JP2021013100A - Image processing device, image processing method, and program - Google Patents

Abstract

To satisfactorily determine a metallic luster region for read data on a document regardless of a paper type of the document.SOLUTION: An image processing device includes: first acquisition means for acquiring first image data obtained by irradiating a document with light and reading reflected light of a diffuse reflection component; second acquisition means for acquiring second image data obtained by irradiating the document with light and reading reflected light incorporated with a specular reflection component; setting means for setting a threshold value for color information based on information related to the paper type of the document; and determination means for determining whether a pixel included in the image data of the document is a metallic color based on the result of comparison between the difference in color information between the first image data and the second image data and a threshold value set by the setting means.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image processing apparatus, an image processing method, and a program.

As an image reading device, an image scanner using an image sensor is known. When scanning an image, the original is irradiated with a light source to read the reflected light from the original, but in order to make it less susceptible to the difference in gloss and smoothness of the original itself, it is diffusely reflected instead of the reflected light of the specular component. It is common to read the reflected light of the component.

Patent Document 1 proposes a method for reading a metallic color with a good color when a metallic color having a very high gloss such as gold or silver is recorded in the original document. In this method, an image obtained by reading the reflected light of the diffused reflection component and an image obtained by reading the reflected light in a state where the reflected light of the positive reflection component is incorporated by diffusely reflecting the reflected light from the original document. Whether or not it is a metallic gloss region is determined by the difference for each color component. A metallic color with very high gloss has a large amount of specular reflection components and a significantly small amount of diffuse reflection components, so that an image obtained by a general image reader becomes darker than the visual impression. However, in Patent Document 1, the metallic color region can be read in a good color by using an image obtained by diffusely reflecting and reading the reflected light in a state where the reflected light of the specular reflection component is taken in.

Japanese Patent No. 4024737

However, depending on the paper type of the document on which a metallic color such as gold or silver is recorded, as a result of scanning, the area where a color other than the metallic color is recorded may be erroneously determined to be the metallic color. .. In Patent Document 1, the difference between the color components of the two images is taken by utilizing the fact that the reflected light of the specular reflection component of the metallic color is large and the reflected light of the diffuse reflection component is small, and the judgment is made by comparing with the threshold value. ing. However, in the case of a paper type with high reflectance such as glossy paper, even if the color is not metallic, the reflected light of the positive reflection component increases due to the reflection by the paper even if it is not as strong as the metallic color, and the reflected light of the diffuse reflection component increases. Will be less. In this case, even in the area where a color other than the metallic color is recorded, it is erroneously determined to be the metallic color.

Therefore, an object of the present invention is to satisfactorily determine the metallic luster region with respect to the read data of the original document.

In order to solve the above problems, the present invention has the following configuration. That is, in the image processing apparatus, the first acquisition means for irradiating the document with light and acquiring the first image data obtained by reading the reflected light of the diffused reflection component, and the document with light. Based on the second acquisition means for acquiring the second image data obtained by reading the reflected light in the state of incorporating the reflected light of the positive reflection component and the information related to the paper type of the original, the threshold value for the color information is set. It is included in the image data of the manuscript based on the result of comparison between the setting means to be set, the difference between the color information of the first image data and the second image data, and the threshold value set by the setting means. It has a determination means for determining whether or not the pixel to be light is metallic.

According to the present invention, the determination of the metallic luster region is good with respect to the scanned data of the original document.

Overview perspective view of the reading device according to the present invention. The figure for demonstrating the reading operation of the document which concerns on this invention. The figure which shows the example of the internal structure of the reading apparatus which concerns on this invention. The flowchart of image processing in the reading apparatus which concerns on this invention. The flowchart of the reading operation which concerns on 1st Embodiment. The flowchart of the metallic luster region determination which concerns on 1st Embodiment. The figure for demonstrating the reflection of light at the time of image reading. The flowchart of the reading image generation which concerns on 1st Embodiment. The flowchart of the metallic luster region determination which concerns on 2nd Embodiment. The flowchart of the metallic luster region determination which concerns on 3rd Embodiment. The flowchart of the reading image generation which concerns on 4th Embodiment. The figure for demonstrating the three-dimensional color correction table which concerns on 4th Embodiment. The figure for demonstrating tetrahedral interpolation which concerns on 4th Embodiment. The figure which shows the example of the internal structure of the copying apparatus to which this invention is applied. The figure for demonstrating the threshold setting which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the present invention according to the claims, and not all combinations of features described in the present embodiment are essential for the means for solving the present invention. .. The same components are given the same reference numbers, and the description thereof will be omitted.

<First Embodiment>
[Device configuration]
FIG. 1 is an overview perspective view of a reading device 100 applicable as an image processing device according to the present embodiment. Here, as the reading device 100, a so-called flatbed type scanner will be described as an example. As shown in FIG. 1, the scanning device 100 includes a document base cover 101 for holding a set document, a document table 102 for placing a document, and a document scanning unit 103 for scanning a set document. When the user places the document on the platen 102, closes the platen cover 101, and presses the scanner button key 104, the document scanning unit 103 starts scanning the document. Buttons are assigned to the scanner button keys 104 according to the reading mode, and the user presses the buttons according to the mode to be used. The scanning device 100 according to the present embodiment can read a document in which a metal color such as gold or silver is recorded, a color scan mode in which the document can be read in color, a monochrome scan mode in which the document can be read in monochrome. It has a metallic scan mode that can be used. In this embodiment, a color other than the metallic color is referred to as a non-metallic color. In the present embodiment, the metallic scan mode will be described, and the color scan mode and the monochrome scan mode will be omitted.

