JP5863000B2 - Image processing apparatus, image forming apparatus, and program - Google Patents

Description

  The present invention relates to an image processing apparatus, an image forming apparatus, and a program.

  In Patent Document 1, when screen processing is performed on multi-valued image data, high line number screen processing is performed on pixels at the edge portion, and low line number screen processing is performed on pixels at the non-edge portion. Techniques to apply are disclosed.

  Further, in Patent Document 2, edge determination is performed again on pixels that are not adjacent to a negative line, with respect to multi-valued image data from which negative lines and edge portions, which are lower density lines than the background, are extracted. A technique is disclosed in which high-line-number screen processing is performed on pixels at edge portions that are not adjacent to negative lines, and low-line-number screen processing is performed on other pixels.

JP 2006-262204 A JP 2010-245591 A

  An object of the present invention is set by an on-pixel thin line and a continuous off-pixel which are thin lines having a width equal to or smaller than a set width composed of continuous on-pixels in binary image data subjected to screen processing. It is an object to provide an image processing apparatus, an image forming apparatus, and a program that can accurately determine an off-pixel thin line that is a thin line having a width equal to or less than a width as compared with a case where this configuration is not provided.

[Image processing device]
According to the first aspect of the present invention, edge detection is performed by determining whether or not each pixel of binary image data subjected to screen processing is a pixel constituting an edge and detecting a pixel at an edge portion. Means,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an on pixel, and is a continuous number of on pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest When the number of ON pixels is equal to or less than a preset number and the number of ON pixels in a predetermined range of the determination area is equal to or greater than a preset first threshold, On-pixel thin line determination means for determining a pixel constituted by a pixel having an on-pixel thin line whose width formed by the pixels is a thin line having the number of continuous on-pixels,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an off pixel, and is a continuous number of off pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest The number of off pixels is equal to or less than a preset number, the number of on pixels in the judgment area in the preset range is greater than or equal to a preset second threshold value, and the number of off pixels in the judgment area is preset. An off-pixel thin line determination unit that determines that the width of the pixel of interest is a pixel of an off-pixel thin line that is a thin line of the number of continuous off-pixels when the target pixel is equal to or greater than the third threshold value,
The edge portion sac Chi detected by the edge portion detection means is constituted by the on-pixel thin line determination means and and the ON pixels has not been determined to any ON pixels thin line and off pixels thin line by OFF pixels thin line determination means The edge portion is converted so as to reduce the number of on-pixels, and neither the on-pixel thin line nor the off-pixel thin line is determined by the on-pixel thin line determination unit and the off-pixel thin line determination unit and On-edge conversion means for converting so as to add on-pixels to the configured edge portion ;
Is an image processing apparatus.

According to a second aspect of the present invention, the first threshold value is set based on the number of continuously on pixels,
The image processing apparatus according to claim 1, wherein the second threshold value and the third threshold value are set based on the number of consecutive off pixels.

  The present invention according to claim 3 is the image processing apparatus according to claim 1, wherein a range of the determination region is set based on the number of continuous on pixels or the number of continuous off pixels.

[Image forming apparatus]
According to the fourth aspect of the present invention, edge detection is performed by determining whether or not each pixel of binary image data subjected to screen processing is a pixel constituting an edge and detecting a pixel at an edge portion. Means,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an on pixel, and is a continuous number of on pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest When the number of ON pixels is equal to or less than a preset number and the number of ON pixels in a predetermined range of the determination area is equal to or greater than a preset first threshold, On-pixel thin line determination means for determining a pixel constituted by a pixel having an on-pixel thin line whose width formed by the pixels is a thin line having the number of continuous on-pixels,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an off pixel, and is a continuous number of off pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest The number of off pixels is equal to or less than a preset number, the number of on pixels in the judgment area in the preset range is greater than or equal to a preset second threshold value, and the number of off pixels in the judgment area is preset. An off-pixel thin line determination unit that determines that the width of the pixel of interest is a pixel of an off-pixel thin line that is a thin line of the number of continuous off-pixels when the target pixel is equal to or greater than the third threshold value,
The edge portion sac Chi detected by the edge portion detection means is constituted by the on-pixel thin line determination means and and the ON pixels has not been determined to any ON pixels thin line and off pixels thin line by OFF pixels thin line determination means The edge portion is converted so as to reduce the number of on-pixels, and neither the on-pixel thin line nor the off-pixel thin line is determined by the on-pixel thin line determination unit and the off-pixel thin line determination unit and On-edge conversion means for converting so as to add on-pixels to the configured edge portion ;
Output means for outputting the image data converted by the on-pixel conversion means;
An image forming apparatus having

