JP2011143671A - Image processing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem with a recorder having a different resolution in a main scanning and a sub-scanning, wherein an image is degraded and a printed character is hardly visible, when a narrow line is recorded vertically in the direction of a low resolution side. <P>SOLUTION: An image processing apparatus has a character-direction determiner (203) for determining the direction of a character contained in a digital image data, an image rotator (205) which rotates the digital image data by 90 degree when the determined direction of the character is equal to the sub-scanning direction of the recorder, and a controller (206) for controlling the recorder so as to print the rotated digital image. The direction of the character is determined, and the narrow line of the character is rotated so as to be parallel to the scanning direction of the low resolution side, to be printed. When received instruction of copy execution by button pressing down of an operation panel (107) in S301, the CPU (206) instructs execution of scanning operation for a scanner unit part (101) according to a program stored in a ROM (209). Then, in S302, the CPU (206) checks a manuscript size. Further, in S303, the CPU (206) determines the direction of the character. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement in image quality of a recording apparatus having different main scanning and sub-scanning resolutions.

  Conventional electrophotographic recording apparatuses include recording apparatuses having different main scanning and sub-scanning resolutions. In this case, normally, the resolution of main scanning is high and the resolution of sub-scanning is low.

  The resolution of main scanning is determined by the speed at which the laser is turned on and off. This is realized by speeding up the drive circuit of the laser transmitter and the PWM signal generation circuit (for example, Non-Patent Document 1). On the other hand, the resolution of the sub-scan is determined by the speed of the developing device, the recording medium transport device, the toner fixing device, and the like. These are determined by the material of the developing device, the accuracy of the material of the conveying device, the performance of the motor, and the performance of the fixing device. That is, the increase in the speed of the sub-scanning is directly linked to the increase in the price, and in recent years, each printer manufacturer has been reducing the resolution of the sub-scanning in order to increase the speed and the price of the recording apparatus.

  Usually, the resolution of the main scanning / sub-scanning of the electronic image input to the recording apparatus and the resolution of the main scanning / sub-scanning of the recording apparatus must be the same. That is, it is necessary to input digital image data of main scanning 600 dpi and sub-scanning 300 dpi to a recording device of main scanning 600 dpi and sub-scanning 300 dpi.

  In this case, it is advantageous to compare the main scanning and sub-scanning resolutions of the input electronic image and select a process that rotates 90 degrees so as to match the resolution of the output device (for example, Patent Document 1). For example, it is assumed that digital image data of main scanning 600 dpi and sub scanning 1200 dpi is printed by a recording device of main scanning 1200 dpi and sub scanning 300 dpi. If the technique for selecting the 90-degree rotation process is not employed, the sub-scanning is reduced from 1200 dpi to 300 dpi, so that a ¼ decimation process is required. On the other hand, when the technique for selecting the 90-degree rotation process is adopted, the main scanning and the sub-scanning are reversed by the rotation process. Since the main scanning is 1200 dpi, there is no need for a thinning process, and in the sub-scanning, a half thinning process is performed from 600 dpi to 300 dpi. That is, it is possible to prevent a reduction in the resolution of the entire image by rotating.

JP 11-320197

“Canon SATARA Monochrome Laser Beam Printer MFP Catalog”, Canon Inc., 2009, p.08

  However, in Patent Document 1, characters in digital image data may not be printed neatly. For example, this is the case of fonts and ruled lines such as Mincho type characters with many horizontal thin lines. When an electronic image of main scanning 600 dpi and sub scanning 1200 dpi is printed as it is without rotation processing, since the main scanning performs high resolution processing from 600 dpi to 1200 dpi, the vertical fine lines are not deteriorated. On the other hand, if the rotation process is performed, the vertical thin line becomes a horizontal thin line, which is significantly deteriorated by the half-thinning process of sub-scanning.

  An object of the present invention is to enable a computer to perform an image output apparatus capable of suppressing degradation of resolution at the time of outputting an image, particularly for a text document or line drawing document, and a process for suppressing degradation of the resolution of an image at the time of image output. Is to provide a program.

