JPH09134438A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a picture processor capable of obtaing approximately fixed output results of respective edge detecting operation even when the variable power rates of main scanning and sub-scanning are changed. SOLUTION: Sub-scanning variable power operation is executed by an original reading part prior to the recognition of an original and main scanning variable power operation is executed by a variable power part 26 after the recognition of the original. At the time of executing processing by equal power e.g. line drawing processing is executed by the same width in both the main scanning and sub-scanning. When 200% processing is executed in both the main scanning and sub-scanning, width for executing line drawing processing is increased only at the time of main scanning. In order to prevent the increase of the width, the expansion width of main scanning is changed by the variable power rate of the main scanning. Thereby the line processing range of the main scanning becomes almost the same width as the line processing range of the sub-scanning due to the effect of the variable power range. Consequently an output result can almost be fixed without being effected by the variable power rate by changing the expansion quantity or contraction quantity of a main scanning or sub- scanning outline by the variable power rate of the main scanning.

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, and more particularly to an image processing apparatus for extracting an edge of a line drawing (character) by referring to a plurality of pixels and switching parameters according to the result to perform an image forming process. .

[0002]

2. Description of the Related Art Conventionally, there is an image processing apparatus capable of changing a parameter for judging the extraction of an edge of a line drawing according to the scaling ratio. The reason for equipping this function is that the characteristics of the image data of the reading unit change according to the scaling ratio.

For the same reason, there is an image processing apparatus in which the image processing filter is changed. For example, in an apparatus that scans image data by scanning four times, the main scanning magnification of the components may be arranged after the document recognition unit, and the sub-scanning magnification may be arranged before the document recognition unit.

[0004]

However, in the image processing apparatus having the arrangement configuration as in the above-mentioned conventional example, since the edge of the line (contour) of the result of the document recognition section is extracted by the magnification, the main scanning is performed. And the width of the sub-scan is different as the output result. In addition, if the main scanning scaling is placed in front of the document recognition section,
It involves the problem of requiring three circuit parts for R, G, and B.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus which makes the output result of each edge detection substantially constant even if the scaling ratio of the main scanning and the sub scanning is changed.

[0006]

In order to achieve the above object, the image processing apparatus of the present invention comprises a sub-scanning scaling unit for scaling the sub-scanning with the sub-scanning scaling factor and a main scanning with the main-scanning scaling factor. A main scanning scaling unit for scaling and a contour extraction unit between the sub scanning scaling unit and the main scanning scaling unit are provided, and the result of contour extraction is expanded according to the sub scanning scaling factor and the main scanning scaling factor. Alternatively, it is characterized by contraction.

The expansion or contraction may be performed independently according to the main scanning scaling factor or the sub-scanning scaling factor, and the result of contour extraction may be an area identification signal for recognizing whether or not it is a character.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an image processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings. FIG.
~ Referring to Fig. 7, there is shown an embodiment of an image processing apparatus of the present invention. 1 is a block diagram of the main configuration of the image processing apparatus, FIGS. 2 to 4 are block diagrams of internal partial configurations, FIG. 5 is a matrix for explaining the operation of white area detection, and FIG.
7 and 8 are conceptual sectional views of the line drawing, and FIGS. 8 and 9 are conceptual diagrams for explaining the procedure for extracting the line drawing of the printed document.

The image processing apparatus reads an original as shown in FIG. 1 and outputs the read data as digital data. An original reading section 11 and an image processing for correcting the image data read by the original reading section 11 and recognizing the original. And an image recording unit 13 that outputs the output image data of the image processing unit 12 onto a sheet.

The image processing unit 12 which is the main part of this embodiment will be described with reference to FIG. The RGBγ correction unit 21 corrects the gray balance of RGB data and converts it into density data.

The delay unit 22 delays the RGB data in order to synchronize with the output result of the document recognition unit 30. The document recognition unit 30 determines whether it is a character region or a pattern region according to the RGB image data, and outputs a C / P signal to the RGB filter unit 23. The logic of the C / P signal is H for letters and L
It is a design.

