JP4049294B2 - Image processing apparatus and image processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to the field of image processing, and more particularly to an image processing apparatus that performs processing corresponding to an image area on color image data of variable magnification obtained by reading a document.
[0002]
  The present invention can be applied not only to a single image processing apparatus but also to an image processing apparatus incorporated in a device such as a color copying machine, a color printer, or a color facsimile.
[0003]
[Prior art]
  For example, in recent years, digital copying machines are generally equipped with an image area separation function. Image area separation is a process of identifying a character area / picture area with reference to a global image area.
[0004]
  The image area separation identification result is reflected in the gradation processing, and processing suitable for each region is performed to improve the image quality. A typical process is to detect a black character area in a character area and reproduce the black character area in a single black color. This process has a great effect on suppressing the coloring of the black character portion. However, processing using the image area separation result also has side effects. It is difficult to completely prevent the occurrence of erroneous separation in which a part of a picture is erroneously determined as a character.
[0005]
  In addition, techniques for reproducing character image quality at the time of picture processing with a resolution and color close to those of character processing are becoming solid. Specifically, higher resolution by increasing the reading pixel density (for example, from 400 dpi to 600 dpi) and enhancement of adaptive processing can be mentioned. Adaptive processing detects feature quantities from local image areas rather than image area separation, and performs processing according to the feature quantities, and has fewer side effects than image area separation, let alone white ground characters. It is also effective for characters on the color ground. For example, a technique for detecting the edge amount and controlling the filtering process or controlling the black amount corresponds to this.
[0006]
  From the above, when comparing the degree of deterioration due to misseparation in the pattern and the degree of deterioration due to separation / mixing in the character image, the degree of deterioration due to separation / mixing in the character image has become considerably smaller. There is a situation.
[0007]
  In view of this, a device has been devised in which the ratio of character determination in image area separation in a character image is reduced to reduce erroneous separation in a picture portion, in other words, the burden of image area separation is reduced. For example, as disclosed in Japanese Patent Application Laid-Open No. 7-203198, there is a conventional technique in which only a thin line is detected as a character by image area separation and a pattern processing is performed for a character having a large width. The aim is to eliminate the influence of scanner MTF and color misregistration in the thin line area, and to suppress high resolution and coloration, and in the bold character part (especially low density characters), only the edge part is processed. Is to suppress the “bordering phenomenon” in which a gap with the inside of the character is generated. Note that separation / switching of separation results occurs before and after the line width specification value (maximum line width identified as characters), which is one of the image area separation control parameters. By using a technique such as adaptive processing for improving the character image quality of the portion to be processed, the boundary between the character processing and the pattern processing can be brought to a level that cannot be recognized visually.
[0008]
  Incidentally, recent digital copying machines generally have a scaling function. Usually, this scaling is electrically performed by interpolation processing in the main scanning direction and mechanically by controlling the reading speed of the scanner in the sub scanning direction. In mechanical scaling, color shift occurs when reading RGB signals mainly due to mechanical vibration, and the amount varies depending on the scaling ratio. Since the vibration is designed so that the magnitude of the vibration is minimized at the same magnification, there is a tendency for vibration to become larger or fluctuated than at the same magnification when zooming. Easy to pick up. Therefore, as shown in FIG. 2, the amount of color misregistration at the time of reading tends to increase as the scaling ratio increases as compared to the case of equal magnification.
[0009]
  In order to eliminate the influence of such color shift at the time of zooming, for example, as seen in Japanese Patent No. 3015308, in the image area separation, the separation result is substantially the same as that at the time of zooming regardless of the zooming process. There is a conventional technique that changes the separation identification operation. This avoids the phenomenon that character determination (black character determination) becomes difficult due to differences in MTF and color misregistration when image area separation is performed using the same determination criteria as in the case of equal magnification during zooming. It is an object.
