JP5693153B2 - Image processing apparatus and image processing method - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing method suitable for creating a copy from a document.

There are various types of recording apparatuses that record information such as characters and images on a sheet-like recording medium such as paper or film. Among them, a method of forming text and images on a recording medium by attaching a recording agent (coloring material) to the recording medium has been put into practical use. Typical examples of such a system include an ink jet recording apparatus, an electrophotographic recording apparatus, and a sublimation type thermal transfer recording apparatus. In recent years, the performance of these recording apparatuses has been improved, and not only monochrome images and text but also color images have been recorded. However, in these recording apparatuses, even if the input signals (for example, R, G, B) input to the recording apparatus are the same, the color to be reproduced differs depending on the type of recording medium used. It is known.
As a technique for solving the above problem, a technique for realizing a desired color reproduction by performing color correction according to the type of recording medium is disclosed (Patent Document 1). In particular, a technique for matching colors reproduced between different recording media is generally well known.

Here, a conventional image processing method (color matching technique) for reproducing an image in which colors are matched to different recording media will be described in detail with reference to FIG. The input signal RGB is converted into a printer color signal R _p G _p B _p by the target color conversion unit 101, the color gamut compression unit 102, and the printer characteristic color conversion unit 103.
The target color conversion unit 101 converts the input signal RGB into a colorimetric color signal L _A a _A b _A for the target recording medium A. As the colorimetric color signals L _A a _A b _A , color signals of the CIE L * a * b * color space, the CIE XYZ color space, and the like are used. This conversion is performed using, for example, a target color conversion lookup table (LUT) 104. The target color conversion LUT 104 is a three-dimensional conversion table (3DLUT), and shows the relationship between the discrete input signal RGB and the colorimetric color signal of the target recording medium. In the conversion, interpolation is performed.
The color gamut compression unit 102 converts the colorimetric color signal L _A a _A b _A into a colorimetric color signal L _M a _M b _M that can be reproduced by the recording medium B that is actually printed. Since the color reproducible range varies depending on the recording medium, when the color reproduction area of the recording medium B is narrower than the color reproduction area of the recording medium A, there may be colors that cannot be reproduced. Therefore, the color gamut compression unit 102 converts all color signals that can be reproduced on the recording medium A into color signals that can be reproduced on the recording medium B so that the color impression does not change. Basically, the color signal that can be reproduced on the recording medium B is reproduced with almost the same color without any major change, and the color signal of the high saturation portion that cannot be reproduced on the recording medium B is compressed with a constant hue. Converted to a color signal. In other words, gamut mapping is performed so that the color reproduction area of the recording medium A is color gamut compressed within the color reproduction area of the recording medium B. The mapping parameter storage unit 105 stores parameters regarding saturation compression conditions. The color gamut compression unit 102 uses this parameter to convert a color signal by a color gamut compression method.
Printer characteristics color conversion unit 103 converts the colorimetric color signals L _M a _M b _M into color signals R _p G _p B _p of the printer. This conversion is performed using, for example, the printer characteristic color conversion LUT 106. The printer characteristic color conversion LUT 106 is also a 3DLUT. The printer characteristic color conversion LUT 106 shows the relationship between the color signals of discrete printers and the colorimetric signals on the recording medium B corresponding to the color signals.

According to such conventional color signal processing, it is possible to match color reproduction characteristics between different recording media. However, in the conventional color signal processing, color matching is performed using the colorimetric color signal, and therefore good color reproduction may not be possible if the gloss characteristics of the recording medium are different. This is because the illumination and sensor geometric conditions in the color measuring device (color measurement device) are different from the illumination and observation direction geometric conditions during image observation. FIG. 2 is a diagram schematically showing a spatial distribution of reflected light when a sample is illuminated with light from a light source. Light illuminated by the light source 201 from a predetermined angle is reflected from the sample 202 at various angles, and is distributed in an envelope shape indicated by 203 and 204. As schematically shown in FIG. 2, the reflected light from the sample is generally roughly classified into two components. One is a diffuse reflected light component 203 that is emitted to the surface of the document after illumination light is incident on the surface of the document and repeatedly reflected and absorbed by the paper fiber and color material a number of times. The other is the gloss characteristics of the document. This is a reflected light component (surface reflected light component) 204 on the related document surface.
FIG. 3 shows a spatial distribution of reflected light of two samples having different gloss characteristics (images printed on a recording medium A having a high glossiness and a recording medium B having a low glossiness), and general geometric conditions of a colorimeter. And an observation direction when the person observes the image. A general colorimeter is called “45-n” which illuminates a sample from a direction inclined by 45 degrees with respect to the normal line of the sample and receives light in a direction inclined by n degrees with respect to the normal line of the sample. Geometric conditions are adopted. FIG. 3 shows the spatial distribution of reflected light when two samples having different gloss characteristics are matched with colorimetric values using a general colorimeter. Here, an example of the geometric condition “45-0” is shown. The sample 302 is illuminated by a light source 301 from a direction inclined 45 degrees with respect to the normal line of the sample. The sensor 306 receives the amount of light in the normal direction (0 degree) of the sample from the spatially distributed reflected light. When the sample 302 is the recording medium A and the recording medium B and the colorimetric values of the images recorded on the sample 302 are matched, the amount of reflected light that is a diffuse reflection component in the normal direction of the sample 302 308 match each other. However, the surface reflection component differs due to the difference in the gloss characteristics of the sample 302. That is, the surface reflection component 304 of the recording medium A and the surface reflection component 305 of the recording medium B are different. On the other hand, the observation direction of the image observer 307 varies depending on the observation conditions in detail, but is typically represented by a direction deviating from a regular reflection direction by a predetermined angle. That is, the image observer 307 observes reflected light in a predetermined observation direction. Therefore, the amount of light observed is different between the recording medium A and the recording medium B in the direction observed by the image observer 307. That is, the amount of reflected light 309 from the recording medium A observed by the image observer 307 and the amount of reflected light 310 from the recording medium B observed by the image observer 307 are different. That is, due to the difference in spatial distribution of the reflected light of the recording medium A and the recording medium B, the colorimetric values are the same, but the reflected light amount (appearance) observed by the image observer 307 is different.
In the technique described in Patent Document 1, since a colorimetric color signal is used to convert an input color signal to a printer color signal, even if color matching is performed depending on the difference in gloss characteristics of the recording medium. , "Appearance" may be different.

