JP3242807B2 - Image processing device - Google Patents

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 printing a color image in color, such as a video printer and a copying machine, especially a color copying machine.

[0002]

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

For example, in a Japanese-language word processor of the 1994 type, a V-shape such as Sharp Corporation is used to create a New Year's card.
The one that captures composite video signals from TRs, the one that inputs images with a dedicated camera attached like Sanyo Electric Co., and the one that reads pictures with a dedicated scanner attached to a printer like Matsushita Electric Industrial Co., Ltd. Has been released. Thus, the use of color printing can be said to be steadily and rapidly expanding.

As a typical example of such an image processing apparatus for color printing, an image processing apparatus in a color copying machine will be described as an example, and a conventional example will be described below. FIG. 13 is a schematic block diagram showing the configuration of an image processing apparatus in a conventional color copying machine. In FIG. 1, an original 1 optically read by a scanner 2 is converted into analog electric signals corresponding to three primary colors of light, that is, red (R), green (G), and blue (B). Scanner 2
The analog / digital (hereinafter abbreviated as "A / D") converter (not shown) incorporated in the A / D converter is sampled by 8 bits (256 gradations) while being sampled. numerical data D _R, D _G, is inputted to the complementary color reversal processing circuit 3 as D _B. On the other hand, it is sent to the edge detection circuit 12 as the video data _DV as it is after the A / D conversion.

The complementary color inversion processing circuit 3 calculates complementary colors for the numerical data D _R , D _G , and D _B to obtain complementary colors for printing to obtain cyan (C), magenta (M), and yellow (Y). 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, the edge detecting circuit 12, and the edge differentiating the video data D _V at the high-pass filter on the plane (not shown), the differential output shaping binary and edge detection signal S _E. The edge detection signal _SE is sent to the edge correction circuit 11. The edge correction circuit 11 processes the aforementioned complementary color data D _C , D _M , and D _Y by a high-pass filter (not shown) on a space whose coefficient changes according to the edge detection signal S _E to determine whether or not an edge exists. The emphasis processing is performed in response.

The complementary color data D _C4 having undergone the edge emphasis,
D _M4 and D _Y4 are sent to the black generation processing circuit 5. In the black generation processing circuit 5, under color removal (UCR, Under Color Re
Moval) to detect the black portion of the color, creating a black data D _K. Here, the UCR performs operations as shown in FIGS. 14A and 14B.

FIG. 14A shows an example of the distribution of three primary colors, in which the amount of yellow is the smallest. The density below the alternate long and short dash line a is replaced with black, and a black portion is generated as shown in FIG. The outputs of the black generation circuit 5 are data D _C5 , D _M5 , and D _Y5 having numerical values corresponding to the density of the hatched portions in FIG.

This UCR is originally unnecessary according to the theory of color reproduction of the three primary colors. However, in reality, if printing is performed with the three primary colors, a sufficient density cannot be obtained in a dark area and the color toner of the three colors is not obtained. Must be strictly adjusted, and a large amount of expensive color toner is consumed. The UCR described above is performed to prevent such a problem.

The complementary color data D _C5 , D _M5 , D _Y5 and the black data D _K5 are corrected in gradation by the gradation correction processing circuit 6 to provide complementary color data D _C6 , D _M6 , D _Y6 and black data D _K6. And sends it to the halftone processing circuit 7. The halftone processing circuit 7 processes the complementary color data D _C6 , D _M6 , D _Y6 and the black data D _K6 so that the half tone can be easily viewed, and the output complementary color data D
_C7 , D _M7 , D _Y7 and output black data D _K7 are sent to the printer 8.

The printer 8 transfers and fixes color toner on paper in accordance with the output complementary color data D _C7 , D _M7 , and D _Y7 and the output black data D _K7 , and outputs a copy output 13 from a color copier. (See, for example,
244876 and the like).

[0012]

However, in the above-described image processing apparatus in a conventional color copying machine,
There is a problem that "bleeding" occurs at an edge portion. In particular, for the original 1 which has been subjected to shading or the like, this problem is as follows for the user.

For example, recent word processors are colorized up to image input as described above, and in technical documents and office documents created by such word processors,
Black shading is often used where the reader wants to emphasize the meaning. Such a technical document or office document has an area including only characters (FIG. 16A), an area including only shading (FIG. 16B), and an area including both characters and shading (FIG. 16). (C)) and other areas. Therefore, simply emphasize the edge just because there is an edge,
Part that the document creator originally wants to emphasize ((c) in FIG. 16)
If the copy output 13 is blurred, it becomes vague and difficult to read.

