JP2011250294A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to print an excellent image which has a hue close to an actual one even for an image of a white board shot in a hue different from the actual hue.SOLUTION: An image forming apparatus 1 performs, to an input color image, a predetermined image formation processing, and includes a part 100 of pen hue mapping processing which, when a color image shot on a white board is input, identifies a color of a color pen used when drawing diagrams and/or characters on the white board, for an arbitrary pixel of the color image, and maps a color value of the arbitrary pixel in the hue of the pen thus identified. After the pen hue mapping processing, the predetermined image formation processing is performed.

Description

  The present invention relates to an image forming apparatus such as a printer that performs printing of a color image obtained by photographing a whiteboard, and an image forming method.

In recent years, in office work, a meeting or the like is performed using a whiteboard, and an operation of recording necessary items with several color pens is performed on a daily basis. In addition, effective use of information has been attempted, such as printing a whiteboard record on paper and distributing it to related parties.
For example, in the case of an electronic whiteboard, image information can be read on the spot with an attached scanner device, and a whiteboard record can be printed immediately with an attached printing device.
However, general electronic whiteboards often have monochrome printing specifications, and it may be difficult to view the contents recorded with a color pen.

Therefore, in Patent Document 1, image processing is performed so that the color image data of the basic color and the color image data other than the basic color are visually distinguished, and the color image data obtained by the image processing is printed. An image reading and printing apparatus is disclosed. According to the image reading apparatus, the user can easily visually confirm the distinction between the basic color and the color other than the basic color in the printing result.
Further, Patent Document 2 discloses an electronic blackboard that can identify a marker color based on the spectral sensitivity of an image sensor output and, as a result, can perform shade printing according to the marker color.

JP-A-4-339473 JP-A 63-48050

However, the techniques disclosed in either Patent Document 1 or Patent Document 2 are premised on a whiteboard provided with image reading means such as a scanner in advance.
That is, such a conventional technique is not effective for a user who uses a general whiteboard that does not include an image reading unit. In this case, the user takes an image with an electronic still camera (hereinafter referred to as DSC). The purpose was achieved by printing a whiteboard image.

By the way, when a white board is photographed by a general DSC, most of the photographed image is occupied by a white portion, and thus various adjustment functions often do not operate properly. For this reason, it was not photographed as an appropriate image, and as a result, there was a problem that an image lacking visibility was printed.
For example, since the white part of the whiteboard occupies the majority, the DSC automatic exposure function (AE function) may not work properly. In this case, the white part of the whiteboard becomes colored gray, There was a problem that pen colors such as blue, green, etc. were shot blackish.

In addition, the white balance function may not work properly at night, etc. where the light source depends on fluorescent lamps (fluorescent lamps used in offices tend to have such a tendency due to poor color development). In some cases, there has been a problem that the pen color is photographed as being far from the original hue.
In particular, a DSC built in a mobile phone is often used in office work because of its superior convenience, but on the other hand, the adjustment function and adjustment range are often more limited than a general DSC. The above problem has become more prominent.

  The present invention has been proposed in order to solve the above-described problems of the conventional technology, and even when an image of a whiteboard is taken with a hue different from the original hue, the original hue is restored. An object of the present invention is to provide an image forming apparatus and an image forming method capable of printing as a close good image.

  In order to achieve the above object, an image forming apparatus of the present invention is an image forming apparatus that performs a predetermined image forming process on an input color image, and a color image obtained by photographing a drawing on a white ground is input. A pen hue mapping processing unit for identifying the color of the color pen used for the drawing with respect to an arbitrary pixel of the color image and mapping the color value of the arbitrary pixel within the identified pen hue; A predetermined image forming process is performed after the process.

  The image forming method of the present invention is an image forming method for performing a predetermined image forming process on an input color image. When a color image obtained by photographing a drawing on a white ground is input, the color image A pen hue mapping processing step of identifying a pen color used for the drawing for the arbitrary pixel and mapping the color value of the arbitrary pixel within the identified pen hue, and forming a predetermined image after the pen hue mapping processing. This is a method for processing.

  According to the image forming apparatus and the image forming method of the present invention, even a whiteboard image photographed with a hue different from the original hue can be printed as a good image close to the original hue.