  As a technique for solving this problem, a method for matching the “appearance” in a predetermined direction is disclosed instead of matching the colorimetric values when color matching is performed between recording media having different gloss characteristics. (Patent Document 2). The technique described in Patent Document 2 uses, as a color signal, a light amount measured at a predetermined angle other than 0 degrees instead of a colorimetric color signal used when converting an input color signal to a printer color signal. This is a method of matching “appearance”. FIG. 4 shows the spatial distribution of reflected light when the “appearance” is matched between different recording media. The reflected light quantity 403 in the observation direction of the image observer 307 is used instead of the colorimetric color signal to make the “appearance” of the recording medium B coincide with the “appearance” of the recording medium A. That is, the surface reflection component 402 from the recording medium B is made smaller than the surface reflection component 305 in FIG. 3 so that the amount of reflected light in the observation direction of the image observer 307 matches. Accordingly, the amount of light read by a sensor of a general colorimeter differs between the amount of reflected light 308 from the recording medium A and the amount of reflected light 404 from the recording medium B.

JP-A-8-90838 JP 2005-286996 A

  In many cases, the direction in which an observer observes an image cannot be defined unconditionally. Therefore, it is necessary to assume that the printed image is observed from various angles. However, in the conventional general color matching technique, the colorimetric values are matched, and “appearance” differs between samples having different gloss characteristics. In addition, in the technique described in Patent Document 2, since the “appearance” determined in any one direction is matched, when the samples having different gloss characteristics are observed from a direction other than a predetermined observation direction, both of them are observed. The “look” may be different. That is, when the observation angle cannot be defined, it is difficult to make the “appearance” sufficiently coincident.

  An object of the present invention is to provide an image processing apparatus, an image processing method, and the like that can obtain good color matching between print media having different gloss characteristics regardless of the viewing direction.

An image processing apparatus according to the present invention includes an image signal acquisition unit that acquires an image signal, and a first reflection characteristic acquisition unit that acquires a first reflection characteristic of a first print medium that is a target for reading the image signal. A second reflection characteristic acquisition unit that acquires a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired by the image signal acquisition unit; and the first reflection characteristic. and of the second reflection characteristics, or that to calculate the correction amount using the comparison data calculated from a plurality of reflected light in the same geometrical conditions from each other, or the first reflection characteristic and the second reflection Correction amount calculation means for calculating a correction amount using comparison data calculated from reflected light amounts in different geometric conditions with respect to characteristics, and image correction means for correcting the image signal using the correction amount. Have The features.

  According to the present invention, since the image signal is corrected based on the reflection characteristics of two types of print media, good color reproduction can be realized between these print media regardless of the viewing direction.

It is a figure which shows the conventional image processing method (color matching technique). It is a figure which shows the spatial distribution of reflected light. It is a figure which shows the spatial distribution of the reflected light at the time of making a colorimetric value correspond. It is a figure which shows the spatial distribution of the reflected light at the time of making "appearance" match. It is a block diagram which shows the structure of an image processing apparatus. It is a block diagram which shows the detail of an image process part. It is a flowchart which shows operation | movement of an image processing apparatus. It is a figure which shows an example of a user interface. It is a schematic diagram which shows the measurement of the variable angle reflected light distribution of a recording medium. It is a figure which shows an example of the data table of reflectance data. It is a graph which shows the variable angle reflectance corresponding to FIG. It is a graph which shows the brightness when not performing a color matching process. It is a block diagram which shows the structure of a color conversion process part. It is a graph which shows the example of brightness. It is a graph which shows the other example of the brightness. It is a graph which shows the other example of the brightness. It is a figure which shows an example of the table | surface corresponding to each observation condition of a manuscript and reproduction. It is a flowchart which shows operation | movement of 2nd Embodiment. It is a figure which shows an example of a user interface. It is a figure which shows the relationship between the elevation angle of an illumination and an observation direction, and an azimuth.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

