JP3337724B2 - Image processing apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a read color image.
The present invention relates to an image processing apparatus and method for converting an image into a black and white image .

[0002]

2. Description of the Related Art In recent years, a system has been proposed in which a monochrome image printer is combined with a reader for reading a color image.
Among the input images, the monochrome image is expressed as a gradation image, and an image such as a meaningful color graph color-coded by a plurality of colors as shown in FIG. 2. Description of the Related Art There has been proposed an image processing apparatus that expresses a divided pattern.

Here, a conventional technique will be described below with reference to FIG. In the figure, RG read by a reader etc.
The B signals are input to smoothing circuits 901, 902, and 903, respectively, and the visual characteristics are corrected by the look-up tables 904, 905, and 906, and then input to the achromatic color determination circuit 907 and the hue determination lookup table 908, respectively. You. In the achromatic color determination circuit 907, R
The maximum value and the minimum value of the GB signal are calculated, and “1” is output as an achromatic color determination signal if the value is equal to or less than a predetermined threshold, and “0” is output if the value is equal to or more than the threshold. The hue determination look-up table 908 calculates the hue angle t on the ab plane in the Lab space from the RGB signal.
An an (b / a) is output, and the authorized color determination circuit 909 determines which color is registered from the hue angle tan (b / a). Then, the pattern generator 910 generates a pattern according to the color determined by the authorized color determination circuit 909.

The G signal corrected by the look-up table 905 is input to a look-up table 911 and converted into a density signal. Then, the selector 91
Reference numeral 2 selects and outputs the converted density signal when the achromatic signal is "1" and the pattern signal from the pattern generator 910 when the achromatic signal is "0".

[0005]

However, in the above conventional example, if the smoothing area is widened, black characters and the like in chromatic colors are not judged to be achromatic. Conversely, if the smoothing area is narrowed, coarse color halftone dots and the like will be formed. It could not be smoothly converted to a pattern image. Further, even if the black characters (40%, 30%, 25%) in the chromatic colors shown in FIG. 6 are determined to be achromatic, the reproduction result is such that the characters are arranged in the pattern image as shown in FIG. However, there is also a disadvantage that it becomes difficult to read.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a black image in a color image can be achromatically accurately.
It is an object of the present invention to provide an image processing apparatus and method which can determine a color and can reproduce all of black characters in chromatic colors, coarse color halftone dots, thin color lines in white, and the like with high image quality.

[0007]

In order to achieve the above object, the present invention provides an image processing apparatus for converting a read color image into a black and white image, wherein the image processing apparatus converts the read color image into a black and white image based on a color separation signal of the color image. Black determining means for determining whether or not the color image is a black image; smoothing means for smoothing the color image when the black determining means determines that the image is not a black image; and the smoothing means. In a subsequent stage, a determination unit that determines whether the color image is achromatic or chromatic based on a color separation signal of the color image, and when the determination unit determines that the color image is a chromatic color, a chromatic color image is generated. Converting means for converting the pattern into an achromatic pattern image having a different pattern according to the chromatic hue. According to another aspect of the present invention, there is provided an image processing method for converting a read color image into a black-and-white image, wherein the color image is a black image based on a color separation signal of the color image. A black determining step of determining whether or not the color image is not a black image in the black determining step; a smoothing step of performing a smoothing process on the color image; and when said color image based on the color separation signals is determined and the determination step of determining achromatic or chromatic color, chromatic color in the determining step of the chromatic
Pattern of the color image according to the hue of the chromatic color.
And a conversion step of converting the image into a formed achromatic pattern image.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of the image processing apparatus according to the present embodiment. In the drawing, 1 is a black discriminating circuit for discriminating a black portion, 2.3.4 is a smoothing circuit, 5.6.7 is a lookup table, 8
Is an achromatic color determination circuit that determines an achromatic color from the difference between the maximum value and the minimum value of the R, B, and G signals; 9 is a hue determination lookup table that determines an angle on the ab plane in Lab space;
Reference numeral 10 denotes a certified color discriminating circuit for discriminating which color is registered in advance, 11 and 12 denote comparators, and 13 and 14.
21, 22, and 23 are AND circuits; 15, 16, and 17 are OR operation circuits that take ORs in respective areas;
25 is an XOR circuit, 20 is a NOT circuit, 24 is an OR circuit, 26 is a NAND circuit, 27 is a pattern generator for generating a pattern according to the color determined by the certified color determination circuit 10, and 28 is the highest density. A black pattern generator for generating a certain black pattern; 29, a white pattern generator for generating a "0"signal; 30, 31, 32, multipliers; 33, a lookup table for converting a luminance signal into a density signal;
Is an adder, and 35 is a selector for selecting one of the above-mentioned density signal and pattern signal in accordance with the achromatic signal from the achromatic color judgment circuit 8.