1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. It is the figure which represented HCB space three-dimensionally. It is the figure which showed the lightness axis in the HCB space shown in FIG. FIG. 4 is a diagram showing the HCB space shown in FIG. 3 based on the viewpoint from the direction of the end point (point W or point K) of the brightness axis. It is the figure which represented FIG. 4 three-dimensionally. It is the figure which represented the hue surface containing arbitrary color values two-dimensionally. It is a figure showing the hue surface containing arbitrary color values and a mapping hue surface. It is a figure for demonstrating the method of calculating | requiring the area of each triangle containing the point A, and its area ratio previously, in order to obtain | require the positional relationship of the arbitrary points A contained in the hue surface on color space. It is a functional block diagram which shows the detailed structure of the pen hue mapping process part which concerns on this embodiment. It is the figure which showed the hue range used for identification of a pen hue. It is a functional block diagram which shows the detailed structure of the pen hue mapping process part which concerns on 2nd embodiment. It is a functional block diagram of an image range correction processing unit. It is the figure which showed the example of correction | amendment of an image range. It is a functional block diagram which shows the detailed structure of the pen hue mapping process part which concerns on 3rd embodiment. It is the figure which showed the hue range used for identification of the pen hue in 3rd embodiment. It is a functional block diagram which shows the detailed structure of the pen hue mapping process part which concerns on 4th embodiment. It is the figure which showed the low saturation pixel achromatic process and black component removal process in 4th embodiment.

[First embodiment]
Hereinafter, a configuration of an image forming apparatus according to an embodiment of the present disclosure will be described with reference to the drawings.
The image forming apparatus 1 according to the present embodiment is a printing apparatus such as a color printer, for example, and includes control elements such as a CPU (Central Process Unit) and a chip set, a ROM (Read Only Memory), and a RAM (Random Access Memory). ) And the like. The CPU is an arithmetic processing device that executes a program. The ROM is a non-volatile memory that stores programs and data in advance. The RAM is a memory that temporarily stores the program and data when the program is executed and uses it as a work area. The program stored in the ROM is read by the control means of the CPU, thereby causing the computer to perform predetermined processing. Thus, functional components are realized in the computer of the image forming apparatus 1 by the cooperation between the program and the computer.

As shown in FIG. 1, the image forming apparatus 1 has a functional configuration realized by the cooperation of a program and a computer, and a pen that performs predetermined image processing when a color image obtained by photographing a whiteboard is input. Hue mapping processing unit 100, color conversion processing unit 200 for converting a target image having a predetermined color value (RGB format) into image data of a color value (CMYK format) that can be output by a predetermined color conversion table, and output density correction A gamma correction processing unit 300 to perform and a screen processing unit 400 to perform pseudo gradation processing are provided.
The image forming apparatus 1 includes an image input device and an output device (not shown) as hardware configurations, and is connected to a computer and an input device (not shown) directly or via a cable or the like. Here, the image input device inputs image information composed of RGB data, and the output device outputs image data subjected to pen hue mapping processing, color conversion processing, gamma correction processing, and screen processing.

That is, in the image forming apparatus 1 according to the present embodiment, the image input device inputs target image information, and the pen hue mapping processing unit 100, the color conversion processing unit 200, the gamma correction processing unit 300, and the screen processing unit 400 Necessary processing is performed on the image, and then the output device performs image output processing.
As described above, the image forming apparatus 1 according to the present embodiment is realized by cooperation of software and hardware resources.

Here, the pen hue mapping processing unit 100 according to the present embodiment will be described in detail.
When a color image obtained by photographing a whiteboard is input to the image forming apparatus 1, the pen hue mapping processing unit 100 uses the color pen color used when drawing a figure or a character on the whiteboard for an arbitrary pixel of the color image. And a process of mapping the color value of an arbitrary pixel in the identified pen hue. By performing the existing printing process (predetermined image forming process) after such a pen hue mapping process, even a whiteboard image shot with a hue different from the original hue is good close to the original hue Can be printed as a simple image.

FIG. 2 is a diagram showing the HCB space three-dimensionally, and FIG. 3 is a diagram showing the lightness axis in the HCB space shown in FIG.
In the present embodiment, when performing the pen hue mapping process, the mapping process using the HCB space is performed. The HCB space is a color space in which color values are represented by hue values (H: Hue), saturation values (C: Chroma), and lightness values (B: Brightness). As shown in FIGS. As a three-dimensional representation.
Each vertex of the cube, that is, R, G, B1, C, M, Y, K, and W, indicates red, green, blue, cyan, magenta, yellow, black, and white, respectively.
In the present embodiment, the coordinates of the vertices of the cube are R = {255, 0, 0}, G = {0, 255, 0}, Bl = {0, 0, 255}, C = {0, 255, 255}, M = {255, 0, 255}, Y = {255, 255, 0}, K = {0, 0, 0}, W = {255, 255, 255}.
For example, by considering the lightness axis with W and K as endpoints, the lightness for an arbitrary color value can be recognized.