[0010]
[Problems to be solved by the invention]
  However, the control as shown in Japanese Patent No. 3015308 may not be optimal in the image area separation specification in which only the above-mentioned fine lines are character-determined. If the amount of color misregistration at the time of reading is large, coloring cannot be suppressed by adaptive processing that can only refer to local area information, so the line width character portion that is not judged by image area separation will exceed the color tolerance. It will be at a level that can be clearly recognized by human eyes.
[0011]
  In such a case, it is better to suppress the coloring by using image area separation that can refer to a global area even in the bold character part. In other words, it is better to obtain different image area separation results at the time of scaling and at the same magnification so that only the fine line is determined at the same magnification, and the character is determined including the thick character at the time of enlargement / reduction.
[0012]
  Based on this consideration, the present invention is an image processing apparatus capable of suppressing the occurrence of an abnormal image due to erroneous separation in a picture at the same magnification, and suppressing coloring around a character due to a color shift at the time of magnification. Is to provide.
[0013]
[Means for Solving the Problems]
  In order to achieve the above object, an image processing apparatus according to the present invention is as described in claim 1.
An image input means for scanning a document and inputting color image data of the document, and performing scaling in the sub-scanning direction by controlling a reading speed;
Image area separation means for image area separation of input color image data by the image input means;
Processing means for applying character area processing or pattern area processing to the input color image data in accordance with the result of image area separation by the image area separation means, and outputting processed color image data;
as well as
Control means for changing the image area separation control parameter by the image area separation means in accordance with the magnification of the input color image data scaled by the image input means;
The control parameter of the image area separation that is changed by the control means is a line width specification value,
The image area separating means identifies only a character edge that is an edge of a character line having a line width equal to or smaller than the line width specification value as a character area,
The control means, when the input color image data is enlarged and scaled, the input color image data has the same magnification as the occupation ratio of the area identified as the character area by the image area separation means in the document. In this case, the line width specification value is increased as compared with the case where the input color image data has the same magnification so as to be increased from the occupation ratio in the case of.
[0014]
  Moreover, the image processing apparatus of the present invention, as described in claim 2,
An image input means for scanning a document and inputting color image data of the document, and performing scaling in the sub-scanning direction by controlling a reading speed;
Image area separation means for image area separation of input color image data by the image input means;
Processing means for applying character area processing or pattern area processing to the input color image data according to the result of image area separation by the image area separation means, and outputting the processed color image data;
as well as
Control means for changing the image area separation control parameter by the image area separation means according to the magnification of the input color image data scaled by the image input device;
The control parameter of the image area separation that is changed by the control means is an expansion amount specification value,
The image area separating means performs an expansion process of expanding a character edge identified as a character area to a peripheral area by an expansion amount corresponding to the expansion amount specification value, and finally the character edge area after the expansion process Identified as an area,
The control means, when the input color image data is enlarged and scaled, the input color image data has the same magnification as the occupation ratio of the area identified as the character area by the image area separation means in the document. In this case, the expansion amount specification value is increased as compared with the case where the input color image data has the same magnification so as to be increased from the occupation ratio in the case of the above.
[0015]
  According to another aspect of the image processing apparatus of the present invention, as described in claim 3, in the configuration according to claim 2, the expansion processing is a two-dimensional expansion that expands a character edge in the main scanning direction and the sub-scanning direction. It is in mask processing.
[0016]
  The image processing method of the present invention is as described in claim 4,
An image input step of inputting color image data of an original by scanning the original and inputting color image data of the original image by image input means for performing scaling in the sub-scanning direction by controlling the reading speed;
An image area separation step for image area separation of input color image data by the image input step;
In accordance with the result of the image area separation in the image area separation process, a process step of performing character area processing or pattern area processing on the input color image data and outputting the processed color image data;
as well as
A control step for changing the control parameter of the image area separation by the image area separation step in accordance with a scaling factor of the scaling of the input color image data performed by the image input means;
The control parameter of the image area separation that the control process changes is a line width specification value,
The image area separation step identifies only a character edge that is an edge of a character line having a line width equal to or smaller than the line width specification value as a character area
In the control step, when the input color image data is enlarged and scaled, an occupancy rate in the document of an area identified as a character area by the image area separation step is determined as the input color image. The line width specification value is increased more than that when the input color image data is the same size so that the occupation ratio is increased when the data is the same size.