FIG. 2 is a diagram showing an operation of reading a document by the reading device 100. The document reading unit 103 is driven by a motor (not shown). For example, the document reading unit 103 is composed of a line sensor along a predetermined direction, and reads a document while being driven by a motor (not shown) in a direction orthogonal to the predetermined direction. The light source 201 installed in the document reading unit 103 irradiates the document, and the light of the diffuse reflection component reflected from the document is passed through the rod lens array 202 and read by the sensor 203 that detects the reflected signal.

FIG. 3 is a block diagram showing an example of the internal configuration of the reading device 100. The CPU 301 controls the operation of the reading device 100. The ROM 302 is a non-volatile storage area, and stores various programs for executing the control of the CPU 301 and the operations of other parts. For example, a program corresponding to the processing in the flowchart of various processing according to the present invention described later is stored in the ROM 302. The CPU 301 realizes various processes by reading and executing the program stored in the ROM 302. Further, the ROM 302 stores various values, tables, and data used for image processing such as shading correction described later.

The scan unit 303 reads an image from the original, digitizes the acquired read signal values (analog luminance data of red (R), green (G), and blue (B)) by AD conversion, and outputs the data. The image processing unit 304 performs image processing such as correction of the read signal value digitized by AD conversion and image coding. RAM 308 is used when data needs to be temporarily stored during image processing. The operation unit 305 includes a scanner button key (not shown), detects a key press state, and transmits an instruction corresponding to each key to each unit. The drive unit 306 includes a driver circuit that controls a motor in order to operate the scan unit 303. The PC interface 307 is an interface with an external device such as a PC (Personal Computer), and the reading device 100 transfers data with the external device via the PC interface 307. RAM 308 is used when a buffer is required for data transfer to an external device.

[Processing flow]
FIG. 4 is a flowchart of image processing executed by the image processing unit 304 of the reading device 100 according to the present embodiment.

In S401, the image processing unit 304 performs shading correction on the image data read by the scan unit 303 and AD-converted. The shading correction is a process of reading the white reference and the black reference prepared in advance by the sensor 203, correcting the reading value of each image sensor of the sensor 203, and correcting the variation of the image sensor in the scan unit 303.

In S402, the image processing unit 304 performs gamma correction on the image data after shading correction. The gamma correction is a process of correcting the brightness value so that the brightness value of the image obtained by the reading device 100 becomes a natural value, and is performed using a gamma value table (not shown) previously stored in the ROM 302. be able to.

The shading correction and the gamma correction are executed each time the reading operation in the present embodiment is performed. Hereinafter, for convenience of explanation, the description of the shading correction and the gamma correction will be omitted in the flowchart of FIG. Further, a known method may be used for shading correction and gamma correction, and detailed description thereof will be omitted here.

(Reading operation in metallic scan mode)
FIG. 5 is a flowchart for executing the reading operation in the metallic scan mode, which is a feature of the present embodiment. In this process, the metallic luster region is determined and the scanned image is generated. The metallic luster region indicates a region composed of metallic color pixels, and the non-metallic luster region indicates an region composed of non-metallic color pixels. The processing flow of FIG. 5 is executed by the scan unit 303 and the image processing unit 304 according to the program stored in the ROM 302. In the present embodiment, the processing flow is started when the button key corresponding to the metallic scan mode of the scanner button keys 104 included in the reading device 100 is pressed.

In S501, the CPU 301 causes the scan unit 303 to read the document installed on the platen 102 as a normal scan. The purpose of reading in this step is to acquire an image by the reflected light of the diffuse reflection component of the document.

In S502, the CPU 301 causes the scan unit 303 to read the document installed on the platen 102 as a diffuse reflection scan. The purpose of reading in this step is to acquire an image by the reflected light in a state where the reflected light of the specular reflection component of the original is taken in. In order to take in the reflected light of the specular reflection component, it is necessary to use a member having high transparency between the platen 102 and the original and diffusely reflecting the light. In the present embodiment, the reflected light of the specular reflection component is taken in by placing a thin polypropylene sheet and reading it. For example, during diffuse reflection scanning, the reading device 100 may drive a motor (not shown) to install a sheet (not shown) between the document reading unit 103 and the document. Alternatively, the user may be allowed to place the sheet on the platen 102.

In S503, the image processing unit 304 sets the threshold value to be used in S504 using the image read in S501. In the present embodiment, an appropriate threshold value is set by determining the surface smoothness of the original from the image. First, in order to specify the white area in the image, the image is divided into a predetermined number of sections, the average signal value for each section is calculated, and the white area is determined based on the calculated average signal value.

Next, the surface state of the paper surface is read from the determined white paper section, and the surface smoothness is determined based on the surface roughness, the surface shape, and the like. Specifically, the depth of the surface unevenness is defined as the surface roughness, and the period of the surface unevenness is defined as the characteristic of the surface shape, and the surface smoothness is determined by paying attention to these characteristics. For example, comparing semi-glossy paper and glossy paper, semi-glossy paper is characterized by deep surface irregularities and a low irregularity cycle. Based on this feature, the unevenness depth is estimated by calculating the brightness difference in the white paper section. In addition, the white paper section is binarized, and the unevenness cycle is detected based on the number of changes. The surface smoothness is determined by the unevenness depth and the unevenness period obtained by this. As a method for determining the surface smoothness of the original, another method of detecting the unevenness period using the run length or estimating the unevenness depth by the histogram may be used.