FIG. 4 is a diagram showing such an HCB space based on the viewpoint from the direction of the end point (point W or point K) of the brightness axis. In this way, the hue value can be expressed in a ring shape.
For example, in the figure, it can be recognized that RGB data A = {r, g, b} exists on the red hue plane.
FIG. 5 is a three-dimensional representation of FIG.
According to the figure, it can be recognized three-dimensionally that the point A exists on the red hue plane (ΔWKR).
Thus, in general, the hue plane can be represented by a triangular plane (hue plane) composed of the maximum saturation point P corresponding to arbitrary RGB data A and the end points W and K on the brightness axis.
The maximum saturation point P is indicated by the intersection of the hue plane including the target point and the brightness axis and the line segment M-B1-C-G-Y-R-M. Therefore, in the example of the present embodiment, the maximum saturation point P corresponding to the point A in FIGS.

Here, a specific method for mapping the color value of an arbitrary pixel of the input image to another hue plane will be described in detail with reference to FIGS.
First, as shown in FIG. 6, a hue plane including a point A corresponding to the color value of an arbitrary pixel is extracted. In the figure, the x direction and the y direction indicate saturation and lightness, respectively, indicating that the values increase in proportion to the direction of the arrow. That is, the maximum saturation point of the hue plane WKP2 shown in the figure is P2, and the lightness axis is the line segment WK.
The maximum saturation point (maximum saturation value) Pa can be obtained by the following equation (1).
Pa = (A−min [A]) / max (A−min [A]) × 255 (1)
(However, min [A] is the smallest value in {r, g, b}, max [A] is the largest value in {r, g, b}, and A-min [A] is This means subtracting min [A] from each element of point A.
For example, when the RGB data of an arbitrary point A existing in ΔWKP2 is A = {95, 63, 63}, the maximum saturation point P2 is set to P2 = {255, 255, 0} can be calculated.

Next, the mapping hue plane that is the mapping destination is taken out.
FIG. 7 is a diagram in which a hue plane including an arbitrary color value and an image hue plane are overlapped.
In the figure, the maximum saturation point P2 of the hue plane ΔWKP2 including the point A is P2 = Y = {255,255,0}, and the maximum saturation point P1 of the hue plane ΔWKP1 is P1 = R. = {255, 0, 0}.
In this way, by fixing the hue value of the HCB space, it is possible to recognize the brightness difference between a certain hue plane and another hue plane.

FIG. 8 is a diagram for explaining a method of obtaining the area of each triangle including the point A and its area ratio in advance in order to obtain the positional relationship of an arbitrary point A included in the hue plane on the color space.
First, in the figure, the following equations (2) to (6) hold.
S = ΔWKP2 (2)
s = ΔAWK / ΔWKP2 (3)
t = ΔAKP2 / ΔWKP2 (4)
u = ΔAP2W / ΔWKP2 (5)
S = s + t + u = 1 (6)

In general, the area S ₀ of ΔODE in the three-dimensional space is assumed to be O = {Or, Og, Ob}, D = {Dr, Dg, Db}, E = {Er, Eg, Eb}. It is computable using Formula (7)-(9).
Vector OD = DO (7)
Vector OE = EO (8)
S ₀ = | OD × OE | / 2 (9)
That is, the area S ₀ of ΔODE can be calculated using the outer product of the vector OD and the vector OE.
For this reason, the area ratios s, t, and u indicating the positional relationship of the point A in ΔWKP2 can be obtained using equations (2) to (9).

Next, a method for calculating RGB data A ′ after mapping arbitrary RGB data A to another hue plane will be described.
The point A ′ in ΔWKP1 needs to be equal to the positional relationship of the point A in ΔWKP2 before mapping. That is, the area ratios s, t, and u of ΔAWK, ΔAKP2, and ΔAP2W in ΔWKP2 need to be mapped so as to be the same as ΔA′WK, ΔA′KP1, and ΔA′P1W in ΔWKP1. is there.

For this reason, the coordinates of the point A ′ are calculated by substituting s, t, and u obtained in advance using the equations (3) to (5) into the following equation (10).
A ′ {r, g, b} = s · P1 {r, g, b} + t · W {r, g, b} + u · K {r, g, b}
... (10)

Next, details of the pen hue mapping processing unit 100 according to the present embodiment will be described with reference to FIGS. 9 and 10.
FIG. 9 is a functional block diagram showing a detailed configuration of the pen hue mapping processing unit according to the present embodiment.
As shown in this figure, the pen hue mapping processing unit 100 of this embodiment includes a pen color setting unit 101, an included hue maximum saturation point calculation unit 102, a corresponding pen hue estimation unit 103, an included hue in-plane division ratio calculation unit. 104, a pen hue color value conversion unit 105, and the like.

The pen color setting unit 101 sets the color of the color pen (maximum saturation point of the pen hue) used when drawing a graphic or character on the whiteboard.
For example, when the pen color is expressed by a numerical value between 0 and 1 in the RGB format, the red, blue, black, and green pen colors are red {1, 0, 0} and blue {0, 0, respectively. 1}, black {0, 0, 0}, green {0, 1, 0}.

