JP3658095B2 - Image processing apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and method, and more particularly, to an image processing apparatus and method for converting a designated color in an image into a different designated color.
[0002]
[Prior art]
Some image processing apparatuses such as current color copying machines have a so-called “color conversion” function that determines a desired color in an original image and replaces it with another color. In this conversion format, a color range that satisfies a predetermined judgment formula based on a specified “color before conversion” (sometimes referred to as “original color”) is converted to a specified “color after conversion” (“target color”). "Contrast with no shading" that fills in with a "color", or "Conversion with shading" to maintain the density of that part and change the color to "the color after conversion" if the judgment formula is satisfied is there. In addition, a method has been proposed in which colors are judged using the HSL system with hue, saturation, and lightness as indices, and colors closer to the target are replaced with colors closer to the `` color before conversion '' to make the joint look natural. ing.
[0003]
[Problems to be solved by the invention]
However, the above-described technique has the following problems. In other words, the above color conversion replaces a color that is close to the specified color (within a certain distance range), so that color discontinuity occurs in the color portion close to the boundary that is not replaced, which is unnatural. It becomes an image. Further, the image read by the scanner has a color blur at the boundary between different colors. When such an image is color-converted, the blurred portion is often out of the conversion range, the original color remains at the end of the color-converted object, and the image quality deteriorates. Furthermore, when the boundary is processed by color conversion in the HSL system, if the hue between the original color and the target color is about 180 degrees apart, the hue changes like a rainbow, which results in an unnatural color change. There is a case.
[0004]
SUMMARY An advantage of some aspects of the invention is that it provides an image processing apparatus and method capable of obtaining a natural color conversion result.
[0005]
[Means for Solving the Problems]
The present invention has the following configuration as one means for achieving the above object.
[0006]
An image processing apparatus according to the present invention is an image processing apparatus that converts designated first color data into designated second color data, and storage means for storing the first and second color data. A calculation means for calculating a conversion rate according to a difference between the input image data and the first color data; and a user for the first color data and the first color data in the input image data. converting the color data having a difference in a predetermined range specified in the second color data, the predetermined range of outer the conversion the color data of and said second converting means for converting the color data corresponding to color data It is characterized by having .
[0007]
An image processing method according to the present invention is an image processing method for converting designated first color data into designated second color data, according to a difference between input image data and the first color data. and the conversion rate is calculated, in the input image data, color data having a difference in a predetermined range designated by the user with respect to the first color data and said first color data into said second color data And converting the color data outside the predetermined range into color data corresponding to the conversion rate and the second color data .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following, an example in which the present invention is applied to a digital full-color copying machine will be described.
[0009]
[Image signal flow]
FIG. 1 is a block diagram showing the flow of image signals in the color copying machine of this embodiment.
[0010]
The analog image signal output from the CCD 101 is converted into a digital signal by the A / D converter 102 to become digital image signals R0, G0, B0 representing the amounts of light of three colors, and further, a known shading correction circuit 103, By the input masking circuit 104, the three-color image signals R, G, B in the standard color space are obtained.
[0011]
These image signals are compressed within the color reproduction range of the printer 112 by the color space compression circuit 105, and then the density signals of cyan, magenta, and yellow are respectively obtained by a light quantity / density conversion circuit (hereinafter referred to as "LOG conversion circuit") 106. Converted to C0, M0, Y0. The image signals C0, M0, and Y0 are subjected to product-sum operation by the UCR / output masking circuit 107 to become toner color, that is, four-color recording density signals of C, M, Y, and Bk (black).
[0012]
In the normal processing, the editing circuit 108 at the next stage outputs a color signal (X) currently recorded by the printer 112 among the four-color recording density signals C, M, Y, and Bk. The signal X is output to the printer 112 through the F value correction circuit 109, the variable power / italic circuit 110, and the spatial filter 111. On the other hand, when an editing function such as painting or color conversion is set in the editing circuit 108, the editing circuit 108 edits the image accordingly, and then the current printer 112 out of the four-color recording density signals C, M, Y, and Bk. Outputs the signal X of the color recorded by.