[0017]
  The image processing method of the present invention is as described in claim 5,
An image input step of inputting color image data of an original by scanning the original and inputting color image data of the original by an image input means that performs scaling in the sub-scanning direction by controlling the reading speed;
An image area separation step for image area separation of input color image data by the image input step;
In accordance with the result of the image area separation in the image area separation process, a process step of performing character area processing or pattern area processing on the input color image data and outputting the processed color image data;
as well as
A control step for changing the control parameter of the image area separation by the image area separation step in accordance with a scaling factor of the scaling of the input color image data performed by the image input means;
The control parameter of the image area separation to be changed by the control process is an expansion amount specification value,
The image area separation step performs an expansion process of expanding the character edge identified as the character area to the peripheral area by an expansion amount corresponding to the expansion amount specification value, and finally the character edge area after the expansion process Identified as an area,
In the control step, when the input color image data is enlarged / magnified, the input color image data has an equal magnification of the occupation rate in the document of the region identified as the character region by the image region separation step. In this case, the expansion amount specification value is increased as compared with the case where the input color image data has the same magnification so as to be increased from the occupation ratio in the case of the above.
[0018]
  According to another aspect of the image processing method of the present invention, as described in claim 6, in the configuration according to claim 5, the expansion processing is a two-dimensional expansion that expands a character edge in the main scanning direction and the sub-scanning direction. It is in mask processing.
[0019]
  The characteristics of the present invention described above or other characteristics and effects thereof will be specifically described in relation to the embodiment of the present invention.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
  FIG. 1 is a block diagram for explaining an embodiment of the present invention. In FIG. 1, an image input unit 1 is a 600 dpi color scanner, for example, and scans a document to obtain RGB signals of the document image, and the machine in the sub-scanning direction according to the magnification specified by the user on the operation panel 7. Zooming in. The scaling processing unit 2 performs scaling in the main scanning direction on the RGB signal input from the image input unit 1 according to the scaling factor specified by the user by interpolation processing.
[0021]
  The image area separation unit 5 identifies a character / picture area for the RGB signal (input color image data) input from the scaling processing unit 2 to the gradation processing unit 10. The gradation processing unit 10 is a part that performs gradation processing on the RGB signal input from the scaling processing unit 2 according to the image region separation result by the image region separation unit 5. In the example shown here, the gradation processing unit 10 includes a character region gradation processing unit 3 that performs gradation processing suitable for the character region on the input RGB signal, and a level suitable for the design region on the input RGB signal. If the image region gradation processing unit 4 that performs the tone processing and the image region separation result by the image region separation unit 5 are characters, the CMYK signal output from the character region gradation processing unit 3 is used, and the image region separation result is the pattern. Then, it comprises a selector 6 for selecting CMYK signals output from the image area gradation processing unit 4 as output image signals (output color image data). The image area separation specification value setting unit 8 sets a specification value, which is a control parameter for image area separation, to the image area separation unit 5, and a user can input a specific specification value on the operation panel 7 as described later. Change according to the specified scaling factor.
[0022]
  Among the components described above, the image area separation unit 5, the image area separation specification value setting unit 8, and the gradation processing unit 10 are indispensable elements for the present invention. When the present invention is applied to, for example, a color copying machine, an image output unit for creating an image based on an output image signal of the gradation processing unit 10 is added in addition to the components shown in FIG. . When the present invention is applied to a color facsimile, in addition to the constituent elements shown in FIG. 1, an image output unit for forming an image using the output image signal of the gradation processing unit 10 and the output image signal are compressed. Then, an element for transmitting is added. When the present invention is applied to a color printer, the image input unit 1 is replaced with an interface for capturing RGB signals from an external personal computer, and the scaling unit 2 is left as it is, or an external personal computer is used. If it is assumed that the main scanning scaling is performed, the scaling processing unit 2 is deleted, and an image output unit for creating an image by the output image signal of the gradation processing unit 10 is added. Become.