The included hue maximum saturation point calculation unit 102 calculates a maximum saturation point Pa of a hue including an arbitrary pixel in an arbitrary pixel of a color image obtained by photographing the whiteboard.
For example, when the RGB color value of an arbitrary point A is expressed by normalization with a value between 0 and 1, the RGB value of the maximum saturation point Pa of the hue including the point A is expressed by the above equation (1). Can be sought.
When the point A is a point on the lightness axis (on the gray value axis), there is no solution based on the saturation being zero, but a white value may be given for convenience.

A calculation example of the included hue maximum saturation point calculation unit 102 will be specifically described using numerical values. For example, when the color value of the point A is expressed by 0 to 255, if A1: {255,128,128}, it is normalized by dividing by 255, and An1: {1,0.5,0.5}.
Then, according to the equation (1), the maximum saturation point Pa1: {1, 0, 0} in the same hue can be obtained.
If the color value of the point A2 is A2: {255, 192, 128}, An2: {1, 0.75, 0.50}, Pa2: {1, 0.50, 0} It can be asked.

The corresponding pen hue estimation unit 103 identifies the color of the pen used to draw the arbitrary pixel portion based on the maximum saturation point Pa of the arbitrary pixel calculated by the inclusion hue maximum saturation point calculation unit 102.
In the present embodiment, in the hue including the color value of an arbitrary point A in the whiteboard image, one of the color values constituting the maximum saturation point Pa {r, g, b} is zero. Or 1 is used to identify whether the point A is drawn in the pen color set by the pen color setting unit 101 using the point between 0 and 1 .
Specifically, in the rgb value of the point Pa, if r = 1, the pen color is red, if g = 1, the pen color is green, and if b = 1, the pen color is blue. The pen color can be temporarily identified.

For example, if the value of the point A is A2: {255, 192, 128}, it looks like an orange hue rather than red on the monitor screen, but the maximum saturation point of the same hue is Pa2: {1,0 .50,0} and r = 1, the pen color is identified as “red”.
This makes it possible to identify the pen color used in the hue range as shown in FIG.
In the above description, a method for identifying a pixel drawn with a black pen is omitted, but the black pen identification process is optional. For example, even if a pixel drawn with a black pen is identified as a different pen color, the position mapped to that hue is extremely low in saturation and the hue becomes small. There is no problem even if omitted. Alternatively, a black pen identification condition (for example, the area of ΔAKP is less than a predetermined value) may be set, and a pixel satisfying this condition may be mapped to a black point.

The included hue in-plane division ratio calculation unit 104 is a triangle in a color space formed by the maximum saturation point Pa, white point W, and black point K of an arbitrary pixel calculated by the included hue maximum saturation point calculation unit 102. The area ratio of the region divided by the points corresponding to the color values of arbitrary pixels is calculated.
For example, it can be calculated using the above-described equations (2) to (9).

The pen hue color value conversion unit 105 converts the color value of an arbitrary pixel based on the pen hue identified by the corresponding pen hue estimation unit 103 and the division ratio calculated by the included hue in-plane division ratio calculation unit 104. , And convert to a mapping point within the identified pen hue.
For example, the color value (RGB value) after mapping into the identified pen hue can be calculated using the above-described equation (10).

  According to the present embodiment configured as described above, the image forming apparatus 1 performs a predetermined image forming process on an input color image, and when a color image obtained by photographing a whiteboard is input, For a given pixel of the color image, a pen hue mapping processing unit 100 that identifies the color of the color pen used when drawing a figure or a character on the whiteboard and maps the color value of the arbitrary pixel within the identified pen hue. In addition, since the predetermined image forming process is performed after the pen hue mapping process, even a whiteboard image shot with a hue different from the original hue can be printed as a good image close to the original hue. it can.

  The pen hue mapping processing unit 100 includes a pen color setting unit 101 for setting a color pen color used when drawing a figure or a character on a whiteboard, and an arbitrary pixel among arbitrary pixels of a color image obtained by photographing the whiteboard. Based on the maximum saturation point Pa of an arbitrary pixel calculated by the included hue maximum saturation point calculation unit 102 and the included hue maximum saturation point calculation unit 102 that calculates the maximum saturation point Pa of a hue including A corresponding pen hue estimation unit 103 that identifies the pen color used to draw the arbitrary pixel portion, and the maximum saturation point Pa and white point W of the arbitrary pixel calculated by the included hue maximum saturation point calculation unit 102. Inclusive hue in-plane division ratio calculation unit 10 that calculates an area ratio of a region divided by points corresponding to color values of arbitrary pixels in a triangle in the color space formed by the black point K. Based on the pen hue identified by the corresponding pen hue estimation unit 103 and the division ratio calculated by the in-hue-in-plane division ratio calculation unit 104, the color value of an arbitrary pixel is calculated from the identified pen hue. A color value conversion unit 105 in the pen hue for conversion to a mapping point, so that the color value of an arbitrary pixel can be converted to a mapping point on the pen hue plane while maintaining the position on the original hue plane, As a result, image degradation due to mapping processing can also be prevented.

