JP2009105943A - Image-forming apparatus, linewidth control method, and linewidth control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus can forming a high-quality image by enhancing reproducibility of a thin line. <P>SOLUTION: The image-forming apparatus detects a line width in a line-width detector 105 by means of attribute data input from an attribute-data input unit 101, and a line color in a color detector 117. An edge is detected in an edge detector 109 by image data input from an image-data input unit 103. These logic products are calculated in a logic-product calculator 107. An individually established coefficient is stored according to the line width in a respective color in a coefficient storage unit 113. A line-width correction coefficient calculator 111 corrects the line width of the edge and a detected pixel, by obtaining a corrective coefficient in accordance with the detected line width and the line color to multiply it to the line width. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, a line width control method, and a line width control program, and more particularly, to an image forming apparatus, a line width control method, and a line width control program that can reproduce fine lines with high quality.

  When an image is read by moving an original with an image input device such as a facsimile, the output in the scanning direction (horizontal thin line) is higher than that in the sub-scanning direction (vertical thin line) even if a thin line having the same line width is read. Therefore, the correction in the sub-scanning direction is weaker than the correction in the main scanning direction. As a result, image quality degradation such as thin line breakage occurs in the horizontal thin line corresponding to the sub-scanning direction.

  In order to cope with this problem, Japanese Patent Application Laid-Open No. 6-30267 (hereinafter referred to as Patent Document 1) proposes an image reading apparatus that prevents horizontal fine lines from being cut and improves image quality. In this image reading apparatus, when the minimum output characteristic with respect to the line width in the image input unit is higher in the minimum horizontal thin line output than in the vertical thin line minimum output, the image processing unit performs MFT correction on the pixels in the sub-scanning direction. By making the weighting factor larger than the weighting factor of the pixels in the main scanning direction, line omission is prevented during horizontal thin line reading.

JP-A-6-30267

  However, even with the image data input in this way, when a font is printed in an image forming apparatus such as an MFP (Multi Function Peripheral), the dots tend to expand due to the performance of the engine. As a result, there is a problem that the reproducibility of the thin line is lowered.

  When the reproducibility of the thin line is lowered, there is a problem that the thin line is not reproduced and the font type cannot be identified. Further, there is a problem that the fine line is not output as a fine line, and the quality of the output image is lowered. In addition, there is a problem that a small font may not be able to be identified.

  The present invention has been made in view of such problems, and an image forming apparatus, a line width control method, and a line width control program capable of forming a high-quality image by improving the reproducibility of thin lines. The purpose is to provide.

  In order to achieve the above object, according to one aspect of the present invention, an image forming apparatus includes a line width detecting unit that detects a line width of a line included in image data from attribute data corresponding to the image data, and image data. Edge detection means for detecting edge pixels, color detection means for detecting line colors from image data, storage means for storing a line width correction coefficient corresponding to the line width for each color, and line widths for edge pixels The line width correction coefficient corresponding to the line width detected by the detection means and the color detected by the color detection means is acquired from the storage means, and the gradation of the edge pixel is corrected using the line width and the line width correction coefficient. And correcting means for correcting the line width.

  Preferably, the line width detection means performs erosion processing on the attribute data using a matrix filter of 1 pixel * 1 pixel to n pixels * n pixels, and erosion using the filter of each matrix. For the processing, the first dilation processing means for performing dilation processing using a filter of the same size as the erosion processing, and the erosion processing using the filter of each matrix are 2 times larger than the size used for the erosion processing. Second dilation processing means for performing dilation processing using a filter having a large pixel matrix, a first line width based on the processing result in the first dilation processing means, and a second based on the processing result in the second dilation processing means. Line width output means for outputting the line width.

  More preferably, the maximum value n of the size of the filter used in the erosion processing can be arbitrarily set, and the erosion processing means does not perform the erosion processing when the line width is larger than n.

  Preferably, the edge detection means includes a primary differentiation operation means for firstly differentiating the image data, a secondary differentiation operation means for secondarily differentiating the image data, and the logic of the result of the primary differentiation and the result of the secondary differentiation. Edge dilation processing means for performing dilation processing on the product, edge erosion processing means for performing erosion processing on the result of the dilation processing, and both pixels adjacent in the main scanning direction for each pixel of the image data Generating means for generating a PWM print position code indicating from which side of both pixels adjacent to the pixel within the pixel the print dot growth starts, and the result of the erosion process Based on the PWM print position code generated by the generation means as the code for controlling the print pulse output position in the pixel of the pixel, The shaped pulse output position and a selection means for selecting whether a central printing position code indicating that the center of the pixel.

  Preferably, the storage unit stores a line width correction coefficient corresponding to the line width for each color for each mode and / or language of the image data, and the correction unit detects the edge pixel by the line width detection unit. A line width correction coefficient corresponding to the line width and color detected by the color detection means and the mode and / or language of the image data is acquired from the storage means, and the edge pixel levels are obtained using the line width and the line width correction coefficient. The line width is corrected by correcting the key.

  According to another aspect of the present invention, the line width control method is a method for controlling the width of a line included in an image formed in the image forming apparatus, and the image forming apparatus uses a line corresponding to the line width for each color. The image forming apparatus includes a storage unit that stores a width correction coefficient, and the image forming apparatus acquires an image data and attribute data corresponding to the image data, and detects a line width of the line included in the image data from the attribute data. A line width detecting step, a color detecting step for detecting a line color from the image data, an edge detecting step for detecting an edge pixel from the image data, and a line width and color detection detected for the edge pixel in the line width detecting step. Correction for correcting the line width by acquiring the line width correction coefficient corresponding to the color detected in the step from the storage means, and correcting the gradation of the edge pixel using the line width and the line width correction coefficient And a step.

  Preferably, in the line width detection step, an erosion processing step of performing erosion processing on the attribute data using a filter of a matrix of 1 pixel * 1 pixel to n pixels * n pixels, and an erosion using a filter of each matrix For the processing, a first dilation processing step for performing dilation processing using a filter of the same size as the erosion processing, and for the erosion processing using the filter of each matrix, the size is 2 A second dilation processing step for performing dilation processing using a filter with a large pixel matrix, a first line width based on the processing result in the first dilation processing step, and a second based on the processing result in the second dilation processing step. Line width output that outputs the line width of And a step.

