US20120147437A1 - Image processing apparatus and image processing method - Google Patents

Image processing apparatus and image processing method Download PDF

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Publication number
US20120147437A1
US20120147437A1 US13/302,638 US201113302638A US2012147437A1 US 20120147437 A1 US20120147437 A1 US 20120147437A1 US 201113302638 A US201113302638 A US 201113302638A US 2012147437 A1 US2012147437 A1 US 2012147437A1
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region
scanning direction
dots
dot
black
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Jun Nagai
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Canon Inc
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Canon Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/40093—Modification of content of picture, e.g. retouching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/387—Composing, repositioning or otherwise geometrically modifying originals
    • H04N1/3871—Composing, repositioning or otherwise geometrically modifying originals the composed originals being of different kinds, e.g. low- and high-resolution originals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/40—Picture signal circuits
    • H04N1/409—Edge or detail enhancement; Noise or error suppression
    • H04N1/4092—Edge or detail enhancement

Definitions

  • the present invention relates to an image processing apparatus and an image processing method, for example, to an image processing apparatus and an image processing method for controlling a placement amount of color material.
  • image processing apparatuses such as multi function machines and printers for printing image data sent from an input unit such as a host computer or an image scanner are widely used.
  • a photosensitive drum is evenly charged with a charging roller etc.
  • an electrostatic latent image is formed on the photosensitive drum.
  • the formed electrostatic latent image is developed with a developing unit, and the developed toner image is transferred to a material to be transferred by a transfer roller etc.
  • the toner image becomes fixed to the material to be transferred by a fixing unit to thereby enable the image to be printed.
  • the tailing phenomenon is apt to occur in an image region having specified features. Accordingly, by extracting an image region having such features and performing thinning processing on the image data of the extracted image region, the adhesion amount of toner was able to be decreased with a reduced adverse effect on the image quality (for example, Japanese Patent Laid-Open No. 2004-314308).
  • Japanese Patent Laid-Open No. 2004-314308 in order to extract the image region having the specified features, input image data to be a processing object is converted into a binary image, and an edge determination of a solid image region is performed to determine whether or not the image region of a target pixel is an object region of the processing. Furthermore, regarding the extraction of the image region, in Japanese Patent Laid-Open No. 2009-152766, by obtaining the binarization threshold from the density of a peripheral pixel of the target pixel, the image data of the processing object is expanded to a multi-value image.
  • the binarization threshold is estimated from the density of peripheral pixels of the target pixel, and, after subjecting the multi-value image to a binarization processing, edge determination processing similar to that for a binary image is performed.
  • the calculation of the optimum threshold requires a large processing load, and, in particular, realization of determination processing with a practical processing speed through the use of software is difficult.
  • a purpose of the present invention is to provide an image processing apparatus and an image processing method capable of detecting an image region that is an object of thinning processing appropriately and through the use of simple processing.
  • the image processing apparatus is an image processing apparatus detecting an image region from an input image, including a unit configured to detect a white pixel region being a line having only white dots and extending in the main scanning direction, a unit configured to detect a non-white pixel region being a line having at least one black dot and extending in the main scanning direction, a unit configured to detect a black pixel region being a line having only black dots and extending in the main scanning direction, a unit configured to detect a line region sandwiched by the white pixel regions and including only the non-white pixel region, a unit configured to detect a thinning candidate region being a region sandwiched between the black pixel regions in the line region, and a unit configured to detect a region located at a predetermined distance from the black pixel region located at the front end in the sub scanning direction to rearward of the sub scanning direction in the thinning candidate region and having a predetermined width in the sub scanning direction, as a thinning region.
  • an image processing apparatus and an image processing method capable of detecting an image region that is an object of thinning processing suitably and through the use of simple processing.