[Second Embodiment]
Next, the image forming apparatus 1 according to the second embodiment of the present invention will be described with reference to FIGS. However, about the part which is common in the said embodiment, the description of the said embodiment is used by attaching | subjecting the code | symbol of the said embodiment.

FIG. 11 is a functional block diagram illustrating a detailed configuration of the pen hue mapping processing unit according to the second embodiment.
As shown in this figure, the pen hue mapping processing unit 100 of the image forming apparatus 1 according to the second embodiment performs a color including an arbitrary pixel before converting the color value of the arbitrary pixel into a mapping point in the pen hue. This embodiment is different from the above-described embodiment in that it includes an image range correction processing unit 110 that creates a histogram related to the color value of an image and corrects the image range of the color image based on the analysis result of the histogram.

FIG. 12 is a functional block diagram of the image range correction processing unit.
As shown in this figure, the image range correction processing unit 110 of this embodiment includes an analysis image generation unit 111, an image analysis unit 112, an image range correction unit 113, and the like.
The analysis image generation unit 111 extracts all or part of the color image obtained by photographing the whiteboard as an analysis image.
For example, an analysis image having a predetermined size (ratio to the overall size of the image) is extracted near the center of the color image obtained by photographing the whiteboard.
Alternatively, the entire color image obtained by photographing the whiteboard may be converted into a thumbnail and used as an analysis image.

The image analysis unit 112 creates a histogram related to the color value of the analysis image and obtains the mode value of the histogram.
For example, as shown in the upper side of FIG. 13, a histogram indicating the frequency of the color value {r, g, b} is created for each pixel of the analysis image, and the mode value {166, 166, 166} is obtained.
When the color value of the analysis image is 8-bit data, the histogram may be created after conversion to 6-bit data or 4-bit data.
In calculating the mode value, the degree of variation with the mode value as the center value may be calculated, and a plurality of values close to the mode value may be selected to estimate the true mode value.

Further, the image analysis unit 112 may estimate the color, white point, and black point of the pen used when drawing the whiteboard image based on the cluster analysis of the analysis image.
When such a cluster analysis is performed, if a black pen was used, a representative value of the color value equivalent to the black pen can be obtained, and from this and the color value equivalent to the white part of the whiteboard, the whiteboard In addition to image range correction of images, white balance correction can also be performed.
Further, if it is estimated that the black pen was not used when drawing the whiteboard image as a result of the cluster analysis, the range correction may be performed by setting the black point to {0, 0, 0}.

The image range correction unit 113 corrects the image range of a color image on the assumption that the mode of the histogram is the white part of the whiteboard.
Specifically, if the mode value is M {rm, gm, bm}, an arbitrary point A (ra, ga, ba) of the whiteboard image is corrected by the following equation.
A ′ = (ra / rm, ga / gm, ba / bm) × 255
Further, at this time, pixels that are 255 or more may be rounded to 255.
As a result, as shown in the lower side of FIG. 13, the mode value is corrected as a white point of {255, 255, 255}.
If the most frequent value is corrected with the white point {255, 255, 255} in the above formula, there is a possibility that the area saturated with white may be excessive. In such a case, In the calculation, the saturation region can be reduced by not multiplying 255 and multiplying by a value smaller than 255.

  According to the second embodiment configured as described above, the pen hue mapping processing unit 100 converts the color value of the color image including the arbitrary pixel before converting the color value of the arbitrary pixel into the mapping point in the pen hue. Since the image range correction processing unit 110 that generates a histogram relating to the value and corrects the image range of the color image based on the analysis result of the histogram is provided, the overall saturation of the whiteboard image is optimized, and the pen color Can be further improved.

  Further, the image range correction processing unit 110 creates an analysis image generation unit 111 that extracts all or part of a color image obtained by photographing a whiteboard as an analysis image, and creates a histogram related to the color value of the analysis image. Since the image analysis unit 112 that obtains the mode value and the image range correction unit 113 that corrects the image range of the color image on the assumption that the mode value of the histogram is the white part of the whiteboard, it is gray. Not only can the white part of the photographed whiteboard be converted to the original white color, but also the saturation of the pen color can be raised.

[Third embodiment]
Next, an image forming apparatus 1 according to a third embodiment of the present invention will be described with reference to FIGS. However, about the part which is common in the said embodiment, the description of the said embodiment is used by attaching | subjecting the code | symbol of the said embodiment.