  An image processing apparatus for controlling a recording apparatus having a sub-scanning resolution smaller than a main-scanning resolution, wherein the character direction determining means determines the character direction included in the digital image data, and the determined character direction is the sub-scanning of the recording apparatus An image processing apparatus is provided that includes an image rotation unit that rotates digital image data by 90 degrees when the direction coincides with a direction, and a control unit that controls a recording apparatus to print the rotated digital image.

  According to the present invention, it is possible to suppress degradation of the resolution of characters and line drawings in a printed matter output by a recording apparatus having low resolution in sub-scanning.

1 is an overall view of an MFP used in an embodiment of the present invention. It is a controller configuration of the MFP shown in FIG. It is a flowchart common to Examples 1-3. 3 is a flowchart of character direction determination (method using a band-pass filter) according to the first embodiment. It is an example of a main scanning band pass filter. It is an example of a sub-scanning band pass filter. 3 is a flowchart of character direction determination (a method using pixel continuity detection) according to the first exemplary embodiment. 12 is a user input flowchart for character direction determination according to the second exemplary embodiment. It is an example of the user input screen of Example 2. 10 is a flowchart of character direction determination according to the third embodiment.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In the following description, “character direction” indicates the vertical direction of one character.

<Example 1>
FIG. 1 is a configuration diagram of an MFP (multifunction printer) constituting this embodiment. The MFP includes a scanner unit (101), a recording device (102), a manual feed port (103), a first-stage recording paper cassette (104), a second-stage recording paper cassette (105), and a paper discharge section (106 ) And an operation panel (107). In addition, a controller board is installed in the MFP and is controlled by the controller board. The scanner unit (101) and the recording device (102) are capable of handling originals and recording papers up to A3 vertical size. Of course, the manual feed slot (103) and recording paper cassettes (103, 104) are also available. According to

  Next, the controller board will be described in detail with reference to FIG. An operation unit interface (201) 201 connects the operation panel (107) and the data bus (207). A scanner interface 202 connects the scanner unit unit (101) and the data bus (207). A character direction determination unit 203 performs a character direction determination process. An image processing unit 204 performs spatial filter processing, resolution conversion processing, and binarization processing. Reference numeral 205 denotes an image rotation unit that performs rotation processing such as 90 degrees, 180 degrees, and 270 degrees. Note that 203-205 may be realized as hardware or implemented as a program. Reference numeral 206 denotes a CPU which executes control of each unit, calculation on digital image data, and the like according to a program stored in the ROM (209) (control means). A RAM 208 is used as a storage area for temporarily storing digital image data, program data, counter values, and the like. A printer interface 210 connects the recording device (102) and the data bus (207). Reference numerals 211 and 212 denote USB and LAN interfaces, which are interfaces for connecting to a personal computer (not shown).

  Next, the implementation procedure of Example 1 is demonstrated along the flowchart of FIG. In S301, when a copy execution command is received by pressing a button on the operation panel (107), the CPU (206) commands the scanner unit (101) to execute a scan operation according to a program stored in the ROM (209). . The scanner unit unit (101) converts a document into electronic image data by reading a document mounted on a document table (not shown). The electronic image data is converted into a digital image by the scanner unit unit (101). Since this is discretized data, the resolution of main scanning and sub scanning is set. In the present embodiment, the description will be continued on the assumption that the image data is converted into digital image data of main scanning 600 dpi and sub-scanning 600 dpi, which is common in recent electrophotographic MFPs. The digital image data transmitted from the scanner unit (101) is temporarily stored in the RAM (208) through the data bus (207).

  In this embodiment, the digital image data is generated by the scanner unit (101), but the present invention is not limited to this. That is, digital image data can also be input from the LAN interface (212) or the USB interface (211) according to a print instruction from a personal computer (not shown). In this case, the transferred digital image data is temporarily stored in the RAM (208), and thereafter processed in the same manner as when the scanner unit (101) is used.

  In step S302, the CPU (206) confirms the document size. In general, document size information is sent from a scanner unit (101) or a personal computer (not shown). It is also possible to acquire document size information by input from the operation panel. At this time, it is determined whether or not the document size corresponds to the present invention. In the case of the recording apparatus (102) capable of printing up to A3 vertical size, the corresponding original size is up to A4 size in the present invention. This is because, in the embodiment of the present invention, there is a case where printing is performed by rotating 90 degrees, and the recording device (102) up to A3 vertical size cannot print on A3 horizontal size media. If the document is compatible with the corresponding document size, the process of the CPU (206) proceeds to S303, and if not, the process proceeds to S307.