[program]
According to a fifth aspect of the present invention, there is provided a step of detecting whether or not each pixel of binary image data subjected to screen processing is a pixel constituting an edge and detecting a pixel at an edge portion. ,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an on pixel, and is a continuous number of on pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest When the number of ON pixels is equal to or less than a preset number and the number of ON pixels in a predetermined range of the determination area is equal to or greater than a preset first threshold, Determining the width of the pixel to be a pixel of an on-pixel thin line that is a thin line of the number of continuous on-pixels;
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an off pixel, and is a continuous number of off pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest The number of off pixels is equal to or less than a preset number, the number of on pixels in the judgment area in the preset range is greater than or equal to a preset second threshold value, and the number of off pixels in the judgment area is preset. Determining that the pixel of interest is a pixel of an off-pixel thin line that is a thin line of the number of consecutive off-pixels when the pixel of interest is equal to or greater than the third threshold,
Detected edge portion sac Chi, for the edge portion formed by and on pixels not been determined to any ON pixels thin line and off pixels thin line, converts to reduce the on-pixel, on a pixel For an edge portion that is not determined to be either a fine line or an off-pixel thin line and is composed of off-pixels, a step of converting to add on-pixels ;
Is a program for causing a computer to execute.

  According to the first aspect of the present invention, the image processing device includes the on-pixel thin line and the continuous off-pixel which are thin lines having a width equal to or smaller than the set width composed of the continuous on-pixel in the binary image data subjected to the screen processing. It is possible to provide an image processing apparatus that can accurately determine an off-pixel thin line that is a thin line with a width equal to or smaller than a set width compared to a case where the present configuration is not provided.

  According to the second aspect of the present invention, in addition to the effect obtained by the first aspect, the on-pixel thin line and the off-pixel thin line can be more accurately determined according to the line width.

  According to the third aspect of the present invention, in addition to the effect obtained by the first or second aspect, the on-pixel thin line and the off-pixel thin line can be more accurately determined according to the line width.

  According to the fourth aspect of the present invention, the binary image data subjected to the screen processing is constituted by the on-pixel thin line and the continuous off-pixel which are thin lines having a width equal to or smaller than the set width constituted by the continuous on-pixel. Thus, it is possible to provide an image forming apparatus that can accurately determine an off-pixel thin line that is a thin line having a width equal to or smaller than a set width as compared with a case where this configuration is not provided.

  According to the fifth aspect of the present invention, the binary image data subjected to the screen processing is constituted by the on-pixel thin line and the continuous off-pixel which are thin lines having a width equal to or smaller than the set width constituted by the continuous on-pixel. It is possible to provide a program that can accurately determine an off-pixel thin line that is a thin line having a width equal to or smaller than a set width compared to a case where the present configuration is not provided.

It is a figure which shows the printing system of one Embodiment of this invention. 1 is a block diagram illustrating a hardware configuration of an image forming apparatus 1 according to an embodiment of the present invention. It is a block diagram which shows the function structure of the image processing apparatus 4 in one Embodiment of this invention. It is a flowchart which shows the flow of the whole process in the image processing apparatus 4 of one Embodiment of this invention. It is a flowchart which shows the flow of the edge detection in the edge detection part 43 of one Embodiment of this invention. It is a flowchart which shows the flow which determines the positive line in the positive thin line determination part 41 of one Embodiment of this invention. It is a figure which shows the pixel of each row | line and the pixel of each column around the attention pixel in one Embodiment of this invention. It is a figure which shows an example of the continuous ON pixel 52 in one Embodiment of this invention. It is a figure which shows an example of the on-pixel threshold value in the positive thin line determination of one Embodiment of this invention. It is the figure showing an example of the conditions in the positive thin line determination of one Embodiment of this invention in the table | surface. It is a figure which shows an example of the positive thin line information at the time of determining with the pixel of the positive thin line in one Embodiment of this invention. It is a figure which shows an example of the positive thin line information at the time of not determining with the pixel of the positive thin line in one Embodiment of this invention. It is a flowchart which shows the flow which determines the negative line in the negative thin line determination part 42 of one Embodiment of this invention. It is a figure which shows an example of the continuous off pixel in one Embodiment of this invention. It is a figure which shows an example of the on pixel threshold value in the negative thin line determination of one Embodiment of this invention, and an off pixel threshold value. It is the figure showing an example of conditions in negative thin line judgment of one embodiment of the present invention by a table. It is a figure which shows an example of the negative thin line information at the time of determining with the pixel of a negative thin line in one Embodiment of this invention. It is a figure which shows an example of the negative thin line information at the time of not determining with the pixel of a negative thin line in one Embodiment of this invention.