FIG. 14 is a functional block diagram showing a detailed configuration of the pen hue mapping processing unit according to the third embodiment.
As shown in this figure, the pen hue mapping processing unit 100 of the image forming apparatus 1 according to the third embodiment converts the color value of an arbitrary pixel into a mapping point in the pen hue before converting the color value of the arbitrary pixel. The above-described embodiment includes the pen achromatic range pixel achromatic processing unit 120 that determines whether or not the pixel is included in a predetermined pen hue range, and achromatics any pixel that is determined not to be included in the pen hue range. It is different from the form.

The pen hue range non-pixel achromatic processing unit 120 of the present embodiment includes a pen hue range setting unit 121, a pen hue range determination unit 122, an achromatic processing unit 123, a composition processing unit 124, and the like.
The pen hue range setting unit 121 sets a hue range regarded as a pen hue.
For example, when the pen color is red, the range of the red system color mapped to the red phase is expressed as {1, a, 0}, {1, 0, b} using a and b, Set the range.
In particular,
In {1, a, 0}, 0 ≦ a ≦ 0.3
In {1, 0, b}, 0 ≦ b ≦ 0.5
In this way, as shown in FIG. 15, the pen hue range to be identified as the hue of each pen can be narrowed down.

The pen hue range determination unit 122 determines whether the color value of an arbitrary pixel is included in a predetermined pen hue range.
For example, it is determined whether or not the color value of the maximum saturation point Pa of a hue including an arbitrary pixel is included in the pen hue range set by the pen hue range setting unit 121.

The achromatic color processing unit 123 achromatics any pixel that is determined not to be included in the pen hue range.
For example, for an arbitrary pixel that is determined not to be included in the pen hue range, the division ratio in the included hue is acquired from the in-hue-in-plane division ratio calculation unit 104, and is mapped onto the gray axis based on the division ratio. By doing so, an arbitrary pixel is achromatic.
In achromatic color, for example, the mapped value A ″ {r ″, g ″, b ″} color value after achromatic color may be obtained using the following equation.
A ″ {r ″, g ″, b ″} = (Sp + Sw) × W {1,1,1} + Sk × {0,0,0}
However,
Sp = △ KAW / △ WPK
Sw = △ PAK / △ WPK
Sk = △ WAP / △ WPK

The combination processing unit 124 combines the chromatic color portion and the achromatic color portion of the color image.
In other words, a whiteboard image is obtained in which only the pixels corresponding to the pen hue are chromatic and the pixels corresponding to the non-pen hue are achromatic.

  According to the third embodiment configured as described above, the pen hue mapping processing unit 100 converts the color value of an arbitrary pixel into a predetermined pen before converting the color value of the arbitrary pixel into a mapping point in the pen hue. Since a pixel achromatic processing unit 120 that determines whether or not the pixel is included in the hue range and decolorizes an arbitrary pixel that is determined not to be included in the pen hue range is provided. It is possible to obtain a whiteboard image in which only pixels are chromatic and achromatic pixels corresponding to a non-pen hue are achromatic. Accordingly, it is possible to solve the problem that the pixels of the non-pen hue equivalent color are mapped to the pen hue and the visibility of the whiteboard image is lowered.

  In addition, the pen achromatic range pixel achromatic processing unit 120 includes a pen hue range setting unit 121 that sets a hue range that is regarded as a pen hue, and whether or not the color value of an arbitrary pixel is included in a predetermined pen hue range. A pen hue range determination unit 122 for determining whether or not, an achromatic processing unit 123 for achromatically rendering an arbitrary pixel determined not to be included in the pen hue range, and a chromatic and achromatic portion of the color image And a synthesizing processing unit 124. Therefore, it is possible to accurately determine a pixel corresponding to a non-pen hue color based on a preset hue range and to make the color achromatic.

[Fourth embodiment]
Next, an image forming apparatus 1 according to a fourth embodiment of the present invention will be described with reference to FIGS. However, about the part which is common in the said embodiment, the description of the said embodiment is used by attaching | subjecting the code | symbol of the said embodiment.

FIG. 16 is a functional block diagram illustrating a detailed configuration of the pen hue mapping processing unit according to the fourth embodiment.
As shown in this figure, the pen hue mapping processing unit 100 of the image forming apparatus 1 according to the fourth embodiment performs arbitrary processing before or after converting the color value of an arbitrary pixel into a mapping point in the pen hue. Judgment of pixel saturation, low saturation pixel achromatic processing unit 130A that achromatically lowers pixels whose saturation is lower than a predetermined threshold, and removal of black component of pixels whose saturation is higher than the predetermined threshold The point which is provided with the black component removal process part 130B to perform differs from the said embodiment.

The low saturation pixel achromatic processing unit 130A includes a saturation determination unit 131 that determines whether the saturation of an arbitrary pixel is lower than a predetermined threshold, and a pixel whose saturation is lower than the predetermined threshold. An achromatic color processing unit 123 for combining the chromatic color portion and the achromatic color portion of the color image.
The achromatic color processing unit 123 and the composition processing unit 124 are the same as those in the above-described embodiment, and thus detailed description thereof is omitted.