  • FIG. 1 is a block diagram showing a functional configuration of a copier according to the embodiment
  • FIG. 2 is a system block diagram showing a configuration of an image forming apparatus in the embodiment
  • FIG. 3 is a block diagram showing details of an image conversion unit
  • FIGS. 4A to 4D are diagrams explaining the extraction processing and the thinning processing of an image region by a related art
  • FIG. 5 is a diagram showing a flow of the extraction processing of an image region by a related art
  • FIGS. 6A to 6C are diagrams explaining the extraction processing and the thinning processing of an image region
  • FIGS. 7A to 7E are diagrams explaining the extraction processing and the thinning processing of the image region in Example 1;
  • FIG. 8 is a diagram showing the flow of the extraction processing of the image region in Example 1;
  • FIGS. 9A to 9E are diagrams explaining the extraction processing and the thinning processing of the image region in Example 2;
  • FIGS. 10A and 10B are diagrams showing a line width counter and execution of the processing in the extraction processing of an image region by a related art.
  • FIG. 11 is a diagram showing the counter and the execution of the processing in the extraction processing of an image region in Example 1 of the invention.
  • the present invention is not limited to this, and can be applied to image processing apparatuses of an electrophotographic system such as arbitrary printers or facsimiles, in the range that does not deviate from the purport.
  • FIG. 1 is a block diagram showing a functional configuration of the copier in the embodiment.
  • the copier is provided and constituted with an image input device 102 , an image forming apparatus 103 , and an image output device 104 .
  • image input device 102 an image input device 102
  • image forming apparatus 103 an image output device 104
  • FIG. 1 processing in which a draw command transmitted from a host computer 101 is received and printed, will be explained by using FIG. 1 .
  • the generated draw command is transmitted to the image forming apparatus 103 connected through a network etc.
  • the image forming apparatus 103 is constituted by including a draw command processing unit 105 , an input image processing unit 106 , an output image processing unit 107 , and a memory unit 108 .
  • the image output device 104 is connected to the image forming apparatus 103 , and is provided with a printer engine 111 .
  • the printer engine 111 receives image data generated in a predetermined image format from the image forming apparatus 103 , and prints the same on paper.
  • the need to perform low gradation output such as 2-, 4- or 16-gradations arises.
  • the input to the printer engine is image data corresponding to four recording materials of cyan (C), magenta (M), yellow (Y) and black (B). Accordingly, the format of image data input to the printer engine is a low gradation CMYK image of about 2- to 16-gradations.
  • the draw command processing unit 105 performs analysis processing on the draw command sent from the host computer 101 , generates a draw object, and furthermore performs rasterizing processing, to thereby generate a bit-mapped image.
  • the output image processing unit 107 the generated bit-mapped image is converted into an image format capable of being received by the printer engine.
  • the bit-mapped image generated here is an RGB image
  • color data conversion processing is performed, in which color data conversion is performed from RGB to CMYK utilizing a look-up table etc.
  • the bit-mapped image is a multiple gradation image
  • image processing as pseudo halftone processing in which the image is converted into an image of lower gradation by using a dither method etc., is performed in the output image processing unit 107 .
  • the image data thus generated is sent to the image output device 104 .
  • the image output device 104 outputs the received image data on paper by the printer engine 111 .
  • the scanner 109 is connected to an image forming apparatus 103 , and scans optically an image printed on paper or a film, measures the intensity of reflected light or transmitted light and performs analog-digital conversion to read the bit-mapped image.
  • the digital camera 110 converts the intensity of light to an electric signal with a CCD formed by arranging photodiodes to acquire a shot image as a bit-mapped image.
  • the bit-mapped image obtained here is generally an RGB image.
  • the bit-mapped image sent from the scanner 109 or the digital camera 110 is converted into a low gradation CMYK image in the input image processing unit 106 and the output image processing unit 107 .
  • the image data generated here is transferred to the printer engine 111 and an image is output on paper.