[background]
First, in order to help understanding of the present invention, the background that led to the present invention will be described.

  In electrophotography, when characters and lines are output on paper, there is a problem that characters and lines actually output on paper become thicker than original images and latent image data due to the influence of dot gain and the like.

  In response to the above problem, for example, as described in Patent Document 1, edge detection is performed, and the density of the edge portion is reduced to adjust the line width of characters and lines when output to paper. Corrections have been made.

  However, there is a problem that, when the density is adjusted to be thinner than the fine fine line having a higher density than the background among the fine lines having a certain line width or less, the positive fine line is faded. In addition, there is a problem that a white portion of a negative fine line having a lower density than the background is blurred.

  Therefore, Patent Document 2 discloses a technique in which the density of only edge portions other than the positive thin line and the negative thin line is changed without changing the density for the positive thin line and the negative thin line.

  On the other hand, the above technique has no problem for multi-valued image data, but when it is binary image data subjected to screen processing, it has not been possible to accurately detect positive fine lines and negative fine lines. This is because, in the screened image data, halftone dots and other isolated points due to dirt may be determined as positive thin lines or negative thin lines.

  Therefore, there has been a demand for a technique for accurately determining positive fine lines and negative fine lines in binary image data subjected to screen processing.

[Embodiment]
Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an image forming system according to an embodiment of the present invention.

  The image forming apparatus 1 in the present embodiment is connected to the terminal device 2 via the network 3. The image forming apparatus 1 prints image data transmitted from the terminal device 2 via the network 3 and image data transmitted from a reading device such as a printer (not shown) that optically reads an image on a sheet. In the present embodiment, the image forming apparatus 1 is provided with an image processing apparatus.

  Next, the hardware configuration of the image forming apparatus 1 will be described in detail with reference to FIG.

  As shown in FIG. 2, the image forming apparatus 1 transmits and receives data to and from an external device or the like via a CPU 11, a memory 12, a storage device 13 such as a hard disk drive (HDD), and a network 3. It has a communication interface (IF) 14, a user interface (UI) device 15 including a touch panel or a liquid crystal display and a keyboard, a scanner 16, and a printer 17. These components are connected to each other via a control bus 18.

  The CPU 11 executes predetermined processing based on a control program stored in the memory 12 or the storage device 13 and controls the operation of the image forming apparatus installed in the image forming apparatus 1. In the present embodiment, the CPU 11 has been described as reading and executing a control program stored in the memory 12 or the storage device 13, but the program is stored in a storage medium such as a CD-ROM and stored in the CPU 11. It is also possible to provide.

  FIG. 3 is a block diagram showing a functional configuration of the image processing apparatus 4 in the image forming apparatus 1 realized by executing the control program.

  As illustrated in FIG. 4, the image processing apparatus 4 includes a positive thin line determination unit 41, a negative thin line determination unit 42, an edge detection unit 43, a halftone detection unit 44, a data processing unit 45, and an on-pixel conversion unit 46. A printer 17 that outputs the image data subjected to the on-pixel conversion by the on-pixel conversion unit 46 to a sheet is connected to the image processing apparatus 4. In the present embodiment, the image processing apparatus 4 is described as being installed inside the image forming apparatus 1, but the present invention is not limited to such a configuration and is independent from the image forming apparatus 1. May be.

  In the following description, it is assumed that the image forming apparatus 1 receives binary image data that has undergone screen processing, and this image data is input to the image processing apparatus 4 as input image data.

  The positive thin line determination unit 41 sequentially selects one of the pixels of the input image data as a pixel of interest, and this pixel of interest is an on pixel, and the on pixel that is continuous in the horizontal direction or the vertical direction including this pixel of interest If the number of consecutive on pixels, which is the number of pixels, is 4 or less and the number of on pixels in the determination area in the range set based on the number of consecutive on pixels is equal to or greater than the first threshold, Are determined to be positive thin line (on pixel thin line) pixels corresponding to the number of continuous on pixels. Here, the positive fine line is a thin line having the number of continuous on-pixels constituted by continuous on-pixels.