[0023]
  Note that the gradation processing unit 10, the image area separation unit 5, and the image area separation specification value setting unit 8 may be realized by hardware, or all or a part thereof may be a general-purpose or dedicated program-controlled processor or digital. You may implement | achieve by software using a signal processor.
[0024]
  Embodiment 1
  In the first embodiment of the present invention, as shown in FIG. 3, for example, as shown in FIG. 3, the image area separation is performed in consideration of the relationship between the amount of color misregistration at the time of image input and the scaling factor. The image area separation is performed so that the ratio (area occupation ratio determined as characters on the same document) is reduced at the same magnification (magnification 100%) and increased at magnification. The line width specification value M (maximum value of the line width identified as a character) is changed according to the scaling factor. However, FIG. 3 is for conceptually showing the control of the line width specification value of the image area separation, and is simply expressed linearly in the figure, but is not limited thereto.
[0025]
  FIG. 4 is a diagram schematically showing a change in image area separation by controlling the line width specification value M in the present embodiment. For the character portion as in (a), at the same magnification, only a portion having a relatively narrow line width as indicated by reference numeral 100 in (b) is determined as a character. On the other hand, at the time of scaling, characters are determined including even a character edge having a line width wider than that at the time of equal magnification. For example, at a scaling factor of 400%, characters are determined including a thickness that almost covers a bold character as indicated by reference numeral 101 in (c).
[0026]
  In order to realize such character determination according to the scaling factor, according to one embodiment, a scaling factor / line width specification value conversion table as shown in FIG. 5 is used in the image area separation specification value setting unit 8. . Thus, in this embodiment, the image area separation unit 5 has a line width specification value as one of the image area separation specification values, and the image area separation specification value setting unit 8 is a line set in the image area separation unit 5. The width specification value is changed as shown in FIG. By controlling the line width specification value, the image area separation unit 5 determines only a thin line having a line width of 8 dots or less as a character at the same magnification, but for example, character determination is performed up to a line width of 64 dots at 200% enlargement magnification. When 400% enlargement / magnification is changed, characters are detected up to a line width of 128 dots. The numerical values and shapes of the scaling factor / line width specification value conversion table shown in FIG. 5 are merely examples and can be changed. However, in order to obtain an image area separation result as shown in FIG. It is necessary to set it to a rising shape.
[0027]
  FIG. 6 is a block diagram showing an example of the image area separation unit 5 in the present embodiment. The image area separation unit 5 shown here includes a character edge detection unit 501 for detecting a character edge, a halftone area detection unit 502 for detecting a halftone area, and a white background area detection for detecting a white background area. 503, and a character determination unit 506 that determines a character / picture area based on the detection results of these three detection units. The condition that the character determination unit 506 determines to be a character is “the detection result of the character edge detection unit 501 is“ character edge ”and the detection result of the halftone dot region detection unit 502 is“ non-halftone dot region ”. In addition, the detection result of the white background area detection unit 503 is “white background area”, and the pattern area is determined under other conditions.
[0028]
  The white background region detection unit 503 is a binarization unit 504 that converts an input RGB signal into a black and white binary with a predetermined threshold value, and a correction that corrects the binarized signal by the binarization unit 504 based on a line width specification value. The signal corrected by the correction unit 505 is input to the character determination unit 506.
[0029]
  FIG. 7 is an explanatory diagram of the operation of the white background area detection unit 503. However, the case where the line width specification value M = 8 is set is shown. In FIG. 7, (a) is a signal binarized by the binarization unit 504. The correction unit 505 refers to the left and right M pixel blocks (or the upper and lower M pixel blocks) of the target pixel for the binarized signal. (B) shows the window when referring to the left and right blocks of the pixel of interest. When the white pixel exists in both the left block and the right block of the target pixel (or when the white pixel exists in both the upper block and the lower block of the target pixel), the target pixel is determined as the white background. If the condition is not satisfied, the target pixel is determined as a non-white background. In this way, the binarized signal shown in (a) is corrected as shown in (c). Therefore, in this example, the character determination result by the character determination unit 506 is as shown in (d), a character having a line width of 3 dots is determined as a character, and a character having a line width of 9 dots is not determined. Here, in order to simplify the description, the determination is made in one dimension only in the main scanning direction, but it is natural that the determination may be made in two dimensions in both the main and sub scanning directions.