[0013]
Further, when a partial area in the image is designated by a digitizer or the like (not shown), the area generation circuit 113 generates an area signal AREA in which an area code is assigned to that area. The operation unit 114 is for the user to set “color before conversion”, “color after conversion”, “range d considered to be the same color”, “gradation change rate G”, etc., which will be described later.
[0014]
[Edit circuit]
2 is a block diagram showing a configuration example of the editing circuit 108, FIG. 3 is a diagram showing a configuration example of a function code generated for each area, and FIG. 4 shows an example of a correspondence relationship between the function code CODE and the editing function. FIG.
[0015]
The function code RAM 201 sets a 13-bit function code CODE as shown in FIGS. 3 and 4 according to the editing function set in advance for each area, and generates an area signal generated by the area generating means 113 at the time of image formation. Outputs function code CODE corresponding to AREA. Each block to be described later executes an editing process based on this function code CODE.
[0016]
The composition ratio generation unit 202 generates an image and color or a composition ratio r for generating an edited image by calculating the color and color according to the following equation according to bit 1 of the function code CODE.
x = (1-r) x A + r x B (1)
However, 0 ≤ r ≤ 1
[0017]
FIG. 5 is a block diagram illustrating a detailed configuration example of the synthesis ratio signal generation unit 202. The gradation generation unit 401 generates a synthesis ratio r0 that changes stepwise. In an editing function for changing the composition ratio such as gradation paint (when bit 1 of the function code CODE is “1”), the composition ratio r0 is selected and output by the selector 402 as it is. In this example, there is only one kind of gradation pattern, but the invention is not limited to this.
[0018]
On the other hand, when the composition ratio in the area may be fixed such as color filtering (when bit 1 of the function code CODE is “0”), the composition ratio stored in the color memory 204 is selected and output by the selector 402. The The color memory 204 is used to set “color before conversion” in editing functions using color differences such as color conversion, and “second color” in gradation paint in addition to the composition ratio. The On the other hand, the color memory 205 stores “converted color” for each area in color conversion, and “designated color” in paint or the like.
[0019]
The color difference signal generation unit 203 compares the input four-color image signals Cin, Min, Yin, Bkin and the color C1 designated for each region as the color before conversion and stored in the color memory 204, and compares the two color signals. A color difference signal r1 and a density signal ND corresponding to the distance and the gradation change rate (gradient) specified in advance by the user are generated.
[0020]
The selector 206 receives four color signals from the input image signal, the color memory 204, and the color memory 205, and selects the signals V, C1, and C2 for one color corresponding to the current formation color COLOR. The selector 207 selects the synthesis ratio signal r or the color difference signal r1 as a synthesis parameter used for the calculation of Expression (1) according to the editing function (bit 3 of the function code CODE), and outputs it as the signal R1. The selector 208 selects the signal V selected from the input image signal or the designated color C1 as one of the images to be combined. The synthesis circuit 209 selects two from the density signal ND, the output of the selector 208 (one of the images to be synthesized), and the specified color C2 of the color memory 205 according to the editing function (bits 4 to 6 of the function code CODE). Then, the calculation (image synthesis) of Expression (1) is executed.
[0021]
The binarization circuit 210 binarizes the density signal ND in order to generate an image having a certain density or more as a “character signal”. When an editing function using a character signal such as “character processing” is designated in the bitmap memory 211, the character signal CHR generated by the binarization circuit 210 at the time of pre-scan is written. The character processing circuit 212 generates a contour signal and a shadow signal based on the character signal CHR read from the bitmap memory 211 during image formation. Since this generation requires a line delay, reading from the bitmap memory 211 starts in advance earlier than the start of image reading by the amount of the line delay.
[0022]
The character editing circuit 213 passes through the input image signal V according to the editing function (bits 7 to 12 of the function code CODE), or the synthesized image or the designated color C2 obtained by the synthesizing circuit 209 and the character processing circuit 212. The contour signal and the shadow signal (or the background signal which is an inverted signal thereof) generated in the above are processed. Note that the character color memory 214 stores colors to be added to characters, shadows, and contours for each region.