  Further, in the positive thin line determination unit 41, the first threshold value and the determination region are set based on the number of consecutive ON pixels. Then, the positive thin line determination unit 41 generates positive thin line information that is information indicating whether or not each pixel of the input image data is a positive thin line pixel.

  The negative thin line determination unit 42 sequentially selects one of the pixels of the input image data as a pixel of interest, and this pixel of interest is an off pixel. The off pixel continues in the horizontal direction or the vertical direction including the pixel of interest. The number of continuous off pixels, which is the number of pixels, is four or less, the number of on pixels in the determination region in the range set based on the number of continuous off pixels is greater than or equal to the second threshold, and the number of off pixels in the determination region is the first When the threshold value is equal to or greater than 3, the pixel of interest is determined to be a negative thin line (off pixel thin line) pixel whose width is the number of consecutive off pixels. Here, the negative thin line is a thin line having a width composed of continuous off pixels and having a number of continuous off pixels.

  Further, in the negative thin line determination unit 42, the second threshold value, the third threshold value, and the determination region are set based on the number of continuous off pixels. Then, the negative thin line determination unit 42 generates negative thin line information that is information indicating whether or not each pixel of the input image data is a negative thin line pixel.

  The edge detection unit 43 determines whether or not each pixel of the input image data is a pixel constituting an edge, and detects a pixel in the edge part. Then, the edge detection unit 43 generates edge information that is information indicating whether each pixel of the input image data is an edge part.

  The halftone detection unit 44 detects an intermediate tone (halftone) region expressed by an area ratio of a white background and a black spot in the input image data. Then, the halftone detection unit 44 generates halftone information indicating whether each pixel of the input image data is a halftone region.

  The data processing unit 45 instructs the on-pixel conversion unit 46 to convert the input image data based on the positive thin line information, the negative thin line information, the edge information, and the halftone information. Here, the data processing unit 45 instructs the on-pixel conversion unit 46 to change the number of on-pixels of pixels that are not determined to be positive thin lines and negative thin lines in the edge portion but are not halftone regions. .

  The on-pixel conversion unit 46 converts the on-pixel of the input image data based on an instruction from the data processing unit 45. Here, the on-pixel conversion unit 46 performs conversion so as to reduce the number of on-pixels with respect to the black edge portion that is an edge constituted by on-pixels, and the white edge portion that is an edge constituted by off-pixels Converts to add on pixels.

  Next, the operation of the image processing apparatus 4 of this embodiment will be described in detail with reference to the drawings.

  First, the overall flow of the operation of the image processing apparatus 4 will be described with reference to FIG.

  First, the halftone detector 44 detects a halftone area in the input image data and generates halftone information (step S101).

  Next, the edge detection unit 43 determines whether or not each pixel of the input image data is a pixel constituting an edge, detects a pixel in the edge part, and generates edge information (step S102). . Details of the edge detection method will be described later.

  Then, the positive thin line determination unit 41 and the negative thin line determination unit 42 determine positive thin lines and negative thin lines in the input image data, and generate positive thin line information and negative thin line information (steps S103 and S104). A positive thin line determination method and a negative thin line determination method will also be described later.

  Next, based on the halftone information, edge information, positive thin line information, and negative thin line information obtained by the processing in steps S101 to S104, the data processing unit 45 is not a halftone but a pixel that is an edge portion. Among them, the on-pixel conversion unit 46 is instructed to change the number of on-pixels of pixels that are not positive thin lines and pixels that are not negative thin lines (step S105).

  Finally, the on-pixel conversion unit 46 is configured by the on-pixel among the edge portions that are not determined to be a positive tone line and a negative fine line, based on an instruction from the data processing unit 45 with respect to the image data. The black edge that is the edge to be converted is converted so as to reduce the ON pixels, and the ON edge is changed to be added to the white edge that is the edge constituted by the OFF pixels (step S106).

  Next, the edge detection method in step S102 will be described in detail with reference to FIG.

  First, the edge detection unit 43 selects one of the pixels of the input image data as a target pixel (step S201).

  If the on-pixel arrangement pattern of the eight pixels in the vicinity of the target pixel matches the preset pattern, the process proceeds to step S203, and the on-pixel arrangement pattern of the eight pixels in the vicinity of the target pixel is set in advance. If not, the process proceeds to step S204 (step S202).

  Next, in step S202, when it is determined that the on-pixel arrangement pattern of the 8 pixels in the vicinity of the target pixel matches the preset pattern, the edge detection unit 43 determines that the target pixel is the edge pixel. Is determined (step S203). Further, the edge detection unit 43 generates edge information indicating whether or not the pixel selected as the target pixel is an edge part.