  • the output image processing unit 107 performs thinning processing on input image data, or image data to be transferred to the printer engine 111 . Specifically, the output image processing unit 107 extracts an image region to be an object of the thinning processing from the image data and performs the thinning processing on the extracted image region, with an adjusted thinning amount. Details of the thinning processing will be explained later.
  • FIG. 2 is a system block diagram showing the basic configuration of the image forming apparatus 103 in the embodiment.
  • the image forming apparatus 103 is provided with a CPU 201 , a ROM 202 , a RAM 203 , an external memory unit 204 , a display unit 205 , an operation unit 206 , an engine interface 207 , a network interface 208 , an external interface 209 , and a system bus 210 .
  • the CPU 201 is a central processing unit performing the control of the whole apparatus, arithmetic processing etc., and executes each of processing shown below based on a program stored in the ROM 202 .
  • the ROM 202 is a read only memory.
  • the ROM 202 is a storage region of a system start program, a program for controlling the printer engine, and data such as character data, character code information etc.
  • the RAM 203 is a random access memory.
  • the RAM 203 font data additionally registered by the downloading is stored, and, to the RAM, a program or data are loaded for every various processing. Furthermore, in the RAM 203 , various kinds of programs are expanded to be executed. Furthermore, the RAM 203 can be used as a data storage region of received image data.
  • the external memory unit 204 is constituted, for example, by a hard disk etc.
  • the external memory unit 204 is occasionally used for spooling data, storing a program and respective information files/image data, and is utilized as a region for operation.
  • the display unit 205 is a unit for performing display, for example, by liquid crystal etc.
  • the display unit 205 is used for displaying the setting state of the apparatus, and the present processing, error state or the like inside the apparatus.
  • the operation unit 206 is used for performing the change and reset of the setting.
  • the operation unit 206 can display, with the display unit 205 , the operation screen at the time of thinning pattern selection processing for the thinning processing, as described later.
  • the engine interface 207 is an interface inputting/outputting a command or the like for actually controlling the printer engine 111 .
  • the network interface 208 is an interface for connecting the image forming apparatus 103 to a network.
  • the image forming apparatus 103 sends/receives image data with the host computer 101 via the network and the network interface 208 .
  • the external interface 209 is connected with the scanner 109 or the digital camera 110 being an image input device via an interface of parallel (or serial) etc.
  • the system bus 210 serves as a data path between constituent components.
  • a processing procedure shown by a flow chart to be described later is stored in any memory unit of the ROM 202 , the RAM 203 and the external memory unit 204 , and is executed by the CPU 201 .
  • the occurrence condition of the tailing phenomenon is varied according to image forming apparatuses, it is known that, in an image of 600 dpi, it is particularly apt to occur when the width of the sub scanning direction (a feed direction of paper) of a strait line image in the main scanning direction is 4 dots to 8 dots (150 to 300 micrometers). Moreover, by subjecting an image data to the thinning processing, the height of toner on a recording material can be suppressed. Accordingly, by performing the thinning processing, it is possible to reduce toner at the upper part of the toner to be the cause of the occurrence of the tailing phenomenon, and to reduce the occurrence of the tailing phenomenon.
  • FIG. 3 is a block diagram showing details of the image conversion unit 301 performing the extraction processing and the thinning processing of an image region in the output image processing unit 107 .
  • An image region extraction unit 302 performs the extraction of an image region to be subjected to the thinning processing from input image data.
  • the tailing phenomenon is apt to occur in an image region being a straight line having a specified line width in the sub scanning direction parallel to the feed direction of a material to be transferred and having the main scanning direction perpendicular to the feed direction of the material to be transferred (in the former example, the line width is 4 to 8 dots when a resolving power is 600 dpi). Accordingly, in the image region extraction unit 302 , an image region of an image of a straight line in the main scanning direction having a specified width in the sub scanning direction is extracted from input image data.