Based on the determined surface smoothness, a setting is made from a plurality of threshold values held in advance in the ROM 302. When the surface smoothness is high (that is, it corresponds to glossy paper), the threshold value Th_L1 is set. On the other hand, when the surface smoothness is low (that is, it corresponds to semi-glossy paper), the threshold value Th_L2 is set. The higher the surface smoothness of the original, the stronger the reflected light of the specular reflection component than the reflected light of the diffuse reflection component, so the threshold value needs to be increased. That is, it is assumed that the threshold value Th_L1 and the threshold value Th_L2 are set higher than the threshold value Th_L1 (Th_L1> Th_L2).

If there is no white paper section as a result of the determination of the white paper section, the process may be performed by selecting the section having the brightest average signal value for each section as the section close to the white paper. Further, when the entire surface is a metallic luster region, all the sections are similarly darkened. In this case, the surface smoothness may not be determined and a low threshold value may be set. In the case of this embodiment, the threshold value Th_L2 may be set. By setting a low threshold value, it becomes possible to determine the metallic luster region regardless of the surface condition.

In S504, the image processing unit 304 performs a determination process of determining whether or not it is a metallic luster region from the image read by the normal scan in S501 and the image read by the diffuse reflection scan in S502. The determination process is performed on a pixel-by-pixel basis, and determination is made by comparing pixels at the same coordinates in two images. Details of the determination method will be described later with reference to FIG.

In S505, the image processing unit 304 generates a read image based on the result determined in S504. Details of the generation method will be described later with reference to FIG.

(Metallic luster area judgment processing)
Hereinafter, details of the metallic luster region determination process in S504 of FIG. 5 will be described. FIG. 6 is a flowchart for determining the metallic luster region according to the present embodiment.

・・・式（１）
本実施形態において、画像の所定の位置を原点（０，０）とし、その座標の画素から順に着目画素として処理を行うものとする。 In S601, the image processing unit 304 sets the signal values (R, G, B) of the pixels (pixels of interest) at the coordinates (X, Y) of the normal scan image acquired in S501 and the diffused reflection scan image acquired in S502. ) Is converted to lightness. In this embodiment, the lightness L of the HLS color space is used as a method of converting the RGB signal value into the lightness which is one of the color information as shown in the following formula (1). The brightness is not limited to this, and may be converted into the brightness of the HSV color space or the Lab color space. In the equation (1), the function MAX () is a function that outputs the maximum value among the values of a plurality of arguments. Further, the function MIN () is a function that outputs the minimum value among the values of a plurality of arguments.

... Equation (1)
In the present embodiment, a predetermined position of the image is set as the origin (0,0), and processing is performed as the pixel of interest in order from the pixel at that coordinate.

In S602, the image processing unit 304 compares the signal values of the two images converted into brightness in S601. FIG. 7A is a diagram showing how the light emitted from the light source 201 is reflected in the metallic luster region recorded on the glossy paper. When the position where the light is irradiated is a metallic luster region, the reflected light of the specular reflection component is very large, and the reflected light of the diffuse reflection component is remarkably small. Here, the amount of reflected light is conceptually shown by the length of the arrow.

FIG. 7B is a diagram showing how the light emitted from the light source 201 is reflected in the non-metallic luster region recorded on the glossy paper. When the position where the light is irradiated is a non-metallic luster region, the reflected light of the positive reflection component is less than that of the metallic luster region, and the reflected light of the diffuse reflection component is larger than that of the metallic luster region. From this, the difference in brightness between the scanned image of the diffuse reflection scan incorporating the reflected light of the specular reflection component and the scanned image of the normal scan is larger in the metallic luster region than in the non-metallic luster region. Therefore, a difference is taken between the brightness of the diffuse reflection scan and the normal scan, and when the difference in brightness is larger than the threshold value set in S503 (YES in S602), the process proceeds to S603. On the other hand, when the difference in brightness between the diffuse reflection scan and the normal scan is smaller than the threshold value (NO in S602), the process proceeds to S604.

In the present embodiment, the threshold value set in S503 is applied as the threshold value applied in S602. FIG. 7C is a diagram showing how the light emitted from the light source 201 is reflected in the metallic luster region recorded on the semi-glossy paper. Further, FIG. 7D is a diagram showing how the light emitted from the light source 201 is reflected in the non-metallic luster region recorded on the semi-glossy paper. As described above, since the semi-glossy paper has irregularities on the surface of the paper as compared with the glossy paper, the reflected light is diffused, and the difference between the reflected light of the normal reflection component and the reflected light of the diffuse reflection component is small.

The threshold value Th_L1 is set to a relatively high value so that a region having high smoothness as shown in FIG. 7B is not determined as a metallic luster region. On the other hand, when the threshold value Th_L1 is used for the semi-glossy paper, the value is high, so that the metallic luster region as shown in FIG. 7C may be erroneously determined as the non-metallic luster region. Therefore, the threshold value Th_L2 applied when the smoothness is low such as semi-glossy paper is set to be lower than the threshold value Th_L1 applied when the smoothness is high such as glossy paper. As a result, good area determination can be performed for both documents.

In S603, the image processing unit 304 determines that the corresponding pixel (X, Y) is a metallic luster region. Then, the process proceeds to S605.

In S604, the image processing unit 304 determines that the corresponding pixel (X, Y) is a non-metallic luster region. Then, the process proceeds to S605.

In S605, the image processing unit 304 executes a determination as to whether or not the processing has been completed for all the pixels. When the processing is not completed for all the pixels (NO in S605), the process returns to S601 and the processing is repeated for the unprocessed pixels. Here, by updating the X and Y values, which are the coordinate values of the pixels, the processing for the unprocessed pixels is repeated. When the processing for all pixels is completed (YES in S605), this processing flow ends.

(Read image generation process)
Hereinafter, the details of the scanned image generation process in S505 of FIG. 5 will be described. FIG. 8 is a flowchart of reading image generation according to the present embodiment.