The black component removal processing unit 130B determines the color value of a pixel whose saturation is higher than a predetermined threshold, the white point and the maximum saturation point in a hue including the color value of the pixel, and the saturation determination unit 131 described above. And the same hue ridge line mapping processing unit 132 for converting into mapping points on the connected line segments.
Hereinafter, the saturation determination unit 131 and the same hue ridge line mapping processing unit 132 will be described in detail.

The saturation determination unit 131 determines whether the saturation of an arbitrary pixel is lower than a predetermined threshold.
For example, as shown in FIG. 17, in ΔWPK, a point M (saturation determination threshold) is provided on the side KP, and whether the point A is inside ΔWMK, whether it is on ΔWMP, or inside ΔWMP. If it is within ΔWMK, it is determined that the saturation is insufficient.
For example, in ΔWMK, after calculating the vector AW, the vector AM, the outer product AW · AM of the vector AK, the outer product AM / AK, and the outer product AK / AW in ΔWMK, these units When vectors are obtained, if the vector directions of the three outer products coincide with each other, it can be determined that the point A exists inside, and if there are those pointing in the opposite direction, the point A exists outside.
Alternatively, a perpendicular line is drawn from the point A to the line segment WK, and the distance is calculated to determine whether or not the saturation of the point A is sufficient based on whether or not the prescribed threshold is satisfied. Good.

The same hue ridge line mapping processing unit 132 maps the color value of a pixel whose saturation is higher than a predetermined threshold to a mapping point on the line segment connecting the white point and the maximum saturation point in the hue including the color value of the pixel. Convert to
For example, as shown in FIG. 17, when the mapping point is A1, it can be calculated by the following equation.
A1 {r, g1, b1} = (Sp + Sk) × W {1,1,1} + Sw × Pa {r, g, b}
However,
Sp = △ KAW / △ WPK
Sw = △ PAK / △ WPK
Sk = △ WAP / △ WPK

  According to the fourth embodiment configured as described above, the pen hue mapping processing unit 100 converts the color value of an arbitrary pixel before or after converting the color value of the arbitrary pixel into a mapping point in the pen hue. Since the low-saturation pixel achromatization processing unit 130A for judging the degree of color and achromatizing pixels whose saturation is lower than a predetermined threshold value is provided, noise mapped in the pen hue or possibly noise The achromatic pixels can be achromatic, and the visibility of the whiteboard image can be further improved.

  Further, the low saturation pixel achromatic processing unit 130A includes a saturation determination unit 131 that determines whether the saturation of an arbitrary pixel is lower than a predetermined threshold, and a pixel whose saturation is lower than the predetermined threshold. Since the achromatization processing unit 123 for achromatic color and the synthesis processing unit 124 for synthesizing the chromatic color part and the achromatic color part of the color image are provided, a white board with a noisy pixel achromatic color is obtained. be able to.

  In addition, the pen hue mapping processing unit 100 determines the saturation of the arbitrary pixel before or after converting the color value of the arbitrary pixel to the mapping point in the pen hue, and the saturation is greater than a predetermined threshold value. Since the black component removal processing unit 130B for removing the black component of the high pixel is provided, the black component of the pen hue pixel can be removed to further improve the visibility of the whiteboard image.

  Further, the black component removal processing unit 130B determines whether or not the saturation of the arbitrary pixel is lower than a predetermined threshold, and the color determination value of the pixel whose saturation is higher than the predetermined threshold. The same hue ridge line mapping processing unit 132 for converting to a mapping point on the line segment connecting the white point and the maximum saturation point in the hue including the color value of the pixel is included, so that the saturation is higher than a predetermined threshold value. The black component of the pixel can be removed well.

  The image forming apparatus according to the present invention has been described with reference to the preferred embodiment. However, the image forming apparatus according to the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. It goes without saying that implementation is possible.

  The present invention can be suitably used in an image forming apparatus such as a printer that prints a color image obtained by photographing a whiteboard.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 100 Pen hue mapping process part 101 Pen color setting part 102 Inclusion hue maximum saturation point calculating part 103 Applicable pen hue estimation part 104 Inclusion hue in-plane division | segmentation ratio calculating part 105 Pen hue value conversion part 110 Image range Correction processing unit 111 Analysis image generation unit 112 Image analysis unit 113 Image range correction unit 120 Pen hue range out-of-pixel pixel achromatic processing unit 121 Pen hue range setting unit 122 Pen hue range determination unit 123 Achromatic processing unit 124 Composition processing unit 130A Low saturation pixel achromatic processing unit 130B Black component removal processing unit 131 Saturation determination unit 132 Same hue ridge line mapping processing unit 200 Color conversion processing unit 300 Gamma correction processing unit 400 Screen processing unit

