JPH04186968A - Method and device for processing color image - Google Patents

Abstract

PURPOSE:To almost satisfy the faithful color reproduction of a printer, and also, to record and reproduce other color than a color reproduction range, as well by holding its continuity by executing faithfully the color reproduction with respect to the greater part of the color reproduction range of the printer, etc., and executing a processing so that a part thereof becomes a compressed space of a full color space. CONSTITUTION:A color converting part 101 converts image data of R, G and B inputted successively to color spaces of Y, I and Q. The image data converted to the color spaces of Y, I and Q by the color converting part 101 are inputted to an angle calculating part 102. In the figure, a closed curve 201 containing a point F shows an outer edge of a full color space, and a closed curve 202 containing a point E shows an outer edge of a color space of a range in which a printer can execute a color reproduction. In the full color space, color information contained in a color space surrounded by a closed curve 204 passing through a point D is reproduced as it is by the printer. Subsequently, in the case of reproducing a color in a color space surrounded by the closed curve 204 and the closed curve 201 by the printer, a segment DF on cutting is compressed onto a segment DE, and each point on the segment DE is compressed in an equal ratio.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a color image processing method and apparatus for converting the color space of color image data according to the color reproduction range of a color image reproduction device.

[Conventional technology]

2. Description of the Related Art Conventionally, there is an apparatus that inputs color image data (multivalued data) from a color scanner and performs color printing using a color printer based on the color image data. In this case, the color characteristics (read color characteristics) of the color scanner and the color reproduction characteristics (color reproduction range) of the printer may not match. Even in such a case, for example, the possible values (0 to 8 bits) of multivalued image data (8 bits) from a scanner
255), the printer interprets it as image data that fits the color space range that it can handle and records it based on that multivalued image data, without determining which range in the color space it indicates. Ta.

[Problem to be solved by the invention]

For this reason, conventionally, when making a hard copy or soft copy of an original image, there is a problem that the colors of the original original or original image data are not faithfully reproduced on the printer side, but are reproduced in different colors. there were. The present invention has been made in view of the above-mentioned conventional example, and is designed so that, in the color reproduction range of a color image forming apparatus, most of the color reproducible range is faithfully reproduced, and one part is a compressed space of the golden color space. It is an object of the present invention to provide a color image processing method and apparatus capable of processing color image data so as to reproduce a color image while maintaining color continuity even outside the color reproduction range of a color image forming apparatus by configuring a color image. purpose.

[Means to solve the problem]

In order to achieve the above object, the color image processing method of the present invention has the following configuration. That is, the color image processing method converts the color space range of color image data and outputs the converted color image data to a color image forming apparatus, the color component data of the color image data corresponding to most of the color reproduction range of the color image forming apparatus. Color image data that exceeds the color reproduction range is converted into color image data corresponding to the closest outermost edge position within the space of the color reproduction range. Further, the color image processing device of the present invention has the following configuration. That is, a color image processing device converts the color space range of color image data and outputs the converted color image data to a color image forming device, the color image data included in the color reproduction range of the color image forming device being included in the color image data. an output means for outputting the color image data as it is to the color image device; and conversion means for converting into color image data corresponding to the position.

[Effect]

In the above configuration, the color component data of the color image data corresponding to most of the color reproduction range of the color image forming apparatus is not converted, and the color image data exceeding the color reproduction range is
It operates to convert into color image data corresponding to the closest outermost edge position within the space of the color reproduction range. Further, the color image device of the present invention outputs the color image data included in the color reproduction range of the color image forming device as it is out of the color image data, and also outputs the color image data included in the color reproduction range of the color image forming device as it is. It operates to convert color image data components that exceed the color reproduction range of the forming device into color image data corresponding to the closest outermost edge position within the space of the color reproduction range.