Further, the chromatic area or the achromatic area of the original area is determined, and the B / C signal is output to the RGB filter section 23. The logic of the B / C signal is H in the achromatic region and L in the chromatic region. The C / P signal includes an RGB filter unit 23, a color correction unit 24, a VCR unit 25, a scaling unit 26, a CMYBk filter unit 27, a CMYBkγ correction unit 28, and a gradation processing unit 2.
9 is connected in cascade, and the signal I is synchronized with the image data.
Output MG.

Each block switches between character processing and picture processing by the C / P signal and the B / C signal. The B / C signal is supplied to the RGB filter unit 23 and the color correction unit 2.
4. Cascade-connected to the VCR unit 25 and output in synchronization with the image data.

The RGB filter section 23 is a filter for MTF correction of R, G, B data, and is composed of an N × N matrix. When the C / P signal is H, the sharpening process is performed, and when the C / P signal is L, the smoothing process is performed. Color correction unit 24
For R / G / B data by primary masking, etc.
Convert to Y data.

The VCR section 25 expresses four colors of C, M, Y and Bk in order to improve the color reproduction of the image data. C
・ VCR (addition color removal) is performed on the common part of M and Y, and B
Generate k data. When the C / P signal is L, skeleton black Bk is generated. When the C / P signal is H, full black processing is performed. Further, when the C / P signal is H and the B / C signal is H, the C, M and Y data are erased. This is because in the case of a black character, it is expressed only by the black component. The output IMG is C, M, Y,
It is a frame sequential color that outputs one color of Bk. That is, full color (4 color) data is created by reading the original document four times.

The scaling unit 26 enlarges / reduces in the main scanning direction,
Alternatively, the same size processing is executed. The CMYBk filter unit 27 uses the NXN spatial filter according to the frequency characteristics of the image recording unit 13 and the C / P signal to perform smoothing processing and sharpening processing. The CMYBkγ correction unit 28 changes the γ curve according to the frequency characteristics of the image recording unit 13 and the C / P signal and performs processing. When the C / P signal is "L", the image is reproduced faithfully, and when the C / P signal is "H", the image is drawn to enhance the contrast.

The gradation processing unit 29 performs quantization such as dither processing according to the gradation characteristics of the image recording unit 13 and the C / P signal. When the C / P signal is "L", gradation-oriented processing is performed, and when the C / P signal is "H", resolution-oriented processing is performed. Further, as shown in FIG. 3, the document recognizing unit 30 includes a line drawing recognizing unit 31 for detecting line drawing likeness and a color judging unit 32 for judging whether a specific region of the document is chromatic or achromatic.

The output logic of the C / P signal of the line drawing recognition unit 31 outputs "H" if it is an edge of a line drawing, and outputs "L" otherwise. Further, the B / C signal output logic of the color determination unit 32 outputs “L” when it is a chromatic area,
Otherwise, "H" is output. The output result is a signal in which 4 × 4 pixels are associated with one pixel. In the following, the unit of the output result is one block.

In the present embodiment, an original reading unit having a reading density of about 400 DPI will be described as an example. The line drawing recognition unit 31, which is a main part of this embodiment, will be described with reference to FIG. In FIG. 4, the line drawing recognition unit 31 includes a monochromeization unit 41, a Laplacian unit 42, Y pattern matching units A, B, and C (43 to 45), an isolated point removal unit 46, and an expansion unit 47.

The monochromator 41 converts the R, G, B data into luminance data or the like to obtain a monochrome signal. For example, the darkest data among R, G, and B may be selected instead of the luminance data, or G may be used as the luminance data. The output data indicates that a large number is dark and a small number is thin.

The Laplacian section 42 extracts the edge of the line drawing and simultaneously detects the white area and the black pixel. By detecting the white area, it is used as the data for extracting the line drawing on the white background. The operation of white area detection will be described using the symbolized matrix in FIG. For example, assuming that the matrix of the white area is 3 × 3, the following is obtained.