  • the image region extraction unit 302 extracts an image region where the tailing phenomenon is apt to occur from input image data based on a condition predetermined as a condition under which the tailing phenomenon is apt to occur. Details of the extraction processing of an image region will be described later.
  • a thinning processing unit 304 performs the thinning processing on the image region extracted in the image region extraction unit 302 by applying the thinning pattern obtained from a thinning pattern obtaining unit 303 . Meanwhile, the thinning pattern obtained from the thinning pattern obtaining unit 303 is determined by the selection of a thinning pattern by a user via the display unit 205 and the operation unit 206 . The method of determining the thinning pattern obtained from the pattern obtaining unit 303 is not limited to this, but may be set to be performed by any known method.
  • FIGS. 4A to 4D are diagrams explaining the extraction processing and the thinning processing of an image region by a related art.
  • FIG. 4A here, an example, in which processing is performed on image data of a line having a 5-dot width in the sub scanning direction as an input, will be explained.
  • FIG. 4B here, an example of processing is shown, in which a unit of processing is 8 dots in the lateral direction regarding the extraction processing of an image region for a high-speed processing.
  • the horizontal edge is determined and, from the information of the line width on this occasion, image regions to be subjected to the thinning processing are extracted.
  • the horizontal edge being a line of 1-dot width at the front end of the 5-dot width line in the sub scanning direction is not set as an extraction region.
  • A-2 dot width line adjacent to the horizontal edge on the backside in the sub scanning direction is set as the extraction region. Extracted image regions are shown in hatched parts in FIG. 4C . An example in which the thinning processing is applied to an extracted image region is shown in FIG. 4D .
  • FIG. 5 shows a flow of the extraction processing of an image region by a related art.
  • each of x and y is the main scanning position and sub scanning position in image data, respectively, and D(x,y) indicates the density of image data at the position (x,y).
  • image data are sequentially determined (S 501 , S 502 ).
  • it is determined whether or not all of 8 dots of an image region being the object to be determined among the input image data are white, that is, D 0 for all dots. Meanwhile, in the example, speeding-up can be achieved by determining 8 dots collectively.
  • the line width is determined from the value of the line width counter (S 504 ).
  • the line width counter shows 4 to 8 dots width in the sub scanning direction in which the tailing phenomenon is apt to occur (S 504 ; Yes)
  • the extraction of a region to be subjected to the thinning processing is performed (S 505 ).
  • a line of a specified width is left at the edge and inside regions thereof are set to be the extraction region.
  • the determination processing is performed, first, in the sub scanning direction, that is, in the direction in which the counter of y is increased, but the method is not limited to this. Depending on how the image data is retained, the determination processing may be performed sequentially in the sub scanning direction, that is, in the direction in which the counter of x is increased.
  • FIG. 10A shows the relation between the line width counter and the execution of the processing when a thinning region extraction processing by a related art is performed on image data shown in FIG. 4A according to the flow of processing shown in FIG. 5 .
  • the determination is performed sequentially in the sub scanning direction, and, after the line width counter has become 5, the extraction processing of the thinning region of the inside by 1 dot is performed.
  • FIGS. 6A to 6C show diagrams of an example of image data obtained by an image scanner, and of the explanation of an image region extraction processing and a thinning processing for the image data by a related art.
  • FIG. 6A when a horizontal line is read with an image scanner, the edge part thereof does not have a straight line but has unevenness. Moreover, there is a case where noise occurring at the time of the reading, or the like exists inside the line. What indicates extracted regions when performing extraction processing of an image region shown by the flow in FIG. 5 on such an input image data is the hatched portion in FIG. 6B . Furthermore, FIG. 6C shows an example of performing the thinning processing on the extracted image region. It is known that, in FIG. 60 , the interference between unevenness existing at the edge part of the original input image data and the thinning processing brings about the lowering of the image quality.
  • FIG. 10B shows the relation between the line width counter and the execution of the processing when the thinning region extraction processing is performed on the image data shown in FIG. 6A by a related art.