[0014] The cause of the "bleeding" which causes such a problem and the degree of its influence will be briefly described below for the future. FIGS. 15A to 15D are diagrams showing the cause of the occurrence of bleeding. FIG. 15A shows the density of an image read by the scanner 2. When such an image is differentiated by a high-pass filter, waveforms 25a and 25b as shown in FIG.
Becomes These two waveforms are combined and printed.

Here, the meaning of using such a high-pass filter is as follows. MTF (Modulation) which is a 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. To correct the dullness, it is best to use a spatial filter having an inverse characteristic of MTF, but such an inverse characteristic filter cannot be realized with a simple configuration and is not industrial. Therefore, differentiation is simply performed using a spatial high-pass filter, and the above-described processing is performed.

However, as indicated by a dashed line 26 in FIG. 15B, the density range (dynamic range) in which the printer 8 can print normally is finite, and the shaded lines in the waveforms 25a and 25b emphasized by this differentiation processing. Parts like parts will be crushed. This "crush"
In the case of the dynamic range in the electric circuit, the waveform is simply clipped. In the case of printing, however, the toner once output on the paper is irreversible. This is scattered around the print spot 23 (corresponding to each pixel) like the line 24 in (d). This is the bleed
Is the main cause of

Further, since the processing of the above-mentioned spatial high-pass filter is performed for a finite number of pixels, the differential characteristic peaks in the spatial frequency domain, and the effect of emphasizing edges is not sufficient. And the need to interpose a low-pass spatial filter for noise removal. In addition, these problems are not only represented by a color copier, but also using ink,
The same can be said for a color print output of a video printer or CAD.

The present invention has been made in view of the above problems, and provides an image processing apparatus which emphasizes an image to be copied by paying particular attention to the detection of a black edge so as to make a color copy output easier to see. The purpose is to:

[0019]

To achieve the above objects resolving means for the ## image processing apparatus of the present invention, generates a change signal whose value varies according to the contour of the image composed of Jo Tokoro pixel unit (ST ') And a contour signal in which an area inside the contour in the image is determined based on the change signal (ST ′).
An edge pixel determination circuit (46 ) that outputs (S _ED ), and an edge pixel correction circuit (47) that outputs a correction signal (S _CE ) corrected so that this outline signal matches the outline of the image.
Means for changing the image according to the correction signal
(14) . In addition, here
Reference numerals are used to make it easier to understand the correspondence with the embodiment described later.
The reference numerals attached to the drawings are entered.

In this case, the generating means converts the image into a numerical image having a numerical value corresponding to its density.
(2) a ternary value for converting this numerical image into a ternary signal composed of three values by comparing the numerical image with a first reference value and a second reference value
A circuit (44), is removed in accordance with the ternary signal region composed of smaller number of pixels than a predetermined number from among the image
And an isolated point removing circuit (45) .

[0021]The edge pixel determination circuit (46)
Provides a predetermined pixel of interest in accordance with the change signal,
The pixel near the target pixel is determined including the value of the ternary signal.
The contour signal when the pattern matches the predetermined first pattern.
OutputIs what you do.

[0022]The edge pixel correction circuit (47)
Is a pattern in which the values of the contour signal are spatially arranged,
Matches the second pattern ofWhen the above edge pixelcorrection
signalOutputThings.

[0023]

According to the above construction, according to the first aspect, a change signal whose value changes in accordance with the contour of an image composed of a predetermined pixel unit is generated by the generation means, and this change signal is generated by the edge signal.
The pixel determination circuit processes the signal into a contour signal in which an area inside the contour of the image is determined, and the edge pixel correction circuit corrects the contour signal so as to match the contour of the image. By using the correction signal to change the image in the changing means, the color copy output can be easily viewed even if the image to be copied is emphasized particularly with attention paid to the detection of a black edge.

[0024] In this case, generating means, after once converted into numerical image to numerical values corresponding to the concentration of the image in the first conversion unit, 3-valued reference values the numerical image first in the circuit and the second And converts it into a ternary signal consisting of three values, and in the isolated point elimination circuit , according to the ternary signal, an area consisting of a smaller number of pixels than a predetermined number in the image. Since unnecessary points such as dirt can be removed, even if an image to be copied is emphasized particularly with attention paid to the detection of a black edge, a color copy output can be easily viewed.

