JPH08191392A - Image processor - Google Patents

Abstract

PURPOSE: To make a color copy output easy to be seen by noticing the inside, the outside and the dot of a black edge, in particular, and performing an emphasis processing for an image to be copied. CONSTITUTION: The R, G and B data read by a scanner 2 from an original 1 is converted into the complementary color data composed of C, M and Y in a complementary color invertion processing circuit 3. As for this complementary color data, a dot area is detected in a dot area decision circuit 10, the inside and the outside of a black edge are detected in a black edge decision circuit 11, and the edge emphasis processing according to each area is performed in the adaptive processing circuit 4 classified by areas. The output of this adaptive processing circuit 4 classified by areas becomes a copy output 9 via a black generation processing circuit 5, a gradation correction processing circuit 6, a halftone processing circuit 7 and a printer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus suitable for a system for color printing a color image such as a video printer or a copying machine, especially a color copying machine.

[0002]

2. Description of the Related Art In recent years, image processing apparatuses have been steadily progressing from conventional black and white to color. In color printing, an image is separated into three primary colors, captured in an apparatus, and subjected to various processes to perform color printing on paper. Various spatial filters, pattern recognition techniques, and the like are frequently used for these processes. This technology has produced a wide variety of applications including the case of printing color images such as NTSC and HDTV video signals, photographs and CAD data, including color copying machines.

For example, in a Japanese word processor of the 1994 type, a V-type word processor, like Sharp Corporation, is used to create a New Year's card.
There are those that take in composite video signals from TR etc., those that input images with a special camera such as Sanyo Electric Co., Ltd., those that read photos with a special scanner attached to the printer such as Matsushita Electric Industrial Co., Ltd. It is on sale. Thus, it can be said that the uses of color printing are steadily and rapidly expanding.

Now, as a typical example of such an image processing apparatus for color printing, an image processing apparatus in a color copying machine will be taken as an example, and a conventional example will be described below. FIG. 21 is a block schematic diagram showing the configuration of an image processing apparatus in a conventional color copying machine. In the figure, the original 1 optically read by the scanner 2 is converted into analog electric signals corresponding to the three primary colors of light, that is, red (R), green (G), and blue (B), and this Scanner 2
While sampling by an analog / digital (hereinafter abbreviated as "A / D") converter (not shown) built in the A / D converter, 8-bit (256 gradations) A / D conversion is performed to correspond to each sampling point. Numerical data D _R , D _G , and D _B are input to the complementary color inversion processing circuit 3. On the other hand, it is sent to the edge detection circuit 12 as the A / D-converted video data D _V.

In the complementary color reversal processing circuit 3, the numerical data D _R , D _G , D _B are calculated as complementary colors for printing, and cyan (C), magenta (M), and yellow (Y) are calculated. Complementary color data D _C , D _M and D _Y consisting of primary colors are output. These complementary color data D _C , D _M , and D _Y are sent to the edge correction circuit 11.

On the other hand, in the edge detection circuit 12, the image data D _V is edge-differentiated by a high-pass filter (not shown) on the plane and the differential output is binarized to be an edge detection signal S _E. The edge detection signal S _E is sent to the edge correction circuit 14. The edge correction circuit 14 processes the above-described complementary color data D _C , D _M , and D _Y with a spatial high-pass filter (not shown) whose coefficient changes according to the edge detection signal S _E to determine whether or not there is an edge. The corresponding enhancement processing is performed.

Complementary color data D _C4 subjected to the edge emphasis,
D _M4 and D _Y4 are sent to the black generation processing circuit 5. In this black generation processing circuit 5, under color removal (UCR, Under Color Re
Moval) to detect the black portion of the color and create black data D _K. Here, this UCR refers to the operation as shown in (a) and (b) of FIG.

FIG. 22 (a) is a diagram showing an example of the distribution of the three primary colors, in which the amount of yellow is the smallest. The density below the dashed-dotted line a in the same figure is replaced with black, and a black portion is generated as shown in FIG. The output of the black generation circuit 5 is data D _C5 , D _M5 , and D _Y5 having numerical values corresponding to the density of the shaded area in FIG.

This UCR is originally unnecessary according to the theory of color reproduction of the three primary colors, but in reality, if printing is performed with the three primary colors, sufficient density cannot be obtained in the dark area and three color toners are used. It is necessary to strictly adjust the amount of the toner, and a large amount of expensive color toner is consumed. The above-mentioned UCR is performed in order to prevent such a problem.

The complementary color data D _C5 , D _M5 , D _Y5 and the black data D _K5 are subjected to gradation correction in the gradation correction processing circuit 6 to obtain complementary color data D _C6 , D _M6 , D _Y6 and black data D _K6. To the halftone processing circuit 7. In the halftone processing circuit 7, the complementary color data D _C6 , D _M6 , D _Y6 and the black data D _K6 are processed so that the halftone becomes easy to see, and the output complementary color data D
_It is sent to the printer 8 as _C7 , D _M7 , D _Y7 and output black data D _K7 .

The printer 8 transfers and fixes the color toner on the paper according to the output complementary color data D _C7 , D _M7 , D _Y7 and the output black data D _K7 , and outputs it as a copy output 13 from the color copying machine. (For example, JP-A-2-
244876 publication).