(First embodiment)
First, the first embodiment will be described. FIG. 5 is a block diagram showing the configuration of the image processing apparatus according to the first embodiment of the present invention. This image processing apparatus includes an image input unit 501, an image processing unit 502, an image output unit 503, an input paper type setting unit 504, an output paper type setting unit 505, and a gloss characteristic information storage unit 506.
The image input unit 501 is an image input device such as a scanner, and inputs an image to be printed as an image signal acquisition unit. The input paper type setting unit 504 sets the type of the recording medium of the input document that is the first print medium in accordance with a user input or the like. The output paper type setting unit 505 sets the type of the recording medium that is the target for outputting the image input by the image input unit 501 that is the second print medium, in accordance with a user input or the like. In the gloss characteristic information storage unit 506, information on the gloss characteristic of the recording medium is stored in advance as information on the first reflection characteristic and the second reflection characteristic. The gloss characteristic (reflection characteristic) includes, for example, a reflected light amount group under various geometric conditions of illumination in the colorimeter and a sensor (light reception). The image processing unit 502 refers to the gloss characteristic information storage unit 506, and records each image set by the input paper type setting unit 504 and the output paper type setting unit 505 with respect to the image signal of the image input by the image input unit 501. Gloss characteristic information of the medium is acquired and image processing is performed. The image output unit 503 is a recording device such as a printer, and prints the image processed by the image processing unit 502 on a recording medium set by the output paper type setting unit 505.

FIG. 6 is a block diagram illustrating details of the image processing unit 502. The image processing unit 502 includes an input γ correction unit 601, a color conversion processing unit 602, a color separation processing unit 603, an output γ correction processing unit 604, a halftone processing unit 605, and a color separation lookup table (LUT) 606. It has been.
The input γ correction unit 601 performs a conversion process that linearizes the relationship between the image signal of the image input by the image input unit 501 and the luminance. Although details will be described later, the color conversion processing unit 602 corresponds to the gloss characteristic information of each recording medium set by the input paper type setting unit 504 and the output paper type setting unit 505 from the image signal (for example, RGB values). Conversion to an image signal (for example, RGB values of a printer) of the image output unit 503 is performed. The color separation processing unit 603 converts the RGB values after conversion by the color conversion processing unit 602 into signal values (for example, CMYK values) of each color material color mounted on the image output unit 503. As this conversion, for example, conversion to the signal value of each color material color with reference to the color separation LUT 606 is performed. The output γ correction processing unit 604 performs lightness conversion processing (for example, gamma correction processing) for improving the gradation of the image printed on the recording medium with respect to the signal value converted by the color separation processing unit 603. For this lightness conversion process, for example, information such as luminance, lightness, and density is used. The halftone processing unit 605 converts the image signal of each color material color after the gamma correction processing by the output γ correction processing unit 604 into the number of bits that can be processed by the image output unit 503.

Next, details of the color conversion processing unit 602 in the first embodiment will be described. In the present embodiment, when an arbitrary document is read by an image input unit 501 such as a scanner and a copy is created, a color conversion process is performed to make the “appearance” impression of the document and the copy closer, regardless of the viewing angle. Do. FIG. 7 is a flowchart showing the operation of the image processing apparatus according to the first embodiment.
First, in step S701, the image input unit 501 acquires an image signal of an input image from a document.
In step S702, the input paper type setting unit 504 acquires the type of the recording medium used for the original. In step S703, the output paper type setting unit 505 acquires the type of the recording medium used for copying. FIG. 8 shows an example of a user interface (UI) for acquiring the type of recording medium. The input paper type setting unit 504 and the output paper type setting unit 505 acquire the type of the recording medium based on, for example, a user input via the UI illustrated in FIG. The UI shown in FIG. 8 is provided with two list boxes 801 and 802 for selecting the types of originals and recording media used for copying, an OK button 803, and a cancel button 804. In the lists of the list boxes 801 and 802, recording medium types (for example, typical recording media such as photo paper <gloss>, photo paper <semi-gloss>, matte paper, plain paper, etc.) corresponding to the recording apparatus are registered in advance. Has been. Then, the user selects one corresponding to the type of the original or duplicate recording medium from the list. When the OK button 803 is pressed, the type of the recording medium selected in the list boxes 801 and 802 is confirmed, and when the cancel button 804 is pressed, the selection of the list boxes 801 and 802 is ignored, The set contents are maintained.

Thereafter, in step S704, the image processing unit 502 acquires gloss characteristic information corresponding to the type of the recording medium set in step S702 from the gloss characteristic information storage unit 506 as a first reflection characteristic acquisition unit. Further, in step S705, the image processing unit 502 acquires gloss characteristic information corresponding to the type of the recording medium set in step S703 from the gloss characteristic information storage unit 506 as a second reflection characteristic acquisition unit. As the gloss characteristic information, for example, measured values at a plurality of angles of the variable reflectance distribution are used. The variable angle reflectance distribution can be measured by a commercially available variable angle photometer, and the gloss characteristic information storage unit 506 stores in advance the types of typical recording media registered in the list boxes 801 and 802 in advance. The measured data is registered.
FIG. 9 is a schematic diagram when the variable angle reflected light distribution 903 of the recording medium 902 is measured at 0 degrees, 15 degrees, and 30 degrees using a variable angle photometer. FIG. 10 shows an example of a data table of reflectance data at a plurality of angles for each image signal measured for each recording medium using the goniophotometer. Further, FIG. 11 shows a graph of the variable angle reflectance corresponding to FIG. 10 measured for each recording medium using the variable angle photometer. As shown in FIG. 11, when the recording medium to be printed is different, the difference in reflectance is different at each angle. FIG. 12 shows brightness graphs at various angles of the recording medium A and the recording medium B when the color matching process is not performed.