In S801, the image processing unit 304 determines whether or not the pixel of the coordinates (X, Y) in the image is a metallic luster region based on the determination result of the metallic luster region determination processing described with reference to FIG. To judge. In the case of a metallic luster region, the process proceeds to S802 (YES in S801), and in the case of a non-metallic luster region, the process proceeds to S803 (NO in S801). Here, as in the process of FIG. 6, it is assumed that a predetermined position of the image is set as the origin (0, 0), and the process is performed as the pixel of interest in order from the pixel at that coordinate.

In S802, the image processing unit 304 reads the signal values (R, G, B) of the image obtained by the diffuse reflection scan in S502 with respect to the pixels (X, Y) determined to be in the metallic luster region. Generated as (pixel value). Then, the process proceeds to S804.

In S803, the image processing unit 304 reads the signal values (R, G, B) of the image obtained by the normal scan in S501 for the pixels (X, Y) determined to be in the non-metallic luster region. Generated as an image (pixel value). Then, the process proceeds to S804.

In S804, the image processing unit 304 executes a determination as to whether or not the processing has been completed for all the pixels. When the processing is not completed for all the pixels (NO in S804), the process returns to S801, and the processing is repeated for the unprocessed pixels. Here, by updating the X and Y values, which are the coordinate values of the pixels, the processing for the unprocessed pixels is repeated. When the processing for all pixels is completed (NO in S804), this processing flow ends.

As described above, according to the present embodiment, it is possible to make a good determination as to whether or not the region in the scanned image of the original is a metallic luster region regardless of the paper type of the original. In particular, different thresholds are set based on smoothness (information related to paper type). This makes it possible to perform good region determination even for different paper types. Further, a suitable image can be provided to the user by generating an image (selecting a pixel value) according to the determination result of the metallic luster region. Furthermore, by saving the determination result of the metallic luster region as attribute data in the image, it is possible to make it known that the color is metallic by adding an effect when displaying the image.

In the present embodiment, two types of paper, glossy paper and semi-glossy paper, have been used as the paper type of the original, but this is an example of paper types having different surface smoothness. It is not limited to this. Further, in the threshold value setting of S503, the threshold value may be set more finely depending on the surface smoothness. By setting the threshold value finely, it is possible to further improve the determination accuracy when using a document having a smoothness close to that. The threshold value according to the paper type and the surface smoothness of the paper may be defined in advance by a table or the like.

Further, in the present embodiment, an appropriate threshold value is set by determining the surface smoothness of the original from the scanned image (S503 in FIG. 5), but the user is allowed to select the original type and based on the information. The threshold value may be set to. When the user selects the scan mode, the same effect can be obtained by preparing a metallic scan mode for glossy paper or a metallic scan mode for semi-glossy paper and letting the user select from among them.

Further, in order to acquire an image by the reflected light in a state where the reflected light of the specular reflection component is taken in during the diffuse reflection scan (S502 in FIG. 5), a member that diffusely reflects the light between the platen 102 and the document is used. ing. However, the device configuration may be such that the reflected light of the specular reflection component is directly read without using a member. Specifically, by preparing the rod lens array 202 and the sensor 203 not only in the diffuse reflection direction of the light emitted from the light source 201 in the document reading unit 103 but also in the specular reflection direction, the specular reflection component can be obtained. It becomes possible to acquire an image by reflected light.

<Second embodiment>
Hereinafter, a second embodiment of the present invention will be described. The configuration that overlaps with the first embodiment will be omitted, and the difference configuration will be described.

In the first embodiment, the method for determining the metallic luster region has been described by comparing the brightness of the image of the normal scan and the image of the diffused reflection scan. In the second embodiment, the method for determining the metallic luster region will be described by comparing the saturation, which is another color information, in addition to the comparison of the brightness.

In the first embodiment, in the process of S503 of FIG. 5, the image processing unit 304 sets a threshold value to be used in the metallic luster region determination process (S504) using the image read in S501. In the first embodiment, the brightness threshold value is set from a plurality of threshold values previously held in the ROM 302 by determining the surface smoothness of the document from the image. On the other hand, in the second embodiment, the threshold values of lightness and saturation are set. Similar to the brightness, the saturation threshold is set higher when the surface smoothness of the document is higher. That is, in the thresholds Th_S1 and Th_S2 for saturation, the threshold Th_S1 set when the surface smoothness is high and the threshold Th_S2 set when the smoothness is low set the threshold Th_S1 to a higher value (Th_S1> Th_S2). ..

(Metallic luster area judgment processing)
Hereinafter, details of the determination of the metallic luster region according to the present embodiment will be described. FIG. 9 is a flowchart for determining the metallic luster region according to the present embodiment, and is the process performed in S504 of FIG.

In S901, the image processing unit 304 converts the signal values (R, G, B) of the pixels of the coordinates (X, Y) of the two images into brightness. The processing content in this step may be the same as S601 in FIG. 6 of the first embodiment.

In S902, the image processing unit 304 compares the brightness of the two images. The processing content in this step may be the same as in S602 of FIG. 6 of the first embodiment. When the difference in brightness between the diffuse reflection scan and the normal scan is larger than the threshold value set in S503 of FIG. 5 (YES in S902), the process proceeds to S903. On the other hand, when the difference in brightness between the diffused reflection scan and the normal scan is smaller than the threshold value set in S503 of FIG. 5 (NO in S902), the process proceeds to S906.