[0012]

However, in the image processing apparatus in the conventional color copying machine as described above,
There is a problem that "blurring" occurs at the edge portion. In particular, with respect to the original 1 which has been subjected to a process such as shading, this problem becomes the following problem for the user. Also, especially in systems that also use reversal development,
There is a problem that the thin line portion is further thinned by this "blurring", and it becomes difficult to emphasize the thin line portion such as a character area.

For example, in a recent word processor, even the image input is colorized as described above. In a technical document or an office document created by such a word processor,
Black shading is often used in areas where we want to emphasize the meaning to the reader. In such a technical document or office document, an area including only characters ((a) in FIG. 25), an area including only shaded areas ((b) in FIG. 25), and an area in which characters and shaded areas coexist (see FIG. 25). (C)) and other areas. Therefore, just emphasize that there is an edge,
The part that the creator of the document originally wants to emphasize ((c) of FIG. 25)
If the copy output 13 of No. 1 is bleeding, there is a problem that the copy becomes ambiguous and difficult for the user to read.

The cause of this "bleeding" and the degree of its influence will be briefly described below for the future. 23 (a) to (d) and FIG. 24 (a) to
(D) is a figure showing the cause of bleeding occurrence. In these drawings, (a) of FIG. 23 and (a) of FIG. 24 represent the densities of the images read by the scanner 2. When such an image is differentiated by a high-pass filter, it has waveforms like 231a and 231b in FIG. 23B and waveforms like 241a and 241b in FIG. These waveforms are combined and printed.

Here, the meaning of using such a high-pass filter is as follows. The MTF (Modulation) which is the spatial frequency characteristic of the optical system and the photodetector of the scanner 2
Since the transfer function has a low-pass filter characteristic by using a lens (not shown) having a finite radius, the waveform detected by the scanner 2 becomes dull. Although it is best to use a spatial filter having an inverse characteristic of MTF to correct this dullness, such an inverse characteristic filter cannot be realized with a simple configuration and is not industrial. Therefore, the above processing is performed by simply differentiating with a spatial high-pass filter.

However, the density range (dynamic range) in which the printer 8 can normally print is finite, and if it is an inner edge, it is emphasized by this differentiation processing in FIG.
Waveform 231 above the dashed-dotted line 230 in FIG.
A and 231b (hatched portion) will be crushed. If it is an outer edge, by adding waveforms 241a and 241b as shown in FIG. 24 (b), the edge becomes narrower as shown in FIG. 24 (c) and further exceeds the one-dot chain line 240. The part will be crushed and the "bleeding" will spread.

This "crush" is such that the waveform is simply clipped if it is in the dynamic range of the electric circuit, but in the case of printing, the toner once output on the paper is irreversible, so rollers in the copying machine, etc. 23. The area around the print spot 233 (corresponding to each pixel) as shown by the line 232 in FIG. 23D and the periphery of the print spot 243 (corresponding to each pixel) as shown by the line 242 in FIG. Will be scattered around. This is the main cause of "bleeding".

Further, since the above-described processing of the spatial high-pass filter is performed for a finite number of pixels, the differential characteristic reaches a ceiling in the spatial frequency domain and the effect of edge enhancement is not sufficient. There is also a cause that a low pass spatial filter for noise removal must be interposed. Incidentally, these problems are not only represented by a color copying machine, but also by using ink,
The same applies to the color print output of a video printer or CAD.

The present invention has been made in view of the above problems, and particularly provides an image processing apparatus which emphasizes an image to be copied by paying attention to a black edge and makes the color copy output easy to see. To aim.

[0020]

In order to achieve the above object, the image processing apparatus of the present invention, in claim 1, generates a change signal whose value changes in accordance with the contour of an image composed of a predetermined pixel unit. Generating means for outputting the first contour signal for determining the region inside the contour in the image based on the change signal, and the first determining signal for matching the first contour signal with the contour of the image. First correction means for outputting a corrected first correction signal; second determination means for outputting a second contour signal for determining a region outside the contour in the image based on the change signal; Second correction means for outputting a second correction signal that is corrected so that the contour signal of the first correction signal matches the contour of the image, and the image is changed according to the second correction signal and the first correction signal. And means for changing .

According to a second aspect of the present invention, the generating means converts the image into a numerical image having a numerical value corresponding to its density, and the numerical image has a first reference value and a second reference value. Comparing means for comparing and converting into a ternary signal composed of three values, and removing means for removing a region having a number of pixels smaller than a predetermined number from the image according to the ternary signal. is there.

According to a third aspect of the present invention, the first determining means provides a predetermined pixel of interest in accordance with the change signal, and a pixel in the vicinity of the pixel of interest includes a value of the ternary signal. It is determined that the first contour signal is to be output when the first contour pattern matches the first pattern.

According to a fourth aspect of the present invention, the second determining means provides a predetermined pixel of interest according to the change signal, and a pixel in the vicinity of the pixel of interest includes a value of the ternary signal. It is determined that the second contour signal is output when the second contour signal matches the second pattern.

Further, in the present invention, the first correction means determines that the figure in which the values of the first contour signal are spatially arranged matches the predetermined third pattern, and then the first correction means. It is used as a correction signal.

According to a sixth aspect of the present invention, the second correction means determines that the figure in which the values of the second contour signal are spatially arranged matches the predetermined fourth pattern, and then the second correction means. It is used as a correction signal.

According to a seventh aspect of the invention, the changing means detects the area including a spatially repeated portion in the image, the output of the detecting means, the first correction signal, and the second correction. And a multiplying unit for multiplying a coefficient proportional to the signal by a value proportional to the density of the image.