[0030]
  As described above, according to the present embodiment, since only the fine line is determined by the image area separation unit 5 at the same magnification, it is possible to suppress erroneous separation in the pattern and to increase the bold character. The edging can be suppressed. On the other hand, at the time of enlargement / magnification, since the image area separation unit 5 performs character determination including the thick character edge, it is possible to suppress coloring of the character edge portion due to the color shift at the time of reading.
[0031]
    << Embodiment 2 >>
  In the first embodiment, the line width specification value among the image area separation specification values is switched according to the magnification. On the other hand, in the second embodiment of the present invention, the expansion amount specification value N (the expansion amount of the character edge identified as a character) among the image area separation specification values is switched by the scaling factor. As shown in FIG. 3, control of the occupation rate of the character determination area is realized.
[0032]
  The expansion process of character judgment results has the effect of suppressing coloring around characters, improving the reproducibility by processing characters including the inside of thin line characters, and correcting partial misseparation of characters even at the same magnification. is there. Such expansion processing itself is a technique that has been generally used in the past, but if the expansion amount is too large, erroneous separation will occur in the nearby picture area. Was set to a moderate fixed value that was not too large. However, since the amount of color misregistration at the time of reading increases at the time of enlargement / magnification scaling, if the amount of color misregistration is larger than the amount of expansion, coloring cannot be suppressed with the same expansion amount as at the same magnification.
[0033]
  Therefore, in the present embodiment, the expansion amount is reduced by switching the expansion amount specification value according to the variable magnification so that the expansion amount is small at the same magnification and is larger than that at the same magnification at the time of variable magnification. Coloring can be effectively suppressed even during zooming. That is, since the amount of color misregistration at the time of reading is small at the same magnification, the expansion amount specification value is set such that “suppression of erroneous separation in the picture” is emphasized and the expansion amount is kept to the minimum necessary amount. On the other hand, since the amount of color shift at the time of reading is large at the time of enlargement / magnification, an expansion amount specification value is set so as to increase the expansion amount with an emphasis on “suppression of the effect of color shift”.
[0034]
  FIG. 8 is a diagram schematically showing a change in image area separation by controlling the expansion amount specification value in the present embodiment. When the same magnification,smallBy setting the value to a small value, the character portion as shown in (a) is determined to be a narrow character edge portion as indicated by reference numbers 110 and 111 in (b). On the other hand, for example, when the scaling factor is 400%, the expansion amount specification value is set to a large value, so that a thick character edge portion as indicated by reference numerals 112 and 113 in FIG.
[0035]
  In order to realize such character determination according to the magnification, according to one embodiment, a magnification / expansion amount specification value conversion table as shown in FIG. 9 is used as the image area separation specification value setting value 8. Thus, in this embodiment, the image area separation unit 5 has an expansion amount specification value as one of the image area separation specification values, and the image area separation specification value setting unit 8 sets the expansion amount to be set in the image area separation unit 5. The specification value is changed as shown in FIG. 9, for example, according to the magnification. By controlling the expansion amount specification value, the image area separation unit 5 expands the character determination result by 2 dots (internal and external 1 dot) at the same magnification, but for example, at 200% magnification, 6 dots (internal and external 3 dots). ) It expands and expands 12 dots (6 dots inside and outside) at 400% magnification. Note that the numerical values and shapes of the scaling factor / expansion amount specification value conversion table shown in FIG. 9 are examples and can be changed, but in order to obtain the image area separation results as shown in FIG. It is necessary to set it to a rising shape.