・・・式（２）
本実施形態において、画像の所定の位置を原点（０，０）とし、その座標の画素から順に着目画素として処理を行うものとする。 In S903, the image processing unit 304 sets the signal values (R, G, B) of the pixels of the coordinates (X, Y) of the normal scan image acquired in S501 of FIG. 5 and the diffused reflection scan image acquired in S502. Convert to saturation. In this embodiment, the saturation S of the HLS color space is used as a method of converting the RGB signal value into the saturation as shown in the following equation (2). It should be noted that the present invention is not limited to this, and those converted into saturation by using the saturation of the HSV color space or the ab of the Lab color space may be used. In the equation (2), the function MAX () is a function that outputs the maximum value among the values of a plurality of arguments. Further, the function MIN () is a function that outputs the minimum value among the values of a plurality of arguments.

... Equation (2)
In the present embodiment, a predetermined position of the image is set as the origin (0,0), and processing is performed as the pixel of interest in order from the pixel at that coordinate.

In S904, the image processing unit 304 compares the signal values of the two images (the image obtained by the normal scan and the image obtained by the diffuse reflection scan) converted into saturation in S903. A detailed explanation is added below. In S902, it is determined whether or not it is a metallic luster region by comparing the brightness. However, only by comparing the brightness, there is a possibility that an erroneous determination is made when a low-brightness color such as blue is recorded on high-gloss paper.

As shown in FIG. 7 (b), in the case of a non-metallic luster region recorded on glossy paper, the reflected light of the positive reflection component is less than the metallic luster region shown in FIG. 7 (a), and the diffuse reflection component. The reflected light of is more than the metallic luster region. However, in the case of high-gloss paper, the reflected light of the specular reflection component is sufficiently strong due to the reflection by the paper even in the non-metallic gloss region, so that the signal value of the obtained image becomes a sufficiently bright value. Further, as for the reflected light of the diffuse reflection component, when a color such as blue having low brightness is recorded, the light is absorbed by the coloring material, so that the signal value of the obtained image becomes a dark numerical value. As a result, although there is a difference in the state of light reflection as shown in FIGS. 7 (a) and 7 (b), when the difference is taken only from the viewpoint of the brightness of the obtained image, the numerical value is close. In some cases, an erroneous judgment may be made.

Therefore, in the present embodiment, the region determined to be the metallic luster region from the viewpoint of lightness in S902 is further compared based on the saturation in S904. As described above, the reflected light of the specular reflection component in the non-metallic gloss region when high-gloss paper is used becomes stronger due to the influence of the specular reflection by the paper. Further, because of the influence of the specular reflection by the paper, the color of the coloring material is not so much added to the reflected light of the specular reflection component, and the light of the light source is reflected as it is. That is, the image of the non-metallic luster region obtained by the diffuse reflection scan is strongly influenced by white, which is the color of the light source, and thus the saturation is reduced. On the other hand, since the metallic luster region is specularly reflected by the metallic color, there is little decrease in saturation as in the non-metallic luster region. For example, if it is gold, the color of specular reflection will be yellow as it is. Therefore, the difference is taken between the saturation of the diffused reflection scan and the normal scan, and when the decrease in the saturation of the diffused reflection scan is larger than the threshold value set in S503 (YES in S904), the process proceeds to S906. On the other hand, when the decrease in saturation of the diffuse reflection scan is smaller than the threshold value (NO in S904), the process proceeds to S905.

Further, also in this embodiment, the threshold value applied in S904 uses the threshold value set in S503. As described in the first embodiment, the paper type having a low surface smoothness such as semi-glossy paper has unevenness on the surface of the paper as compared with the glossy paper, so that the reflected light is diffused and the positive reflection component is present. The difference between the reflected light and the reflected light of the diffuse reflection component is small. Therefore, the threshold value Th_S2 applied when the surface smoothness is low such as semi-glossy paper is set in advance to be lower than the threshold value Th_S1 applied when the surface smoothness is high such as glossy paper. By setting it, a good area determination can be performed for both documents.

In S905, the image processing unit 304 determines that the corresponding pixel (X, Y) is a metallic luster region. Then, the process proceeds to S907.

In S906, the image processing unit 304 determines that the corresponding pixel (X, Y) is a non-metallic luster region. Then, the process proceeds to S907.

In S907, the image processing unit 304 executes a determination as to whether or not the processing has been completed for all the pixels. When the processing is not completed for all the pixels (NO in S907), the process returns to S901, and the processing is repeated for the unprocessed pixels. Here, by updating the X and Y values, which are the coordinate values of the pixels, the processing for the unprocessed pixels is repeated. When the processing for all pixels is completed (YES in S907), this processing flow ends.

As described above, in the present embodiment, from the regions determined to be metallic luster regions from the viewpoint of lightness, those regions in which a threshold value is further set for the decrease in saturation and the value of the decrease in saturation is large are added as non-metallic luster regions. Is being judged. Therefore, according to this embodiment, the accuracy of determining the metallic luster region can be improved as compared with the first embodiment. For example, even in a region where the saturation is originally low such as silver and the saturation of the diffuse reflection scan and the normal scan do not change, it is possible to determine without excluding the region from the metallic luster region.

<Third embodiment>
Hereinafter, a third embodiment of the present invention will be described. The configuration that overlaps with the above embodiment will be omitted, and the difference configuration will be described.

In the first embodiment, the method for determining the metallic luster region has been described by comparing the brightness of the image of the normal scan and the image of the diffused reflection scan. Further, in the second embodiment, the method of determining by comparing the saturation in addition to the comparison of the lightness has been described. In the third embodiment, the method for determining the metallic luster region will be described by comparing only the saturation.