In such a configuration, the input RGB signals are input to the black discrimination circuit 1. In the black determination circuit 1,
The difference between the minimum value and the maximum value of RGB is calculated, and a black determination signal is output. The RGB signals are also input to the smoothing circuits 2, 3, and 4 at the same time. Smoothing circuit 2.3
In step 4, smoothing is not performed when the image is determined to be black based on the black determination signal.
Perform × 5 smoothing. Look-up table 5
Steps 6 and 7 correct the luminance signal so as to match the visual characteristics. The corrected signal is input to an achromatic color determination circuit 8 and a hue determination look-up table 9. The achromatic judgment circuit 8 is RGB
And outputs an achromatic signal of "1" when the difference is equal to or smaller than a predetermined threshold and "0" when the difference is equal to or larger than the predetermined threshold. On the other hand, the hue determination look-up table 9 outputs tan (b / a) for the RGB signals. The certified color determination circuit 10 determines which certified color belongs to tan (b / a).

The G signal is input to comparators 11 and 12. Here, the comparator 11 sets “1” when the value is equal to or larger than the threshold,
When the value is equal to or smaller than the threshold value, a bright portion determination signal of “0” is output to the comparator 1
2 outputs a dark part determination signal of "1" when the value is equal to or less than the threshold value and "0" when the value is equal to or more than the threshold value. The AND circuit 13 performs an AND operation on the bright portion determination signal and the achromatic color determination signal, and outputs a white determination signal. The AND circuit 14 ANDs the dark part determination signal and the achromatic color determination signal, and outputs a black determination signal. The outputted black judgment signal is inputted to OR operation circuits 15 and 16 and the white judgment signal is inputted to an OR operation circuit 17 to be OR-operated, respectively, XORed by XOR circuits 18 and 19, and the white and black parts are turned around. It is determined whether there is. And NOT circuit 20
NOT signal of achromatic determination signal passed through and AND circuit 21
In steps 22 and 23, an AND operation is performed to determine the position of the boundary between the chromatic color and the achromatic color. And the OR circuit 24
, Whether to print in black, not to print by the XOR circuit 25, or to print in a pattern by the NAND circuit 26. The three determination results are added to the signals output from the respective pattern generators 27, 28, and 29 by the multiplier 3
Multiplied by 0.31,32.

On the other hand, the above-mentioned G signal is also inputted to the look-up table 33 from the look-up table 6 and converted into a density signal. Then, the selector 35 selects the density signal when the above-mentioned achromatic color determination signal is “1”,
When "0", the pattern signal output from the adder 34 is selected and output. By performing the above processing, the boundary between the chromatic part and the white part / black part as shown in FIG. 2 is converted as shown in FIG. 3, and the graph and the like shown in FIG.
Reproduced as shown in

[0012]

Next, another embodiment of the present invention will be described in detail with reference to the drawings. FIGS. 10 and 11 are block diagrams showing the configuration of an image processing apparatus according to another embodiment. In the figure, reference numeral 101 denotes a black discriminating circuit for discriminating a black portion, 102, 103, and 104 denote smoothing circuits,
5, 106, 107 are lookup tables, 108 is an achromatic color determination circuit that determines an achromatic color from the difference between the maximum and minimum values of the R, G, B signals, and 109 is an angle on the ab plane in Lab space. Lookup table for hue determination, 110 is a certified color determination circuit for determining which color is registered in advance, 111 is a calculator for calculating luminous luminance from RGB signals, 112 and 113 are comparators, 11
4. 115. 129 to 134 are AND circuits, 116 to 1
Reference numeral 21 denotes an OR operator for performing an OR operation in each area.
2 to 127 are XOR circuits, 128 is NOT circuits, 135
Is based on the color determined by the certified color determination circuit 110,
A pattern generator 136 for generating a pattern, a lookup table 136 for converting a luminance signal into a density signal, a calculation device 137 for calculating a ratio between a density signal and a pattern signal from each boundary position signal, 138 and 139 multipliers, 1
40 is an adder.