Embodiment J Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. <Explanation of an example of color space conversion (FIGS. 2 and 3)> FIG. 2 is a diagram showing the range of color space. In FIG. 2, a closed curve 201 including point F indicates the outer edge of the golden space, and a closed curve 202 including point E indicates the outer edge of the color space within the color reproducible range of the printer. In this embodiment, color reproducibility in the printer is improved by spatially compressing the color space of the closed curve 201 including the point F, that is, the golden space, into the color space of the closed curve 202 including the point E. In this example, Fig. 2 (A) beams, a, b, Y, I
, Q, etc. are shown, but other color spaces may be used. When the color space in FIG. 2(A) is cut along the cutting line 203, FIG. 2(B) shows how the color space is compressed in that cross section. Second
In Figure (B), F indicates the outer edge of the golden space, E indicates the outer edge of the range that can be reproduced by the printer, D indicates the reproduction range where no color shift occurs due to the printer, and C indicates the center of the color space. It shows. The color information contained in the color space surrounded by the closed curve 204 passing through the dots in the golden space is reproduced as is by the printer. When a printer reproduces a color in the color space surrounded by the closed curve 204 and the closed curve 201, the color shown in FIG.
), the line segment DF on the cut is compressed onto the line segment DE,
Each point on the line segment DE is compressed at an equal rate. FIG. 3 is a diagram showing an example of color space conversion, where 81 indicates a case in which each color component of a given gold space is 8 bits (255). Then, under the same conditions, the second
As shown in Figure (B), the range of values that each color component can take when spatially compressed is indicated by 82. Further, S3 shows the case where the range in which the printer can reproduce colors is fully utilized in 8 bits.Finally, the point D1 in the golden space becomes r when the printer can reproduce the colors, the point F in the golden space, It is sufficient if it is converted to E. <Description of Image Conversion Circuit (FIG. 1)> FIG. 1 is a block diagram showing the configuration of the image conversion circuit of this embodiment for realizing the color space compression described above. Reference numeral 101 denotes a color conversion unit, in which R and G are sequentially input. B image data is converted to Y, I, Q color space. Here, it is also possible to convert R, G, and B image data to Lab space, take Y, and treat I and a, and Q and b in the same way, but the 0 color conversion unit 101 will omit the explanation here. The image data converted into the Y, I, Q color space is input to the angle calculation unit 102. In this angle calculation section 102,
As shown in FIG. 4, an angle θ indicating how many times the pixel data P of the image data in the I, Q orthogonal coordinate system is rotated from the Q axis is determined. If the pixel data P (I, Q) coordinates are (i, q), then the angle θ can be found by using one of the following formulas. Further, the output of the color conversion unit 101 is also input to the γ calculation unit 103, and in this γ calculation unit 103, γ=i
+q1- is calculated, and the distance from the center position C of the color space is also calculated. As a result, the coordinates (γ, θ) of the image data P in the polar coordinate system are determined. Furthermore, in the orthogonal coordinate system, it can also be expressed as (i, q)=(γsinθ, γCOSθ). The output θ of the angle calculation unit 102 is calculated based on the D table 104, the integration coefficient a table 105, and the daily integration coefficient b table 106.
is input. Note that the values F, , E in the golden space in FIG. , Dl vary depending on the angle θ, and the blink color reproduction ranges E, , D also vary depending on the angle θ. The colors in the actual golden space range for each angle θ are shown in the lines ,E,,F in FIG. Here, the angles , E, and F with respect to the angle θ are represented by D, (θ), E (θ), and Fi (θ), respectively. In FIG. 5, if the maximum among F(0) to F(359) is 8 bits, it becomes "255"'. Here, although the minimum unit of the angle θ is 1 degree, it is not limited to this,
It may be smaller or larger than this, and
The difference in this angle θ may not be uniform (it is fine. In this embodiment, quantized data within the color reproduction range of the printer is obtained corresponding to each angle. It is determined by measuring the color reproduction characteristics of the printer, etc. In this way, /D is written for each angle θ in the b table 106, and (E, -D, )/( The output γ of the γ calculation unit 103 is input to the comparator 108, and the subtraction unit 107 calculates γ2=γ−D, (θ). Here, D, (θ) is the data pressed from the D table 104 and indicates the ratio to the angle θ. The output of the multiplier 109 is added to the output of the multiplier 117 in the adder 111. , (θ)
From the product coefficient b table 106, (θ) /DI(
θ) is input, and pr(θ) is output as a result. In this way, the output of the adder 111 is the pixel data P(
P(γ', θ) after color space compression of γ, θ). However, this is the case where γ of the pixel data P(γ. θ) is F and (θ)≧γ≧D. On the other hand, the output of the product coefficient b table 106 is given to a multiplier 110, where it is multiplied by γ of the image data P(γ. θ). As a result, γ'' of the image data P(γ', θ) after color space compression when D, (θ)≧γ is obtained. These γ' and γ'' are input to the selector 112, and it is determined which One is selected and output as γ3. The output γ of the γ calculation unit 103 is input to the comparator 108, where it is compared to see if (θ)≧γ, and the comparison result is provided as a selection signal to the selector 112. As a result, when D, (θ)≧γ, γ3 = γ'' is selected, and otherwise γ3 = γ'. After the color space compression obtained in this way The data γ3 and the output θ of the angle calculation unit 102 are combined into P(γ3.
θ) becomes one data. From P(γ3.θ), the color calculation unit 114 calculates ■=γ3・s
inθ, Q=γ3・cosθ is calculated, and the color conversion unit 10
Receive Y data from 1. Y, assembled in this way,
The I, Q data are converted into Y, I, Q data by the compliance conversion unit 115.
is converted into R, G, and B signals. Note that the conversion between R, G, B, Y, I, and Q in the color conversion unit 101 and the compliance conversion unit 115 is a linear linear conversion, and this operation is a product using a multiplier and an adder. This can be achieved using a sum operation. Furthermore, a method of substituting a ROM for the sum of products of a portion thereof is generally known. Also, since the I and Q spatial widths change depending on the luminance signal Y, the first