[0023]
[Color conversion processing]
Next, an example of color conversion in the editing circuit 108 will be described. In other words, this is a case where the user inputs an instruction “convert color A before conversion to color B after conversion on the entire image (AREA = 0)”.
[0024]
First, the color A components Ac, Am, Ay, Ak are written to the address corresponding to AREA = 0 in the color memory 204, and the color B components Bc, Bm, By are written to the address corresponding to AREA = 0 in the color memory 205. , Bk is written.
[0025]
FIG. 6 is a diagram for explaining the color difference signal r1 generated by the color difference signal generation unit 203, and the horizontal axis represents the input image signal value Xin (X = C, M, Y, Bk) and C1x (x = c, m, y , k), and the vertical axis represents the color difference signal r1. Color difference signal for the difference delta C r1 is determined by the function defined by the range d regarded as the same color, the change rate of the gradient (the gradient) G (oblique lines shown in FIG.). The range d and the gradient G are set to desired values by the user from an operation unit (not shown), for example.
[0026]
The selector 207 selects the color difference signal r1 generated by the color difference generation unit 203 and sends it to the synthesis circuit 209. The selector 208 selects the input image signal V as a synthesis target and sends it to the synthesis circuit 209. The synthesis circuit 209 selects the input image signal V and the post-conversion color C2 from the color memory 205, and executes the calculation of the following equation.
X = (r1 / 255) ・ C2 + V ・(1- r1 / 255 ) … (2)
[0027]
Here, r1 = 255 indicates that the content of the color memory 204 (color before conversion) and the color of the image signal V are “matched”. At this time, the output X of the synthesis circuit 209 is Matches the content (color after conversion). r1 = 0 indicates that the content of the color memory 204 and the color of the image signal V are “very different”, and the output X matches the image signal V.
[0028]
In this case, since character processing is not performed, the character editing circuit 213 outputs the image signal output from the synthesis circuit 209 through.
[0029]
As described above, the color conversion process according to the present embodiment obtains the color difference ΔC between the input image signal and the converted color, and obtains a color (| ΔC |) that is close to the specified color before conversion (specified by the range d). <d) replaces the converted color, and for the unreplaced boundary, the color before conversion is converted according to the data r1 (conversion rate) converted from the color difference ΔC based on the gradation change rate G. Replace with the converted color. Accordingly, the color portion before conversion is replaced with the color after conversion, and the color boundary portion is color-converted in a gradation, so that no color discontinuity occurs and a natural image can be obtained.
[0030]
Similarly, an image read by a scanner has a color blur at the boundary between different colors, but when such an image is color-converted, the blur portion is not out of the conversion range. The original color remains at the end of the converted object, and the image quality does not deteriorate.
[0031]
Furthermore, when the boundary is processed by color conversion in the HSL system, a natural image can be obtained even if the hue between the original color and the target color is approximately 180 degrees apart.
[0032]
[Other Embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), or a device (for example, a copier, a facsimile device, etc.) including a single device. You may apply to.
[0033]
Another object of the present invention is to supply a storage medium storing software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium Needless to say, this can also be achieved by reading and executing the program code stored in the. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0034]
In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the OS running on the computer based on the instruction of the program code performs the actual processing. Needless to say, a case where the function of the above-described embodiment is realized by performing part or all of the processing is also included.