  • FIGS. 7A to 7E are diagrams explaining the extraction processing and the thinning processing of the image region, in an Example according to the invention.
  • the image data shown in FIG. 7A is one obtained by taking in a horizontal line with an image scanner, which is equivalent to that shown in FIG. 6A .
  • the determination processing of the image region is performed by using 8 dots in the horizontal (main scanning) direction as a processing unit, for realizing speeding-up of the processing. The processing is performed sequentially in the sub scanning direction.
  • a region being the boundary between a region where all object regions to be determined that is, regions of 8 dots in the main scanning direction
  • regions of 8 dots in the main scanning direction that is, regions of 8 dots in the main scanning direction
  • a region where all are not white but at least 1 dot is black (the non-white pixel region) and a region extending in the main scanning direction
  • a line of 1-dot width in the sub scanning direction being adjacent to the boundary and located in the non-white pixel region is set as a line edge region.
  • a region in which a region sandwiched between two line edge regions and consisting of a non-white pixel region alone, and the two line edge regions (that is, a region sandwiched between two white pixel regions and consisting of a non-white pixel region alone) are included, is set as a line region. Furthermore, a width of the line region in the sub scanning direction is set as a line width.
  • Each of black pixel regions (a region in which all object regions to be determined are black) closest to each of two line edge regions in the line region is set as a black edge region.
  • a region sandwiched by two black edge regions in the line region is set as a thinning candidate region.
  • a region starting from a position away from a predetermined distance (1 dot in this example) from a black edge region on the backside in the sub scanning direction to the front side in the sub scanning direction in the thinning candidate region and having a predetermined width (2-dot width in this example) to the front in the sub scanning direction is shown by a hatched region in FIG. 7D .
  • the front in the sub scanning direction means the upper end part of input image data in FIG. 7A , which is an area printed first when printed on paper.
  • the backside of the sub scanning direction means the lower edge part of input image data in FIG. 7A , which is an area printed last when printed on paper.
  • the region shown by the hatched part in FIG. 7D is extracted as an image region to be subjected to the thinning processing. That is, among thinning candidate regions sandwiched by two black edge regions, an object image region for the thinning processing having a predetermined width in the sub scanning direction is extracted. In line regions, the scattering of toner is larger on the backside in the sub scanning direction than the front side. Consequently, in the Example, a region having 2-dot width from a position away from 1 dot from a black edge region on the backside in the sub scanning direction to the front side in the sub scanning direction in a thinning candidate region is extracted as a region to be subjected to the thinning processing.
  • all regions in the thinning candidate region may be set as the image region to be the object of the thinning processing, or a region on the front side in the sub scanning direction in a thinning candidate region may be set as the image region to be the object of the thinning processing.
  • sizes of respective regions such as the width of the unit of processing in the main scanning direction, the width of the black edge region in the sub scanning direction and the width of the image region to be the object of the thinning processing in the sub scanning direction can be set to be an arbitrary size, and are not limited to the sizes described above.
  • the determination standard for detecting a line region differs from the determination standard for detecting a thinning region. That is, the line edge region for detecting the line region is the non-white pixel region, and the black edge region for detecting the thinning region is the black pixel region.
  • FIG. 7E shows an example of applying the thinning processing to an image region extracted according to the embodiment.
  • the thinning processing refers to processing to change some black dots in the image region to be the object of the thinning processing into white dots.
  • the determination standard for detecting the line region differs from the determination standard for detecting the thinning region, the interference between unevenness of the edge part as shown in FIG. 6C and the thinning processing does not occur. Consequently, according to the embodiment, while reducing the lowering of the image quality, an object region for the thinning processing can be extracted.