[0025]According to claim 2, an edge pixel determination circuit
Provides a predetermined pixel of interest in accordance with the above change signal,
Of the pixel in the vicinity of the pixel of interest includes the value of the above ternary signal.
When the pattern matches the predetermined first pattern,
Output a guo signal, so pay particular attention to the detection of black edges.
Color copy output even if the image to be copied is emphasized
Will be easier to see.

According to the third aspect , the above edge pixel correction is performed.
Since the circuit uses the correction signal only when it is determined that the figure in which the values of the contour signal are spatially arranged matches the predetermined second pattern, the circuit can distinguish characters from other characters. Even if the image to be copied is emphasized by paying attention to the detection of the black edge, the color copy output can be easily viewed.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image processing apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing a hardware configuration when an image processing apparatus according to one 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 is omitted. The feature of the present application lies in that a black edge processing circuit 4 and a black edge detection circuit 10 for controlling the black edge 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, the configuration of the black edge detection circuit 10 will be described with reference to the block diagram shown in FIG. In the figure, 21 is an edge detection circuit, 22 is a pixel color judgment circuit, and 23 is a result synthesizing unit, which is composed of one AND circuit.

The edge detection circuit 21 receives the complementary color data D _M , D _C , and D _Y to detect an edge portion of a character and the like, and an edge detection signal S which becomes a logical “1” in the edge area.
Output as _CE . Further, similarly complementary color data D _M the pixel color determining circuit 22, D _C, and subjected to D _Y, determines the color of the loaded pixel, is if Kurokere if logic "1" and becomes black determination signal S _B Is output. This edge detection signal S _CE
And black determination signal S _B is taken a logical product in the results combiner 23, the logic for only the pixels of the black edge region "
A black edge signal S _BE which becomes 1 "is output.

The edge detecting circuit 21 and the pixel color determining circuit 22 are configured as follows. First, the pixel color determination circuit 22 is represented by a block diagram shown in FIG. In the figure, complementary color data D _C , D _M , and D _Y from a complementary color inversion processing circuit 3 are sent to a minimum value detection circuit 31 and a maximum value detection circuit 32, respectively. The value Dmx is determined. The minimum value Dmn output from the minimum value circuit 31 is equal to a large reference value D _R1 (for example, “2
00 ") is compared to, greater than the reference value D _R1, and outputs a signal S1 of a logic" 1 ".

Further, the minimum value Dmn and maximum value Dmx, in the digital computing circuit _{34, D AB = | Dmn-} Dmx | done with (1) becomes operational, its output D _AB is input to a digital comparator 35, A small reference value D _R2 (for example, “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 33, the reference value _DR1 is a reference value of the print density, and the output S1
Becomes logic "1" when the density is high, and becomes logic "0" when the density is low. On the other hand, the digital comparator 35
, The reference value _DR2 is a criterion value for determining whether or not the color is a chromatic color. The output S2 has a logic "1" for an achromatic color and a logic "0" for a chromatic color.

Here, it is known that the relationship of D _C ≒ D _M ≒ D _Y (2) is generally established for black. Thus, three colors complementary cyan, magenta, complementary color data D _C indicating a numerical value corresponding to the concentration of the three colors yellow, D _M, if substantially the same maximum value and the minimum value of D _Y, it is achromatic I understand. Thus, the output S _B of the AND circuit 36, when a high concentration and achromatic color, that is, logical "1" when a black.

Next, the configuration and operation of the edge detection circuit 21 will be described. FIG. 4 is a schematic block diagram showing the configuration of the edge detection circuit 21. In the figure, the black data generation circuit 41 converts the complementary color data D _C , D _M , and D _Y from the complementary color inversion processing circuit 3 in FIG. Generate D _K7 .
This circuit can be omitted, for example, when data is obtained from a circuit subsequent to the black generation processing circuit 5 in FIG.

The black data D _K7 is once smoothed by a low-pass spatial filter of three rows and three columns having a structure as shown in FIG. 5 in the smoothing filter 42, and is output as smoothed data D _L. The purpose of this process is simply noise removal. The smoothed data D _L is subjected to edge extraction by a low-pass elimination spatial filter of 3 rows and 5 columns having a structure as shown in FIG. 6 in the edge extraction filter 43, and is output as edge data D _E. Here, if a cross section of the output from each of the spatial filters 42 and 43 is taken and expressed one-dimensionally, the waveforms are as shown in FIGS. 12A and 12B, respectively.