  Then, the edge detection unit 43 determines whether there is a pixel that is not selected as the target pixel in the input image data (step S204). If there is still a pixel that has not been selected as the pixel of interest, the edge detection unit 43 returns to step S201 and detects the edge portion by the above processing. When the edge determination is performed for all the pixels of the input image data and the edge information is generated, the edge detection unit 43 ends the edge detection process.

  In the present embodiment, it has been described that the edge is detected by determining whether or not the arrangement pattern of the ON pixels of the 8 pixels in the vicinity of the target pixel matches a preset pattern. Is not limited to the above method as long as the edge portion is detected. For example, it may be determined whether or not the number of on-pixels in the vicinity of the pixel of interest is equal to or greater than a preset threshold value.

  Next, the positive thin line determination method in step S103 will be described in detail with reference to FIG.

  First, the positive thin line determination unit 41 sequentially selects one pixel of the input image data as a target pixel (step S301). Here, it is assumed that the positive thin line determination unit 41 has selected the 41st pixel of the image data of 9 rows × 9 columns as shown in FIG. Here, in FIG. 7, in order to help the understanding of the subsequent processing, numbers are assigned to each row, each column, and each pixel of the region of 9 rows × 9 columns centering on the pixel of interest in the input image data. It is a figure.

  Next, the positive thin line determination unit 41 determines whether the selected target pixel is an on pixel or an off pixel (step S302). If the target pixel 51 is an on pixel, the process proceeds to step S303. If the target pixel is an off pixel, the process proceeds to step S307.

  Next, the positive fine line determination unit 41 determines whether or not the number of ON pixels that are continuous in the horizontal direction or the vertical direction including the target pixel 51 is four or less (step S303). If the number of ON pixels that are continuous in the horizontal direction or the vertical direction is 4 or less, the process proceeds to step S304. If the number of ON pixels that are continuous in the horizontal direction and the vertical direction is more than 4, the process proceeds to step S307. Proceed to

  Next, the positive thin line determination unit 41 sets a first threshold value and a determination region (step S303).

  In this step S303, the positive thin line determination unit 41, as shown in FIG. 8A, if there is one continuous on-pixel 52 including the target pixel 51, the positive thin line of 1 dot width shown in FIG. The determination threshold value 1dPON is set as the first threshold value, and an area of 5 rows × 5 columns centering on the target pixel 51 is set as the determination area. Further, as shown in FIG. 8B, the positive thin line determination unit 41 has a two-dot width shown in FIG. 9 when there are two consecutive on pixels 52 including the target pixel 51 in the left-right direction. The positive line determination threshold 2dPON is set as the first threshold, and an area of 5 rows × 5 columns centered on the target pixel 51 is set as the determination area.

  Further, as shown in FIG. 8C, the positive thin line determination unit 41 has a three-dot width shown in FIG. 9 when there are three consecutive ON pixels 52 including the target pixel 51 in the vertical direction. The positive line determination threshold 3dPON is set as the first threshold, and an area of 7 rows × 7 columns centered on the target pixel 51 is set as the determination area. Then, as shown in FIG. 8D, the positive thin line determination unit 41 has a 4-dot width shown in FIG. 9 when there are four consecutive ON pixels 52 including the target pixel 51 in the left-right direction. A positive line determination threshold 4dPON is set as the first threshold, and an area of 9 rows × 9 columns centering on the pixel 51 of interest is set as the determination area.

  Next, the positive thin line determination unit 41 compares the first threshold value with the number of ON pixels in the determination region (step S304).

  If the number of on-pixels in the determination area is greater than or equal to the first threshold value in step S304, the target pixel 51 is determined to be a positive thin line pixel and the process proceeds to step S306, where the number of on-pixels in the determination area is the first. If it is less than the threshold, the process proceeds to step S307 (step S305).

  FIG. 10 shows a list of conditions determined to be positive thin line pixels described above. Here, the numbers for dot determination and background determination in FIG. 10 represent the pixel values of the pixels corresponding to the numbers in FIG. 7, that is, whether they are on or off.

  For example, as shown in FIG. 10, the 41st pixel, the 40th pixel, and the 39th pixel including the 41st pixel which is the target pixel are ON pixels, and the 38th pixel and 42nd pixel are When the pixel is an off pixel, the positive thin line determination unit 41 sets the determination region from the second row and the second column to the eighth row and the eighth column in FIG. 7, and the threshold value 3dPON is set as the first threshold value. Then, the positive thin line determination unit 41 determines that the 41st pixel is a pixel of a three-dot positive thin line when the number of ON pixels in the determination region is equal to or greater than the threshold value 3dPON.

  Next, the positive thin line determination unit 41 generates positive thin line information indicating that the pixel of interest is a positive thin line pixel (step S306). For example, the positive thin line determination unit 41 sets the ON pixel 52 determined to be a positive thin line pixel as shown in FIG. 11B to “1”, with respect to the positive thin line as shown in FIG. Positive thin line information with the pixel set to “0” is generated.

  Further, a case will be described in which the positive thin line determination unit 41 determines an isolated point constituted by on-pixels as shown in FIG. 12A or a halftone dot in halftone processing. For example, when determining the region as shown in FIG. 12A in the input image data, since the number of consecutive ON pixels in the left-right direction is two, 7 is set as the threshold 2dPON. The number of ON pixels is 6 and is smaller than the threshold value 2dPON. Further, since the number of consecutive ON pixels in the vertical direction is 3, the threshold value 3dPON is set to 10, but the number of ON pixels in the determination region is 6, which is smaller than the threshold value 3dPON. Accordingly, since the ON pixel 52 shown in FIG. 12A does not match the condition shown in FIG. 10, the positive thin line determination unit 41 changes the ON pixel 52 shown in FIG. Assuming that there is no information, information set to “0” is generated as shown in FIG.

  When positive thin line information is generated by determining whether or not all the pixels of the input image data are positive thin line pixels by the processing of steps S301 to S306, the positive thin line determination unit 41 performs positive thin line determination. The process ends (step 307).

  Next, the negative thin line determination method in step S104 will be described in detail with reference to FIG.

  First, the negative thin line determination unit 42 sequentially selects one pixel of the input image data as a target pixel (step S401). Here, it is assumed that the negative thin line determination unit 42 has selected the 41st pixel of the image data of 9 rows × 9 columns as shown in FIG.

  Next, the negative thin line determination unit 42 determines whether the selected target pixel is an on pixel or an off pixel (step S402). If the target pixel 51 is an off pixel, the process proceeds to step S403. If the target pixel is an off pixel, the process proceeds to step S407.

  Next, the negative thin line determination unit 42 determines whether or not the number of off pixels continuous in the horizontal direction or the vertical direction including the target pixel 51 is four or less (step S403). Here, when the number of consecutive off pixels in the left-right direction or the up-down direction is four or less, the process proceeds to step S404. When the number of off-pixels continuous in the left-right direction and the up-down direction is more than four, step S407 is performed. Proceed to

  Next, the negative thin line determination unit 42 sets a second threshold value, a third threshold value, and a determination region (step S403).

  In this step S403, the negative thin line determination unit 42, as shown in FIG. 14A, if there is one continuous off pixel 53 including the target pixel 51, the negative thin line having a 1-dot width shown in FIG. The determination threshold value 1dNOFF is set as the second threshold value, the threshold value 1dNON is set as the third threshold value, and an area of 5 rows × 5 columns centering on the target pixel 51 is set as the determination area. Further, as shown in FIG. 14B, the negative thin line determination unit 42 has a two-dot width shown in FIG. 15 when two consecutive off pixels 53 including the target pixel 51 are continuous. A negative line determination threshold value 2dNOFF is set as a second threshold value, a threshold value 2dNON is set as a third threshold value, and an area of 5 rows × 5 columns centering on the target pixel 51 is set as a determination area.

  Further, as shown in FIG. 14C, the negative thin line determination unit 42 has a three-dot width shown in FIG. 15 when three consecutive off pixels 53 including the target pixel 51 are consecutive. The negative line determination threshold value 3dNOFF is set as the second threshold value, the threshold value 3dNON is set as the third threshold value, and an area of 7 rows × 7 columns centering on the target pixel 51 is set as the determination area. Then, as shown in FIG. 14D, the negative thin line determination unit 42 has a 4-dot width shown in FIG. 15 when four consecutive off pixels 53 including the target pixel 51 are continuous. A negative line determination threshold value 4dNOFF is set as a second threshold value, a threshold value 4dNON is set as a third threshold value, and an area of 9 rows × 9 columns centering on the target pixel 51 is set as a determination area.

  Next, the positive thin line determination unit 41 compares the second threshold value with the number of off pixels in the determination region, and the third threshold value with the number of on pixels in the determination region (step S404).

  If the number of off pixels in the determination area is equal to or greater than the second threshold value and the number of on pixels in the determination area is equal to or greater than the third threshold value in step S404, the target pixel 51 is determined as a negative thin line pixel. The process proceeds to S406, and if the number of off pixels in the determination area is less than the second threshold or the number of on pixels in the determination area is less than the third threshold, the process proceeds to step S407 (step S405).

  FIG. 16 shows a list of conditions determined to be negative thin line pixels described above. Here, the numbers for dot determination and background determination in FIG. 16 indicate the numbers in FIG. 7 and the pixel values of the corresponding pixels, that is, whether they are on or off.

  For example, as shown in FIG. 16, the 41st pixel including the 41st pixel as the target pixel, the 32nd pixel is an off pixel, and the 23rd pixel and the 50th pixel are on pixels. The positive thin line determination unit 41 uses the third row and third column to the seventh row and seventh column in FIG. 7 as the determination region, and the threshold value 2dNOFF is set as the second threshold value, and the threshold value 2dNON is set as the third threshold value. Then, the positive thin line determination unit 41 determines that the 41st pixel is a pixel of a two-dot negative thin line when the number of OFF pixels in the determination region is equal to or greater than the threshold value 2dNOFF and the number of ON pixels in the determination region is equal to or greater than the threshold value 2dNON. .

  Next, the negative thin line determination unit 42 generates negative thin line information indicating that the target pixel 51 is a negative thin line pixel (step S406). For example, the negative thin line determination unit 42 sets the off pixel 53 determined to be a negative thin line pixel as shown in FIG. 17B to “2” for the negative thin line as shown in FIG. Negative thin line information with the pixel 52 set to “0” is generated.

  Further, a case will be described in which the negative thin line determination unit 42 determines an isolated point constituted by the off pixel 53 as shown in FIG. 18A or a halftone dot in halftone processing. For example, when determining the region as shown in FIG. 18A in the input image data, since the number of consecutive OFF pixels in the left-right direction is 2, the threshold 2dNOFF is set to 7 and the threshold 2dNON is set to 13. The number of off pixels in the determination area is 6, which is smaller than the threshold value 2dNOFF. Further, since the number of consecutive OFF pixels in the vertical direction is 3, the threshold 3dNOFF is set to 10 and the threshold 3dNON is set to 25. However, the number of OFF pixels in the determination region is 6, which is smaller than the threshold 3dNOFF. Therefore, since the off pixel 53 as shown in FIG. 18A does not match the condition as shown in FIG. 16, the negative thin line determination unit 42 changes the off pixel 53 shown in FIG. Assuming that the line is not a positive thin line, information “0” is generated as shown in FIG.

  When the negative thin line information is generated by determining whether or not all the pixels of the input image data are negative thin line pixels by the processes in steps S401 to S406, the negative thin line determination unit 42 performs negative thin line determination. The process ends (step 407).

  In this embodiment, the positive thin line when the number of continuous on pixels is 4 pixels or less and the negative thin line when the number of continuous off pixels is 4 pixels or less are described. However, the upper limit of the width of the thin line is determined. The present invention can be similarly applied even when the upper limit of the width of the thin line is defined as more than 4 pixels or less than 4 pixels.

In addition, as a result of experiments on various images, when determining a positive thin line, it was possible to accurately determine without determining by the number of off pixels. In this embodiment, a method that does not determine by the number of off pixels is adopted. However, even if the determination based on the number of off-pixels is performed in the present invention, the determination of the positive thin line can be similarly performed.
Further, in the present embodiment, when the negative thin line is determined, it is described that the determination based on the number of on pixels as well as the determination based on the number of off pixels is performed. This is because there was a certain condition. According to the present invention, it is possible to determine the negative thin line only by the determination based on the number of off pixels without performing the determination based on the number of on pixels when determining the negative thin line.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Terminal apparatus 3 Network 4 Image processing apparatus 11 CPU
12 Memory 13 Storage device 14 Communication IF
DESCRIPTION OF SYMBOLS 15 UI apparatus 16 Scanner 17 Printer 18 Control bus 41 Positive line determination part 42 Negative line determination part 43 Edge detection part 44 Halftone detection part 45 Data processing part 46 On pixel conversion part 51 Target pixel 52 On pixel 53 Off pixel

Claims (5)