((A ₀₀ <thw) and (a ₀₁ <thw) and (a ₀₂ <thw) and (a ₁₀ <thw) and (a ₁₁ <thw) and (a ₁₂ <thw)) or ((a ₁₀ <thw) and (a ₁₁ <thw) and (a ₁₂ <thw) and (a ₂₀ <thw) and (a ₂₁ <thw) and (a ₂₂ <thw)) or ((a ₀₀ <thw) and ( a ₁₀ <thw) and (a ₂₀ <thw) and (a ₀₁ <thw) and (a ₁₁ <thw) and (a ₂₁ <thw)) or ((a ₀₁ <thw) and (a ₁₁ <thw) and (a ₂₁ <thw) and (a ₀₂ <thw) and (a ₁₂ <thw) and (a ₂₂ <thw))

When the peripheral data including the pixel of interest is smaller than the threshold value thw, it is defined as a white area. This pattern is an orthogonal pattern, but a diagonal pattern or the like may be added.

In the black pixel detection, a sufficiently dark pixel is set as a black pixel. When expressed by an equation, a ₂₂ > thB. In the extraction of the edge amount, the edge amount is calculated with a 5 × 5 matrix as follows.

X = (a ₂₂ × 2) − (a ₂₁ + a ₂₃ ) y = (a ₂₂ × 2) − (a ₁₂ + a ₃₂ ) z = i × x + j × y where x is the main scanning direction. Edge amount, y is the edge amount in the sub-scanning direction, and z is weighted on x and y to obtain the total edge amount.

Here, both i and j = are selective coefficients,
When designing hardware, factors such as 1,1.115,1.25,1.375,1.5,1.625,1.7 that gate size becomes smaller.
It is set to 5, 1.875, 2 (fixed point arithmetic). By doing so, blurring of the MTF (optical system and traveling system) of the main scanning and the sub scanning is corrected.

Generally, the MTFs of the main scanning and the sub-scanning are different, and the scaling of the sub-scanning is performed by the reading area of the reading device.
TF is different. In the present embodiment, the main scanning scaling is not necessary since it is after the document recognition unit. Further, when the sub-scanning magnification is large, for example, 200%, it is possible to select the edge amount as follows.

X = (a ₂₂ × 2) − (a ₂₀ + a ₂₄ ) y = (a ₂₂ × 2) − (a ₀₂ + a ₄₂ ) z = i × x + j × y

By doing so, it is possible to deal with the sub-scanning scaling processing. The output outputs the white area signal, the black pixel, the signal and the edge amount. The white area signal indicates a white area by H, and the black pixel signal indicates an black pixel by H.

FIG. 6 is a cross-sectional view of a line drawing, which is a conceptual diagram showing the relationship between white areas, black pixels, and threshold values. Further, FIG. 7 is a diagram showing the relationship of the edge amount (z).

Next, the pattern matching units A, B and C will be described. In the block of the pattern matching part A43,
Extract the black edge around the white area. Here, the white area pattern (W) is a signal of the white area, and the black pattern (K)
Is H when a black pixel or an edge amount is larger than the threshold value thRB. The black pattern is not simply extracted with black pixels, but the blur at the time of reading the original is corrected by the edge amount. The conceptual diagrams are shown in FIGS. 6 and 7. An example of the pattern is (7 × 7) in the following equation.

(K ₂₂ AND k ₂₃ AND k ₂₄ AND k ₃₂ AND k ₃₃ AND k ₃₄ AND ((w ₅₂ AND w ₅₃ AND w ₅₄ ) or (w ₆₂ AND w ₆₃ AND w ₆₄ ) or (w ₁₂ AND w ₁₃ AND w ₁₄ ) or (w ₀₂ AND w ₀₃ AND w ₀₄ ))) or (k ₂₂ AND k ₃₂ AND k ₄₂ AND k ₂₃ AND k ₃₃ AND k ₄₃ AND ((w ₂₅ AND w ₃₅ AND w ₄₅ ) or (w ₂₆ AND w ₃₆ AND w ₄₆ ) or (w ₂₁ AND w ₃₁ AND w ₄₁ ) or (w ₂₀ AND w ₃₀ AND w ₄₀ ))))

Although only the horizontal and vertical components are shown, the pattern of the licking component is similarly extracted. In this way, the edge on the white area is extracted. Since there are many white areas, it is possible to extract a line drawing of a white area without erroneously recognizing halftone dots as a line drawing.