In the ternarization circuit 44, FIG.
Edge data D _E, such as, for example, the value + Th and -Th
Waveform shaping with two thresholds t ₁ and t ₂ with, and outputs it as the signal S _T of the ternary. Note that these two threshold values are t ₁ > t
Any number of ₂ is acceptable. Thereby, the ternarization circuit 4
Output S _T 4 becomes S _T = L when _{S T = M D E ≦ t} 2 when _{S T = H t 2 <D} E <t 1 when D _E ≧ t _1. Here, H indicates a high level, that is, a portion where the density change is sharp, M indicates an intermediate level, that is, a portion where the density change is gradual, and L indicates a low level, that is, a base portion adjacent to the edge.

In the ternary image data, noise that cannot be removed because of its large size in the smoothing filter 42 in the isolated point removing circuit 45 is removed. This is performed as a pre-process for determining a subsequent edge pixel, as an independent high-density or low-density single pixel that is spread around at an intermediate level regardless of the surroundings, such as black spots on the original 1. Is to be removed.

In this process, as shown in FIG. 7A, when the value of the target pixel indicated by the hatched portion is "H", and when all eight surrounding pixels are "M", the value is indicated by an arrow. When the value of the target pixel indicated by the hatched portion is “L” as shown in FIG. 7B, and when all eight surrounding pixels are “M”, the value is indicated by an arrow. As shown, it is replaced with the value "M".

The edge pixel determination circuit 46 determines a pixel inside the edge based on the ternary signal _ST 'having undergone such isolated point removal processing. The conditions for determining this edge include the patterns shown in FIGS. 8A and 8B and FIGS. 9A to 9K. It should be noted that the hatched portion at the center in FIG. That is, when the target pixel is “M”, the values of the elements a to h in FIG. 8A consist only of “M” and “H”, and as shown in FIG. When all the surrounding eight pixels are “H”, the output _SED of the edge pixel determination circuit 46 becomes logic “1”.

When the pixel of interest is "H", the output of the edge pixel determination circuit 46 is determined when the four neighboring pixels match the patterns shown in FIGS. _SED becomes logic "1". For this processing, a known pattern matching technique described later may be used. Here, in FIG. 9, the pixels marked with “*” and the pixels not specified are “
It may be any of "H", "M" or "L".

Further, when the pixel of interest is "L", or when the pixel of interest is "M" and the pattern is other than the pattern shown in FIG. 8, even if the pixel of interest is "H", FIG. In the case of the pattern shown, the output S of the edge pixel determination circuit 46
_ED becomes logic "0". The patterns shown in FIGS. 8 and 9 are stored in the ROM (R
ePad Only Memory), for example, MPU (Micro P
ALU (Arithmetic Logic Un
It may be compared by it).

Now, such an edge pixel determination circuit 46
The output S _ED of is sent to the edge pixel correction circuit 47 determines whether the final edge inside the pixel. This is because the patterns indicating the pixels in the character area or the halftone area are determined in twelve ways as shown in FIGS.

As a method of searching for such a pattern,
What is necessary is just to use a pattern matching technique like the edge pixel determination circuit 46 mentioned above. FIG. 11 is a conceptual diagram showing the operation of such a pattern matching technique. In the same figure, each grid represents one pixel, and a thick line graphic 71 represented by a dotted line
Numerals 73 indicate positions of the pattern of FIG. 10A at each time. X-axis direction (horizontal direction in the figure) as indicated by the arrow
The edge pixel correction circuit 47 outputs an edge correction signal _SCE which becomes logic "1" only when the patterns match, while shifting the pattern one pixel at a time.

Such an operation is performed on the entire surface of the document 1 read by the scanner 2 in the y-axis direction (vertical direction in the figure).
The same processing is repeated for all the patterns (a) to (l) shown in FIG. In FIG. 11, the patterns 71 to 73 are intentionally shifted slightly for ease of identification by the reader.

This edge correction signal S _CE is _supplied to the result synthesizing section 2
3 and the subsequent processing is as described above. As a technique used for the edge pixel determination circuit 46 and the edge pixel correction circuit 47, not only the above-described pattern matching technique, but also a method of generating a vector or a symbol sequence from an image and calculating a correlation between the vector or the symbol sequence. That is, a technique of so-called “pattern recognition” may be used or used in combination.