[0036]
  FIG. 10 is a block diagram showing an example of the image area separation unit 5 in the present embodiment. The image area separation unit 5 shown here includes a character edge detection unit 507, a halftone dot region detection unit 508, a white background region detection unit 509, and a character determination unit that identifies a character / picture region based on the outputs of these detection units. 510, an expansion processing unit 511 that expands an area determined to be a character by the character determination unit 510 according to the expansion amount specification value N. The determination conditions of the character determination unit 510 are the same as those of the character determination unit 506 shown in FIG. The white background area detection unit 509 may have the same configuration as the white background area detection unit 503 shown in FIG. 6, but the line width specification value M is a fixed value, and the character determined by the character determination unit 510 is character-determined. The minimum width of the edge portion is 2 dots.
[0037]
  FIG. 11 is an explanatory diagram of the operation of the expansion processing unit 511. However, the case where the expansion amount specification value N = 6 is set is shown. The dilation processing unit 511 refers to the determination result of the character determination unit 510 with a mask of (N + 1) × (N + 1) pixels centered on the target pixel as shown in FIG. If even one pixel has a pixel determined to be a character, the determination result of the target pixel is taken as a character. For example, when a character edge having a 2-dot width as indicated by reference numerals 120 and 121 in FIG. 11A is determined as a character area by the character determination unit 510, the character determination area is determined by the expansion processing of the expansion processing unit 511. Is expanded by 3 dots to the inside and outside of the character, and as a result, the character determination area expands to a width of 8 dots as indicated by reference numerals 122 and 123 in FIG.
  As described above, according to the present embodiment, the expansion amount of the character determination result is larger at the time of enlargement / magnification than at the time of equal magnification, so that erroneous separation in the pattern area near the character edge at the same magnification is suppressed. In addition, it is possible to suppress coloring around the character at the time of zooming.
[0038]
  << Embodiment 3 >>
  In the first or second embodiment, the occupation rate of the character determination area is monotonously increased as shown in FIG. When the character judgment area is monotonously increased in this way, the frequency of occurrence of misseparation in the pattern and coloringVisual characteristicsThe relationship is as shown in FIG. The solid curve in FIG. 12 represents the frequency of occurrence of erroneous separation in the pattern, and the alternate long and short dash line represents the visual characteristic with respect to coloring.
[0039]
  As can be seen in FIG. 12, as the character determination area increases, the error separation in the pattern naturally increases. On the other hand, coloring becomes less worrisome for human eyes as the magnification rate increases. This is the same principle that even if the edge portion of the thick black line is colored, it can be visually identified as a black character, but when the edge portion of the thin black line is colored, it appears as a colored character. Thus, since one is an ascending line and the other is a descending line, if the enlargement ratio is large, the relationship between the two is reversed, and the influence of erroneous separation in the pattern may be greater than the coloring. The point at which the relationship is reversed, that is, the magnification (X%) of the intersection of the two characteristic curves differs depending on the image area separation performance and the magnitude of vibration inherent in the scanner, and is derived empirically.
[0040]
  In view of the above points, in another embodiment of the present invention, when the X% is present at a position smaller than the maximum magnification of the scanner, as shown in FIG. The image area separation specification value is controlled so that the character determination area is monotonously decreased with the occupancy rate at the magnification X% peaking at a magnification ratio of X%. To do. By doing in this way, generation | occurrence | production of the misseparation after intersection X% can be suppressed.
[0041]
  In order to control the ratio of the character determination area as shown in FIG. 13, according to one embodiment, a magnification / line width specification value conversion table as shown in FIG. . In this embodiment, the image area separation unit 5 is configured as shown in FIG. 6, for example. According to another embodiment, a magnification / expansion amount specification value conversion table as shown in FIG. 15 is used in the image area separation specification value setting unit 8. In this embodiment, the image area separation unit 5 is configured as shown in FIG.
[0042]
  The conversion tables shown in FIGS. 14 and 15 all have a similar shape with the magnification X% shown in FIG. 13 as a peak. However, the numerical value can be changed as appropriate.