A fine line is detected in the block of the pattern matching section B44. The thin line corresponds to a key line or a character in the document. Here, the white pattern (w) is
H is a white area or an edge amount smaller than the threshold value thRw (since it is a negative component, the absolute value is large). In the black pattern (k), H is defined as a black pixel or a pixel whose edge amount is larger than the threshold thRB. Here th
RB does not have to be the same as the pattern matching unit C45. The correction of the edge amount component for both the black pattern and the white pattern raises the contrast of the fine line. An example of the pattern is as shown in the following equation (7 × 7).

((W ₁₂ AND w ₁₃ AND w ₁₄ ) AND (w ₀₂ AND w ₀₃ AND w ₀₄ ) AND k ₃₂ AND k ₃₃ AND k ₃₄ AND (w ₅₂ AND w ₅₃ AND w ₅₄ ) AND (w ₆₂ AND w ₆₃ AND w ₆₄ )) or ((w ₂₁ AND w ₃₁ AND w ₄₁ ) AND (w ₂₀ AND w ₃₀ AND w ₄₀ ) AND k ₂₃ AND k ₃₃ AND k ₄₃ AND (w ₂₅ AND w ₃₅ AND w ₄₅ )) AND (w ₂₆ AND w ₃₆ AND w ₄₆ ))

Although only the horizontal component and the vertical component are shown, the pattern of the licking component is similarly extracted. In this way, both sides of the black pattern are extracted as thin lines when they are sandwiched between the white patterns. Further, when there is a white area, it is highly likely that it is a line drawing, so pattern matching may be omitted. For example, The white area is designated as symbol a.

((W ₁₂ AND w ₁₃ AND w ₁₄ ) AND a ₀₃ AND k ₃₂ AND k ₃₃ AND k ₃₄ AND (w ₅₂ AND w ₅₃ AND w ₅₄ ) AND (w ₆₂ AND w ₆₃ AND w ₆₄ )) or ((w ₁₂ AND w ₁₃ AND w ₁₄ ) AND (w ₀₂ AND w ₀₃ AND w ₀₄ ) AND k ₃₂ AND k ₃₃ AND k ₃₄ AND (w ₅₂ AND w ₅₃ AND w ₅₄ ) AND a ₆₃

Etc. may be added. Although only the horizontal component is shown here, the vertical component and the diagonal component are similarly extracted. Further, in contrast to this pattern, if both sides of the white pattern are sandwiched by the white pattern, it is a thin line, so it may be added with such a pattern, or pattern matching centered on the white pattern But it's okay.

The block of the pattern matching section C45 is an auxiliary of the pattern matching section A43, and is composed of three white edge components in order to extract the black edge on the white area.
Pattern matching with one element. Here, the white area pattern (a) is a signal of the white area, and the black pattern (k)
Is a black pixel or a pixel whose edge amount is larger than the threshold value thRB is H. The white pattern (w) is H if it is a white region or has an edge amount smaller than the threshold thRw (since it is a negative component, the absolute value is large). An example of the pattern is as shown in the following equation (7 × 7).

[0040]

Although only the horizontal component is shown here, only the vertical and horizontal components are shown in the same manner, but the diagonal component is extracted in the same manner. As a result, it is possible to extract a character with a good contrast. Then, since the white edge component is detected, even if the width of the black pattern is reduced, small characters can be extracted without erroneously detecting halftone dots. The thresholds here, thRB, and thRw may not be the same. In this embodiment, 7 × 7 is used, but the matrix size may be any size. Further, when the matrix of the pattern matching units A, B, and C is used as a component, a line memory is used, but it may be shared instead of being performed independently.