  Next, in S303, the CPU (206) determines the character direction. Here, it is determined whether or not to rotate, and the rotation flag is set as an output value. The CPU (206) transfers the digital image data stored in the RAM (208) to the character direction determination unit (203). The character direction determination unit (203) executes a process for obtaining a rotation flag. Flow charts of processing of the character direction determination unit (203) are shown in FIGS. FIG. 4 shows a method using band-pass filters for main scanning and sub-scanning. FIG. 7 shows a method using pixel continuity detection in main scanning and sub-scanning. In the embodiment of the present invention, either of the methods shown in FIGS. 4 and 7 may be used.

(Method using band-pass filter)
In S401 of FIG. 4, the digital image data stored in the RAM (208) is read into an area called Img of the character direction determination unit (203). Note that the storage area of the character direction determination unit (203) is not particularly illustrated because it is common to share the storage area of the RAM (208).

  S402 is a loop end for scanning the entire area of main scanning and sub-scanning. x is the main scanning direction, and y is the sub-scanning direction. The number of pixels is Nx pixels for main scanning and Ny pixels for sub-scanning.

In step S403, the character direction determination unit (203) performs band pass filtering in the main scanning direction, and stores the filtered image data in an area called Img ′. An example of the band pass filter used at this time is shown in FIG. Note that the size and constant of the band-pass filter are arbitrary because they depend on the size of characters to be extracted. Furthermore, when there are a plurality of extracted bands, a method of adding to the output (Img ') using a plurality of filters is also conceivable.

  In S404, the character direction determination unit (203) compares Img ′ [x, y] with the threshold value 1. If the value is larger than the threshold value 1, MainCount is incremented in S405. The threshold value 1 is an arbitrary value, and by adjusting this, the MainCount count can be adjusted. If Img ′ [x, y] is a threshold value 1 or less in S404, MainCount is not counted up.

  The above operation is performed for all areas of the digital image data (S406). Finally, the value of MainCount is obtained. MainCount is a feature quantity of main scanning.

  S407 to S412 execute a process of obtaining SubCount (sub-scan feature quantity) corresponding to S401 to S406, which is the process of acquiring the main scan feature quantity described above. However, S409, S410, and S411 are changed for sub-scanning. An example of the band-pass filter of S409 is shown in FIG.

  In S410, Img ′ [x, y] is compared with the threshold value 2. If the value is larger than the threshold value 2, SubCount is incremented in S411. The threshold value 2 is an arbitrary value like the threshold value 1. If Img ′ [x, y] is a value equal to or smaller than the threshold 2 in S410, SubCount is not counted up.

  In S413, the character direction determination unit (203) compares SubCount and MainCount. When SubCount is larger, the feature amount is larger in the sub-scanning direction than in the main scanning direction. That is, it can be determined that there are many horizontal lines in the character portion. Therefore, 1 is set to the rotation flag in S414. If SubCount is less than or equal to MainCount, the rotation flag is set to 0.

(Method using pixel continuity detection)
In S701 of FIG. 7, the character direction determination unit (203) reads the digital image data stored in the RAM (208) into an area called Img of the character direction determination unit (203). Note that the storage area of the character direction determination unit (203) is not particularly illustrated because it is common to share the storage area of the RAM (208).

  S702 is a loop end for scanning the entire area of main scanning and sub-scanning. x is the main scanning direction, and y is the sub-scanning direction. The number of pixels is Nx pixels for main scanning and Ny pixels for sub-scanning.

  In S703, the character direction determination unit (203) performs an image binarization process. The binarization processing method is not particularly specified, but here, simple binary processing is performed. Arbitrary binarization threshold is prepared. The scanner unit unit 101 expresses luminance information, that is, white: 255, black: 0. Therefore, if the value is lower than the binarization threshold, “1” (black) is set, and if the value is higher, “0” (white) is set so as to be inverted with respect to the luminance information.