[0027]

According to the above structure, in the first aspect, the change signal whose value changes according to the contour of the image formed of a predetermined pixel unit is generated by the generation means, and the change signal is generated by the first determination means. Is processed into a first contour signal for determining a region inside the contour in the second and a second contour signal for determining a region outside the contour in the image by the second determining means, and the first correcting signal is processed by the first correcting means. A first correction signal corrected so that the first contour signal matches the contour of the image, and a second correction signal corrected by the second correction means so that the second contour signal matches the contour of the image. Is converted to. By changing the image by the changing means using the first and second correction signals, the image to be copied is emphasized by paying particular attention to the black edge so that the color copy output can be easily seen.

According to a second aspect of the present invention, in the generating means of the first aspect, the converting means first converts the image into a numerical image having a numerical value corresponding to its density, and then the comparing means uses the numerical image as a first reference. The value is compared with the second reference value to be converted into a ternary signal consisting of three values, and the removing means removes the region consisting of the number of pixels smaller than a predetermined number from the image according to the ternary signal. Therefore, since unnecessary points such as stains can be removed, the image to be copied is emphasized by paying attention to the black edge so that the color copy output can be easily seen.

According to a third aspect of the present invention, the first judging means of the first aspect provides a predetermined pixel of interest in accordance with the converted signal, and a pixel near the pixel of interest includes the value of the ternary signal. Since the first contour signal is output when it matches the predetermined first pattern determined by the above, it is possible to emphasize the image to be copied by paying particular attention to the black edge to make the color copy output easier to see. Become.

In a fourth aspect of the present invention, the second determining means of the first aspect provides a predetermined target pixel according to the converted signal, and a pixel in the vicinity of the target pixel includes the value of the ternary signal. Since the second contour signal is output when it matches the predetermined second pattern determined by the above, it is possible to emphasize the image to be copied by paying particular attention to the black edge to make the color copy output easier to see. Become.

According to a fifth aspect of the present invention, the first correction means is
The figure in which the values of the above first contour signal are spatially arranged is
Only when it is determined that it matches the predetermined third pattern, the above-mentioned first correction signal is used, so that it is possible to distinguish between characters and other characters, so the image to be copied is emphasized with particular attention to the black edge. This makes it easier to see the color copy output.

In the sixth aspect, the second correction means is
A figure in which the values of the second contour signal are spatially arranged is
Only when it is determined that it matches the predetermined fourth pattern, the above-mentioned second correction signal is used, so that it is possible to distinguish between characters and other characters, so the image to be copied is emphasized with particular attention to the black edge. This makes it easier to see the color copy output.

According to a seventh aspect of the present invention, in the changing means of the first aspect, the detecting means detects the area including the spatially repeated portion in the image, and the multiplying means detects the output of the detecting means, the first correction signal, and the above-mentioned first correction signal. Since the coefficient that changes in accordance with the second correction signal is multiplied by the value proportional to the density of the image, the image to be copied is emphasized with particular attention to the black edge to make the color copy output easier to see.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image processing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a block schematic diagram showing a hardware configuration when an image processing apparatus according to an embodiment of the present invention is applied to a color copying machine. In the figure,
The original 1, the scanner 2, the complementary color inversion processing circuit 3, the black generation processing circuit 5, the gradation correction processing circuit 6, the halftone processing circuit 7, and the printer 8 are the same as those in the conventional example, and the description thereof will be omitted. The feature of the present application is that the adaptive processing circuit 4 for each area, the black edge determination circuit 11 and the halftone dot area determination circuit 10 for controlling the adaptive processing circuit 4 are provided.

The operation of the image processing apparatus of the present invention configured as described above will be described below. First, regarding the configuration of the adaptive processing circuit 4 for each area and the black edge determination circuit 11,
Description will be given with reference to the block diagram shown in FIG. In the figure, complementary color data D _C , D _M , and D _Y are input to the region-based adaptive processing circuit 4, the black edge determination circuit 11, and the halftone dot region determination circuit 10. The black edge determination circuit 11 includes a first edge pixel determination circuit 11a for detecting an inner edge of the image and a second edge pixel for detecting an outer edge of the image as shown in the figure.
Edge pixel determination circuit 11b.

Now, the structure and operation of the halftone dot area judgment circuit 10 will be described. FIG. 3 is a block schematic diagram showing the configuration of the halftone dot area determination circuit 10 in this embodiment. In the figure, 10a to 10c show the main part of the halftone dot area judging circuit, and 10d is an OR circuit. The operation of the halftone dot area determination circuit 10 configured as described above will be described below.

Each of the blocks 10a to 10c comprises a peak detection circuit 81, a pitch detection circuit 82 and a periodicity determination circuit 83, and receives complementary color data D _C , D _M and D _Y , respectively. The outputs of the blocks 10a to 10c are ORed in the OR circuit 10d and output as a halftone dot signal S _A. The operation of each of the blocks 10a to 10c will be described below on behalf of the block 10a.