As shown by the broken line in the figure, D table 104. Product coefficient a table 105. It is more desirable to switch between a plurality of product coefficient b tables 106 and change their output values. <Other Embodiments (Fig. 6)> Fig. 6 shows color space compression in another embodiment of the present invention.
1202 (FIG. 2) is reproduced as is, and other color spaces are converted onto a closed curve 202 including the limit point E. FIG. 10 corresponds to FIG. 3 of the first embodiment described above, in which E is expressed as a distance from the center point C of the color space, and this is assumed to be 8 bits. This distance only needs to be converted from the center point C to E in the printer reproduction range. In this way, all points on the line segment E, -E become E. FIG. 8 is a block diagram showing an image processing circuit of a second embodiment that realizes this color space compression. Portions common to those of the first embodiment described above are designated by the same numbers, and their explanation will be omitted. In this second embodiment, an E table 402 is used in place of the D table 104. This E table 402 is the table shown in the fifth embodiment. Then, in the comparator 108, if γ of P(γ, θ) is E, (θ)<γ, the output γ5 of the E table 402 from the selector 112 = E,
(θ) is selected and input to the synthesis unit 113. Further, the output θ of the angle calculation unit 102 is given to a product coefficient C table 602, and a product coefficient is output based on Y and θ. This product coefficient is E for θ, (θ)/E, (θ)
These values are stored as a table for each angle θ. Further, separate tables may be provided depending on the luminance signal Y. Therefore, the multiplier 110 performs the calculation γ6=γ×Ef(θ)/E, (θ) on the pixel data P(γ. θ) to obtain data after color space compression. Therefore, when E, (θ)≧γ, the result of the comparator 108 controls the selector 112 to output the output γ6 of the multiplier 110 as γ3=γ6. FIG. 7 shows color space compression in the third embodiment of the present invention, in which the color space is compressed uniformly within a closed curve including the outermost edge F of the golden space. FIG. 9 is a block diagram showing the configuration of an image processing circuit that realizes this color space compression. The output from the γ calculation unit 103 is multiplied by a multiplier 121 and provided to the synthesis unit 113 as data after color space compression. Therefore, the output of the multiplier 121 is converted from the golden color space to 8 bits (0 to 255), which is the color reproduction space of the printer. This conversion ratio is supplied from the product coefficient d table 603. The contents of this product coefficient d table 603 are E, (θ)/F, (
θ). Also, this product coefficient d table 603
may be provided for each luminance signal Y (, one table content is read and determined by Y information and θ information. Also,
The maximum value that E, (θ), and FI (θ) can take is “2”.
55", and the angle information θ and brightness information Y make it "25".
5" or less. By the way, in this embodiment and other embodiments of the present invention, multipliers are used in all parts to compress the color space, and uniform compression is performed in proportion to the distance from the center position of the color space. However, the present invention is not limited to this. For example, the color difference in color space compression may be varied depending on the distance γ from the center position. Also, the degree of compression may be varied depending on the angle θ. Furthermore, since the golden color space differs depending on Y, the degree of compression of the luminance component Y may also be different.As explained above, according to this embodiment, the color reproduction range of a printer, etc. By faithfully reproducing most of the color and processing the - part into a compressed golden space, the printer's faithful color reproduction is almost satisfied, and even colors outside the brown reproduction range are recorded and recorded while maintaining continuity. In addition, according to this embodiment, the entire color reproduction range of the printer can be faithfully reproduced, other colors can be approximated to the outer edges of the printer's color reproduction range, and the entire color space can be reproduced by the printer. In this embodiment, γ indicates the saturation direction and θ indicates the hue. Therefore, in this embodiment, γ is converted and θ
By not converting the components, only the saturation can be converted without changing the hue through color space compression. [Effects of the Invention] As explained above, according to the present invention, in the color reproduction range of a color image forming apparatus, most of the color reproduction range is faithfully reproduced, and one part is a compressed golden space. By configuring a color image in this manner, it is possible to reproduce the color image while maintaining color continuity even outside the color reproduction range of the color image forming apparatus.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an image processing circuit 5 according to the first embodiment of the present invention, FIGS. 2 and 4 are diagrams showing the range of color space, and FIG.
Figures 6, 7, and 10 are diagrams showing examples of color space conversion. Figure 5 is a diagram for explaining the data contents of various tables corresponding to each angle. Figure 8 is a diagram showing the data contents of various tables corresponding to each angle. A block diagram showing the configuration of the image processing circuit of the embodiment, and FIG. 9 is a block diagram showing the configuration of the image processing circuit of the third embodiment. In the figure, 101...color conversion unit, 102...angle calculation unit, 103...γ calculation unit, 104...D table, 1
05... Product coefficient a table, 106... Product coefficient b table, 107... Subtractor, 108... Comparator, 1
09.110, 117, 121... Multiplier, 111.
...Adder, 112...Selector, 113...Composition section, 114...Color calculation section, 115...Compliant conversion section,
402... E table, 602... Product coefficient C table, 603... Product coefficient d table. Patent Applicant Canon Co., Ltd. Agent Patent Attorney Yasunori Otsuka (and 1 other person) Figure 2 (A) Q Sekiwa Figure 2 (B) 1M direction Figure 4 Figure 5 Figure 6 Figure I! 9 Ranshi Hong Figure 7

