color value and the target color value for each of the plurality of image output modes, and selecting an image output mode having the smallest color difference ;
An image processing apparatus comprising: output means for outputting image data for forming an image arranged in the observation environment according to the selected image output mode. Wherein the image output mode, the image processing apparatus according to claim 1 or 2 diffuse reflection characteristics and / or specular characteristics of the image formed on the recording medium changes. The observation conditions include at least the brightness of light irradiated on the image from the regular reflection direction with respect to the observation position of the image arranged in the observation environment, and irradiation on the image from a direction other than the regular reflection direction. The image processing apparatus according to any one of claims 1 to 3 , wherein the image processing apparatus indicates brightness of the emitted light. The observation condition is that the image is irradiated from a direction other than the regular reflection direction, and a color value of light emitted from the regular reflection direction to the observation position of the image arranged in the observation environment. The image processing apparatus according to any one of claims 1 to 3 , further comprising information for calculating a color value of light. The output means includes color matching means for performing image processing on the image data, color separation means, density correction means, halftone processing means,
At least one of a color profile used by the color matching unit, a color separation table used by the color separation unit, a correction table used by the density correction unit, and a halftone table used by the halftone processing unit is used as the selected image output mode. Correspondingly the image processing apparatus according to any one of claims 1 to 5 that varies. And the output means, image processing apparatus according to any one of claims 1 to 5 for outputting the image data in an image forming condition according to the selection of the image output mode. Further, image processing apparatus according to any one of claims 1 to 7 having an image forming means for forming an image on a recording medium based on image data to which the output means outputs. Obtain the viewing conditions indicating the viewing environment of the image,
For each of multiple image output modes, it retains diffuse reflection and specular reflection characteristics as image reflection characteristics.
As the reflected light of the image under the observation condition, a color value of the diffuse reflected light of the image under the observation condition is calculated based on the diffuse reflection characteristic, and the specular reflection light of the image under the observation condition based on the specular reflection characteristic To calculate the color value of
For each of the plurality of image output modes, the sum of the color value of the diffuse reflection light and the color value of the specular reflection light is calculated, and the image output mode in which the brightness indicated by the sum of the color values is minimum, or the color Select the image output mode with the maximum saturation indicated by the sum of the values ,
An image processing method for outputting image data for forming an image arranged in the observation environment in accordance with the selected image output mode. Enter the target color value,
Obtain the viewing conditions indicating the viewing environment of the image,
For each of a plurality of image output modes, the reflection characteristics of the image corresponding to each of a plurality of color values are retained,
Based on the reflection characteristics of the image corresponding to the target color value, the reflected light of the image corresponding to the target color value in the observation condition is calculated,
Calculating a color difference between the reflected light color value and the target color value for each of the plurality of image output modes, and selecting an image output mode in which the color difference is minimum ;
An image processing method for outputting image data for forming an image arranged in the observation environment in accordance with the selected image output mode. A program for causing a computer to function as each unit of the image processing apparatus according to any one of claims 1 to 8 . A computer-readable recording medium on which the program according to claim 11 is recorded.