  • the determination processing for an object region to be determined (that is, in this example, a region of 8 dots in the main scanning direction) is only the determination processing for either of following regions, that is, either of (1) a region in which all dots are white (a white pixel region), (2) a region in which all dots are black (a black pixel region), and (3) a region of neither the white pixel region nor the black pixel region. Accordingly, since the processing is simple as compared with a case performing the determination processing for an object region to be determined by using a threshold value of a color value, etc., speeding-up of the processing can be achieved.
  • FIG. 8 shows a flow of extraction processing of an image region by an Example according to the invention.
  • each of x, y is the main scanning position and the sub scanning position in image data, respectively, and D(x, y) indicates the density of image data at the position (x, y).
  • image data are determined sequentially (S 801 , S 802 ).
  • an image region that is the object to be determined is a region in which all of 8 dots are not white, that is, even 1 dot is a black dot (the non-white pixel region) (S 803 ; No)
  • the image region that is the object to be determined is determined to be a line region, and the line width counter is counted (S 811 ).
  • the line width counter is a counter which counts the width (dot number) in the sub scanning direction of a region in which all determined image regions are the non-white pixel region (the line region).
  • the line width counter starts counting at the moment when the non-white pixel region adjacent to the white pixel region in the sub scanning direction is detected, and counts up every time continuous non-white pixel regions are detected.
  • all of 8 dots are black, since image data are of 1 bit, it can be determined whether 8 dots collectively are of 0 ⁇ FF.
  • the gray width counter is a counter which counts numbers of regions that are neither the black pixel region nor the white pixel region and continue in the sub scanning direction.
  • a flag of the thinning region is placed (S 814 ), and the count-up of the thinning region width is performed (S 815 ).
  • the thinning region flag is a flag switched ON when a black pixel region appearing first in the sub scanning direction in a line region is detected.
  • a thinning region width counter is a counter counting the width (dot number) of a region to be a candidate of an object of thinning processing in the sub scanning direction.
  • the thinning region width counter is a counter which counts the width in the sub scanning direction of a region constituted of the non-white pixel region starting from a black pixel region and continuing in the sub scanning direction, in a line region.
  • the line width of the line region is a predetermined width from the value of the line width counter (S 804 ).
  • the line width counter indicates 4- to 8-dot width in the sub scanning direction that is apt to generate the tailing phenomenon (S 804 ; Yes)
  • the extraction of a region to be subjected to the thinning processing is performed by using the count value of the thinning region width and the count value of the gray width (S 805 ). Specifically, first, by subtracting the count value of the gray width from the count value of the thinning region width, the width of a region obtained by adding the black edge region and thinning candidate region surrounded by the black edge region is calculated.
  • the position of the thinning candidate region is extracted.
  • the count value of the thinning region width is calculated.
  • the gray width count value is calculated.
  • a region obtained by eliminating the black edge region from the region having the calculated width is extracted as a thinning candidate region.
  • the inside of the line left is to be extracted as a region to be subjected to the thinning processing.
  • the processing at S 805 will specifically be explained.
  • the y coordinate value when S 805 in FIG. 8 is executed is 10
  • the count value of the thinning region width is 7
  • the count value of the gray width is 2
  • the width of the region surrounded by the black edge region and the black edge region (the thinning candidate region) is 5 (see FIG. 11 ).
  • the count value of the gray width and the count value of the thinning region width are cleared at S 807 and S 808 after the processing at S 805 .
  • the region to be the object of the thinning processing for reducing the tailing phenomenon can be extracted through the use of simple processing and appropriately.
  • the detailed processing shown in FIG. 8 is only an example, and, if a region shown by the hatched part in FIG. 7D can be extracted, the extraction may be performed by another processing.
  • FIG. 11 shows the relation of the y coordinate (the position in the sub scanning direction), the image data, the line width counter, the gray width counter, the thinning region width counter, the thinning region flag and the execution of the processing, when an extraction processing of an image region by an Example according to the invention is performed on the input image data in FIGS. 6A to 6C .