Claims (4)

[Claims] (1) A color image processing method that converts the color space range of color image data and outputs it to a color image forming device, which converts the color components of the color image data that correspond to most of the color reproduction range of the color image forming device. A color image processing method, characterized in that without converting data, color image data exceeding the color reproduction range is converted into color image data corresponding to the closest outermost edge position within the space of the color reproduction range. (2) A color image processing method that converts the color space range of a color image signal and outputs it to a color image forming device, which converts the color components of color image data that correspond to most of the color reproduction range of the color image forming device. A color image processing method characterized in that color image data exceeding the color reproduction range is compressed or converted into a reproduction color space within the space of the color reproduction range without converting the data. (3) A color image processing device that converts the color space range of color image data and outputs the converted color image data to a color image forming device, the color image being included in the color reproduction range of the color image forming device among the color image data. an output means for outputting the data as is to the color image device; and a color image data component of the color image data that exceeds the color reproduction range of the color image forming device to the nearest outermost edge in the space of the color reproduction range. A color image processing device comprising: a conversion means for converting into color image data corresponding to a position of . (4) A color image processing method for converting the color space range of a color image signal and outputting it to a color image forming apparatus, the color image being included in the color reproduction range of the color image forming apparatus among the color image data. It is characterized by comprising: an output means for outputting the data as it is to the color image device; and a conversion means for compressing/converting color image data exceeding the color reproduction range into a reproduction color space within the space of the color reproduction range. color image processing device.