In this configuration, both the white judgment signal and the black judgment signal output from the AND circuits 114 and 115 are set to 3
Boundary position determination is performed by performing calculations on different types of regions (7 × 7, 5 × 5, 3 × 3), and a density signal and a pattern signal are mixed based on the boundary position signal.
The boundary between the pattern and the gradation image can be smoothly connected.

According to the embodiment described above, the smoothing area and the coefficient are reduced in the dark black portion, and the smoothing area and the coefficient are increased in the other portions.
In addition, the boundary between chromatic and white areas is made black, etc., and the boundary between chromatic and black areas is made thicker and the area around it is extracted as white, converting coarse color halftone dots into a uniform pattern. This makes black characters in chromatic colors easier to see, and color thin lines in white can be reproduced as black thin lines instead of patterns.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0016]

As described above, according to the present invention,
A black image in a color image is determined to be achromatic with high accuracy
And black characters in chromatic colors, coarse color dots,
It is possible to reproduce all the color thin lines and the like in white with high image quality.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment.

FIG. 2 is a diagram showing a boundary between a chromatic part and a white part / black part.

FIG. 3 is a diagram showing a state in which a boundary portion in FIG. 2 is converted.

FIG. 4 is a diagram showing a color-coded image such as a color graph.

FIG. 5 is a diagram in which the image of FIG. 4 is represented by patterning for each color.

FIG. 6 is a diagram showing an image in which black characters in chromatic colors are arranged.

FIG. 7 is a diagram in which the image of FIG. 6 is reproduced by boundary processing in the present embodiment.

FIG. 8 is a diagram in which the image of FIG. 6 is reproduced by boundary processing in a conventional example.

FIG. 9 is a block diagram illustrating a configuration of an image processing apparatus in a conventional example.

FIG. 10 is a block diagram illustrating a configuration of an image processing apparatus according to another embodiment.

FIG. 11 is a block diagram illustrating a configuration of an image processing apparatus according to another embodiment.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/46-1/64 G06T 5/00 100

Claims (4)

(57) [Claims] 1. An image processing apparatus for converting a read color image into a black and white image, comprising: a black determination unit that determines whether or not the color image is a black image based on a color separation signal of the color image And if the black determination unit determines that the image is not a black image, a smoothing unit that smoothes the color image; and a stage subsequent to the smoothing unit, based on a color separation signal of the color image. Determining means for determining whether the image is achromatic or chromatic; if the determining means determines that the image is chromatic, the pattern of the chromatic color image is different according to the hue of the chromatic color;
The image processing apparatus characterized by having conversion means for converting the achromatic pattern image obtained. 2. The image processing apparatus according to claim 1, wherein when the determination unit determines that the chromatic color is a chromatic color, the conversion unit detects whether the chromatic color is adjacent to the achromatic black image, and determines whether the chromatic color is adjacent to the achromatic black image. If so, the color image is converted to the achromatic pattern image.
The image processing apparatus according to claim 1, wherein the image is converted into a black image without conversion. 3. The conversion means detects whether the chromatic color is adjacent to an achromatic white image when the determination means determines that the chromatic color is a chromatic color, and determines whether the chromatic color is adjacent to the achromatic white image. If so, the color image is converted to the achromatic pattern image.
The image processing apparatus according to claim 1, wherein the image is converted into a black image without conversion. 4. An image processing method for converting a read color image into a black and white image, comprising: a black determination step of determining whether the color image is a black image based on a color separation signal of the color image. And a smoothing step of smoothing the color image when it is determined that the color image is not a black image in the black determination step; and, following the smoothing step, the color based on a color separation signal of the color image. image a determination step of determining achromatic or chromatic, when it is determined that chromatic color in the determining step, mosquito chromatic
If the pattern is different according to the hue of the chromatic color
And a conversion step of converting the image into an achromatic color pattern image.