The black edge signal S _BE indicating the inside of the edge of the image generated as described above is sent to the black edge processing circuit 4. For example, the value of the pixel corresponding to the black edge signal S _BE is set to a predetermined value. Edge correction is performed by reducing the amount by an amount, or by switching the coefficient of an edge differential filter, and the processed data is sent to the black generation processing circuit 5 as processed complementary color data D _C0 , D _M0 , and D _Y0 .

The 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 _DK0, and is 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 is omitted. The names of the output data in the circuits are different simply because the inputs of the circuits are different due to the processing in the black edge processing circuit 4.

The output complementary color data D having undergone such processing
_C2 , D _M2 , D _Y2 , and D _K2 are output from the printer 8 to copy paper. The density distribution has a sharp rising edge as shown in FIG. 12C, and the printing result shown in FIG.
As shown in FIG. 2 (d), it is possible to obtain a copy output 9 in which the blur 82 around the print dot 81 is reduced.

According to this embodiment as described above, for example,
The black edge processing circuit 4 that performs edge correction by reducing the pixel value by a predetermined amount or switching the coefficients of the edge differential filter is controlled by the black edge signal S _BE output from the black edge detection circuit 10. As a result, as shown in FIG. 12 (d), the occurrence of bleeding can be suppressed, so that the resolution of the character can be improved for black characters ((a) of FIG. 16) other than the halftone dot region. (Figure 1
6 (b)) and black characters on the halftone dot area ((c) in FIG. 16)
Thus, there is an effect that it is possible to achieve both improvement of expression power.

In this embodiment, the black edge detection circuit 10
Input the complementary color data D _C , D _M , and D _Y , but may input the outputs D _C0 , D _M0 , D _Y0 , and D _K0 of the black generation processing circuit 5. In this case, the black edge processing circuit 4 may be a subsequent stage of the black generation processing circuit 5. At this time, the black data generation circuit 41 may be omitted. Further, complementary color conversion may be independently performed using the numerical data D _R , D _G , and D _B output from the scanner 2 as inputs.

Although only a color copier has been described as an embodiment, a word processor having an image input can implement the present invention by the completely same configuration.
In a video printer, the scanner 2 may be a circuit for converting a composite or YC-separated video signal into three RGB signals, and the present invention can be applied to the processing after the complementary color inversion processing circuit 3. And the present invention.

Also, when printing digital compressed image data from a video compact disk, digital video disk, digital video tape recorder or the like as an input, the processing stage before the scanner 2 is simply a digital input from a coaxial cable or optical cable. What is necessary is just to replace it with a decompression circuit, and it is easily applicable.

Although the present embodiment is based on the premise that color printing is performed, three signals of RGB and CM
The three signals of Y may be one signal simply indicating the density. In this case, the black generation processing circuit 5 becomes unnecessary, and 3
What is necessary is just to omit the processing corresponding to the two complementary colors and black to one system of only black. In addition, the present invention can be variously modified without departing from the scope of the invention.

[0054]

According to the present invention as described above, according to the present invention, the change signal whose value varies according to the contour of the image composed of Jo Tokoro for each pixel is generated by the generating means, the varying signal edges
The pixel determination circuit processes the signal into a contour signal in which an area inside the contour of the image is determined, and the edge pixel correction circuit corrects the contour signal so as to match the contour of the image. By using the correction signal to change the image by the changing means, the image to be copied is emphasized, particularly with a focus on the detection of black edges, so that bleeding is reduced and the color copy output can be easily viewed. effective.

In addition, this makes it possible to improve the resolution of characters in black characters (FIG. 16 (a)) other than the halftone dot region, and to improve the resolution of the halftone only region (FIG. 16 (b)) and the halftone dot region. Black characters ((c) in FIG. 16) have the effect of improving expression power.

In this case, the generating means first converts the image into a numerical image having a numerical value corresponding to the density by the converting means, and then converts the numerical image into a first reference value in a ternarization circuit . In comparison with the second reference value, the signal is converted into a ternary signal consisting of three values, and an area consisting of a smaller number of pixels than a predetermined number in the image is converted into a ternary signal by the isolated point removing circuit. Unnecessary points such as dirt can be removed because it is removed according to the signal, so even if the image to be copied is emphasized, especially focusing on the detection of black edges, even the noise is not emphasized. This has the effect of making the copy output easier to see.