In the first embodiment, in S503 of FIG. 5, the image processing unit 304 sets a threshold value to be used in the metallic luster determination process (S504) using the image read in S501. On the other hand, in the third embodiment, the saturation threshold value is set from a plurality of threshold values previously held in the ROM 302 by determining the surface smoothness of the document from the image. Similar to the second embodiment, the threshold Th_S1 set when the smoothness is high and the threshold Th_S2 set when the surface smoothness is low are set to higher values (Th_S1> Th_S2).

(Metallic luster area judgment processing)
Hereinafter, details of the determination of the metallic luster region according to the present embodiment will be described. FIG. 10 is a flowchart for determining the metallic luster region according to the present embodiment, and is the process performed in S504 of FIG.

In S1001, the image processing unit 304 converts the signal values (R, G, B) of the pixels of the coordinates (X, Y) of the two images into saturation. The processing content in this step may be the same as S903 in FIG. 9 of the second embodiment.

In S1002, the image processing unit 304 compares the signal values of the two images (the image by the normal scan and the image by the diffuse reflection scan) converted into saturation in S1001. A detailed explanation is added below. As described in the second embodiment, the reflected light of the specular reflection component in the non-metallic luster region is reflected by the paper, so that the tint of the coloring material is not so much applied and the light of the light source is reflected as it is. Further, since the reflected light of the specular reflection component in the metallic luster region is reflected by the metallic color, the metallic color itself is reflected. Further, the reflected light of the diffuse reflection component in the metallic luster region has a weak intensity and becomes dark, so that the color becomes close to black. That is, when the reflected light of the diffuse reflection component and the reflected light of the specular reflection component are compared, the saturation of the specular reflection component is high in the metallic gloss region. Therefore, when the difference is taken between the saturation of the diffused reflection scan and the normal scan, the saturation difference is larger than the threshold value set in S503, and the diffused reflection scan is more vivid (YES in S1002), the process proceeds to S1003. On the other hand, when the saturation difference between the diffuse reflection scan and the normal scan is smaller than the threshold value (NO in S1002), the process proceeds to S1004.

In S1003, the image processing unit 304 determines that the corresponding pixel (X, Y) is a metallic luster region. Then, the process proceeds to S1005.

In S1004, the image processing unit 304 determines that the corresponding pixel (X, Y) is a non-metallic luster region. Then, the process proceeds to S1005.

In S1005, the image processing unit 304 executes a determination as to whether or not the processing is completed for all the pixels. When the processing is not completed for all the pixels (NO in S1005), the process returns to S1001 and the processing is repeated for the unprocessed pixels. Here, by updating the X and Y values, which are the coordinate values of the pixels, the processing for the unprocessed pixels is repeated. When the processing for all pixels is completed (YES in S1005), this processing flow ends.

As described above, in the present embodiment, the metallic luster region is determined only from the viewpoint of saturation. That is, with respect to an achromatic metallic color such as silver, the reflected light of the specular reflection component remains achromatic and cannot be correctly determined. However, in the present embodiment, it is possible to determine even a color that would be erroneously determined in the determination of the metallic luster region having only the lightness performed in the first embodiment. For example, as described in the second embodiment, a low-brightness color such as blue is recorded on high-gloss paper. Further, since the comparison processing is not performed in a plurality of ways as in the second embodiment, the processing speed can be increased as compared with the second embodiment.

It should be noted that the configuration may be such that the user can select which method is used for determining the metallic luster region described in the first to third embodiments. For example, a more detailed mode may be selected from the metallic scan modes according to the document to be read.

<Fourth Embodiment>
Hereinafter, a fourth embodiment of the present invention will be described. The configuration that overlaps with the above embodiment will be omitted, and the difference configuration will be described.

In the first embodiment, the method of generating the scanned image has been described to be generated by synthesizing the image obtained by the diffuse reflection scan and the image obtained by the normal scan. In the fourth embodiment, the method of generating the scanned image will be described by performing an appropriate color conversion process based on the determination result.

(Read image generation process)
The details of the scanned image generation according to the present embodiment will be described below. FIG. 11 is a flowchart for generating a read image according to the present embodiment, and is a process performed in S505 of FIG.

In S1101, the image processing unit 304 determines whether or not the pixel at the coordinates (X, Y) in the image is a metallic luster region based on the determination result of the metallic luster region determination processing. If it is a metallic luster region, the process proceeds to S1102 (YES in S1101), and if it is a non-metallic luster region, the process proceeds to S1103 (NO in S1101). The processing content here may be the same as in S801 of FIG.

In S1102 and S1103, the image processing unit 304 performs color conversion processing of the signal values (R, G, B) of the image obtained by the normal scan for the pixels (X, Y) according to the determination result of the area. I do. The color conversion can be performed by an operation such as a matrix, but in the present embodiment, a three-dimensional color correction table is used in order to perform flexible color conversion according to the determination result. A detailed explanation is added below.

When the RGB value input for each pixel is 8 bits (256 gradations) for each color, it is not realistic to hold all combinations from the viewpoint of data capacity. Therefore, in this embodiment, a color correction table is used. Uses those thinned out at predetermined intervals. FIG. 12 shows an example of a color correction table according to the present embodiment. In this example, each color has 256 gradations as 17 grid points, and a table in which the corresponding RGB values after color conversion are described (17 * 17 * 17 = 4913 grid points).