  More preferably, the maximum value n of the size of the filter used in the erosion process can be arbitrarily set. In the erosion process step, when the line width is larger than n, the erosion process is not performed.

  Preferably, the edge detecting step includes a first derivative operation step for firstly differentiating the image data, a second derivative operation step for secondarily differentiating the image data, a logic of the result of the first differentiation and the result of the second differentiation. By calculating the product, an edge extraction step of extracting edge pixels from the image data, and a pixel product extracted as the edge pixel is obtained with respect to the logical product of the result of the primary differentiation and the result of the secondary differentiation. An edge dilation processing step for performing an adjustment process, an edge erosion processing step for performing an erosion process on the result of the dilation process, and a gradation between each pixel adjacent to the main scanning direction for each pixel of the image data Based on the difference, a PWM print position code indicating from which side of both pixels adjacent to the pixel the print dot growth starts in the pixel. When the pixel is detected as an edge pixel based on the result of the erosion process and the generation step for generating the output signal, the PWM generated in the generation step is used as a code for controlling the print pulse output position within the pixel of the pixel. When a pixel is not detected as an edge pixel based on the first output step for outputting the print position code and the result of the erosion process, a code for controlling the print pulse output position within the pixel of the pixel is used. And a second output step of outputting a central print position code indicating that the print pulse output position is the center of the pixel.

  Preferably, the storage unit stores a line width correction coefficient corresponding to the line width for each color for each mode and / or language of the image data, and the correction step is detected in the line width detection step for the edge pixel. A line width correction coefficient corresponding to the color detected in the line width and color detection step and the mode and / or language of the image data is acquired from the storage means, and the edge pixel levels are obtained using the line width and the line width correction coefficient. The line width is corrected by correcting the key.

  According to still another aspect of the present invention, the line width control program is a program for causing a computer to execute processing for controlling the width of a line included in an image to be formed, and in the image forming apparatus, image data and image data Acquisition step for acquiring attribute data corresponding to, line width detection step for detecting the line width of the line included in the image data from the attribute data, color detection step for detecting the color of the line from the image data, An edge detection step for detecting edge pixels from image data, and a line width correction coefficient corresponding to the line width detected in the line width detection step and the color detected in the color detection step for the edge pixels for each color. Is obtained from a storage device that stores the line width correction coefficient corresponding to the line width, and the line width is corrected by correcting the gradation of the edge pixel using the line width and the line width correction coefficient. And a step to be executed.

  Preferably, in the line width detection step, an erosion processing step of performing erosion processing on the attribute data using a filter of a matrix of 1 pixel * 1 pixel to n pixels * n pixels, and an erosion using a filter of each matrix For the processing, a first dilation processing step for performing dilation processing using a filter of the same size as the erosion processing, and for the erosion processing using the filter of each matrix, the size is 2 A second dilation processing step for performing dilation processing using a filter having a large pixel matrix, a first line width based on the processing result in the first dilation processing step, and a first line width based on the processing result in the second dilation processing step. Line width output that outputs 2 line widths And a step.

  More preferably, the maximum value n of the size of the filter used in the erosion process can be arbitrarily set. In the erosion process step, when the line width is larger than n, the erosion process is not performed.

  Preferably, the edge detecting step includes a first derivative operation step for firstly differentiating the image data, a second derivative operation step for secondarily differentiating the image data, a logic of the result of the first differentiation and the result of the second differentiation. By calculating the product, an edge extraction step of extracting edge pixels from the image data, and a pixel product extracted as the edge pixel is obtained with respect to the logical product of the result of the primary differentiation and the result of the secondary differentiation. An edge dilation processing step for performing an adjustment process, an edge erosion processing step for performing an erosion process on the result of the dilation process, and a gradation between each pixel adjacent to the main scanning direction for each pixel of the image data Based on the difference, a PWM print position code indicating from which side of both pixels adjacent to the pixel the print dot growth starts in the pixel. When the pixel is detected as an edge pixel based on the result of the erosion process and the generation step for generating the output signal, the PWM generated in the generation step is used as a code for controlling the print pulse output position within the pixel of the pixel. When a pixel is not detected as an edge pixel based on the first output step for outputting the print position code and the result of the erosion process, a code for controlling the print pulse output position within the pixel of the pixel is used. And a second output step of outputting a central print position code indicating that the print pulse output position is the center of the pixel.

  Preferably, the storage device stores a line width correction coefficient corresponding to the line width for each color for each mode and / or language of the image data, and the correction step is detected in the line width detection step for the edge pixel. The line width correction coefficient corresponding to the color detected in the line width and color detection step and the mode and / or language of the image data is acquired from the storage device, and the edge pixel levels are obtained using the line width and the line width correction coefficient. The line width is corrected by correcting the key.

  By configuring the image forming apparatus according to the present invention in this way, the line width can be reproduced in the image formation regardless of the engine characteristics of the image forming apparatus. For this reason, the reproducibility of the font in the formed image can be improved. In addition, the reproducibility of thin ruled lines can be improved. As a result, a high quality image can be formed.