  In step S704, the character direction determination unit (203) performs vertical line counting. The method of counting vertical thin lines detects a place where black continues in the main scanning direction. If the number of continuous blacks in the main scanning direction is, for example, 25 pixels or more and less than 50 pixels (about 1 mm to 2 mm at 600 dpi), it is determined as a vertical line and 1 is added to the count (MainCount). By performing the above process in the sub-scanning direction, vertical lines are counted.

  Next, in S705, the character direction determination unit (203) performs horizontal line counting. The horizontal thin line is counted by detecting a place where black continues in the sub-scanning direction. If the number of continuous blacks in the sub-scanning direction is, for example, 25 pixels or more and less than 50 pixels (about 1 mm to 2 mm at 600 dpi), it is determined as a horizontal line and 1 is added to the count (SubCount). By performing the above processing in the main scanning direction, horizontal lines are counted.

  The above operation is performed for all areas of the digital image data (S706). Finally, MainCount (main scanning feature value) and SubCount (sub-scanning feature value) are obtained.

  In S707, the character direction determination unit (203) compares the results of the fine line counts in the vertical (MainCount) and horizontal (SubCount). If the horizontal line is larger as a result of the comparison, 1 is set in the rotation flag in S708. That is, it is determined that there are many horizontal lines, and the rotation output is selected. If the horizontal line is below the vertical line, the rotation flag is set to 0.

  This is the end of the description of the character direction determination unit (203), and the description returns to FIG. In S304, the CPU (206) detects whether 1 is set in the rotation flag. If the rotation flag is 1, the process proceeds to S305, and if the rotation flag is 0, the process proceeds to S307.

  If the rotation flag is 1 in S304, it is determined in S305 whether or not recording paper suitable for the rotation process can be fed. If it is determined that the paper can be fed, the process proceeds to S306, and if it is determined that the paper cannot be fed, the process proceeds to S307.

  In S306, a 90-degree rotation process is performed. At this time, the character direction determination unit (203) uses the image rotation unit (205) of FIG.

  In step S307, sub-scanning resolution conversion processing is performed. In step S308, main-scanning resolution conversion processing is performed. In the first embodiment, it is assumed that a recording device (102) with 600 dpi main scanning and 300 dpi sub scanning is used. Further, as described above, the resolution read by the scanner unit unit (101) is assumed to be main scanning 600 dpi and sub scanning 600 dpi. Therefore, in S307, a half thinning process is performed in the sub-scanning direction. The implementation method is not particularly specified in the present invention, but generally linear interpolation is used.

  In step S309, the CPU (206) performs image calculation processing. This S309 can be performed by the image processing unit (204) in FIG. Specifically, density conversion processing, spatial filter processing, and halftone processing. Since these processes are not particularly specified in the present invention, the details are omitted. However, it is assumed that a binary pseudo gradation image is obtained as a result of these processes.

  Next, in S310, the CPU (206) performs a printing process. At this time, it is assumed that A4 horizontal recording paper is loaded in the first cassette (104) of FIG. 1, and A4 vertical recording paper is loaded in the second cassette (105). For example, if the document is an A4 size document, the A4 landscape recording sheet is fed from the first stage cassette (104) unless the rotation process of S306 is performed. On the other hand, when the rotation processing is performed in S306, A4 vertical recording paper is fed from the second cassette (105). However, if there is no appropriate size recording paper in the cassette, a message prompting the user to feed paper from the manual feed slot (103) is displayed on the screen of the operation panel (107) through the operation unit interface (201). indicate.

  According to the present embodiment described above, it is possible to automatically suppress degradation of the resolution of characters and line drawings in a printed matter output by the recording apparatus (102) whose sub-scan has a low resolution. With the above-described configuration, in the case of a Chinese character that requires the resolution of the horizontal line, the problem of the horizontal line being crushed / disappearing due to the low resolution of the sub-scan can be solved.

<Example 2>
In the second embodiment, in the character direction determination step of S303 in FIG. 3, screen display is performed to prompt the user to select and input. FIG. 8 shows a flow relating to this processing. Since other processes are the same as those in the first embodiment, the description thereof is omitted.

  In S801, the CPU (206) instructs the operation unit interface (201) to display a UI screen. An example of the UI screen is shown in FIG. The user selects a desired character direction and original direction from the samples (i) to (iv) displayed on the UI screen (S802).