The peak detection circuit 81 receives the complementary color data D _C and detects the peak of the amplitude (that is, density) change of the complementary color data D _C. Here, in the halftone dot area, for example, the dots 90 and the like are arranged at substantially constant intervals as shown in FIG. When such dots 40 are scanned as shown by the broken line in the figure, the density of the read document shows a temporal change as shown in FIG. In FIG. 4B, the points a to where the waveform 41 intersects each one-dot chain line in the vertical direction.
“E” is the “peak” here. As a method of detecting such a peak, it may be detected that the value at an arbitrary point x is larger than the upper, lower, left, and right values A, B, C, and D as shown in FIG.

Now, the intervals A to D of the peaks of the waveform 41 are measured by the pitch detection circuit 32 as a numerical value P (n). Here, n is a finite natural number. As a method for this measurement, for example, a high-frequency clock may be used to count the number of clock pulses counted during the time between the peaks a and b, b and c, c and d, d and e, and the like. .

This numerical value P (n) is the periodicity determination circuit 43.
Is once each compared in, | P (n) -P ( n + 1) | logic when it is ≦ P _D (1) is detected by a predetermined number of times "
A signal S _PC of 1 ″ is output. Here, P _D is a finite natural number. Such processing is performed by blocks 10b and 10b.
The same is done for c, and the signals S _PM and S _PY are output respectively, and the halftone dot signal S _A is obtained as described above.

Next, the configurations of the first edge pixel determination circuit 11a and the second edge pixel determination circuit 11b are shown in FIG.
Description will be given with reference to the block diagram shown in FIG. In the figure, 61 is an inner edge detection circuit, 62 is an outer edge detection circuit, 63 is a pixel color determination circuit, 64 is a first result combining section, and 65 is a second result combining section. The unit 64 and the second result combiner 65 each include one AND circuit. Here, the first edge pixel determination circuit 1
1a is an inner edge detection circuit 61, a pixel color determination circuit 63
The second edge pixel determination circuit 11b includes the outer edge detection circuit 62, the pixel color determination circuit 63, and the second result synthesis unit 65.

The inner edge detection circuit 61 receives the complementary color data D _M , D _C , and D _Y to detect the edge portion of the character and the like, and the inner edge detection signal S _CE1 which becomes a logic “1” in the inner edge region. Is output as the outer edge detection circuit 6
2, the complementary color data D _M , D _C , and D _Y are received, the edge portion of the character is detected, and the logical edge is detected in the outer edge region.
It is output as the outer edge detection signal S _CE2 of 1 ″. Further, in the pixel color determination circuit 63, the complementary color data D is also output.
Upon receiving _M , D _C , and D _Y , the color of the read pixel is determined, and if it is black, the black determination signal S _{B that} is logical “1” is output.

Inside edge detection signal S _CE1 and black determination signal S _B
Outputs the inner black edge signal S _BE1 that is logically ANDed in the first result synthesizing unit 64 and becomes logical “1” only for the pixels in the inner black edge region. Further, the outer edge detection signal S _CE2 and the black determination signal S _B are logically ANDed in the second result synthesizing unit 65, and the outer black edge signal becomes logical “1” only for the pixels in the outer black edge region. Output S _BE2 .

The inside edge detecting circuit 61, the outside edge detecting circuit 62 and the pixel color judging circuit 63 are configured as follows. First, the pixel color determination circuit 63
It is represented by the block diagram shown in FIG. In the figure, the complementary color data D _C , D _M and D _Y from the complementary color inversion processing circuit 3 are
Minimum value detection circuit 71 and maximum value detection circuit 72, respectively
And the minimum value Dmn and the minimum value Dmx at each sampling point are obtained. The minimum value Dmn output from the minimum value circuit 71 is compared with a large reference value D _R1 (for example, “200”) in the digital comparator 73, and if it is larger than this reference value D _R1 , the signal S1 of logic “1” is obtained.
Is output.

Further, the minimum value Dmn and maximum value Dmx, in the digital arithmetic circuit _{74, D AB = | Dmn-} Dmx | done (2) becomes operational, its output D _AB is input to a digital comparator 75, Small reference value D _R2 (eg "1
0 "), and if smaller than this reference value D _R2 ,
The signal S2 of logic "1" is output.

Here, the meaning of these processes is as follows. In the digital comparator 73, the reference value D _R1 is the reference value of the print density, and the output S1
Becomes a logical "1" when the density is high and a logical "0" when the density is low. On the other hand, the digital comparator 75
In, the reference value D _R2 is a reference value for determining whether or not it is a chromatic color, and the output S2 is a logical "1" in the case of an achromatic color and a logical "0" in the case of a chromatic color.

Here, it is known that the relationship of D _C ≈D _M ≈D _Y (3) generally holds for black. Therefore, if the maximum value and the minimum value of the complementary color data D _C , D _M , and D _Y showing the numerical values corresponding to the densities of the three complementary colors of cyan, magenta, and yellow are substantially the same, it is an achromatic color. I understand. As a result, the output S _B of the AND circuit 76 becomes a logic “1” in the case of high density and achromatic color, that is, in the case of black.

Now, the configurations and operations of the inner edge detection circuit 61 and the outer edge detection circuit 62 will be described. FIG. 8 is a schematic block diagram showing the configurations of the inner edge detection circuit 61 and the outer edge detection circuit 62. In the figure, a black data generation circuit 81, a smoothing filter 82, an edge extraction filter 83, a ternarization circuit 84 and an isolated point removal circuit 8
5, the black data generation circuit 81 is common to the inner edge detection circuit 61 and the outer edge detection circuit 62,
It is summarized as shown.