As an example, if thw and thk are the same, they can be shared and may be coded by using the magnitude relationship. The following is an example of encoding.

ThRw of pattern 2 is thRw ₂ , thRB, thRB _{2 of} pattern 3 is thRw ₃ , thRB is thRB ₃

Here, if the magnitude relation is thRw ₂ > thRw ₃ > thRB ₃ > thRB ₂ > thRB ₃ , usually 5 bits × n lines, but if the code is as follows, it becomes 3 bits × n lines. Become.

P> thRw ₁ → Code 0 thRw ₂ >P> thw ₃ → Code 1 thRw ₃ >P> thRB ₃ → Code 2 thRB ₃ >P> thRB ₂ → Code 3 thRB ₂ >P> thRB ₃ → Code 4 thRB ₃ > P → Code 5

Here, P is the edge amount. The code is
Since it is 0 to 5, it can be expressed with 3 bits. When unpacking the code, you can do the reverse. It goes without saying that it is better to be able to change the size relationship, even if it is not fixed. In the isolated point removal, the line drawing is made up of continuous lines, so the isolated points are removed. An isolated point occurs when a halftone dot is erroneously detected as a line drawing.

When any one or more of the pattern matching section A43, the pattern matching section B44, and the pattern matching section C45 has extracted, it is regarded as an extracted pattern. For example, in 5 × 5 pattern matching, if the peripheral pixel does not have an extraction pattern and the target pixel is the extraction pattern, the target pixel is removed. An example is shown by a formula. Here, the extraction pattern is represented by the symbol a.

[0048]

[Outside 1]

Instead of pattern matching, the number in the matrix may be considered for the determination.

In the expansion section 47, the extraction pattern is expanded to connect the intersections of the characters, and the line drawing and its surroundings are further subjected to the line drawing processing.

In the above-mentioned pattern matching, cross points cannot be extracted, but they can be connected. The reason why the line drawing and its surroundings are regarded as a line drawing is to allow the black character processing and the spatial filter to work well. An example (7 × 7) is shown in the following equation.

A ₀₀ or a ₀₁ or a ₀₂ or a ₀₃ or a ₀₄ or a ₀₅ or a ₀₆ or a ₁₀ or a ₁₁ or a ₁₂ or a ₁₃ or a ₁₄ or a ₁₅ or a ₁₆ or a ₂₀ or a ₂₁ or a ₂₂ or a ₂₃ or a ₂₄ or a ₂₅ or a ₂₆ or a ₃₀ or a ₃₁ or a ₃₂ or a ₃₃ or a ₃₄ or a ₃₅ or a ₃₆ or a ₄₀ or a ₄₁ or a ₄₂ or a ₄₃ or a ₄₄ or a ₄₅ or a ₄₆ or a ₅₀ or a ₅₁ or a ₅₂ or a ₅₃ or a ₅₄ or a ₅₅ or a ₅₆ or a ₆₀ or a ₆₁ or a ₆₂ or a ₆₃ or a ₆₄ or a ₆₅ or a ₆₆

As a result, the line drawing of the printed document can be extracted well. This is an example of equal magnification, and variable magnification will be described. FIG. 8 and FIG. 9 are conceptual diagrams for explaining the procedure for extracting a line drawing, in which the solid line represents the line drawing, and the dotted line represents the line drawing recognition unit, which represents the area to be determined as the line drawing.

Sub-scanning scaling is performed before document recognition (document reading section 11), and main scanning scaling is performed after document recognition (magnification section 26). As a result, when processing is performed at the same size, for example, line drawing processing is performed with the same width in both main and sub-scanning as shown in FIG. 9, but when processing is performed at 200% in both main and sub-scanning, main-scanning is performed as shown in FIG. The width of performing only the line drawing processing becomes large. Therefore, the expansion width of the main scan is changed according to the magnification of the main scan. A configuration example of the formula is shown below.