・・・式（３）
ここで、ｗ０、ｗ１、ｗ２、ｗ３は、各頂点ｐｉと反対向位置の小四面体の体積比である。上記により、対象となるＲＧＢ値に対応した色変換後のＲＧＢ値を算出するが、階調性を考慮し、出力は８ビット以上でも構わない。なお、色補正テーブルは、Ｓ５０４で実行された判定結果に応じたテーブルを適用する。つまり、本実施形態では、金属光沢領域用の色補正テーブルと、非金属領域用の色補正テーブルが予め保持されているものとする。 The value between the grid points is calculated by using the interpolation process. There are several interpolation methods, but in the present embodiment, processing using tetrahedral interpolation will be described. The tetrahedral interpolation method is a linear interpolation using four grid points with the division unit of the three-dimensional space as a tetrahedron. The procedure first divides into a tetrahedron as shown in FIG. 13 (a). Then, it is determined which of the divided tetrahedrons the target point p belongs to. The four vertices of the tetrahedron are p0, p1, p2, and p3, respectively, and as shown in FIG. 13B, the tetrahedron is further divided into smaller tetrahedrons. When the conversion values of each point are f (p0), f (p1), f (p2), and f (p3), respectively, the interpolation value f (p) can be obtained by the following equation 3.

... Equation (3)
Here, w0, w1, w2, and w3 are volume ratios of the small tetrahedrons at positions opposite to each vertex pi. From the above, the RGB value after color conversion corresponding to the target RGB value is calculated, but the output may be 8 bits or more in consideration of gradation. As the color correction table, a table according to the determination result executed in S504 is applied. That is, in the present embodiment, it is assumed that the color correction table for the metallic luster region and the color correction table for the non-metal region are held in advance.

In S1102, the image processing unit 304 performs color conversion processing of the signal values (R, G, B) of the image obtained by the normal scan on the pixels (X, Y) determined to be in the metallic luster region. Do. In S1102, a color correction table suitable for a metallic luster region is used. The color correction table for the metallic luster region may be created so that when the RGB values of the normal scan image of the metallic luster region are color-converted, the converted RGB values are close to the visual impression. Specifically, a document on which metallic luster patches of various colors are recorded is prepared, and the signal value of an image obtained by normally scanning the document is prepared as an input RGB value. Then, the color measurement value obtained by measuring the color of the original with the reflected light including the specular reflection component using a colorimeter such as an integrating sphere is converted into the sRGB value, which is one of the standards in the monitor display. Is prepared as the RGB value after color conversion. Since the reflected light of the diffuse reflection component is remarkably small in the metallic luster region as described above, the colorimetric measurement including the reflected light of the specular reflection component brings the impression closer to the appearance. By using the input RGB value and the RGB value after color conversion as a combination and using a known method such as a pseudo inverse matrix, it is possible to create a color correction table suitable for a metallic luster region. After this process, the process proceeds to S1104.

In S1103, the image processing unit 304 performs color conversion processing of signal values (R, G, B) of the image obtained by normal scanning for the pixels (X, Y) determined to be in the non-metallic luster region. I do. In S1103, a color correction table suitable for a non-metallic luster region is used. The color correction table for the non-metallic luster region may be created so that when the RGB values of the normal scan image in the non-metallic luster region are color-converted, the converted RGB values are close to the visual impression. Specifically, a document on which non-metallic luster patches of various colors are recorded is prepared, and the signal value of an image obtained by normally scanning the document is prepared as an input RGB value. Then, the color measurement value obtained by measuring the color of the original with the reflected light containing no specular reflection component using a colorimeter such as an integrating sphere is converted into the sRGB value, which is one of the standards in the monitor display. Is prepared as the RGB value after color conversion. As described above, if the non-metallic luster region includes the reflected light of the specular reflection component, the color of the recorded color material cannot be evaluated due to the influence of the reflection by the paper, so the specular reflection By performing color measurement that does not include the reflected light of the components, the impression is close to the appearance. By using the input RGB value and the RGB value after color conversion as a combination and using a known method such as a pseudo inverse matrix, it is possible to create a color correction table suitable for a non-metallic luster region. After this process, the process proceeds to S1104.

In S1104, the image processing unit 304 executes a determination as to whether or not the processing has been completed for all the pixels. When the processing is not completed for all the pixels (YES in S1104), the process returns to S1101 and the processing is repeated for the unprocessed pixels. Here, by updating the X and Y values, which are the coordinate values of the pixels, the processing for the unprocessed pixels is repeated. When the processing for all pixels is completed (NO in S1104), this processing flow ends.

As described above, in the present embodiment, the image obtained by the diffuse reflection scan is used for determining whether or not the image has a metallic luster region, but it is not used for generating the scanned image. In the present embodiment, the diffused reflection scan reads a document in a state where a thin polypropylene sheet (not shown) is placed between the platen 102 and the document as a member for diffusely reflecting light. Therefore, the image obtained by the diffuse reflection scan is slightly out of focus, and a blurred image is acquired. In the present embodiment, since the scanned image is generated only by the normally scanned image, it is possible to generate an image in a state without blur.

As described above, according to this embodiment, the quality of the image can be further improved as compared with the first embodiment.

<Other Embodiments>
In the above embodiment, in the application of the reading device, the threshold value is set by determining the surface smoothness of the original from the image read by the normal scan. Then, an example is described in which a suitable scanned image can be obtained by determining the metallic luster region by comparing the difference between the images of the normal scan and the diffused reflection scan using the threshold value. The present invention is also applicable to other applications utilizing the reading function. For example, as a device that combines reading processing and recording processing as described above to provide convenience to the user, there is a copying device. Since the reading process is also executed in the copying apparatus, the present invention can be applied.

FIG. 14 is a diagram showing an example of an internal configuration of a copying apparatus to which the present invention can be applied. In addition to the configuration of the reading device, it includes a display 1401 for displaying and operating the scanned image and a print unit 1402 for recording the image. By providing the display 1401, the user can set the threshold value by himself / herself in the threshold value setting performed in S503. Other configurations correspond to the configurations shown in FIG.