  After step S705, the image processing unit 502 performs color matching processing with reference to the data table shown in FIG. 10 in step S706. This color matching processing is mainly performed by the color conversion processing unit 602. FIG. 13 is a block diagram illustrating a configuration of the color conversion processing unit 602. The color conversion processing unit 602 includes a target color conversion unit 1301, a recording medium adaptive color conversion unit 1302, a color gamut compression unit 1303, and a printer characteristic color conversion unit 1304. The color conversion processing unit 602 further includes a target color conversion LUT 1305, a mapping parameter storage unit 1306, and a printer characteristic color conversion LUT 1307.

The target color conversion unit 1301 refers to the target color conversion LUT 1305 to convert the color signal X _A (θ) Y _A (θ) Z _A (θ) in the recording medium A that targets the input image signal RGB. Convert. Here, a case where tristimulus values XYZ (CIE XYZ) are used as the variable angle color signal X _A (θ) Y _A (θ) Z _A (θ) will be described as an example.

The recording medium adaptive color conversion unit 1302 uses correction amounts dX (θ), dY (θ), and dZ (θ) at an angle θ as the following (1) for each image signal (0 to 255) as correction amount calculation means. )
dX (θ) = X _B (θ) −X _A (θ)
dY (θ) = Y _B (θ) −Y _A (θ) (1)
dZ (θ) = Z _B (θ) −Z _A (θ)
Here, X _B (θ), Y _B (θ), and Z _B (θ) are the tristimulus values XYZ in the output recording medium B set in step S703. For example, the data table of FIG. Required by reference. The data table shown in FIG. 10 shows reflectance data for simplicity, but the same applies to XYZ.
For example, when the data of the 0-degree angle-change color signal X _A (θ) Y _A (θ) Z _A (θ) are matched, the correction amount dX (0) is used as comparison data according to the following equation (2). , DY (0), dZ (0) are obtained.
dX (0) = X _B (0) −X _A (0)
dY (0) = Y _B (0) −Y _A (0) (2)
dZ (0) = Z _B (0) −Z _A (0)
Correction amounts dX (0), dY (0), and dZ (0) are values (differences) obtained for discrete image signals, and correction amounts other than each image signal stored in advance are known. Is interpolated by the interpolation method.
Further, the recording medium adaptive color conversion unit 1302 uses, for example, the correction amounts dX (θ), dY (θ), and dZ (θ) at the respective angles in each image signal obtained by the expression (1), for example, , The correction amounts dX, dY and dZ are obtained from the equation (3).
dX = w ₀ dX (0) + w ₁₅ dX (15) + w ₃₀ dX (30)
dY = w ₀ dY (0) + w ₁₅ dY (15) + w ₃₀ dY (30) (3)
dZ = w ₀ dZ (0) + w ₁₅ dZ (15) + w ₃₀ dZ (30)
Here, w ₀ , w ₁₅ , and w ₃₀ are weighting coefficients corresponding to correction amounts at a plurality of angles, respectively, and are normalized so that the sum is 1. That is, the recording medium adaptive color conversion unit 1302 uses the weighted average as the correction amount.

FIG. 14 shows a lightness graph at each angle when w ₀ = 0.25, w ₁₅ = 0.25, and w ₃₀ = 0.5. For comparison, FIG. 15 shows a brightness graph at each angle of the recording medium A and the recording medium B when a general color matching process for matching the colorimetric values is performed. Furthermore, for comparison, FIG. 16 shows a brightness graph at each angle when the process of matching the “appearance” at a predetermined angle (here, 30 degrees) described in Patent Document 2 is performed. Show.
In the brightness graph shown in FIG. 15, the brightness of the recording medium A and the recording medium B are substantially the same at 0 degree and 15 degrees, but a large brightness difference is generated at 30 degrees. That is, when viewed at 30 degrees, the “appearance” is different. In the lightness graph shown in FIG. 16, since the process of setting θ in equation (1) to 30 degrees is performed, the lightness of the recording medium A and the recording medium B is almost the same at 30 degrees. However, a large brightness difference occurs at 0 degrees and 15 degrees. That is, when observed at 0 degrees and 15 degrees, the “appearance” is different. These tendencies also apply to hue and saturation.
On the other hand, in the brightness graph shown in FIG. 14, the brightness does not exactly match between the recording medium A and the recording medium B at all angles, but the difference in “appearance” due to the difference in observation angle is suppressed. ing. For example, compared to the brightness graph shown in FIG. 15 (when matched at 0 degree), the brightness difference of 30 degrees is suppressed. Moreover, compared with the lightness graph shown in FIG. 16 (when matched at 30 degrees), the lightness difference of 0 degrees and 15 degrees is suppressed.
Thus, in this embodiment, good color reproduction can be obtained between the recording medium A and the recording medium B having different gloss characteristics regardless of the observation direction.
Then, the recording medium adaptive color conversion unit 1302 uses the correction amounts dX, dY, and dZ as image correction means to convert the angle-change color signal X _A Y _A Z _A into the angle-change color signal X _B Y _B Z _B. .

The color gamut compression unit 1303 converts the variable angle color signal X _B Y _B Z _B into a variable angle color signal X _M Y _M Z _M that can be reproduced by the recording medium B on which printing is actually performed. The mapping parameter storage unit 1306 stores parameters relating to saturation compression conditions. The color gamut compression unit 1303 uses this parameter to convert a color signal by a known color gamut compression method.
The printer characteristic color conversion unit 1304 converts the angle-change color signal X _M Y _M Z _M into a color signal R _p G _p B _p of the image output unit 503 (in this case, a printer). This conversion is performed using a 3DLUT, similar to the target color conversion unit 1201. The printer characteristic color conversion LUT 1307 used here indicates the relationship between the discrete printer color signals and the colorimetric signals on the recording medium B corresponding to the color signals, and can be converted by a known interpolation method. .