  • One feature of the invention lies in the fact that, when a plurality of dots exist with respect to the image region to be the object to be determined, only one point to be determined is whether all are black, all are white, or others. For example, in the case where 8 dots are set to be the unit of processing for an input of a 1 bit binary image, it is sufficient only to determine 0 ⁇ 00, 0 ⁇ FF, or others. Because of this, the speeding-up of the processing can be expected as compared with a case of calculating an average density or performing processing such as providing a threshold value for the number of black/white dots, on the image region that is the object to be determined.
  • the unit of processing 8 dots are exemplified as the unit of processing, but it is needless to say that the unit is not limited to it.
  • the number of dots in a main scanning direction of input image is 8, but the number may be N dots (N is a counting number).
  • N is a counting number.
  • the extraction processing of the image region shown by the invention to an image data having an edge of a comparatively straight line as shown in FIGS. 4A to 4D , it is possible to extract a region equivalent to that according to a region extraction processing by a related art. Accordingly, without regard to the type of input image data such as printed data by PDL and image data taken in with an image scanner, the application of the processing is possible in the same manner.
  • Example 1 of the invention it is possible to realize an image processing apparatus and an image processing method capable of extracting an image region at high-speed and executing the thinning processing based on the determination standard for printed data by PDL even if the input image data is of an image read with an image scanner.
  • Example 1 the processing example for image data in which the input image is a binary image data are mentioned.
  • a technique similar to that in Example 1 can be applied to a region extraction processing of a multi-value image.
  • FIGS. 9A to 9E are diagrams explaining the extraction processing and the thinning processing of the image region in Example 2.
  • the image data shown in FIGS. 9A to 9E are obtained by taking in a horizontal line with an image scanner, and is a multi-value image unlike in the case of Example 1.
  • an example includes an image data of 2-bit 4-gradations.
  • the processing is performed by setting 8 dots in the horizontal direction as the unit of processing, for realizing the speeding-up of the processing.
  • Image regions are determined sequentially in the sub scanning direction, and as shown in FIG. 9B , first, the boundary of the white pixel region in which all objects region to be determined are white and the non-white pixel region in which all are not white (that is, there is b is set as lack in even only one dot) is detected.
  • a line of 1-dot width in the sub scanning direction being adjacent to the boundary and being located in the non-white pixel region is set as a line edge region.
  • each of black pixel regions regions in which all object regions to be determined are black
  • the black edge region is set as the black edge region.
  • a part sandwiched between line edge regions is set as the line region, and the width of the line region in the sub scanning direction is set as the line width.
  • a region present in the line region and sandwiched between black edge regions is set as the thinning candidate region. From the thinning candidate region, a portion shown as the hatched part in FIG. 9D is extracted as an image region to be subjected to the thinning processing.
  • FIG. 9E shows an example of applying the thinning processing to the extracted image region.
  • One of features of the invention lies in the fact that, even when an input image is of multi-value image data, for an image region that is the object to be determined including a plurality of dots, only a determination is made whether all are black, all are white, or others. For example, when 8 dots are set to be the unit of processing for input image data of 2-bit 4-gradations, it is sufficient only to determine whether 0 ⁇ 0000, 0 ⁇ FFFF, or others. Because of this, the speeding-up of the processing can be expected as compared with a case of calculating an average density or performing processing such as providing a threshold value for the gray level, on the image region that is the object to be determined.
  • an image before performing pseudo halftone processing is used as an example
  • the application to an image data after performing pseudo halftone processing based on multiple values is also naturally possible.
  • execution of an edge enhancement processing for example, a filter processing etc.
  • preprocessing of the extraction processing of the invention makes it possible to extract a region more effective for performing the thinning processing.
  • Example 2 of the invention even when input image data are of a multi-value image, it is possible to provide an image processing apparatus and system capable of extracting an image region at high speed and performing the thinning processing based on the determination standard similar to that for a binary image.
  • aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment(s), and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment(s).
  • the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (e.g., computer-readable medium).

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