FIG. 15 is a diagram showing how the user sets the threshold value. The display 1401 displays a screen 1501 showing the binarization result of the difference between the normal scan and the diffuse reflection scan, and the user moves the slide bar 1502 displayed at the bottom of the screen 1501 to set the threshold value used for the binarization. You can change it freely. In addition, by changing the displayed binarization result according to the threshold value operated by the user, the user can adjust the threshold value while looking at the result, so that the optimum threshold value can be set for the read image. It will be possible. Then, the copying apparatus sets the threshold value and performs the image generation process based on the received user operation.

Further, in the copying apparatus, by using the print unit 1402 for a suitable read image, it is possible to record in a color close to the impression of the user's appearance. Further, if the copying apparatus is equipped with silver as a special color material, it is possible to copy the metallic luster color by using silver in the region determined to be the metallic luster region. For example, in the case of gold color determined to be a metallic luster region, gold color copying is possible by first recording the silver color material on the recording medium and then controlling to record the yellow color material. Become.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. But it is feasible. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

The invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the invention. Therefore, a claim is attached to make the scope of the invention public.

100 ... Reader, 103 ... Document reading unit, 201 ... Light source, 203 ... Sensor, 301 ... CPU, 303 ... Scan unit, 304 ... Image processing unit

Claims (14)

A first acquisition means for irradiating the original with light and acquiring the first image data obtained by reading the reflected light of the diffuse reflection component, and
A second acquisition means for acquiring the second image data obtained by irradiating the original with light and reading the reflected light in a state where the reflected light of the specular reflection component is incorporated.
A setting means for setting a threshold value for color information based on information related to the paper type of the manuscript, and
Whether the pixels included in the image data of the document are metallic based on the result of comparison between the difference between the color information of the first image data and the second image data and the threshold value set by the setting means. Judgment means to judge
An image processing device characterized by having. The image processing apparatus according to claim 1, wherein the color information includes at least one of lightness and saturation. The determination means metallizes pixels in which the brightness of the second image data is higher than the brightness of the first image data and the difference in brightness exceeds the threshold value for the brightness set by the setting means. The image processing apparatus according to claim 2, wherein the image processing apparatus is determined as a color. The determination means is a pixel in which the brightness of the second image data is higher than the brightness of the first image data and the difference in brightness exceeds the threshold value for the brightness set by the setting means. A pixel in which the saturation of the first image data is higher than the saturation of the second image data and the difference in saturation exceeds the threshold value for the saturation set by the setting means. The image processing apparatus according to claim 2, wherein the image processing apparatus is determined as a non-metallic color. In the determination means, the saturation of the second image data is higher than the saturation of the first image data, and the difference in saturation exceeds the threshold value for the saturation set by the setting means. The image processing apparatus according to claim 2, wherein the pixels are determined as a metallic color. The setting means is
Using the first image data, the surface smoothness of the original is determined.
The image according to any one of claims 1 to 5, wherein when the surface smoothness is high, a higher value is set for the threshold value for the color information as compared with the case where the surface smoothness is low. Processing equipment. The image according to claim 6, wherein the setting means determines the surface smoothness of the original document based on the depth and period of the surface unevenness in the white paper section included in the first image data. Processing equipment. Further having a means for accepting a user operation regarding setting a threshold value for the color information,
The image processing apparatus according to any one of claims 1 to 5, wherein the setting means sets a threshold value based on the user operation. The pixel value based on the second image data is selected for the pixel determined to be metallic by the determination means, and the pixel value based on the first image data is selected for the pixel determined to be non-metallic color. The image processing apparatus according to any one of claims 1 to 8, further comprising an image generation means for generating image data of the manuscript by selecting the image processing apparatus. The image data of the original is obtained by performing a color conversion process on the first image data using different color correction tables for the pixels determined to be metallic and the pixels determined to be non-metallic by the determination means. The image processing apparatus according to any one of claims 1 to 8, further comprising an image generating means for generating the image. The color correction table used for the pixels determined to be metallic is created using the colorimetric values measured by the reflected light including the specular reflection component.
The image processing apparatus according to claim 10, wherein the color correction table used for the pixels determined to be non-metallic colors is created by using the colorimetric values measured by the reflected light containing no specular reflection component. .. Further having a recording means capable of recording on a recording medium using a silver coloring material,
The recording means is characterized in that, in the image data generated by the image generation means, the pixels determined to be metallic by the determination means are recorded on the recording medium using the silver color material. The image processing apparatus according to any one of claims 9 to 11. The first acquisition step of irradiating the original with light and acquiring the first image data obtained by reading the reflected light of the diffuse reflection component, and
A second acquisition step of irradiating the original with light and acquiring a second image data obtained by reading the reflected light in a state where the reflected light of the specular reflection component is taken in, and a second acquisition step.
A setting process for setting a threshold value for color information based on information related to the paper type of the manuscript, and
Whether the pixels included in the image data of the original are metallic based on the result of comparison between the difference between the color information of the first image data and the second image data and the threshold value set in the setting step. Judgment process to determine
An image processing method characterized by having. The first acquisition step of irradiating the original with light on the computer and acquiring the first image data obtained by reading the reflected light of the diffuse reflection component, and
A second acquisition step of irradiating the original with light and acquiring a second image data obtained by reading the reflected light in a state where the reflected light of the specular reflection component is taken in, and a second acquisition step.
A setting process for setting a threshold value for color information based on information related to the paper type of the manuscript, and
The pixels included in the image data of the original are metallic colors based on the result of comparison between the difference in color information between the first image data and the second image data and the threshold value set in the setting step. Judgment process to determine whether
A program to execute.

Images