FIG. 3 is a block diagram illustrating a specific example of a hardware configuration of an image forming apparatus when the image forming apparatus according to the present embodiment is an MFP. 4 is a block diagram illustrating a specific example of a functional configuration for performing line width control processing in the image forming apparatus according to the present embodiment. FIG. FIG. 3 is a diagram illustrating a specific example of a line width correction coefficient stored in a coefficient storage unit illustrated in FIG. 2. FIG. 3 is a block diagram illustrating a specific example of a detailed configuration of an edge detection unit illustrated in FIG. 2. It is a figure explaining the production | generation method of the PWM printing position code in the PWM printing position code production | generation part shown by FIG. It is a figure explaining the production | generation method of the PWM printing position code in the PWM printing position code production | generation part shown by FIG. It is a figure explaining the production | generation method of the PWM printing position code in the PWM printing position code production | generation part shown by FIG. It is a figure explaining the production | generation method of the PWM printing position code in the PWM printing position code production | generation part shown by FIG. FIG. 3 is a block diagram illustrating a specific example of a detailed configuration of a line width detection unit illustrated in FIG. 2. It is a figure explaining the 1st dilation process in a line | wire width detection part. It is a figure explaining the 2nd dilation process in a line | wire width detection part. It is a figure explaining an extension line width. It is a figure explaining an outside line width. 5 is a flowchart illustrating a specific example of a flow of line width control processing in the image forming apparatus according to the present embodiment. It is a flowchart which shows the line | wire width detection process in FIG.14 S103. It is a flowchart which shows the edge detection process in FIG.14 S105. It is a flowchart which shows the PWM position determination process in step S107 of FIG. It is a block diagram which shows the specific example of a function structure for performing line | wire width control processing in the image forming apparatus concerning a 1st modification. It is a figure which shows the specific example of the line | wire width correction coefficient memorize | stored in the coefficient memory | storage part shown by FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same.

  FIG. 1 is a block diagram showing a specific example of the hardware configuration of the image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 corresponds to a copier, a printer, or a multifunction peripheral (MFP) that is a composite device thereof. In the present embodiment, it is assumed that image forming apparatus 1 is an MFP, and FIG. 1 is a block diagram showing a specific example of the hardware configuration of image forming apparatus 1 that is an MFP.

  Referring to FIG. 1, an image forming apparatus 1 includes a CPU (Central Processing Unit) 11 that controls the entire apparatus, an image reader unit 19 that reads image data from a document, and a printer unit 21 that prints an image on paper. An NIC (Network Interface Card) 15 that is an expansion card for connecting the image forming apparatus 1 to a network or a telephone line or performing short-distance wireless communication, an HD (Hard Disk), a RAM (Random Access Memory) ) And the like, and a storage unit 13 for storing a job and a program such as a line width control program executed by the CPU 11, an operation panel 17 that is an interface with the user, a remaining amount of consumables, and the like. And a sensor unit 23 to be detected.

  The image forming apparatus 1 acquires document data including image data and attribute data, executes line width control processing described later, and outputs image data. The output image data is printed by an image forming process.

  The image data included in the document data acquired by the image forming apparatus 1 is YMCK (Yellow Magenta Cyan Black) data or RGB (Red Green Blue) data. The attribute data indicates, for each pixel of the image data, whether the pixel is text or graphic or neither. The attribute data is added by an image creation application that operates on a terminal such as a PC (Personal Computer) and transmitted to the image forming apparatus 1, or an image read by the image reader unit 19 of the image forming apparatus 1. In some cases, the data is added on the image forming apparatus 1 side by determining the data using an area determination unit (not shown).

  FIG. 2 is a block diagram illustrating a specific example of a functional configuration for performing the line width control processing according to the present embodiment in the image forming apparatus 1. The function configuration shown in FIG. 2 is a function realized mainly by the CPU 11 executing a program stored in the storage unit 13, but a part thereof may be configured by hardware.

  Referring to FIG. 2, functions for performing line width control processing in image forming apparatus 1 are attribute data input unit 101 for inputting attribute data of document data, and an image for inputting image data of document data. A data input unit 103; a line width detection unit 105 that detects line width from attribute data; an edge detection unit 109 that detects edges from image data; a logical product calculation unit 107 that calculates a logical product of these detection results; A coefficient storage unit 113 that stores a coefficient for correction, a line width correction coefficient multiplication unit 111 that performs an operation for correcting the line width, and an image data output unit 115 that outputs the image data with the corrected line width are included. Consists of.

  The line width detection unit 105 performs line width processing described later, and inputs a line width signal indicating the detected line width to the logical product calculation unit 107. The edge detection unit 109 also performs edge detection processing to be described later, and inputs an edge detection signal indicating the detected edge to the logical product calculation unit 107. The logical product calculation unit 107 calculates the logical product of these signals and calculates the edge line width. An edge line width signal indicating the calculated edge line width is input to the line width correction coefficient multiplier 111.

  Further, the edge detection unit 109 performs edge detection processing described later, and inputs a PWM position control signal indicating a PWM (Pulse Width Modulation) position described later to the line width correction coefficient multiplication unit 111.

  The coefficient storage unit 113 is formed mainly by a predetermined area of the storage unit 13 and stores a line width correction coefficient used in the line width correction coefficient multiplication unit 111. The line width correction coefficient is a coefficient individually set for each line width from 1 dot to ndot, and is a coefficient for correcting the line width so as to be an ideal line width at the time of image formation.

  FIG. 3 is a diagram illustrating a specific example of the line width correction coefficient stored in the coefficient storage unit 113. As illustrated in FIG. 3, the coefficient storage unit 113 stores a line width correction coefficient in association with the line width. The specific numerical value of the coefficient shown in FIG. 3 is one specific example, and the present invention is not limited to this numerical value. Since the line width correction coefficient is a coefficient related to the performance of the engine of the image forming apparatus as described above, it is determined in accordance with the performance of the engine. Or it is obtained by experiment etc. Therefore, it is preferable that the line width correction coefficient is stored in the coefficient storage unit 113 in advance. Alternatively, the line width correction coefficient may be changed or created by a user such as an administrator. When changing or creating the line width correction coefficient, it is preferable that a screen for that is displayed on the operation panel 17 to accept input of specific numerical values. Alternatively, a settable range is shown in advance according to the performance of the engine, and it is preferable to accept a selection from the range. Alternatively, it is also preferable that when a numerical value outside the settable range is input, the numerical value is not accepted.

  The line width correction coefficient multiplication unit 111 reads the line width correction coefficient corresponding to the line width from the coefficient storage unit 113 based on the edge line width signal input from the logical product calculation unit 107, and multiplies the line width by the coefficient. To correct the line width. The calculation result is input to the image data output unit 115. The image data output unit 115 outputs the image data with the corrected line width.