  In S803, it is determined which sample in FIG. 9 the user has selected. If it is determined that (i) or (iii) has been selected, the CPU (206) sets 1 to the rotation flag in S804. This is because, as in sample (i) or (iii), when the character is in the horizontal direction with respect to the reading direction of the scanner, that is, when the reading direction of the scanner and the vertical direction of the character match, Because it will increase. If it is determined in S803 that (ii) or (iv) is selected, the rotation flag is set to 0. Thereafter, the process proceeds to S304 in FIG. 3, and the same processing as in the first embodiment is performed.

  With the present embodiment described above, it is possible to suppress degradation of the resolution of characters and line drawings with a simple operation in a printed matter output by the recording apparatus (102) whose sub-scan has a low resolution. With the above-described configuration, in the case of a Chinese character that requires the resolution of the horizontal line, the problem of the horizontal line being crushed / disappearing due to the low resolution of the sub-scan can be solved.

<Example 3>
In the third embodiment, the OCR processing program stored in the ROM (209) is used in the character direction determination step of S303 in FIG. The OCR processing program refers to processing and a program for recognizing characters of digital image data. The OCR processing program determines layout information, vertical writing, and horizontal writing before performing character recognition, and can output such information to the outside. Using this information, the character direction determination step S303 is performed. FIG. 10 shows the flow of this process. Since other processes are the same as those in the first embodiment, the description thereof is omitted.

  In S1001, the CPU (206) reads the digital image data stored in the RAM (208) into the Img area. In S1002, the CPU (206) passes the image in the Img area to the OCR program stored in the ROM (209). The CPU (206) performs arithmetic processing according to the OCR program and creates layout information. The method for creating layout information is based on the OCR program and will not be described in this embodiment. The OCR layout information includes the direction of characters and is obtained.

  In S1003, a rotation flag is set using the result of character direction determination. If the character direction is the positive direction, that is, if the vertical direction of the digital image data matches the vertical direction of the character, 1 is set in the rotation flag in S1004. This is because there are many horizontal lines when the character direction is positive. If the character direction is not positive, the rotation flag is set to 0. Thereafter, the process proceeds to S304 in FIG. 3, and the same processing as in the first embodiment is performed. Further, only when the character is determined to be a Chinese character by the OCR program, it can be determined that the document includes the Chinese character, and therefore, rotation that is the main point of the present case may be performed.

  By implementing the above invention, it is possible to easily suppress the deterioration of character resolution by using the OCR process in the printed matter output by the recording apparatus (102) having the low resolution sub-scanning. With the above-described configuration, in the case of a Chinese character that requires the resolution of the horizontal line, the problem of the horizontal line being crushed / disappearing due to the low resolution of the sub-scan can be solved.

<Other examples>
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (7)

An image processing apparatus for controlling a recording apparatus having a sub-scanning resolution smaller than a main-scanning resolution,
Character direction determination means (203) for determining the direction of characters included in the digital image data;
An image rotating means (205) for rotating the digital image data by 90 degrees when the character direction determined by the character direction determining means matches the sub-scanning direction of the recording apparatus;
An image processing apparatus comprising: control means (206) for controlling the recording apparatus to print the digital image rotated by the image rotating means.   The image processing apparatus according to claim 1, wherein the character direction determination unit determines the character direction by comparing the size of a feature amount of main scanning and a feature amount of sub-scanning.   The image processing apparatus according to claim 1, wherein the character direction determination unit determines the character direction by comparing the number of vertical thin lines and horizontal thin lines.   The image processing apparatus according to claim 1, wherein the character direction determination unit determines a character direction by an external input.   The image processing apparatus according to claim 1, wherein the character direction determination unit determines a character direction using a result of OCR processing. An image processing method for controlling a recording apparatus having a sub-scanning resolution smaller than a main-scanning resolution,
Determining the direction of characters included in the digital image data;
Rotating the digital image data by 90 degrees when the determined character direction matches the sub-scanning direction of the recording apparatus;
And a step of controlling the recording device to print the rotated digital image.   A storage medium for storing a program for causing a computer to execute the image processing method according to claim 6.

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