Through this series of processing, the input signal RGB is converted into the color signal R _p G _p B _p of the printer.

In the above example, the correction amount is calculated from data of three angles of 0 degrees, 15 degrees, and 30 degrees. However, the correction amount calculation method is not limited to this, and the expression (3) is used. The correction amount calculation method described can be generalized as shown in the following equation (4).
dX = Σw _i dX (θ _i )
dY = Σw _i dY (θ _i ) (4)
dZ = Σw _i dZ (θ _i )

Further, the correction amount may be obtained by the following process from the reflectance at a plurality of angles acquired in steps S704 and S705.
When the reflectance in the angle θ direction corresponding to the recording medium A is R _A (θ) and the reflectance in the angle θ direction corresponding to the copy B is R _B (θ), the correction parameter H ( θ) is expressed by equation (5).
H (θ) = R _B (θ) / R _A (θ) (5)
Therefore, the correction in the angle theta ₁ through? _N parameter _{H (θ 1) ~H (θ} n) is calculated. Similarly to the equation (4), H _m obtained by taking a weighted average of a plurality of correction parameters H (θ ₁ ) to H (θ _n ) is used in actual correction processing.
H _m = Σw _i H (θ _i )
Here, w _{1 to} w _n are weighting coefficients corresponding to correction parameters in a plurality of directions, respectively, and are normalized so that the sum becomes 1. Then, X _B , Y _B , and Z _B are obtained by multiplying X _A , Y _A , and Z _A by H _m .

As the method of determining the weighting factors, for example, _{w 1 = w 2 = ··· =} w n as the correction parameter H (θ ₁₎ ~H may calculate an average value of (theta _n), The document and You may decide by the difference in the gloss characteristic of reproduction. When the “appearance” in the predetermined direction is matched between the two recording media, if the difference in gloss characteristics between the two recording media is large, the colors when viewed from a direction other than the viewing direction will not match. Therefore, when the difference in gloss characteristics is larger than a predetermined value, it is preferable to decrease the weighting coefficient in the observation direction and increase the value of the weighting coefficient corresponding to the angle where the deviation from the observation direction is large.
For example, the following equation (6) is calculated for the correction parameters H (θ ₁ ) to H (θ _n ).
dH (θ _i ) = | H (θ _i ) −1 | (6)
If the value of dH (θ _i ) obtained by equation (6) is small, it means that the reflectance between the recording media at the angle θ _i is close, and if the value of dH (θ _i ) is large, the angle θ _i. This means that the reflectance between the two recording media is different. Therefore, the weighting coefficient at the angle θ _i is calculated by the following equation.
w _i = 1 / dH (θ _i ) (7)
However, the weighting coefficient obtained by the equation (7) is normalized so that the sum becomes 1. By using the expression (7), the influence of the correction parameter at an angle where the difference in reflectance is large becomes relatively small, and an impression of “appearance” other than the predetermined angle is obtained between recording media where the difference in gloss characteristics is large. Correction that makes it closer is possible.

  According to such a first embodiment, it is possible to realize a suitable color matching process in consideration of “appearance” according to the type of recording medium.

As a correction amount, a ratio between the angle-change color signal X _A (θ) Y _A (θ) Z _A (θ) and the angle-change color signal X _B (θ) Y _B (θ) Z _B (θ) may be used. Good.

(Second Embodiment)
Next, a second embodiment will be described. As described above, in the first embodiment, based on the difference in gloss characteristics between the recording media used for the original and the copy, it is possible to make the impression of color “appearance” closer when viewed from any direction. Then, the image signal correction processing is performed. However, the observation environment varies depending on the user, and there is a use in which observation is performed under predetermined observation conditions. Therefore, in the second embodiment, the content of the correction process is switched based on a user instruction. FIG. 17 shows an example of a table corresponding to the observation conditions of the original and the copy. Corresponding to (a) to (h) in FIG. 17, the image processing unit 502 switches the content of the correction processing.

FIG. 18 is a flowchart showing the operation of the second embodiment.
First, in step S1801, the image processing unit 502 acquires observation conditions designated by the user. FIG. 19 shows an example of a UI that allows the user to select an observation condition. In this UI, an observation condition setting window 1901 is provided. The observation condition setting window 1901 is mounted on, for example, a printer driver to be used. In addition, it may be implemented as a separate application. This UI is further provided with radio buttons 1902 and 1903 for selecting either “variable” or “fixed” of the observation angle of the document by the user. When the radio button 1903 is selected, that is, when the document observation angle “fixed” is selected, the group box 1904 can be input. Until the radio button 1903 is selected, it is preferable that the group box 1904 is grayed out and cannot be input. The group box 1904 includes a text box 1905 for inputting an angle with respect to the illumination sample during document observation, and a text box 1906 for inputting an observation angle with respect to the document during document observation. This UI is further provided with radio buttons 1907 and 1908 for selecting “variable” and “fixed” for the observation angle of the copy by the user. When the radio button 1908 is selected, that is, when the replication observation angle “fixed” is selected, the group box 1909 can be input. Until the radio button 1908 is selected, the group box 1909 is preferably grayed out and incapable of input. The group box 1909 includes a text box 1910 for inputting an angle with respect to duplication of illumination at the time of duplicate observation, and a text box 1911 for inputting an observation angle with respect to duplication at the time of duplicate observation. When an OK button 1912 is pressed, the selected document and copy viewing conditions are confirmed, and the image processing unit 502 acquires the contents. When a cancel button 1913 is pressed, the selection contents described above are discarded and the processing is canceled. The radio buttons, group boxes, text boxes, and the like described above are examples, and other objects having equivalent functions can be substituted.