Black data D _K7 is generated from the complementary color data D _C , D _M and D _Y from the complementary color inversion processing circuit 3 of FIG. 1 based on the UCR principle as described in the section of the prior art. Note that this circuit is, for example, the black generation processing circuit 5 in FIG.
It can be omitted when data is obtained from the subsequent circuits.

This black data D _K7 is once smoothed by the low pass spatial filter of 3 rows and 3 columns having the structure shown in FIG. 9 in the smoothing filter 82, and is output as smoothing data D _L. The purpose of this process is simply noise removal. This smoothed data D _L is 3 lines 5 having a structure shown in FIG. 10 in the edge extraction filter 83.
Edges are extracted by the low-pass elimination spatial filter of the column and output as edge data D _E. Here, a cross section of the output from each of the spatial filters 82 and 83 is taken to be 1
Dimensionally, the waveforms are as shown in (a) and (b) of FIG. 19, respectively.

In the ternarization circuit 84, FIG.
Edge data D _E such as, for example, the values + Th and −Th
The waveform is shaped by the _two threshold values t ₁ and t ₂ which have the value of 3 and output as a ternary signal S _T. The two thresholds are t ₁ > t
Any number of ₂ is acceptable. As a result, the ternarization circuit 8
The output S _T of 4 is S _T = H t ₂ <D _E <t ₁ when D _E ≧ t ₁ S _T = M D _E ≦ t ₂ S _T = L Here, H represents a high level, that is, a portion where the density change is abrupt, M represents an intermediate level, that is, a portion where the density change is gentle, and L represents a low level, that is, a base part adjacent to the edge.

In the ternarized image data, noise which could not be removed by the isolated point removing circuit 85 due to the large size of the smoothing filter 82 is removed. This is an independent high-density or low-density single pixel that is generated as a pre-process for the subsequent edge pixel determination, that is, for example, a black spot on the original 1 that spreads in the surroundings at an intermediate level without any difference. Is to be removed.

In this process, if the value of the pixel of interest shown in the shaded area in FIG. 11A is "H", all eight surrounding pixels are "H".
When the value is “M”, the value is replaced with the value “M” as shown by an arrow, or when the value of the pixel of interest shown in the shaded area is “L” as shown in FIG. Is "M", the value is replaced with the value "M" as indicated by the arrow.

In the inner edge pixel determination circuit 86, based on the ternary signal S _T ′ subjected to such isolated point removal processing,
Pixels inside the edge are determined. As conditions for determining this edge, there are patterns listed in (a) and (b) of FIG. 12 and (a) to (k) of FIG.
In the figure, the shaded area in the center is the pixel of interest. That is, when the pixel of interest is “M”, (a) in FIG.
In the case where the values of the respective elements a to h consist only of "M" and "H" in FIG. 12 and when the surrounding eight pixels are all "H" as shown in FIG. S
_ED1 becomes logical "1".

When the pixel of interest is "H", the inner edge pixel determination circuit 8 is used when the adjacent four neighboring pixels match the patterns shown in FIGS. 13 (a) to 13 (i).
The output S _ED1 of 6 becomes logic "1". As this processing, a known pattern matching technique described later may be used. Here, in FIG. 13, the pixel marked with "*" and the undesignated pixel may be "H", "M", or "L".

When the target pixel is "L", or when the target pixel is "M" and the pattern is other than the above-mentioned pattern shown in FIG. In the case of the pattern shown, the output S _ED of the edge pixel determination circuit 86 is logic "0". Such FIG. 12 and FIG.
The pattern shown in is stored in a ROM (Read Only Memory) provided in the inner edge pixel determination circuit 86, for example, M
ALU (Arithmet) as PU (Micro Processor Unit) configuration
ic Logic Unit).

The output S _ED1 of the inside edge pixel determination circuit 86 is sent to the edge pixel correction circuit 87 to determine whether or not the pixel is the final inside edge pixel. This is because the patterns indicating the pixels in the character area or the halftone dot area are determined in 12 patterns as shown in (a) to (l) of FIG.

As a search method for such a pattern,
The pattern matching technique may be used like the inner edge pixel determination circuit 86. FIG. 15 is a conceptual diagram showing the operation of such a pattern matching technique. In the same figure, each lattice represents one pixel, and the bold-line figures 151 to 153 represented by dotted lines indicate the position of the pattern of FIG. 14A at each time. While shifting by one pixel in the x-axis direction (horizontal direction in the figure) as shown by the arrow, it is determined whether the patterns match, and the inner edge pixel correction circuit 87
An edge correction signal S that becomes a logical "1" only when they match
Outputs _CE1 .

The y-axis direction (vertical direction in the drawing) on all the surfaces of the original document 1 read by the scanner 2 with such an operation.
The same process is repeated for all the patterns (a) to (l) shown in FIG. It should be noted that in FIG. 15, the patterns 151 to 153 are intentionally shifted slightly for the sake of easy identification by the reader.

This edge correction signal S _CE1 is sent to the first result combining section 64, and the subsequent processing is as described above.
The technique used for the inner edge pixel determination circuit 86 and the inner edge pixel correction circuit 87 is not limited to the pattern matching technique described above, but a vector or symbol string is generated from an image and the correlation of the vector or symbol string is generated. , A so-called “pattern recognition” technique may be used or used in combination. The inner black edge signal S _BE1 indicating the inner side of the edge of the image generated in this way is sent to the first coefficient arithmetic circuit 22 in the region-specific adaptive processing circuit 4.