  FIG. 4 is a block diagram illustrating a specific example of a detailed configuration of the edge detection unit 109. Referring to FIG. 4, the edge detection unit 109 includes a first-order differential filter operation unit 201 that performs first-order differentiation on the input image data using a first-order differential filter. On the other hand, a secondary differential filter calculation unit 203 that performs a second-order differentiation operation using a second-order differential filter, an edge extraction unit 205 that extracts a pixel that is an edge based on the calculation result, and a pixel that is an edge Edge dilation unit 207 that performs dilation processing, edge erosion unit 209 that performs erosion processing on the processing result, PWM print position code generation unit 211 that generates a PWM print position code for each pixel, and print position code Selector unit 213 for selective input, based on PWM print position code and erosion processing result Edge signal output unit 215 outputs an edge signal, and on the basis of the PWM printing position code includes PWM printing control signal output unit 217 outputs a PWM printing control signal.

  The edge extraction unit 205 is a calculation result obtained by the first-order differential filter calculation unit 201 obtained from the image data through the first-order differential filter, and a calculation result obtained by the second-order differential filter calculation unit 203 obtained from the image data through the second-order differential filter. And an edge is extracted from the image data. The extracted edge is input to the edge dilation unit 207. The edge extraction method in the edge extraction unit 205 is not limited to a specific method in the present invention, and a general method can be adopted.

  The edge dilation unit 207 performs dilation processing on each edge input from the edge extraction unit 205 and inputs the processing result to the edge erosion unit 209. The edge erosion unit 209 performs erosion processing on each dilation processing result, and inputs the processing result to the edge signal output unit 215. The dilation process in the edge dilation unit 207 and the erosion process in the edge erosion unit 209 are general processes called opening processes. These specific processing methods are not limited to specific methods in the present invention. It is not limited.

  The edge signal output unit 215 inputs an edge detection signal indicating a pixel that is an edge to the logical product calculation unit 107 and the selector unit 213 based on the processing result in the edge erosion unit 209.

  The PWM print position code generation unit 211 generates a PWM print position code for determining a PWM growth position for each pixel of the image data. Here, the PWM print position code refers to 2-bit data indicating a pulse output for dot printing in one pixel when the gradation of the target pixel is smaller than the maximum value. . That is, the PWM print position code generation unit 211 determines at which position dot printing is performed for each pixel, in other words, from which position of one pixel to which direction the dot print portion is extended. Here, “from which position of one pixel to which direction the dot print portion is extended” is expressed as “growth position (also referred to as PWM position)”, and a print pulse for printing a dot at that position. Is output.

  Specifically, as shown in FIG. 5, a method for generating a PWM print position code in the PWM print position code generation unit 211 will be described by taking as an example a case where pixels are continuous in the main scanning direction. In FIG. 5, the gradation value of the pixel of interest is D1D, the gradation value of the pixel immediately adjacent to the pixel of interest in the direction of arrow A, which is the main scanning direction, is D0D, and the gradation value of the pixel immediately adjacent to it. Is D2D. In this example, it is assumed that the ruled lines included in the document image are dark (for example, white) ruled lines on a light-colored (for example, white) ground.

The PWM print position code generation unit 211 determines the magnitude relationship between the gradation values D0D, D1D, and D2D for three pixels adjacent in the main scanning direction across the pixel of interest. When the magnitude relationship of these gradation values is as follows (A) to (E), the growth position is determined as follows:
(A) D0D <D1D ≦ D2D: D1D is grown from the D2D side,
(B) D0D ≦ D1D <D2D: D1D is grown from the D2D side,
(C) D0D> D1D ≧ D2D: D1D is grown from the D0D side,
(D) D0D ≧ D1D> D2D: D1D is grown from the D0D side,
(E) D0D> D1D <D2D: D1D is grown evenly from both sides of D0D and D2D.

  In other words, the PWM print position code generation unit 211, as shown in FIG. 6, when the pixel adjacent to the right is darker than the pixel of interest (in the above cases (A) and (B)). The growth position is determined so as to extend the dot printing portion from the right side. When the density of the pixel adjacent to the left is lighter than the pixel of interest (in the above-described cases (C) and (D)), as shown in FIG. 7, the growth position extends the dot printing portion from the left side. To decide. When the pixel of interest is lighter than any adjacent pixel (in the above case (E)), as shown in FIG. 8, the growth position is determined so as to uniformly extend the dot print portion from both the left and right sides. To do. For each pixel, a PWM print position code indicating the determined growth position is generated and input to the selector unit 213.

  The selector unit 213 uses the PWM print position code for pixels detected as edges based on the edge signal input from the edge signal output unit 215 and the PWM print position code input from the PWM print position code generation unit 211. Based on the above, a PWM print control signal, which is a control signal for dot printing at the determined position, is input to the line width correction coefficient multiplier 111. For pixels that are not detected as edges, a PWM print control signal, which is a control signal for setting the dot print portion to the center position of the pixel, is multiplied by a line width correction coefficient based on a print position code stored in advance. Input to the unit 111. The print position code stored in advance is referred to as a central print position code here.

  FIG. 9 is a block diagram illustrating a specific example of a detailed configuration of the line width detection unit 105. Referring to FIG. 9, line width correction unit 105 selects line width correction for selecting attribute data to be subjected to line width correction processing from among the input attribute data for each pixel of image data. Target attribute selection unit 301, erosion processing unit 303 that performs erosion processing on the attribute data to be processed, first dilation processing unit 305 that performs first dilation processing on the processing result, and first dilation An internal line width output unit 307 that detects and outputs an internal line width to be described later based on the processing result, a second dilation processing unit 309 that performs a second dilation process on the erosion processing result, and a second dilation process An outer line width output unit 311 that detects and outputs an outer line width described later based on the result is included.