In step S1802, the input paper type setting unit 504 acquires the type of the recording medium used for the original, and in step S1803, the output paper type setting unit 505 acquires the type of the recording medium used for copying. That is, processing similar to that in steps S702 and S703 is performed.
Thereafter, in step S1804, the image processing unit 502 determines whether or not the types of the original and duplicate recording media are the same. If the types of the original and duplicate recording media are the same, in step S 1805, the image processing unit 502 determines that “the observation angle of both the original and the duplicate is“ variable ”” or “the original and the duplicate are always at the same angle. It is determined whether or not the condition “observed” is satisfied. If this condition is satisfied, the image processing unit 502 performs color matching processing for matching the colorimetric values in step S1809. When the recording media to be used are the same for the original and the copy, if the colorimetric values, that is, the amount of reflected light in a predetermined geometric condition are matched, the variable angle reflectances also match. For this reason, as long as the original and the copy are observed at the same angle, the “appearance” of the colors matches regardless of the angle. Further, when the observation angle of both the original and the copy cannot be defined, it is preferable to obtain the same processing result as that of the first embodiment, that is, the “visible” impression is close even when viewed from any angle. When the recording medium to be used is the same between the original and the copy, the variable reflectivity matches. Accordingly, the same processing result can be obtained by the color matching processing for matching the colorimetric values.

On the other hand, if the types of the original and duplicate recording media are different in step S1804, and if the conditions in step S1805 are not satisfied, in step S1806, the image processing unit 502 sets the recording medium set in step S1802. Gloss characteristic information corresponding to the type of the gloss characteristic is acquired from the gloss characteristic information storage unit 506. Further, in step S1807, the image processing unit 502 acquires gloss characteristic information corresponding to the type of the recording medium set in step S1803 from the gloss characteristic information storage unit 506. That is, the same processing as steps S704 and S705 is performed.
Next, in step S1808, the image processing unit 502 performs color matching processing according to the viewing conditions. This color matching processing is mainly performed by the color conversion processing unit 602. In the following, the contents of processing according to various viewing conditions for the original and the copy will be described for each viewing condition.

First, processing when the observation angle of the original and the copy is “fixed” will be described. As such a case, for example, a case where observation is performed from a position separated by a certain distance or more with a document and a copy hung on a wall or the like can be considered. By observing from a position separated by a certain distance or more, the observation angles become substantially equal.
In the observation condition setting window 1901, when “fixed” and “observation direction 0 degree” are selected as the original and duplicate observation conditions, the color conversion processing unit 602 compares the calculated amounts of reflected light under the same geometric conditions. A general color matching process for matching the colorimetric values is performed using the data. This case corresponds to (a) in FIG. 17, and a brightness graph as shown in FIG. 15 is obtained.
In the observation condition setting window 1901, when “fixed” and “same angle other than 0 degree observation direction” are selected as the original and duplicate observation conditions, the color conversion processing unit 602 reflects the amount of reflected light under the same geometric condition. Using the comparison data calculated from the above, a color matching process for matching the “appearance” at the selected predetermined angle is performed. This case corresponds to (b) in FIG. 17, and a brightness graph as shown in FIG. 16 is obtained.
In the observation condition setting window 1901, when the observation condition of the original and the duplicate is “fixed” and “different observation angles for the original and the duplicate” are selected, the color conversion processing unit 602 displays “ A color matching process for matching “appearance” is performed. That is, the color conversion processing unit 602 performs color matching processing using the comparison data calculated from the reflected light amounts under different geometric conditions. This case corresponds to (c) in FIG. In this case, the color conversion processing unit 602 obtains correction amounts dX, dY, and dZ from the following equation (8). That is, the color conversion processing unit 602 performs a correction process similar to that in the case of matching the “appearance” at a predetermined angle according to the first embodiment.
dX = X _B (θ ₂ ) −X _A (θ ₁ )
dY = Y _B (θ ₂ ) −Y _A (θ ₁ ) (8)
dZ = Z _B (θ ₂ ) −Z _A (θ ₁ )