Now, in the outer edge pixel determination circuit 88,
Pixels outside the edge are determined based on the ternary signal S _T 'that has been subjected to the isolated point removal processing described above. As conditions for determining this edge, there are patterns listed in (a) to (e) of FIG. 16 and (a) to (f) of FIG. In the figure, the shaded area in the center is the pixel of interest. That is, this is a case where the pixel of interest is "L", and
When the eight pixels around the pixel of interest are only "H" and "L" as in (a) to (e), the output S _ED2 of the outer edge pixel determination circuit 88 becomes a logic "1". It should be noted that the pattern of FIG. 16 is limited to a portion.

Further, four adjacent pixels in the neighborhood are shown in FIG.
Output S of the outer edge pixel determination circuit 88 when any of the six patterns such as (a) to (f)
_ED2 becomes logical "1". The pattern matching technique described above may be used for this process. Here, in FIG.
In "," the pixels marked with "*" and undesignated pixels are "H", "
It may be either M "or" L ".

When the pixel of interest is "H", only the edge detection signal S _SE is output as a pixel at the edge, and the output S _ED2 is logic "0". The pixel of interest is "M"
In the case of or when the pixel of interest is "L", (a) to (f) of FIG.
In the case of a pattern other than the pattern shown in (1), the output S _ED2 of the outer edge pixel determination circuit 88 becomes a logic "0". The patterns shown in FIGS. 16 and 17 are stored in the ROM provided in the outer edge pixel determination circuit 88, for example, the MPU.
As the configuration, the ALU may be compared and determined.

The output S _ED2 of the outer edge pixel determination circuit 88 is sent to the outer edge pixel correction circuit 89 to determine whether or not it is the final edge outer pixel, and the outer edge correction signal S _CE2. Is output. This correction processing is the same as that of the inner edge pixel correction circuit 87, and a description thereof will be omitted. The outer edge correction signal S _CE2 is sent to the second result combining section 65, and the subsequent processing is as described above. The outer black edge signal S _BE2 indicating the outer edge of the image thus generated is sent to the second coefficient operation circuit 22 and the thickening processing circuit 23 of the region-specific adaptive processing circuit 4.

The black edge signal S _BE2 is first sent to the thickening processing circuit 23 and is subjected to the thickening processing as shown in FIG. In the figure, the value X0 of the pixel of interest in the center of the figure is designated by the black edge signal S _BE2 , and the values E1, E2, E3 of the surrounding pixels are designated by the edge detection signal S _SE , and X0 = (E1 + E2 + E3) / 3 (4) is performed, and the replacement data D _EX for replacing the pixel value to be thickened is sent to the second coefficient operation circuit 22.

In the first coefficient calculation circuit 21, when the inner black edge signal S _BE1 is logic "1", the data value E of the pixel of interest is set to a value of coefficient A3 (A3> 1.0). The data is multiplied and sent to the area selection circuit 24 as data D1. In other cases, the coefficient is not multiplied and the complementary color data D _C ,
Relay D _M and D _Y to D1.

Further, in the second coefficient calculation circuit 22, when the above-mentioned outer black edge signal S _BE2 is logic "1", the data value E of the pixel of interest is given a value of coefficient A1 (A1 <1.0). It is multiplied and sent to the area selection circuit 24 as data D2. If the edge detection signal S _SE is logic "1", the replacement data D
The value X0 of _EX is multiplied by a coefficient A2 (A2 <1.0) and sent to the area selection circuit 24 as data D2. In other cases, the coefficient is not multiplied and the complementary color data D _C , D _M , and D _Y are relayed to obtain D2.

In the area selecting circuit 24, when the halftone dot signal S _A is logic "1", the terminal A is selected, the data D1 is output from the output terminal Y, and vice versa. In the case of, the terminal B is selected and the data D2 is output from the output terminal Y. The complementary color data D _C , D _M , and D _Y corrected by the above processing are processed complementary color data D _C0 , D _M0 ,
It is sent to the black generation processing circuit 5 as D _Y0 .

This processed complementary color data D _C0 , D _M0 , D
_Y0 is subjected to UCR processing in the black generation processing circuit 5 to generate black data D _K0 and sent to the gradation correction processing circuit 6. Subsequent processes in the gradation correction processing circuit 6 and the halftone processing circuit 7 are the same as those in the conventional example, and the description thereof will be omitted. The name of the output data in each circuit is different simply because the input of each circuit is different due to the processing in the black edge processing circuit 4.

Output complementary color data D subjected to such processing
_C2 , D _M2 , D _Y2 , and D _K2 are output from the printer 8 on copy paper, and inside the edge, the density distribution has a steep rising edge as shown in (c) of FIG. Print dots 1 as shown in FIG.
It is possible to obtain the copy output 9 in which the bleeding 192 around 91 is reduced. On the outside of the edge, the edge of the density distribution is steep as shown in FIG. 20 (c), and the print result is a blur 2 around the print dot 201 as shown in FIG. 20 (d).
It is possible to obtain the copy output 9 in which 02 becomes small.