((Expansion amount-1) / 2 / Magnification ratio) × 2 + 1 That is, (7-1) /2/2×2+1=4.5

Since the expansion amount must be an integer,
5 is assumed. As a result, the processing range of the line processing for the main scanning and the processing for the sub-scanning have almost the same width due to the influence of the scaling factor.
On the contrary, the same effect can be obtained even if the expansion width of the sub-scan is changed by changing the magnification of the main scan. A configuration example of the formula is shown below.

((Expansion amount −1) / 2 × Magnification ratio) × 2 + 1)

The present embodiment can be applied to all contour extraction. Further, when a grandchild copy (generation, copying of an output of a copying machine as an input document) is performed, the above-mentioned parameters are different from those of the print document. Parameters (thw, th
B, thRw, thRB), and the pattern matching unit C45 does not perform the extraction operation.

The output of the current copying machine is 400 DP characters.
A line pattern of 200 DPI is generally used for the I photograph part. Since the line pattern is easily erroneously detected as a line drawing, the pattern matching unit C45 does not perform the extraction operation. Since the copier has a resolution of about 1/10 for printed matter, it does not affect grandchild copying so much. In this way, it is possible to satisfactorily extract a document with a low resolution (grandchild copy).

[0060]

As is apparent from the above description, the image processing apparatus of the present invention scales the sub-scanning with the sub-scanning scaling ratio, the main scanning with the main-scanning scaling ratio, and the sub-scanning scaling ratio. And the result of the contour extraction is expanded or contracted according to the main scanning scaling factor. Therefore, by changing the expansion or contraction amount of the main-scanning or sub-scanning contour according to the main-scanning scaling factor, the output result can be made substantially constant without affecting the scaling factor.

[Brief description of the drawings]

FIG. 1 is a main configuration block diagram showing an embodiment of an image processing apparatus of the present invention.

FIG. 2 is a block diagram showing a configuration example of an image processing unit in FIG.

FIG. 3 is a block diagram showing a configuration example of a document recognition unit in FIG.

FIG. 4 is a block diagram showing a configuration example of a line drawing recognition unit in FIG.

FIG. 5 is a symbolized matrix for explaining the operation of white area detection.

FIG. 6 is a conceptual cross-sectional view of a line drawing, showing a white region, black pixels, and a threshold value.

FIG. 7 is a conceptual cross-sectional view of a line drawing, showing an edge amount and a threshold value.

FIG. 8 is a conceptual diagram 1 for explaining a procedure for extracting a line drawing of a print document.

FIG. 9 is a conceptual diagram 2 for explaining a procedure for extracting a line drawing of a print document.

[Explanation of symbols]

 Reference numeral 11 document reading unit 12 image processing unit 13 image recording unit 21 RGBγ correction unit 22 delay unit 23 RGB filter unit 24 color correction unit 25 VCR unit 26 scaling unit 27 CMYBk filter unit 28 CMYBkγ correction unit 29 gradation processing unit 30 document recognition Part 31 Line drawing recognition part 32 Color determination part 41 Monochrome part 42 Laplacian part 43, 44, 45 Pattern matching part 46 Isolated point removal part 47 Expansion part

Claims (3)

[Claims] 1. A sub-scanning scaling unit for scaling a sub-scanning by a sub-scanning scaling factor, a main-scanning scaling unit for scaling a main scanning by a main-scanning scaling factor, the sub-scanning scaling unit and main scanning. An image processing apparatus comprising: a contour extraction unit between the scaling unit; and expanding or contracting the result of the contour extraction according to the sub-scanning scaling factor and the main-scanning scaling factor. 2. The image processing apparatus according to claim 1, wherein the expansion or contraction is independently performed according to the main-scanning scaling factor or the sub-scanning scaling factor. 3. The image processing apparatus according to claim 1, wherein the result of the contour extraction is an area identification signal for recognizing whether it is a character.