Next, processing when the document observation angle is “fixed” and the copy observation angle is “variable” will be described. In such a case, for example, the original can be observed from a position that is a predetermined distance or more away from being hung on a wall, etc., and a free angle can be obtained while holding a copy or placing it on a desk or the like. It is possible to compare the two while observing. When the viewing angle of the document is “fixed”, even if the viewing angle of the copy is “variable”, when the image observer compares the two, the copy is made at an angle that makes the “view” as close as possible to the “view” of the document. Therefore, it is preferable that the “appearances” match at a certain angle.
In the observation condition setting window 1901, when the document observation condition is selected as “fixed” and “0 degree” and the duplication observation condition is selected as “variable”, the color conversion processing unit 602 displays the duplication observation angle “0 degree”. The color matching process is performed to match the colorimetric values so that the “appearance” matches. This case corresponds to (d) in FIG. 17 and a brightness graph as shown in FIG. 15 is obtained. Further, since the observation angle of the copy cannot be strictly defined, a process of matching the impression of the appearance when the original is observed from 0 degrees and when the copy is observed from a plurality of angles may be performed. That is, the observation angle of the original (recording medium A) is 0 degree, the observation angle of the duplicate (recording medium B) is θ _i degrees, and the correction amounts dX, dY, and dZ may be obtained from the following equation (9). . In this case, the color conversion processing unit 602 performs the same correction process as in the case of matching the “appearance” at a predetermined angle according to the first embodiment.
dX = Σw _i {X _B (0) −X _A (θ _i )}
dY = Σw _i {Y _B (0) −Y _A (θ _i )} (9)
dZ = Σw _i {Z _B (0) −Z _A (θ _i )}
Note that w _i is a weighting coefficient and is normalized so that Σw _i = 1. Further, each value of w _i can be determined by the same processing as in the first embodiment.
In the viewing condition setting window 1901, when the document viewing condition is selected as “fixed” and “other than 0 °” and the replication viewing condition is selected as “variable”, the color conversion processing unit 602 displays the viewing angle of the designated document. A color matching process for matching “appearance” at an angle equal to is performed. This case corresponds to (e) in FIG. 17, and a brightness graph as shown in FIG. 16 is obtained. Further, since the observation angle of the copy cannot be strictly defined, a process of matching the impression of the appearance when the original is observed from 0 degrees and when the copy is observed from a plurality of angles may be performed. That is, even if the observation angle of the original (recording medium A) is θ _A degrees, the observation angle of the duplicate (recording medium B) is θ _i degrees, the correction amounts dX, dY, and dZ can be obtained from the following equation (10). Good. In this case, the color conversion processing unit 602 performs the same correction process as in the case of matching the “appearance” at a predetermined angle according to the first embodiment.
dX = Σw _i {X _B (0) −X _A (θ _i )}
dY = Σw _i {Y _B (0) −Y _A (θ _i )} (10)
dZ = Σw _i {Z _B (0) −Z _A (θ _i )}

Next, processing when the document observation angle is “variable” and the copy observation angle is “fixed” will be described. In such a case, for example, when the copy is hung on a wall or the like, it is observed from a position more than a certain distance, and the manuscript is held in a hand or placed flat on a desk or the like. The case where both are compared while observing from an angle can be considered. When the viewing angle of the document is “variable”, even if the observation angle of the copy is “fixed”, when the image observer compares the two, the document is viewed at an angle that makes the “view” as close as possible to the “view” of the copy. Therefore, it is preferable that the “appearances” match at a certain angle. Further, the angle observed at that time is preferably an angle at which the “look” of the document is felt to be particularly good.
In the observation condition setting window 1901, when the document observation condition is “variable” and the duplication observation condition is selected as “fixed” and “0 degrees”, the color conversion processing unit 602 selects the duplicate “0 degree” color. Is matched at an angle at which the “appearance” of the original is felt to be particularly good. This case corresponds to (f) in FIG. That is, the observation angle at which the appearance of the original (recording medium A) is felt to be particularly good is θ degrees, the observation angle of the duplicate (recording medium B) is 0 degree, and correction amounts dX, dY, and dZ are as follows ( It calculates | requires from Formula 11). In this case, the color conversion processing unit 602 performs the same correction process as in the case of matching the “appearance” at a predetermined angle according to the first embodiment.
dX = X _B (0) −X _A (θ)
dY = Y _B (0) −Y _A (θ) (11)
dZ = Z _B (0) −Z _A (θ)
Note that the observation angle θ degree at which the appearance of the document (recording medium A) is felt to be particularly good is, for example, from a color difference ΔE between a color signal calculated from a certain color change color signal and a preset target color signal, or the like. It may be determined by evaluation or may be determined from subjective evaluation.
In the observation condition setting window 1901, when the document viewing condition is selected as “variable”, and the replication viewing condition is selected as “fixed” and “other than 0 degree”, the color conversion processing unit 602 displays the color at the replication viewing angle. Color matching processing is performed so that the “appearance” of the original matches at an angle at which it feels particularly good. This case corresponds to (g) in FIG. That is, the observation angle at which the appearance of the original (recording medium A) is felt to be particularly good is θ ₁ degree, the observation angle of the copy (recording medium B) is θ ₂ degrees, and the correction amounts dX, dY, and dZ are as follows. (12). In this case, the color conversion processing unit 602 performs the same correction process as in the case of matching the “appearance” at a predetermined angle according to the first embodiment.
dX = X _B (θ ₂ ) −X _A (θ ₁ )
dY = Y _B (θ ₂ ) −Y _A (θ ₁ ) (12)
dZ = Z _B (θ ₂ ) −Z _A (θ ₁ )

  Next, processing when the observation angle of the original and the copy is “variable” will be described. As such a case, for example, a case where both the original and the copy are held in hand or placed flat on a desk or the like may be compared while observing from a free angle. In this case, since the observation angle cannot be defined in both cases, it is preferable that the “visible” impressions coincide with each other even when viewed from any angle. Therefore, the color conversion processing unit 602 performs the same correction process as in the first embodiment. In this case, a brightness graph as shown in FIG. 14 is obtained.

  According to the second embodiment as described above, it is possible to realize a suitable color matching process considering “appearance” in accordance with not only the type of recording medium but also the observation conditions specified by the user.