According to the second aspect , the edge pixel determination is performed.
The circuit provides a predetermined pixel of interest according to the change signal, and when a pixel in the vicinity of the pixel of interest matches a predetermined first pattern determined including the value of the ternary signal, Since the contour signal is output, the emphasis process can be performed only on the portion where the density of the image changes sharply, so that there is an effect that the blur is reduced and the color copy output becomes easy to see.

According to the third aspect, the edge image
Since the elementary correction circuit sets the above-described correction signal only when it is determined that the figure in which the values of the above-mentioned contour signals are spatially arranged matches the predetermined second pattern, it is possible to distinguish between a character and the other. In particular, even if an image to be copied is emphasized by paying particular attention to the detection of a black edge, there is an effect that bleeding is reduced and a color copy output becomes easy to see.

[Brief description of the 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 schematic block diagram showing a configuration of a black edge detection circuit in the embodiment.

FIG. 3 is a block diagram illustrating a configuration of a pixel color determination circuit in a black edge detection circuit in the same embodiment.

FIG. 4 is a schematic block diagram showing a configuration of an edge detection circuit in a black edge detection circuit in the embodiment.

FIG. 5 is a diagram illustrating a configuration of a smoothing filter in an edge detection circuit in a black edge detection circuit according to the same embodiment.

FIG. 6 is a diagram illustrating a configuration of an edge detection filter in an edge detection circuit in a black edge detection circuit according to the same embodiment.

FIG. 7 is a diagram illustrating an operation of an isolated point removing circuit in the edge detection circuit in the black edge detection circuit according to the same embodiment.

FIG. 8 is a first diagram illustrating an operation of the edge pixel determination circuit in the edge detection circuit in the black edge detection circuit according to the same embodiment.

FIG. 9 is a second diagram illustrating the operation of the edge pixel determination circuit in the edge detection circuit in the black edge detection circuit according to the same embodiment.

FIG. 10 is a diagram showing a pattern used in an edge pixel correction circuit in an edge detection circuit in a black edge detection circuit in the embodiment.

FIG. 11 is a diagram illustrating an operation principle of an edge pixel correction circuit in an edge detection circuit in a black edge detection circuit according to the same embodiment.

FIG. 12 is a diagram showing a density change and a final print result in each processing stage when a black edge region is processed in the embodiment.

FIG. 13 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. 14 is a diagram showing the general operation principle of UCR processing.

FIG. 15 is a diagram illustrating a density change and a final print result in each processing stage when a black edge region is processed in the conventional example.

FIG. 16 is a diagram illustrating an example of an image to be subjected to a copying process in a color copying machine.

[Explanation of symbols]

 Reference Signs List 1 original 2 scanner 3 complementary color inversion processing circuit 4 black edge processing circuit 5 black generation processing circuit 6 gradation correction processing circuit 7 halftone processing circuit 8 printer 9 copy output 10 black edge detection circuit

Continuation of the front page (56) References JP-A-4-65969 (JP, A) JP-A-4-53354 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1 / 40-1/409 H04N 1/46-1/64

Claims (3)

(57) [Claims] 1. A generating means for generating a change signal whose value changes in accordance with the contour of an image composed of a predetermined pixel unit, and outputting a contour signal in which an area inside the contour in the image is determined based on the change signal. image processing apparatus including an edge pixel determination circuit, and the edge pixel correction circuit contour signal and outputs a correction signal corrected so as to match the contour of the image, and means for Ru changing the image according to the correction signal Wherein the generating means converts the image into a numerical image having a numerical value corresponding to the density of the image, and compares the numerical image with a first reference value and a second reference value. a ternary coding circuit for converting the ternary signal consisting, and characterized in that it comprises, and isolated point removal circuit for removing according to the ternary signal the area of a predetermined smaller number of pixels than the number from the above image That image processing apparatus. 2. The edge pixel determination circuit according to claim 1, wherein a predetermined pixel of interest is provided according to the change signal, and a pixel in the vicinity of the pixel of interest determines a predetermined first pattern including a value of the ternary signal. 2. The image processing apparatus according to claim 1 , wherein the edge signal is output when the edge signal matches. 3. The edge pixel correction circuit outputs the edge pixel correction signal when a figure in which the values of the contour signal are spatially arranged matches a predetermined second pattern. The image processing apparatus according to claim 1, wherein: