JP2011193074A - Image information processing method and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image information processing method capable of clarifying the contour of a vertical line without changing the original line width against a vertical line part of an average width of one pixel. <P>SOLUTION: The image information processing method modulates an area of a colored image in one pixel, based on a signal showing a multilevel image of three or more values. Four pixels of interest continuous in main scanning direction are extracted. When both ends of the four pixels are white and either or both of two pixels in the middle are not white, as for a left pixel of the two pixels in the middle, a pulse of an area ratio is generated according to a density in a one-sided fashion so that its finishing end may come to the right end of the pixel. As for a right pixel of the two pixels in the middle, a pulse of an area ratio is generated according to the density in a one-sided fashion so that its starting end may come to the left end of the pixel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement in an image information processing method and an image forming apparatus for modulating the area of a concentrated portion (that is, a non-white portion) occupying one pixel based on a signal representing a multi-valued image having three or more values. In particular, the present invention relates to an image information processing system that improves the clarification of vertical lines and an image forming apparatus that employs the system.

2. Description of the Related Art Conventionally, there is an image information processing system that modulates the area of a concentrated portion other than white occupying one pixel based on a signal representing a multi-valued image having three or more values.
In order to express a gradation image such as a halftone without changing the resolution, there is known an image forming apparatus that changes a light and shade level within one pixel. For example, in Patent Document 1, a method of detecting whether or not a vertical line has a width of 1 dot based on pattern data of a pixel of interest and a pixel adjacent in the main scanning direction, and converting the data so that the width of the vertical line becomes thicker. Has been proposed. Patent Document 2 proposes a method for controlling the recording start position based on the density of pixels adjacent to the target pixel.
However, in the technique described in Patent Document 1, when a vertical line having a width of 1 dot is detected, the data is converted so that the vertical line becomes thicker. May become thicker.
Further, in the image processing method disclosed in Patent Document 2, attention is paid only to adjacent pixels, and only the density is referred to. Therefore, a photograph that is not necessarily an image portion that should originally have a clear outline such as a vertical line or a character. The recording start position is controlled even for data representing halftones, and the edges are emphasized, which may be inappropriate for halftone expression.

JP 2001-232858 A JP-A-6-89338

  An object of the present invention is to propose an image information processing method capable of clearly expressing the outline of a character image portion having a vertical line in the sub-scanning direction and a line width of one pixel existing in an image, and an average of 1 It is an object of the present invention to provide an image information processing method capable of clarifying the outline of a vertical line without changing the original line width with respect to the vertical line portion of the pixel width.

In order to achieve the above object, the present invention provides:
An image information processing method for modulating the area of a concentrated portion in one pixel based on a signal representing a multi-valued image of three or more values, extracting four pixels of interest that are continuous in the main scanning direction, If the pixels at both ends of the four pixels are white and one or both of the two intermediate pixels are not white, the area ratio pulse corresponding to the density is applied to the left pixel of the intermediate two pixels. It is generated by shifting it so that the end is at the right end of the pixel, and for the right pixel, it is generated by shifting the pulse with an area ratio corresponding to its density so that the start is at the left end of the pixel. This is an image information processing method.
In the present invention, it is generally possible to employ a method in which the area of the concentrated portion in one pixel is modulated stepwise in accordance with the number of processing bits of the CPU that performs the image forming process.
The image forming processing method according to the present invention is widely used in image forming apparatuses.
.

As described above, according to the present invention, when one or both of the intermediate two pixels are not white, the left pixel of the intermediate two pixels has an area ratio pulse corresponding to the density at the end of the pixel. The right pixel is generated by shifting it so that it comes to the right end of the pixel, and for the right pixel, a pulse with an area ratio corresponding to its density is generated by shifting it so that its starting end comes to the left end of the pixel. The thickness of the vertical line is not changed, and since the white area is not included in the vertical line, a clear vertical line can be formed.

The pixel structure figure for demonstrating the prior art of this invention. 1 is a pixel structure diagram for explaining image processing in an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of processing means of an entire image forming apparatus according to an embodiment of the present invention. 6 is a flowchart showing a processing procedure of a main control unit for explaining the contents of image processing of the image forming apparatus according to the embodiment of the present disclosure.

Next, the outline of the present invention will be described with reference to FIG. 1 (conventional example) and FIG. 2 (present invention).
FIG. 1A schematically shows a part of a gradation image that is a multi-valued image of three or more values captured from an image reading device such as an image scanner. Pixels for one line in the main scanning direction are shown in FIG. Four pixels of the data are extracted and represented. For example, in the case of a gradation image represented by 4 bits, a pixel is 0 for white and 15 for black, and halftone is represented by gradation data representing a density of 1 to 14 therebetween.
The illustrated example shows a pixel by an image information processing system that expresses the density of a pixel by modulating the area of a dense portion occupied in one pixel based on a signal that represents a multi-valued image of three or more values. That is, the width e of the black portion of each pixel P in FIG. 1A corresponds to the density of the pixel. In FIG. 1A, since the areas (width e) of the dense portions of the four pixels are all the same, this represents a set of four pixels with uniform gradation (density).
In FIG. 1B, there are fewer black portions from left to right. In other words, the gradation changes from left to right. However, in the actual gradation, since the variation in density between adjacent pixels is very small, FIG. 1B shows an example in which the variation is extremely large.

In such an image information processing system that expresses the density of a pixel by modulating the area of a dense portion in one pixel, the line segment in the sub-scanning direction (vertical) is the left end and the right end as shown in FIG. There is a white pixel, and a dense pixel including black is sandwiched between white pixels on the left and right. FIG. 1C shows a part of a line segment in the vertical direction (sub-scanning direction) in which two of the four pixels arranged in the main scanning direction have high density. The thicker the line segment, the greater the number of intermediate pixels.
When creating such gradation data, for the above intermediate density pixels, a black area having a different area according to the density is arranged adjacent to the white area, and the higher the pixel density, the larger the area of the black area. Although (width e) is expressed to be wide, in the conventional image information processing method, the rule of arrangement of the black region is constant. For example, in the example of FIG. FIG. 1 (d) shows an example of being shifted to the right end (that is, the end point), and FIG.

  As shown in FIG. 1 (c) or (d), the vertical line represented by the image information processing method representing the density of the pixel by modulating the area of the concentrated image in one pixel as described above. , A white region is sandwiched between two black regions. For this reason, there is a problem in the clarity of the line segment as compared with the case where the black region is arranged as one vertical line, and the vertical line is slightly blurred.

In view of the above, the present invention concentrates the black area so that the white area is not sandwiched between the black areas of the two pixels arranged in the main scanning direction. It aims at clarifying a vertical line by arranging.
Specifically, for example, as shown in FIGS. 2A, 2B, and 2C, for the black regions B2 and B3 included in the intermediate two pixels P2 and P3 that are dense pixels, the left pixel P2 The black region B2 included in the right pixel P3 is shifted to the right end of the left pixel P2, and the black region B3 included in the right pixel P3 is shifted to the left end of the right pixel P3. As a result, the black region B23 of one black color in which the white region is not included between the left black region B2 and the right black region B3. As a result, the vertical lines are clearly expressed without blurring.

In the above example, various widths (indicating density) of one pixel in the main scanning direction can be considered. If the width e of the black area included in the left and right pixels is both half of the total width L of the pixel, the width of the black area B23 concentrated in the center is equal to the width L of the pixel, and is exactly one pixel wide. A vertical line will be formed.
However, since the width e of the black region varies depending on the density of the pixel, the total width of the black region concentrated in the center may be smaller or larger than the total width L of the pixel, but the average If this is the case, it is likely to be applied to a vertical line with a width of one pixel.

The outline of the present invention has been described above. Next, a specific method for carrying out the present invention will be described.
First, the outline of the image forming apparatus X according to the embodiment of the present invention will be described.
FIG. 3 is a configuration block diagram of the image forming apparatus according to the present embodiment. In the image forming apparatus 1 shown in FIG. 3, the main control unit 2 is a control unit including a CPU and the like, and is a processing unit that performs overall control of operations of each unit in the image forming apparatus 1. The operation unit 3 is a control panel including a display unit such as a liquid crystal panel and operation keys, and is an input unit for a user to operate the image forming apparatus 1.
The image processing unit 4 is a processing unit for converting the image data of the original read by the image reading unit 10 into image data for printing that matches the printer (for example, image data that matches the toner to be used). , Image editing (resolution change, enlargement / reduction, rotation, etc.) is also performed.
The image processing unit 4 also performs image information processing that represents the density of a pixel by modulating the area of the concentrated image occupying in one pixel to be processed by the present invention. The contents will be described later with reference to the flowchart of FIG.

  The print control unit 5 is a control unit for printing the printing image data generated by the image processing unit 4 on a sheet. The print control unit 5 controls a transfer unit 7 that transfers toner to a sheet, and also controls a print engine 6 including a printing sheet feeding mechanism (for example, a pressure roller 8a and a fixing roller 8b) to perform a printing operation. Execute.

  The image reading unit (image reading device) 10 is a part that constitutes a scanner that reads a document, and irradiates the document or white reference plate 106 with light from a light source that moves along the contact glass 101, so that the document or white reference is scanned. An optical component such as a CCD 13 that measures reflected light from the plate 106 and converts it into an electrical signal is provided. The image reading control unit 11 in the image reading unit 10 is a control unit including a CPU and the like, and is a processing unit that controls the operation of each unit in the image reading unit 10 in an integrated manner.

  The scanner feeding mechanism 12 is a processing unit that controls a document reading mechanism (for example, a document feeding mechanism or a mirror moving mechanism). The color CCD sensor 13 is a CCD image sensor for reading a document, and is composed of three line sensors for reading each color of R (red), G (green), and B (blue). The line sensors for each color B are composed of two line sensors that read odd lines (ODD) and even lines (EVEN).

  The AFE (analog front end) 14 is a three-channel type analog front end, which amplifies the image signal read from the color CCD sensor 13 and performs digital conversion by ODD / EVEN correction, offset correction, and A / D conversion. Output data.

The gain setting control unit 19 performs gain setting for the amplifier 15 in the AFE 14 based on image data obtained by reading the white reference plate 106 with the color CCD sensor 13. The gain setting control unit 19 includes a color gain setting unit 19A and a monochrome gain setting unit 19B. After the power of the image forming apparatus 1 is turned on, the AFE 14 is repeatedly performed in both the color mode and the monochrome mode. AGC (automatic gain setting control of the amplifier 15) is performed, and the gain setting value for color (gain setting value for color mode) obtained at that time and the gain setting value for monochrome (gain setting value for monochrome mode) ) Is stored in the storage unit 30 composed of SRAM (Static Random Access Memory) or the like.
The procedure for setting the gain is as shown in FIG. 2, and will be further described later.

  In addition, when the gain setting control unit 19 performs the gain setting in the color mode and the monochrome mode by the AGC, the control timing setting for the AFE 14 corresponding to the mode is also performed at the same time. For example, timings such as a synchronization signal and a data reading signal for the AFE 14 are set at the same time. The timing setting information is also stored in the storage unit 30 as color timing setting information and monochrome timing setting information.

  The image data reading unit 20 extracts image data within the range of the document from the image data read from the AFE 14, and the correction processing unit 21 adjusts the image of the image data. The correction processing unit 21 performs MTF (Modulation Transfer Function) correction of the optical system and shading correction based on the white reference data on the image data of the original read from the AFE 14. Note that the shading correction corrects a substantial sensitivity variation among the photoelectric conversion elements due to variations in characteristics of the photoelectric conversion elements of the color CCD sensor 13 or variations in the light emission amount of the light source. However, since it is not directly related to the present invention, a detailed description is omitted here.

  The white reference data setting unit 22 includes a color white reference data setting unit 22A and a monochrome white reference data setting unit 22B, and is based on image data of the white reference plate 106 output from the AFE 14. , A processing unit that acquires white reference data for each of the color mode and the monochrome mode. The color white reference data (color mode white reference data) and monochrome white reference data (monochrome mode white reference data) acquired in this way are stored in the storage unit 30.

  The storage unit 30 stores data necessary for processing in the image forming apparatus 1. The storage unit 30 stores color gain setting values 31, monochrome gain setting values 32, color white reference data 33, monochrome white reference data 34, color timing setting information 35, monochrome timing setting information 36, and correction. Data (MTF, shading correction data, etc.) 37 is stored. The storage unit 30 includes an image memory 38, and image data 39 obtained by reading a document is stored in the image memory 38.

Next, with respect to the image processing for clarifying the vertical lines (line segments in the sub-scanning direction) executed by the image processing unit 4 for the image data 39 stored in the image memory 38, refer to the flowchart of FIG. To explain.
The flowchart shown in FIG. 4 shows the processing procedure of the main control unit 2 that controls the image processing unit 4, and S1, S2,... Are identifiers of processing procedures (steps).
This process is performed when the main control unit 2 reads out the density data of four pixels of interest P1 to P4 arranged in series from one line of data of the image data 39 stored in the image memory 38. Be started.
First, in S1, the main control unit 2 detects the respective image density values for the data of the two pixels P1 and P4 at the left and right ends of the four target pixels P1 to P4, all of which are white pixels ( For example, in the case of 4-bit data, it is determined whether or not 0). If it is determined that the density value of any of the pixels P1 and P4 is other than 0, the process proceeds to normal image processing (S10) that is not vertical line detection processing.
If both the left and right pixels P1 and P2 are determined to have a density value of 0, that is, a white pixel (Yes in S1), the main control unit 2 may have detected a part of the vertical line. Next, in S2, one of or both of the two pixels P2 and P3 in the middle of the four pixels of interest are dense pixels (pixels having a density value other than 0). It is determined whether or not.
Here, when it is determined that both of the middle two pixels P2 and P3 are white pixels, these are not recognized as a part of the vertical line, and therefore the normal processing other than the vertical line detection process is performed. The process proceeds to image processing (S10).

If it is determined in S2 that one or both of the intermediate two pixels P2 and P3 are dense pixels (density value ≠ 0), the left pixel P2 of the intermediate two pixels P2 and P3 is determined. Calculates a pulse with an area ratio corresponding to the density (S3), and generates a signal that is shifted so that the end of the pulse comes to the right end of the pixel (S4).
For the right pixel P3, a pulse having an area ratio corresponding to the density is calculated (S5), and a signal shifted so that the end of the pulse comes to the left end of the pixel is generated (S6).
Thereafter, the main control unit 2 outputs the pulse signal calculated as described above, and the image forming unit that receives the pulse signal performs image forming processing.
As described above, in the present invention, the intermediate two pixels P2 and P3 are shifted so that the respective black areas are in contact with each other, and on average, this is useful for clarifying a vertical line having a width of one pixel. .

In the above description, it is assumed that a vertical line is detected if any one of the two intermediate pixels is a dense pixel. This is because if there is density in any of the intermediate pixels, the left and right ends are white, so it may be considered that there is a line segment there.
In the above embodiment, since attention is paid to four pixels arranged in the main scanning direction, attention is paid to one vertical line having a thickness substantially equivalent to one pixel. An image having a thickness of about one pixel in the vertical direction is applied not only to vertical lines but also to Kanji characters having one vertical character element.
In the above embodiment, all judgment control is performed by the main control unit 2, but it is also within the scope of the present invention to achieve a part or a plurality of these processes by individual circuits. Needless to say.

  The present invention is applied to an image information processing system that expresses the density of a pixel by modulating the area of a concentrated image occupying one pixel and an image forming apparatus that employs this image information processing system.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 2 ... Main control part 4 ... Image processing part 5 ... Print control part 10 ... Image reading part e ... Black area width B1, B2 ... Black area P1-P4 ... Pixel

Claims (3)

  An image information processing method that modulates the area of a colored image in one pixel based on a signal representing a multi-valued image that is ternary or higher, and extracts four pixels of interest that are continuous in the main scanning direction. When the pixels at both ends of the four pixels are white and both of the middle two pixels are not white, for the left pixel of the middle two pixels, a pulse having an area ratio corresponding to the density is terminated at its end. Image information processing that is generated by shifting it so that it comes to the right end of the pixel, and for the right pixel, a pulse with an area ratio corresponding to its density is generated by shifting it so that its starting end comes to the left end of the pixel. method.   2. The image information processing system according to claim 1, wherein the area of the colored image in one pixel is modulated at a stage corresponding to the number of processing bits of a CPU that performs image forming processing.   An image forming apparatus employing the image information processing method according to claim 1.

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