[0035]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0036]
In the above-described embodiment, the example in which the color difference is determined using the four CMYBk colors has been described. However, the determination can be performed based on the three RGB colors before conversion to CMYBk. That is, as shown in an example in FIG. 7, a color difference signal generation circuit 701 is provided at the subsequent stage of the input masking circuit 104 to obtain the color difference ΔC between the RGB three-color signal and the converted color set for each area. The color difference signal r1 may be obtained from the obtained ΔC, and the r1 may be input to the editing circuit 108. In this way, the image signal output from the UCR / masking circuit 107 need only be the image signal X0 for one color corresponding to the color COLOR being formed and the density signal ND, so the configuration of the UCR / masking circuit 107 is simplified. Can be
[0037]
In the above-described embodiment, the example in which the range d and the gradation change rate G that are regarded as the same color are specified by the user has been described. However, the image type is automatically determined, and the automatic determination is performed according to the determination result. Alternatively, the range d and the change rate G may be set. For example, an original that is close to a binary image, such as a character original, often has distinctly different characters and background colors. In such a case, the range d is set to be wide so as not to cause conversion residue in consideration of blurring due to color blur at the time of image reading. In addition, in the halftone image, the designated color itself changes in a gradation, so that the range d is narrowed and the transition is made gentle so that the boundary between the color to be converted and the color to be converted cannot be clearly seen.
[0038]
Also, as an application of the color determination function, there is “marker edit specification” that identifies an area surrounded by a color marker from a black and white original and performs editing according to the color of the marker. It can also be used for editing and color conversion. Marker editing designation requires determination of a plurality of colors at once instead of not requiring gradation processing. FIG. 8 is a diagram illustrating a configuration example of a device that realizes this function, and FIG. 9 is a diagram illustrating a configuration example of the color difference signal generation circuit 701.
[0039]
The selector 1002 selects binary determination signals for eight colors output from the comparator group 1003 according to bit 0 of the function code CODE at the time of pre-scanning when marker editing is designated. The selected signal is output as the color difference signal r1 from the color difference signal generation circuit 701 and input to each bit plane of the area signal generation circuit 114. At the time of image formation, the area generation circuit 114 outputs an area signal AREA generated according to the color determination result, and the editing circuit 108 performs an editing process according to the signal AREA.
[0040]
On the other hand, in order to erase the marker image that is not necessary for the original document image, one of the comparator groups 1003 is set to detect “black”, and by inverting this signal, a signal indicating “other than black” is generated. To do. Based on the signal indicating “non-black”, the editing circuit 108 replaces the non-black portion in the document image with “white”.
[0041]
As described above, in an image processing apparatus having a color conversion function for converting an arbitrary color in an image into an arbitrary different color, the color to be subjected to color conversion and surrounding colors are changed in a gradation. Therefore, it is possible to prevent unnatural color switching and obtain a processed image with good image quality.
[0042]
【The invention's effect】
As described above, according to the present invention, it is possible to provide an image processing apparatus and method for obtaining a natural color conversion result.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a flow of an image signal of a color copying machine according to an embodiment;
FIG. 2 is a block diagram showing a configuration example of the editing circuit shown in FIG.
FIG. 3 is a diagram showing a configuration example of a function code generated for each area;
FIG. 4 is a diagram illustrating an example of a correspondence relationship between a function code CODE and an editing function;
FIG. 5 is a block diagram showing a detailed configuration example of a synthesis ratio signal generation unit shown in FIG.
6 is a diagram for explaining a color difference signal r1 generated by the color difference signal generation unit shown in FIG.
FIG. 7 is a block diagram showing a configuration example of a color copying machine according to another embodiment;
FIG. 8 is a block diagram showing a second example of a color copying machine according to another embodiment;
9 is a diagram illustrating a configuration example of a color difference signal generation circuit illustrated in FIG.

Claims (2)

An image processing apparatus for converting designated first color data into designated second color data,
Storage means for storing the first and second color data;
A computing means for computing a conversion rate according to the difference between the input image data and the first color data;
In the input image data, converts the color data having a difference in a predetermined range designated by the user with respect to the first color data and said first color data into said second color data, of said predetermined range An image processing apparatus comprising: conversion means for converting external color data into color data corresponding to the conversion rate and the second color data . An image processing method for converting designated first color data into designated second color data,
Calculating a conversion rate corresponding to the difference between the the input image data first color data,
Wherein in the input image data, converts the color data having a difference in a predetermined range designated by the user with respect to the first color data and said first color data into said second color data,
An image processing method comprising: converting color data outside the predetermined range into color data corresponding to the conversion rate and the second color data .

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