In the first embodiment and the second embodiment, processing is performed assuming that there is an observer in the plane between the illumination and the normal line of the sample, but the position of the observer is actually It is not limited to this. FIG. 20 shows the relationship between the elevation angle θ _L and the azimuth angle φ _L of the illumination, and the elevation angle θ _O and the azimuth angle φ _{O in} the observation direction. In the case where the process of matching the “appearance” is performed more strictly, X (θ _L , θ _O , φ _L , φ _O ), instead of the angle-change color signal in the first and second embodiments, It is preferable to perform the same processing as described above by using the measured values of Y (θ _L , θ _O , φ _L , φ _O ) and Z (θ _L , θ _O , φ _L , φ _O ).

Even if the present invention is applied to a system constituted by a plurality of devices (for example, a computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copying machine, a facsimile machine, a control device, etc.) comprising a single device. You may apply.
Each process of the present invention can also be realized by executing software (program) acquired via a network or various storage media by a processing device (CPU, processor) such as a personal computer.

  501: Image input unit 502: Image processing unit 503: Image output unit 504: Input paper type setting unit 505: Output paper type setting unit 506: Gloss characteristic information storage unit 602: Color separation processing unit

Claims (12)

Image signal acquisition means for acquiring an image signal;
First reflection characteristic acquisition means for acquiring a first reflection characteristic of a first print medium that is a target for reading the image signal ;
Second reflection characteristic acquisition means for acquiring a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired by the image signal acquisition means;
A correction amount calculating means for calculating a correction amount using comparison data calculated from a plurality of reflected light amounts in the same geometric condition among the first reflection characteristic and the second reflection characteristic;
Image correcting means for correcting the image signal using the correction amount;
An image processing apparatus comprising: Image signal acquisition means for acquiring an image signal;
First reflection characteristic acquisition means for acquiring a first reflection characteristic of a first print medium that is a target for reading the image signal ;
Second reflection characteristic acquisition means for acquiring a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired by the image signal acquisition means;
A correction amount calculating means for calculating a correction amount using comparison data calculated from the amount of reflected light under different geometric conditions between the first reflection characteristic and the second reflection characteristic;
Image correcting means for correcting the image signal using the correction amount;
An image processing apparatus comprising: The image processing apparatus according to claim 1, wherein the first reflection characteristic and the second reflection characteristic include a reflected light amount group in a geometric condition of illumination and light reception. The comparison data, the image processing apparatus according to claim 1 or 2, characterized in that said first reflection characteristic to be the difference between the second reflection characteristic. The comparison data, the image processing apparatus according to claim 1 or 2, characterized in that the ratio of the said first reflection characteristic of the second reflection characteristic. The correction amount calculating means, the image processing apparatus according to the weighted average of the comparison data to any one of claims 1 to 5, characterized in that the said correction amount. The correction amount calculation means includes: an observation condition for the first print medium and an observation condition for the second print medium specified by a user; a type of the first print medium; and a type of the second print medium. based on the image processing according to any one of claims 1 to 6, wherein determining the geometric conditions of the first reflection characteristic and the second reflection characteristic to be used for calculation of the correction amount apparatus. The image processing apparatus according to claim 7 , wherein the observation condition includes an illumination angle and an observation angle with respect to the first print medium and the second print medium. An image signal acquisition step of acquiring an image signal;
A first reflection characteristic acquisition step of acquiring a first reflection characteristic of a first print medium that is a target for reading the image signal ;
A second reflection characteristic acquisition step of acquiring a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired in the image signal acquisition step;
One of the first reflection characteristic and the second reflection characteristic, a correction amount calculating step that to calculate the correction amount using the comparison data calculated from a plurality of reflected light in the same geometrical conditions from each other,
An image correction step of correcting the image signal using the correction amount;
An image processing method comprising: An image signal acquisition step of acquiring an image signal;
A first reflection characteristic acquisition step of acquiring a first reflection characteristic of a first print medium that is a target for reading the image signal;
A second reflection characteristic acquisition step of acquiring a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired in the image signal acquisition step;
A correction amount calculating step of calculating a correction amount using comparison data calculated from reflected light amounts in geometric conditions different from each other between the first reflection characteristic and the second reflection characteristic;
An image correction step of correcting the image signal using the correction amount;
An image processing method comprising: On the computer,
An image signal acquisition step of acquiring an image signal;
A first reflection characteristic acquisition step of acquiring a first reflection characteristic of a first print medium that is a target for reading the image signal ;
A second reflection characteristic acquisition step of acquiring a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired in the image signal acquisition step;
One of the first reflection characteristic and the second reflection characteristic, a correction amount calculating step that to calculate the correction amount using the comparison data calculated from a plurality of reflected light in the same geometrical conditions from each other,
An image correction step of correcting the image signal using the correction amount;
A program characterized by having executed. On the computer,
An image signal acquisition step of acquiring an image signal;
A first reflection characteristic acquisition step of acquiring a first reflection characteristic of a first print medium that is a target for reading the image signal;
A second reflection characteristic acquisition step of acquiring a second reflection characteristic of a second print medium that is a target for recording an image of the image signal acquired in the image signal acquisition step;
A correction amount calculating step of calculating a correction amount using comparison data calculated from reflected light amounts in geometric conditions different from each other between the first reflection characteristic and the second reflection characteristic;
An image correction step of correcting the image signal using the correction amount;
A program characterized by having executed.

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