  As described above, according to the present embodiment, in a scaling factor (a scaling factor greater than X%) in which the problem of erroneous separation in a picture is greater than coloring, character determination is performed with X% as a peak. In order to reduce the area to be processed, it is possible to accurately suppress erroneous separation in a pattern having a large problem.
[0043]
  In each of the embodiments described above, only one of the line width specification value and the expansion amount specification value among the image area separation specification values is changed according to the magnification. However, both specification values are changed according to the magnification. It is obvious that the same effect can be obtained by changing the above. In the above description, the image area separation specification value is controlled only at the time of enlargement / magnification, but some scanners have a clearly large color shift amount at the time of reading even at the time of reduction. In this case, it is obvious that the present invention can be similarly applied to the range of the zooming magnification.
[0044]
【The invention's effect】
  As described above, according to the first and fourth aspects of the invention, at the same magnification, only fine lines having a predetermined line width or less are character-determined to suppress erroneous separation in the pattern, and low-density thick characters. Bordering can be suppressed, and at the time of enlargement / magnification, character determination including a thick character edge can be performed to suppress character edge portion coloring. According to the second, third, fifth, and sixth aspects of the invention, at the same magnification, the character determination expansion amount can be reduced to suppress erroneous separation in the pattern area near the character edge. Can increase the amount of expansion of character determination to suppress coloring of the character edge portion, and so on.
[Brief description of the drawings]
FIG. 1 is a block diagram for explaining an embodiment of the present invention.
FIG. 2 is a graph showing a relationship between a color shift amount at the time of reading and a scaling factor.
FIG. 3 is a graph for explaining control of a ratio of a character determination area according to a scaling factor.
FIG. 4 is a diagram schematically showing a difference between character determination areas when the scaling factor is 100% and 400% in the first embodiment.
FIG. 5 is a graph showing an example of a scaling factor / line width specification value conversion table used in the first embodiment.
FIG. 6 is a block diagram illustrating an example of an image area separation unit according to the first embodiment.
7 is an operation explanatory diagram of a white background region detection unit shown in FIG. 6. FIG.
FIG. 8 is a diagram schematically showing a difference between character determination areas when the scaling factor is 100% and 400% in the second embodiment.
FIG. 9 is a graph showing an example of a scaling factor / expansion amount specification value conversion table used in the second embodiment.
FIG. 10 is a block diagram illustrating an example of an image area separation unit according to a second embodiment.
11 is an operation explanatory diagram of an expansion processing unit shown in FIG.
FIG. 12 is a graph showing a relationship between a visual characteristic and a scaling factor with respect to occurrence frequency and coloring of an erroneous separation in a picture when the ratio of a character determination area is monotonously increased according to a scaling factor.
FIG. 13 is a graph showing a relationship between a scaling factor and a ratio of a character determination area in the third embodiment.
FIG. 14 is a graph showing an example of a scaling factor / line width specification value conversion table used in the third embodiment.
FIG. 15 is a graph showing an example of a scaling factor / expansion amount specification value conversion table used in the third embodiment.