  The line width correction target attribute selection unit 301 analyzes the input attribute data and determines, for each pixel, whether the pixel is text, graphic, or any of them. As a result, the attribute data for the pixels determined to be text and the pixels determined to be ruled lines (graphics) are selected as the attribute data to be processed for correcting the line width, and are sent to the erosion processing unit 303. input. The erosion processing unit 303 performs erosion processing on the input attribute data corresponding to each pixel, using a matrix filter of 1 pixel * 1 pixel to n pixels * n pixels. The erosion processing result is further subjected to first dilation processing and second dilation processing in the first dilation processing unit 305 and the second dilation processing unit 309, respectively. Note that the erosion processing in the erosion processing unit 303 and the dilation processing in the first dilation processing unit 305 and the second dilation processing unit 309 are general processing called closing processing. The processing method is not limited to a specific method in the present invention.

  10 and 11 are diagrams for explaining the first dilation process and the second dilation process.

  Referring to FIG. 10, the first dilation processing unit 305 applies a filter of the same size as the filter used in the erosion processing unit 303 to the processing result in the erosion processing unit 303 as the first dilation processing. To perform dilation processing. The result of the first dilation process is input to the extension line width output unit 307, and an extension line width signal indicating an extension line width, which will be described later, is input to the logical product calculation unit 107 from the extension line width output unit 307 based on the processing result. .

  Referring to FIG. 11, the second dilation processing unit 309 has a size two pixels larger than the filter used in the erosion processing unit 303 with respect to the processing result in the erosion processing unit 303 as the second dilation processing. Dilation processing is executed using the above filter. The result of the second dilation process is input to the outer line width output unit 311, and an outer line width signal indicating an outer line width, which will be described later, is input to the logical product calculation unit 107 from the outer line width output unit 311 based on the processing result. .

12 and 13 are diagrams for explaining the inner line width and the outer line width.
The first dilation processing using the filter of the same size as the filter used in the erosion processing unit 303 is executed in the first dilation processing unit 305 on the processing result in the erosion processing unit 303, Fine lines equal to or smaller than the filter size are eliminated, and a black line BL having a pixel of one pixel as an edge pixel at both ends, which is shown in E portion in FIG. 12, is detected. Then, the width LA of the black line including the edge pixels at both ends of the width DA corresponding to the width of one pixel is detected. Here, the width LA of the black line including the width (DA × 2) of the two edge pixels at both ends is referred to as an internal line width.

  The second dilation processing unit 309 executes the second dilation processing using a filter having a size two pixels larger than the filter used in the erosion processing unit 303 with respect to the processing result in the erosion processing unit 303. Thus, with respect to the black background shown in the BL portion in FIG. 13, a white line WH (hereinafter, white line) shown in the E portion and having one pixel as an edge pixel at both ends is detected. . Then, the width LB of the white line including the edge pixels at both ends of the width DB (= DA) corresponding to the width of one pixel, that is, a line width larger by one pixel on both sides than the actual white line width is detected. Here, the width LB of the white line including the width (DB × 2) of the two edge pixels at both ends is referred to as the outer line width.

  Note that the maximum value n of the filter sizes used in the first dilation processing unit 305 and the second dilation processing unit 309 is not limited to a specific numerical value in the present invention, and may be set to an arbitrary numerical value. As a specific numerical value, about 6-8 is preferable, More preferably, 7 is mentioned. When the line width is larger than the filter size, the first dilation processing unit 305 and the second dilation processing unit 309 output an error signal indicating the fact, and the line width larger than the filter size is detected. It is preferable that the above processing is not performed.

  The logical product calculation unit 107 calculates the logical product of the internal line width signal input from the internal line width output unit 307 and the edge signal input from the edge signal output unit 215, or the external line width signal input from the external line width output unit 311 A logical product with the edge signal input from the edge signal output unit 215 is calculated, and the line width of the edge to be corrected is calculated.

  FIG. 14 is a flowchart showing a specific example of the flow of line width control processing in the image forming apparatus 1 according to the present embodiment. The processing shown in the flowchart of FIG. 14 is realized by the CPU 11 of the image forming apparatus 1 reading and executing a program including the line width control program stored in the storage unit 13 and controlling each unit shown in FIG. Is done.

  Referring to FIG. 14, first, CPU 11 obtains document data obtained by scanning with image reader unit 19, or document data obtained by receiving data transmitted by NIC 15 from another device. (Step S101).

  Among the document data, attribute data is input from the attribute data input unit 101, the line width detection unit 105 detects the line width (step S103), and a line width signal is output.

  Of the original data, image data is input from the image data input unit 103, and the edge detection unit 109 performs edge detection (step S105). The edge detection unit 109 determines the aforementioned PWM position (step S107), and the PWM print control signal output unit 217 outputs a PWM print control signal based on the determined PWM position.

  The logical product calculation unit 107 performs a logical product of the line width signal output based on the line width detected in step S105 and the PWM print control signal output based on the PWM position determined in step S107. (Step S109), the edge line width is calculated.

  The line width correction coefficient multiplication unit 111 acquires a coefficient corresponding to the line width from the line width correction coefficients stored in the coefficient storage unit 113 based on the line width of the edge calculated in step S109. (Step S111), the corrected line width is calculated by multiplying the line width (Step S113).

  The CPU 11 executes an image forming process, the gradation of the pixel is replaced with a new gradation based on the corrected line width calculated in step S113, and the growth of the pixel is performed based on the PWM print control signal. Image formation is performed based on the image data whose position has been determined. The formed image data is output to another device via the printer unit 21 or the NIC 15 (step S115).

  FIG. 15 is a flowchart showing the line width detection process in step S103.

  Referring to FIG. 15, first, the pixel determined to be text and the pixel determined to be a ruled line (graphic) among the attribute data included in the document data in the line width correction target attribute selection unit 301. Is selected as attribute data to be processed for correcting the line width (step S201).

  The erosion processing unit 303 performs erosion processing on the attribute data selected in step S201 using a matrix filter of 1 pixel * 1 pixel to n pixels * n pixels (step S203). Then, the first dilation processing unit 305 performs the first dilation processing using a filter having the same size as the filter (step S205). Based on the result of the first dilation process in step S205, the extension width output unit 307 calculates the aforementioned extension width and outputs an extension width signal indicating the extension width (step S207).

  In addition, the second dilation process is performed on the result of the erosion process in step S203 using a filter having a size two pixels larger than the filter used in step S203 in the second dilation processing unit 309. (Step S209). Based on the result of the second dilation process in step S209, the above-described external line width is calculated from the external line width output unit 311 and an external line width signal indicating the external line width is output (step S211).

  In addition, since the process of said step S205-S207 and the process of step S209-S211 are independent processes, a process order is not limited to the said process order, A reverse order may be sufficient.

  The processes in steps S205 to S207 and the processes in steps S209 to S211 are executed for each attribute data selected in step S201, and the process is completed for all the attribute data selected in step S201. (YES in step S213), the process proceeds to step S105.

  FIG. 16 is a flowchart showing the edge detection process in step S105.

  Referring to FIG. 16, first, a primary differential filter calculation unit 201 performs a calculation using a primary differential filter on image data included in document data (step S301), and a secondary differential filter calculation unit. In 203, an operation using a secondary differential filter is performed on the image data (step S303). Since the process of step S301 and the process of step S303 are independent processes, the process order is not limited to the process order described above, and may be reversed.

  Next, the edge extraction unit 205 extracts pixels that are edges from the processing result in step S301 and the processing result in step S303 (step S305). Dilation processing is executed in the edge dilation unit 207 for the pixel that is the edge extracted in step S305 (step S307), and further, erosion processing is executed in the edge erosion unit 209 for the result (step S307). S309).

  The dilation process in step S307 and the erosion process in step S309 are executed for each pixel extracted as an edge in step S305, and the process is completed for all the pixels extracted as an edge in step S305 ( In step S311, YES, the edge signal output unit 215 outputs an edge detection signal indicating a pixel that is an edge (step S313), and the process proceeds to step S107.

  FIG. 17 is a flowchart showing the PWM position determination process in step S107.

  With reference to FIG. 17, first, the PWM print position code generation unit 211 generates the aforementioned PWM print position code for each pixel of the image data included in the document data (step S401).

  Next, in the selector unit 213, based on the edge signal output from the edge signal output unit 215 in step S313, whether the pixel for which the PWM print position code is generated in step S401 is a pixel extracted as an edge or not. Is determined (step S403). As a result, for a pixel determined to be an edge and extracted pixel (YES in step S403), the PWM printing control signal output unit 217 performs PWM printing control based on the PWM printing position code generated in step S401. A signal is output (step S405). If not (NO in step S403), the PWM print control signal output unit 217 outputs a PWM print control signal based on the above-described central print position code (step S407).

  The processing in steps S401 to S407 is executed for all the pixels of the image data included in the document data acquired in step S101. When the processing is completed for all the pixels (YES in step S409), the processing is performed. Goes to step S109.

  In this specific example, the PWM print position code is generated for all the pixels included in the image data in step S401. However, it is determined in advance in step S403 that the pixel is an edge pixel. The PWM print position code may be generated only for the pixel. In other words, the processing order of this process is not limited to the above order, and step S403 is executed before step S401, and the PWM print position code generation process of step S401 is executed according to the determination result. Also good.

  When the above processing is executed in the image forming apparatus 1 according to the present embodiment, when the edge portion of the character or ruled line has a predetermined thickness, the gradation is replaced using the line width correction coefficient. The line width can be reduced. For this reason, the phenomenon that the edge portions of characters and ruled lines become thick due to the engine characteristics of the image forming apparatus 1 is suppressed, and the reproducibility of the thin lines is enhanced. As a result, the image forming apparatus 1 can form a high-quality image.

[Modification 1]
As shown in FIG. 18, the image forming apparatus 1 according to the first modification is configured to further include a color detection unit 117 that detects a color from image data in addition to the functional configuration shown in FIG. 2. The The color detection unit 117 detects a color for each pixel of the image data, and inputs a color detection signal indicating the detected color to the line width correction coefficient multiplication unit 111. The method for detecting the color from the image data in the color detection unit 117 is not limited to a specific method in the present invention, and any method can be adopted.

  In the coefficient storage unit 113 of the image forming apparatus 1 according to the first modification, as shown in FIG. 19, the line width correction coefficient set for each color is stored for each line width from 1 dot to ndot. ing. In addition, the specific numerical value of the coefficient shown in FIG. 19 is also one specific example, and the present invention is not limited to this numerical value.

  In the image forming apparatus 1 according to the first modified example, the edge detection unit 109 detects an edge from the image data in step S105, and the color detection unit 117 detects a color for each pixel from the image data. In step S111, the line width correction coefficient multiplication unit 111 acquires a corresponding line width correction coefficient based on the line width of the edge calculated in step S109 and the color of the edge detected in step S105. To do.

  As one of the engine specifics, there are cases where the manner of dot expansion (edge thickening) differs depending on the color. As described above, even in the case of different colors, the image forming apparatus 1 according to the first modification corrects the line width for each color using the line width correction coefficient set for each color in this way. The phenomenon that the edge portions of characters and ruled lines become thick due to the engine characteristics of the image forming apparatus 1 is suppressed, and the reproducibility of fine lines is improved. As a result, the image forming apparatus 1 can form a high-quality image.

[Modification 2]
In the second modification, the image forming apparatus 1 acquires the original mode and language information together with the original data.

  The mode is information that defines the type of document data, such as whether the document data is document data, WEB data, or CAD (Computer Aided Design). The mode may be automatically transmitted to the image forming apparatus 1 together with the document data when a print instruction is issued from an application that creates the document data. Further, it may be inputted to the image forming apparatus 1 together with the document data by inputting when the user gives a print instruction from the operation panel 17. The mode may be data different from the document data or may be included in the document data. Alternatively, it may be a part of attribute data included in the document data.

  The language information is information representing the language of the document data. Language information can also be acquired by the image forming apparatus 1 in the same manner as in the above mode. The language information may be data different from the document data or may be included in the document data. Alternatively, it may be a part of attribute data included in the document data.

  The above-described document mode, language information, and the like are transmitted to the image forming apparatus 1 when an application that creates (or changes or modifies) the document data is instructed to print and the document data is transmitted to the image forming apparatus 1. It is generated by a program (controller) for instructing printing, and is transmitted to the image forming apparatus 1 together with document data in accordance with execution of the program. These pieces of information are input to the line width correction coefficient multiplication unit 111.

  In the coefficient storage unit 113 of the image forming apparatus 1 according to the second modification, as shown in FIG. 19, lines set for each document mode and each language for each line width from 1 dot to ndot. A width correction coefficient is stored. In step S111, the line width correction coefficient multiplication unit 111 acquires a corresponding line width correction coefficient based on the line width of the edge calculated in step S109 and the input document mode and language information.

  As one specific engine, the dot expansion method (edge thickening) may differ depending on the document mode and language information. As described above, even when the document mode and language information differ, the image forming apparatus 1 according to the first modification uses the line width correction coefficient set for each document mode and language information as described above. By correcting the line width, the phenomenon that the edge portions of characters and ruled lines become thick due to the engine characteristics of the image forming apparatus 1 is suppressed, and the reproducibility of thin lines is enhanced. As a result, the image forming apparatus 1 can form a high-quality image.

  Furthermore, it is possible to provide a program that causes a computer to execute the line width control according to the above-described embodiment. Such a program is stored in a computer-readable recording medium such as a flexible disk attached to the computer, a CD-ROM (Compact Disk-Read Only Memory), a ROM (Read Only Memory), a RAM (Random Access Memory), and a memory card. And can be provided as a program product. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built in the computer. A program can also be provided by downloading via a network.

  The program according to the present invention is a program module that is provided as a part of a computer operating system (OS) and calls necessary modules in a predetermined arrangement at a predetermined timing to execute processing. Also good. In that case, the program itself does not include the module, and the process is executed in cooperation with the OS. A program that does not include such a module can also be included in the program according to the present invention.

  The program according to the present invention may be provided by being incorporated in a part of another program. Even in this case, the program itself does not include the module included in the other program, and the process is executed in cooperation with the other program. Such a program incorporated in another program can also be included in the program according to the present invention.

  The provided program product is installed in a program storage unit such as a hard disk and executed. The program product includes the program itself and a recording medium on which the program is recorded.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 11 CPU, 13 Memory | storage part, 15 NIC, 17 Operation panel, 19 Image reader part, 21 Printer part, 23 Sensor part, 101 Attribute data input part, 103 Image data input part, 105 Line width detection part, 109 edge detection unit 107 logical product calculation unit 113 coefficient storage unit 111 line width correction coefficient multiplication unit 115 image data output unit 117 color detection unit 201 primary differential filter calculation unit 203 secondary differential filter calculation unit , 205 edge extraction unit, 207 edge dilation unit, 209 edge erosion unit, 211 PWM print position code generation unit, 213 selector unit, 215 edge signal output unit, 217 PWM print control signal output unit, 301 line width correction target attribute selection , 303 Erosion processing unit, 305 First direct Application processing unit, 307 inner line width output unit, 309 second dilation processing unit, 311 outer line width output unit.

Claims (15)

From the attribute data corresponding to the image data, line width detection means for detecting the line width of the line included in the image data,
Edge detection means for detecting edge pixels from the image data;
Color detecting means for detecting the color of the line from the image data;
Storage means for storing a line width correction coefficient corresponding to the line width for each color;
For the edge pixel, a line width correction coefficient corresponding to the line width detected by the line width detection unit and the color detected by the color detection unit is acquired from the storage unit, and the line width and the line width correction are acquired. An image forming apparatus comprising: a correction unit that corrects the line width by correcting a gradation of the edge pixel using a coefficient. The line width detecting means is
Erosion processing means for performing erosion processing on the attribute data using a filter of a matrix of 1 pixel * 1 pixel to n pixels * n pixels;
A first dilation processing means for performing dilation processing using a filter of the same size as the erosion processing, with respect to the erosion processing using the filter of each matrix;
A second dilation processing means for performing dilation processing using a matrix filter larger by two pixels than the size used for the erosion processing, with respect to the erosion processing using the filter of each matrix;
The line width output means for outputting the first line width based on the processing result in the first dilation processing means and the second line width based on the processing result in the second dilation processing means. The image forming apparatus described. The maximum value n of the size of the filter used in the erosion process can be arbitrarily set,
The image forming apparatus according to claim 2, wherein the erosion processing unit does not perform the erosion processing when the line width is larger than n. The edge detection means includes
Primary differential operation means for performing primary differentiation of the image data;
Secondary differential operation means for performing secondary differentiation of the image data;
Edge dilation processing means for performing dilation processing on a logical product of the result of the first derivative and the result of the second derivative;
Edge erosion processing means for performing erosion processing on the result of the dilation processing;
For each pixel of the image data, based on the gradation difference between both pixels adjacent in the main scanning direction, from which side of the pixels adjacent to the pixel the printing dot growth starts in the pixel Generating means for generating a PWM printing position code indicating
Based on the result of the erosion process, the PWM print position code generated by the generating means is used as a code for controlling the print pulse output position of the pixel within the pixel, or the print pulse output position of the pixel is set as the code. 4. The image forming apparatus according to claim 1, further comprising a selection unit that selects whether a center print position code indicating that the center of the pixel is set. The storage means stores a line width correction coefficient corresponding to the line width for each color for each mode and / or language of the image data,
The correction means sets a line width correction coefficient corresponding to the line width detected by the line width detection means, the color detected by the color detection means, and the mode and / or language of the image data for the edge pixel. 5. The image according to claim 1, wherein the image is acquired from the storage unit, and the line width is corrected by correcting a gradation of the edge pixel using the line width and the line width correction coefficient. Forming equipment. A method for controlling the width of a line included in an image formed in an image forming apparatus,
The image forming apparatus includes a storage unit that stores a line width correction coefficient corresponding to the line width for each color,
In the image forming apparatus, an acquisition step of acquiring image data and attribute data corresponding to the image data;
From the attribute data, a line width detection step of detecting a line width of a line included in the image data;
A color detection step of detecting the color of the line from the image data;
An edge detection step of detecting edge pixels from the image data;
A line width correction coefficient corresponding to the line width detected in the line width detection step and the color detected in the color detection step for the edge pixel is acquired from the storage unit, and the line width and the line width correction coefficient are acquired. And a correction step of correcting the line width by correcting the gray level of the edge pixel. The line width detecting step includes
An erosion processing step of performing erosion processing on the attribute data using a filter of a matrix of 1 pixel * 1 pixel to n pixels * n pixels;
A first dilation processing step for performing dilation processing using a filter of the same size as the erosion processing, with respect to the erosion processing using the filter of each matrix;
A second dilation processing step of performing dilation processing using a filter of a matrix that is two pixels larger than the size used for the erosion processing, with respect to the erosion processing using the filter of each matrix;
The line width output step which outputs the 1st line width by the process result in the said 1st dilation process step, and the 2nd line width by the process result in the said 2nd dilation process step is included in Claim 6. The line width control method described. The maximum value n of the size of the filter used in the erosion process can be arbitrarily set,
The line width control method according to claim 7, wherein in the erosion processing step, the erosion processing is not performed when the line width is larger than n. The edge detection step includes
A first-order differential calculation step for first-order differentiation of the image data;
A second order differential operation step for secondarily differentiating the image data;
An edge extraction step of extracting edge pixels from the image data by calculating a logical product of the result of the first derivative and the result of the second derivative;
An edge dilation processing step for performing dilation processing on a logical product of the result of the primary differentiation and the result of the secondary differentiation for the pixel extracted as the edge pixel;
An edge erosion processing step for performing erosion processing on the result of the dilation processing;
For each pixel of the image data, based on the gradation difference between both pixels adjacent in the main scanning direction, from which side of the pixels adjacent to the pixel the printing dot growth starts in the pixel Generating step of generating a PWM printing position code indicating:
When the pixel is detected as an edge pixel based on the result of the erosion process, the PWM print position code generated in the generation step is used as a code for controlling the print pulse output position in the pixel of the pixel. A first output step for outputting;
When the pixel is not detected as an edge pixel based on the result of the erosion process, the print pulse output position of the pixel is set as the code for controlling the print pulse output position in the pixel of the pixel. A line width control method according to claim 6, further comprising: a second output step of outputting a central print position code indicating that The storage means stores a line width correction coefficient corresponding to the line width for each color for each mode and / or language of the image data,
In the correction step, for the edge pixel, a line width correction coefficient corresponding to the line width detected in the line width detection step, the color detected in the color detection step, and the mode and / or language of the image data. The line according to claim 6, wherein the line width is acquired by correcting the line width by correcting the gradation of the edge pixel using the line width and the line width correction coefficient. Width control method. A program for causing a computer to execute processing for controlling the width of a line included in an image to be formed,
In the image forming apparatus, an acquisition step of acquiring image data and attribute data corresponding to the image data;
From the attribute data, a line width detection step of detecting a line width of a line included in the image data;
A color detection step of detecting the color of the line from the image data;
An edge detection step of detecting edge pixels from the image data;
For the edge pixel, the line width correction coefficient corresponding to the line width detected in the line width detection step and the color detected in the color detection step is stored, and the line width correction coefficient corresponding to the line width is stored for each color. A line width control program, which is obtained from a storage device, and executes a correction step of correcting the line width by correcting a gradation of the edge pixel using the line width and the line width correction coefficient. The line width detecting step includes
An erosion processing step of performing erosion processing on the attribute data using a filter of a matrix of 1 pixel * 1 pixel to n pixels * n pixels;
A first dilation processing step for performing dilation processing using a filter of the same size as the erosion processing, with respect to the erosion processing using the filter of each matrix;
A second dilation processing step of performing dilation processing using a filter of a matrix that is two pixels larger than the size used for the erosion processing, with respect to the erosion processing using the filter of each matrix;
The line width output step which outputs the 1st line width by the processing result in the 1st dilation processing step, and the 2nd line width by the processing result in the 2nd dilation processing step is included. The line width control program described. The maximum value n of the size of the filter used in the erosion process can be arbitrarily set,
13. The line width control program according to claim 12, wherein in the erosion processing step, the erosion processing is not performed when the line width is larger than n. The edge detection step includes
A first-order differential calculation step for first-order differentiation of the image data;
A second order differential operation step for secondarily differentiating the image data;
An edge extraction step of extracting edge pixels from the image data by calculating a logical product of the result of the first derivative and the result of the second derivative;
An edge dilation processing step for performing dilation processing on a logical product of the result of the primary differentiation and the result of the secondary differentiation for the pixel extracted as the edge pixel;
An edge erosion processing step for performing erosion processing on the result of the dilation processing;
For each pixel of the image data, based on the gradation difference between both pixels adjacent in the main scanning direction, from which side of the pixels adjacent to the pixel the printing dot growth starts in the pixel Generating step of generating a PWM printing position code indicating:
When the pixel is detected as an edge pixel based on the result of the erosion process, the PWM print position code generated in the generation step is used as a code for controlling the print pulse output position in the pixel of the pixel. A first output step for outputting;
When the pixel is not detected as an edge pixel based on the result of the erosion process, the print pulse output position of the pixel is set as the code for controlling the print pulse output position in the pixel of the pixel. The line width control program according to claim 11, further comprising: a second output step of outputting a central print position code indicating that The storage device stores a line width correction coefficient corresponding to the line width for each color for each mode and / or language of the image data,
In the correction step, for the edge pixel, a line width correction coefficient corresponding to the line width detected in the line width detection step, the color detected in the color detection step, and the mode and / or language of the image data. The line according to claim 11, wherein the line width is acquired by correcting the line width by correcting the gray level of the edge pixel using the line width and the line width correction coefficient obtained from the storage device. Width control program.

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