As described above, according to the present embodiment, the inside and the outside of the edge are detected independently, and when the outside of the edge is detected, the pixel value (in other words, the amount of ink or toner) is set to a predetermined amount. If it is inside the edge, the pixel value is increased by a predetermined amount to correct the edge. Since the pixel value is controlled, the resolution of the character can be improved in black characters ((a) of FIG. 25) other than the halftone dot area, and also in the area of only the halftone dot ((b) of FIG. 25) and the halftone dot area. The black character ((c) in FIG. 25) has an effect that both improvement of expression power can be achieved.

Further, as shown in (d) of FIG. 20, since the occurrence of bleeding can be suppressed, there is an effect that the fine line portion is not crushed even when the reversal development is performed, and the improvement of the expression power can be achieved at the same time.

In this embodiment, the black edge determination circuit 11
, The complementary color data D _C , D _M , and D _Y are input, but the outputs D _C0 , D _M0 , D _Y0 , and D _K0 of the black generation processing circuit 5 may be input, and in this case, the black edge processing circuit 4 may be provided after the black generation processing circuit 5. At this time, the black data generation circuit 81 may be omitted. Further, the complementary color conversion may be independently performed by using the numerical data D _R , D _G and D _B output from the scanner 2 as inputs.

Although only the color copying machine has been described as an embodiment, the present invention can be implemented by a word processor having an image input with the same structure. Further, in the video printer, the scanner 2 may be a conversion circuit for converting a composite or YC separated video signal into three RGB signals, and the present invention can be implemented in the processing after the complementary color inversion processing circuit 3. Is equivalent to the present invention.

When printing digital compressed image data from a video compact disc, a digital video disc, a digital video tape recorder or the like as an input, the processing stage before the scanner 2 is simply digitally input from a coaxial cable or an optical cable. It may be replaced by a decompression circuit and can be easily applied.

In addition, although the present embodiment is premised on color printing, a monochrome image also has three signals of RGB and CM.
The three signals of Y may be one signal that merely indicates the light and shade. In this case, the black generation processing circuit 5 becomes unnecessary and 3
The processing corresponding to the one complementary color and the black color may be omitted for one system of only the black color. In addition, the present invention can be variously modified and implemented without departing from the spirit of the invention.

[0077]

As described above, according to the present invention, claim 1
Then, the change signal whose value changes in accordance with the contour of the image composed of a predetermined pixel unit is generated by the generating means, and the change signal is the first judging means for judging the area inside the contour in the image. Of the contour signal of the image and the second contour signal of which the area outside the contour in the image is determined by the second determining means, and the first contour signal matches the contour of the image by the first correcting means. And a second correction signal corrected by the second correction means so that the second contour signal matches the contour of the image. These first and second
The image to be copied is emphasized by paying particular attention to the inside and outside of the black edge by changing the image in the changing means using the correction signal of, so that the bleeding is reduced and the color copy output is easy to see. The effect is that you can do it. Further, even when the reversal development is performed, there is an effect that the expression power can be improved without deteriorating the resolution of the thin line portion of the character area.

According to a second aspect of the present invention, in the generating means of the first aspect, the converting means first converts the image into a numerical image having a numerical value corresponding to its density, and then the comparing means converts the numerical image into the first numerical image. Is converted into a ternary signal consisting of three values by comparison with the second reference value and the region consisting of a number of pixels smaller than a predetermined number in the image is removed by the removing means in accordance with the ternary signal. Since it is possible to remove unnecessary points such as stains, noise is not emphasized even if the image to be copied is emphasized especially by paying attention to the outside of the black edge, so bleeding is reduced and the color copy output is easy to see. There is an effect that.

According to a third aspect of the present invention, the first determination means of the first aspect provides a predetermined target pixel according to the converted signal, and a pixel in the vicinity of the target pixel has a value of the ternary signal. Since the first contour signal is output when it matches the predetermined first pattern determined by including, it is possible to identify the shape of the image and emphasize only the portion where the density change of the image such as characters is sharp. Since it can be processed, there is an effect that the color copy output can be easily viewed.

According to a fourth aspect of the present invention, the second determination means of the first aspect provides a predetermined target pixel according to the converted signal, and a pixel in the vicinity of the target pixel has a value of the ternary signal. The second contour signal is output when it matches the predetermined second pattern determined by including, so that the shape of the image can be identified and, for example, even in the case of reversal development, the thin line portion is not thinned more than necessary. This has the effect of making it easier to see the color copy output.

According to a fifth aspect of the present invention, the first correction means determines that the figure in which the values of the first contour signal are spatially arranged matches the predetermined third pattern. As long as it is the above-mentioned first correction signal, it is possible to distinguish between characters and other characters, so the image to be copied is emphasized by paying particular attention to the black edge, so that bleeding is reduced and the color copy output is easier to see. effective.

In the sixth aspect, when the second correction means determines that the figure in which the value of the second contour signal is spatially arranged matches the predetermined fourth pattern. Since the second correction signal is used as long as possible, it is possible to distinguish between characters and other characters. Therefore, even if the image to be copied is emphasized with particular attention to the black edge, bleeding is reduced and the color copy output is easier to see. There is an effect.

According to a seventh aspect of the present invention, in the changing means of the first aspect, the detecting means detects the area including the spatially repeated portion in the image, and the multiplying means outputs the output of the detecting means and the first correction signal. And a coefficient that changes according to the second correction signal is multiplied by a value proportional to the density of the image, so that an image to be copied is distinguished by being distinguished into a character area, an area with only halftone dots, and an area with characters and halftone dots. Because it can be processed adaptively,
This has the effect of making it easier to see the color copy output.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a configuration when an image processing apparatus according to an embodiment of the present invention is applied to a color copying machine.