Claims (11)

An image forming apparatus that performs a predetermined image forming process on an input color image,
When a color image of a white ground image is input, the color pen color used for the drawing is identified for any pixel in the color image, and the color value of the arbitrary pixel is mapped within the identified pen hue An image forming apparatus comprising: a pen hue mapping processing unit configured to perform a predetermined image forming process after the pen hue mapping process. The pen hue mapping processor is
A pen color setting section for setting the color of the color pen used for drawing on the white ground,
In an arbitrary pixel of the color image obtained by photographing the drawing, an included hue maximum saturation point calculation unit that calculates a maximum saturation point of a hue including the arbitrary pixel;
Based on the maximum saturation point of the arbitrary pixel calculated by the inclusion hue maximum saturation point calculation unit, a corresponding pen hue estimation unit that identifies the color of the pen used to draw the arbitrary pixel part;
In the triangle in the color space formed by the maximum saturation point, white point, and black point of an arbitrary pixel calculated by the included hue maximum saturation point calculation unit, it is divided by points corresponding to the color value of the arbitrary pixel. An inclusion hue in-plane division ratio calculation unit for calculating the area ratio of the area to be
Based on the pen hue identified by the corresponding pen hue estimation unit and the division ratio calculated by the included hue in-plane division ratio calculation unit, the color value of an arbitrary pixel is determined as a mapping point within the identified pen hue. The image forming apparatus according to claim 1, further comprising: a pen hue in-hue color value conversion unit for converting into a color value. The pen hue mapping processor is
Before converting the color value of an arbitrary pixel to a mapping point in the pen hue, a histogram is generated for the color value of the color image including the arbitrary pixel, and the image range of the color image is determined based on the analysis result of the histogram. The image forming apparatus according to claim 1, further comprising an image range correction processing unit that performs correction. The image range correction processing unit
An analysis image generator that extracts all or part of a color image obtained by photographing a drawing on the white ground as an analysis image;
An image analysis unit that creates a histogram related to the color value of the analysis image and obtains the mode value of the histogram;
The image forming apparatus according to claim 3, further comprising: an image range correction unit that corrects an image range of a color image by assuming that a mode value of a histogram is the white portion on the white ground. The pen hue mapping processor is
Before converting the color value of an arbitrary pixel to a mapping point in the pen hue, it was determined whether the color value of the arbitrary pixel was included in the predetermined pen hue range, and was determined not to be included in the pen hue range The image forming apparatus according to any one of claims 1 to 4, further comprising a pen achromatic range pixel achromatic processing unit that achromatics an arbitrary pixel. The pen achromatic range pixel achromatic processing unit is
A pen hue range setting section for setting a hue range to be regarded as a pen hue;
A pen hue range determination unit that determines whether a color value of an arbitrary pixel is included in a predetermined pen hue range;
An achromatic processing unit that achromatics any pixel that is determined not to be included in the pen hue range;
The image forming apparatus according to claim 5, further comprising: a synthesis processing unit that synthesizes the chromatic color part and the achromatic color part of the color image. The pen hue mapping processor is
Low saturation that determines the saturation of an arbitrary pixel before or after converting the color value of the arbitrary pixel to a mapping point in the pen hue, and achromatics pixels whose saturation is lower than a predetermined threshold The image forming apparatus according to claim 1, further comprising a pixel achromatic processing unit. The low saturation pixel achromatic processing unit
A saturation determination unit for determining whether the saturation of an arbitrary pixel is lower than a predetermined threshold;
An achromatic processing unit that achromatics pixels whose saturation is lower than a predetermined threshold;
The image forming apparatus according to claim 7, further comprising: a synthesis processing unit that synthesizes the chromatic color portion and the achromatic color portion of the color image. The pen hue mapping processor is
A black component that determines the saturation of an arbitrary pixel before or after converting the color value of the arbitrary pixel to a mapping point in the pen hue, and removes the black component of the pixel whose saturation is higher than a predetermined threshold The image forming apparatus according to claim 1, further comprising a removal processing unit. The black component removal processing unit
A saturation determination unit for determining whether the saturation of an arbitrary pixel is lower than a predetermined threshold;
Same-hue ridgeline mapping processing unit that converts a color value of a pixel whose saturation is higher than a predetermined threshold into a mapping point on a line segment connecting the white point and the maximum saturation point in the hue including the color value of the pixel. An image forming apparatus according to claim 9. An image forming method for performing a predetermined image forming process on an input color image,
When a color image obtained by photographing a drawing on the white ground is input, the color of the pen used for the drawing is identified for an arbitrary pixel of the color image, and the color value of the arbitrary pixel is mapped within the identified pen hue An image forming method comprising a pen hue mapping process step, and performing a predetermined image forming process after the pen hue mapping process.

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