[Explanation of symbols]
      1 Image input section
      2 Scaling processing unit
      3 Tone processing part for character area
      4 Pattern area gradation processing section
      5 Image area separation part
      6 Selector
      7 Operation panel
      8 Image area separation specification value setting section
    10 gradation processing section
  501 Character edge detector
  502 Halftone dot detection unit
  503 White background area detection unit
  504 Binarization part
  505 Correction unit
  506 Character determination part
  507 Character edge detector
  508 Halftone dot detection unit
  509 White background area detection unit
  510 Character determination part
  511 Expansion processing unit

Claims (6)

An image input means for scanning a document and inputting color image data of the document, and performing scaling in the sub-scanning direction by controlling a reading speed;
  Image area separation means for image area separation of input color image data by the image input means;
  Processing means for applying character area processing or pattern area processing to the input color image data in accordance with the result of image area separation by the image area separation means, and outputting processed color image data;
as well as
  Control means for changing the image area separation control parameter by the image area separation means in accordance with the magnification of the input color image data scaled by the image input means;
  The control parameter of the image area separation that is changed by the control means is a line width specification value,
  The image area separating means identifies only a character edge that is an edge of a character line having a line width equal to or smaller than the line width specification value as a character area,
  The control means, when the input color image data is enlarged and scaled, the input color image data has the same magnification as the occupation ratio of the area identified as the character area by the image area separation means in the document. The image processing apparatus is characterized in that the line width specification value is increased as compared with the case where the input color image data is the same size so as to be increased from the occupation ratio in the case of. An image input means for scanning a document and inputting color image data of the document, and performing scaling in the sub-scanning direction by controlling a reading speed;
  Image area separation means for image area separation of input color image data by the image input means;
  Processing means for applying character area processing or pattern area processing to the input color image data according to the result of image area separation by the image area separation means, and outputting the processed color image data;
as well as
  Control means for changing the image area separation control parameter by the image area separation means in accordance with the magnification of the input color image data scaled by the image input means;
  The control parameter of the image area separation that is changed by the control means is an expansion amount specification value,
  The image area separating means performs an expansion process of expanding a character edge identified as a character area to a peripheral area by an expansion amount corresponding to the expansion amount specification value, and finally the character edge area after the expansion process Identified as an area,
  The control means, when the input color image data is enlarged and scaled, the input color image data has the same magnification as the occupation ratio of the area identified as the character area by the image area separation means in the document. The expansion amount specification value is increased more than in the case where the input color image data is the same size so as to increase from the occupancy ratio in the above case. 3. The image processing apparatus according to claim 2, wherein the expansion process is a two-dimensional mask process that expands a character edge in the main scanning direction and the sub-scanning direction. An image input step of inputting color image data of an original by scanning the original and inputting color image data of the original image by image input means for performing scaling in the sub-scanning direction by controlling the reading speed;
  An image area separation step for image area separation of input color image data by the image input step;
  In accordance with the result of the image area separation in the image area separation process, a process step of performing character area processing or pattern area processing on the input color image data and outputting the processed color image data;
as well as
  A control step for changing the control parameter of the image area separation by the image area separation step in accordance with a scaling factor of the scaling of the input color image data performed by the image input means;
  The control parameter of the image area separation that the control process changes is a line width specification value,
  The image area separation step identifies only a character edge that is an edge of a character line having a line width equal to or smaller than the line width specification value as a character area,
  In the control step, when the input color image data is enlarged and scaled, an occupancy rate in the document of an area identified as a character area by the image area separation step is determined as the input color image. An image processing method, wherein the line width specification value is increased as compared with a case where the input color image data is an equal magnification so that the occupation ratio is increased when the data is an equal magnification. An image input step of inputting color image data of an original by scanning the original and inputting color image data of the original by an image input means that performs scaling in the sub-scanning direction by controlling the reading speed;
  An image area separation step for image area separation of input color image data by the image input step;
  In accordance with the result of the image area separation in the image area separation process, a process step of performing character area processing or pattern area processing on the input color image data and outputting the processed color image data;
as well as
  A control step for changing the control parameter of the image area separation by the image area separation step in accordance with a scaling factor of the scaling of the input color image data performed by the image input means;
  The control parameter of the image area separation to be changed by the control process is an expansion amount specification value,
  The image area separation step performs an expansion process of expanding the character edge identified as the character area to the peripheral area by an expansion amount corresponding to the expansion amount specification value, and finally the character edge area after the expansion process Identified as an area,
  In the control step, when the input color image data is enlarged / magnified, the input color image data has an equal magnification of the occupation rate in the document of the region identified as the character region by the image region separation step. The image processing method is characterized in that the expansion amount specification value is increased as compared with the case where the input color image data is the same size so as to increase from the occupancy ratio in the above case. 6. The image processing method according to claim 5, wherein the expansion process is a two-dimensional mask process for expanding a character edge in the main scanning direction and the sub-scanning direction.

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