FIG. 2 is a block schematic diagram showing a configuration of a main part in the embodiment.

FIG. 3 is a schematic block diagram showing the configuration of a halftone dot area determination circuit in the embodiment.

FIG. 4 is a waveform diagram showing an example of a halftone dot area and its density change in the same embodiment.

FIG. 5 is an explanatory diagram showing an operation principle of a peak detection circuit in the halftone dot area determination circuit in the embodiment.

FIG. 6 is a block schematic diagram showing a configuration of a black edge determination circuit in the same embodiment.

FIG. 7 is a block diagram showing a configuration of a pixel color determination circuit in the black edge determination circuit according to the embodiment.

FIG. 8 is a schematic block diagram showing a configuration of an inner edge detection circuit and an outer edge detection circuit in the black edge determination circuit in the embodiment.

FIG. 9 is a diagram showing a configuration of a smoothing filter in the black edge determination circuit in the embodiment.

FIG. 10 is a diagram showing a configuration of an edge detection filter in the black edge determination circuit in the embodiment.

FIG. 11 is a diagram showing an operation of the isolated point removal circuit in the black edge determination circuit in the embodiment.

FIG. 12 is a first diagram showing the operation of the inner edge pixel determination circuit in the black edge determination circuit in the embodiment.

FIG. 13 is a second diagram showing the operation of the inner edge pixel determination circuit in the black edge determination circuit in the same example.

FIG. 14 is a diagram showing a pattern used in the inner edge pixel correction circuit in the black edge determination circuit in the embodiment.

FIG. 15 is a diagram showing an operation principle of an inner edge pixel correction circuit in the black edge determination circuit in the embodiment.

FIG. 16 is a first diagram showing the operation of the outer edge pixel determination circuit in the black edge determination circuit in the embodiment.

FIG. 17 is a second diagram showing the operation of the outer edge pixel determination circuit in the black edge determination circuit in the same example.

FIG. 18 is a diagram showing an operation principle of a thickening processing circuit in the area-based adaptive processing circuit in the embodiment.

FIG. 19 is a diagram showing a density change and a final printing result in each processing stage when the inner black edge region is processed in the same example.

FIG. 20 is a diagram showing a density change and a final printing result in each processing stage when the outer black edge region is processed in the same example.

FIG. 21 is a schematic block diagram showing a configuration when an image processing apparatus according to a conventional example of the present invention is applied to a color copying machine.

FIG. 22 is a diagram showing the general operating principle of UCR processing.

FIG. 23 is a diagram showing a density change and a final printing result in each processing stage when an inner black edge region is processed in the conventional example.

FIG. 24 is a diagram showing a density change and a final printing result in each processing stage when an outer black edge region is processed in the conventional example.

FIG. 25 is a diagram showing an example of an image to be processed.

[Explanation of symbols]

 1 Original 2 Scanner 3 Complementary Color Reversal Processing Circuit 4 Adaptive Processing Circuit by Region 5 Black Generation Processing Circuit 6 Gradation Correction Processing Circuit 7 Halftone Processing Circuit 8 Printer 9 Copy Output 10 Halftone Area Determination Circuit 11 Black Edge Determination Circuit

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical indication location H04N 1/40 1/46 H04N 1/40 DF 1/46 Z

Claims (7)

[Claims] 1. A generation unit that generates a change signal whose value changes in accordance with the contour of an image composed of a predetermined pixel unit, and a first contour signal that determines an area inside the contour in the image based on the change signal. And a first correction means for outputting a first correction signal corrected so that the first contour signal matches the contour of the image, and the contour in the image by the change signal. Second determining means for outputting a second contour signal for determining a region outside the area, and second for outputting a second correction signal corrected so that the second contour signal matches the contour of the image. An image processing apparatus comprising: a correction unit; and a changing unit that changes the image according to the second correction signal and the first correction signal. 2. The converting means converts the image into a numerical image whose numerical value corresponds to the density of the image, and compares the numerical image with a first reference value and a second reference value. The comparison means for converting into a ternary signal composed of three values, and the removing means for removing a region having a number of pixels smaller than a predetermined number from the image according to the ternary signal. Image processing device. 3. The first determining means provides a predetermined pixel of interest in accordance with the change signal, and a pixel in the vicinity of the pixel of interest has a predetermined first pixel determined by including the value of the ternary signal. The image processing apparatus according to claim 1, wherein it is determined to output the first contour signal when the pattern matches the pattern. 4. The second determination means provides a predetermined pixel of interest in accordance with the change signal, and a pixel in the vicinity of the pixel of interest includes a predetermined second pixel determined including the value of the ternary signal. The image processing apparatus according to claim 1, wherein it is determined to output the second contour signal when the pattern matches the pattern. 5. The first correction means determines that the graphic in which the values of the first contour signal are spatially arranged matches a predetermined third pattern and sets the figure as the first correction signal. The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. 6. The second correction means determines that the figure in which the values of the second contour signal are spatially arranged matches a predetermined fourth pattern, and sets the figure as the second correction signal. The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. 7. The changing means detects a region including a spatially repeated portion in the image, an output of the detecting means, the first correction signal, and the second correction signal. The image processing apparatus according to claim 1, further comprising: a multiplying unit that multiplies a changing coefficient by a value that is proportional to the density of the image.