Edge detection means for determining whether or not each pixel of binary image data subjected to screen processing is a pixel constituting an edge and detecting a pixel of an edge portion;
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an on pixel, and is a continuous number of on pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest When the number of ON pixels is equal to or less than a preset number and the number of ON pixels in a predetermined range of the determination area is equal to or greater than a preset first threshold, On-pixel thin line determination means for determining a pixel constituted by a pixel having an on-pixel thin line whose width formed by the pixels is a thin line having the number of continuous on-pixels,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an off pixel, and is a continuous number of off pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest The number of off pixels is equal to or less than a preset number, the number of on pixels in the judgment area in the preset range is greater than or equal to a preset second threshold value, and the number of off pixels in the judgment area is preset. An off-pixel thin line determination unit that determines that the width of the pixel of interest is a pixel of an off-pixel thin line that is a thin line of the number of continuous off-pixels when the target pixel is equal to or greater than the third threshold value,
The edge portion sac Chi detected by the edge portion detection means is constituted by the on-pixel thin line determination means and and the ON pixels has not been determined to any ON pixels thin line and off pixels thin line by OFF pixels thin line determination means The edge portion is converted so as to reduce the number of on-pixels, and neither the on-pixel thin line nor the off-pixel thin line is determined by the on-pixel thin line determination unit and the off-pixel thin line determination unit and On-edge conversion means for converting so as to add on-pixels to the configured edge portion ;
An image processing apparatus. The first threshold is set based on the number of consecutive on pixels,
The image processing apparatus according to claim 1, wherein the second threshold value and the third threshold value are set based on the number of consecutive off pixels.   The image processing apparatus according to claim 1, wherein a range of the determination area is set based on the number of continuous on pixels or the number of continuous off pixels. Edge detection means for determining whether or not each pixel of binary image data subjected to screen processing is a pixel constituting an edge and detecting a pixel of an edge portion;
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an on pixel, and is a continuous number of on pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest When the number of ON pixels is equal to or less than a preset number and the number of ON pixels in a predetermined range of the determination area is equal to or greater than a preset first threshold, On-pixel thin line determination means for determining a pixel constituted by a pixel having an on-pixel thin line whose width formed by the pixels is a thin line having the number of continuous on-pixels,
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an off pixel, and is a continuous number of off pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest The number of off pixels is equal to or less than a preset number, the number of on pixels in the judgment area in the preset range is greater than or equal to a preset second threshold value, and the number of off pixels in the judgment area is preset. An off-pixel thin line determination unit that determines that the width of the pixel of interest is a pixel of an off-pixel thin line that is a thin line of the number of continuous off-pixels when the target pixel is equal to or greater than the third threshold value,
The edge portion sac Chi detected by the edge portion detection means is constituted by the on-pixel thin line determination means and and the ON pixels has not been determined to any ON pixels thin line and off pixels thin line by OFF pixels thin line determination means The edge portion is converted so as to reduce the number of on-pixels, and neither the on-pixel thin line nor the off-pixel thin line is determined by the on-pixel thin line determination unit and the off-pixel thin line determination unit and On-edge conversion means for converting so as to add on-pixels to the configured edge portion ;
Output means for outputting the image data converted by the on-pixel conversion means;
An image forming apparatus. For each pixel of binary image data that has undergone screen processing, determining whether or not it is a pixel that constitutes an edge, and detecting a pixel at the edge portion;
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an on pixel, and is a continuous number of on pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest When the number of ON pixels is equal to or less than a preset number and the number of ON pixels in a predetermined range of the determination area is equal to or greater than a preset first threshold, Determining the width of the pixel to be a pixel of an on-pixel thin line that is a thin line of the number of continuous on-pixels;
One of the pixels constituting the image data is sequentially selected as a pixel of interest, the pixel of interest is an off pixel, and is a continuous number of off pixels that are continuous in the horizontal direction or the vertical direction including the pixel of interest The number of off pixels is equal to or less than a preset number, the number of on pixels in the judgment area in the preset range is greater than or equal to a preset second threshold value, and the number of off pixels in the judgment area is preset. Determining that the pixel of interest is a pixel of an off-pixel thin line that is a thin line of the number of consecutive off-pixels when the pixel of interest is equal to or greater than the third threshold,
Detected edge portion sac Chi, for the edge portion formed by and on pixels not been determined to any ON pixels thin line and off pixels thin line, converts to reduce the on-pixel, on a pixel For an edge portion that is not determined to be either a fine line or an off-pixel thin line and is composed of off-pixels, a step of converting to add on-pixels ;
A program that causes a computer to execute.

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