JP2015023445A - Image processing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus and an image forming apparatus capable of faithfully reproducing an object such as a picture, a graphic or a character included in one image independently of a sort and a size of the object.SOLUTION: An image processing apparatus 200 includes a region separation processing part 205, a region area detection part 206, a color correction processing part 207, an output gradation correction part 209, and a gradation reproduction processing part 210. In the image processing apparatus 200, the region separation processing part 205 determines a region of an object to which each pixel of an image belongs and performs separation processing for every region on the basis of an image signal and the region area detection part 206 detects classification of magnitude of an area of each region. Smoothing processing or edge emphasis processing by a space filter processing part 208, adjustment of intermediate density gradation by the output gradation correction part 209 and gradation reproduction processing by the gradation reproduction processing part 210 are performed in accordance with a region discrimination signal D indicating a region to which each pixel belongs and a region area signal E indicating the classification of the magnitude of the area of each region.

Description

  The present invention relates to an image processing apparatus and an image forming apparatus that perform image processing in consideration of input characteristics of an image input apparatus that receives image input and output characteristics of an image output apparatus that outputs an image.

  Some image forming apparatuses such as printers and copiers output an image input from an image input device that is a scanner that reads an image or a digital camera that captures an image to an image output device that is a printer that prints the image. is there. If an image input from the image input device is output to the image output device as it is, the input characteristics of the image input device and the output characteristics of the image output device do not match, so that good image quality cannot be obtained. In order to obtain good image quality, image processing for reproducing an image is performed on an image input from the image input device in consideration of the input characteristics of the image input device and the output characteristics of the image output device. It is necessary to provide an image processing device, correct an image input to the image input device, and output the corrected image output device.

  In the image processing by the conventional image processing apparatus, the same image processing is performed for each of a plurality of areas obtained by dividing the image into a grid pattern, for example, by comparing the magnitude relationship with a specific threshold value and whether or not to add a color. For this reason, if a plurality of different types of objects such as photographs / halftone dots, characters / thin lines, and figures are mixed in one image, the image quality of any type of object deteriorates.

  Therefore, in order to obtain a good image quality regardless of the type of object included in one image, the density gradient, peak position, and number of peaks of the image are detected for each of a plurality of areas obtained by dividing the image into a grid pattern. Depending on the detection result, there is an image processing such as edge enhancement processing that clearly reproduces the region and smoothing processing that smoothes the shading change of the region (for example, see Patent Document 1).

JP 2000-125129 A

  However, in the image processing described in Patent Document 1, for example, in order to improve the readability of characters with respect to a character region, enhancement of peripheral edge regions and contrast enhancement are uniformly performed regardless of the size of the characters. Do. As a result, a small character may have a large width, and a large character may have a higher density in the edge region than in the inner painted region.

  An object of the present invention is to provide an image processing apparatus and an image forming apparatus that can faithfully reproduce an object regardless of the type and size of the object included in one image.

  The image processing apparatus according to the present invention includes a separation unit, a detection unit, and an image processing unit, and performs gradation reproduction of an image. The separation unit separates the image into a plurality of regions for each object such as a photograph, a figure, and a character included in the image. The detection unit detects an area for each of the plurality of regions. The image processing unit performs image processing for reproducing an image according to the type of the object and the area detected by the detection unit for each of the plurality of regions separated by the separation unit.

  In this configuration, the image processing apparatus separates the image into a plurality of regions by the separation unit for each object such as a photograph, a figure, and a character included in the image, and detects the area of the region separated by the separation unit by the detection unit. Let The image processing apparatus performs image processing for reproducing an image according to the type of object included in the region and the area of the region, for example, spatial filter processing, output gradation correction, gradation reproduction for each of the plurality of regions. Perform processing.

  The image processing unit preferably performs at least a spatial filtering process such as a smoothing process or an edge enhancement process as the image process. In the spatial filter process, an edge enhancement process for clearly reproducing an object included in an image and a smoothing process for smoothing a change in shading of the object are performed. For this reason, an object can be reproduced more faithfully by performing different spatial filter processing depending on the type and area of the object.

  Moreover, it is preferable that the area | region of a character and a figure among objects consists of the edge area | region around a character and a figure, and an internal filling area | region, respectively. The image processing device separates an image into a photo, a character edge region, a character filled region, a graphic edge region, and a graphic filled region by a separation unit, and performs different spatial filter processing and gradation reproduction for each of these regions. By performing image processing such as processing, photographs, characters, and figures can be reproduced more faithfully.

  In addition, in the configuration further including a storage unit that stores a threshold value used for detection of the classification of the area size of the area, the detection unit determines the size of the area according to a comparison result between the area and the threshold value for each of the plurality of areas. It is preferable that the image processing unit detect image classification and the image processing unit performs image processing according to the type of object and the classification of the size of the area detected by the detection unit. The image processing apparatus can detect whether the area of the area is large or small by a simple calculation of comparing the area and the threshold value for each area.

  An image forming apparatus of the present invention includes the above-described image processing apparatus and an image forming unit that forms an image after image processing by the image processing apparatus on a sheet. Since the image forming apparatus forms an image after image processing by the above-described image processing apparatus on a sheet, the image can be printed on the sheet more faithfully.

  According to the present invention, an object can be faithfully reproduced regardless of the type and size of the object such as a photograph, a figure, and a character included in one image.

1 is a block diagram illustrating functions and configurations of an image forming apparatus according to a first embodiment of the present invention. 3 is an example of threshold information stored in the image forming apparatus. 3 is an example of optimization information stored in the image forming apparatus. (A) is an example of an image input from the image input apparatus of the image forming apparatus, and (B) is an example of an image divided by the image processing apparatus of the image forming apparatus. It is an example of a part of the optimization information which the image forming apparatus which concerns on 2nd Embodiment of this invention memorize | stores. It is a block diagram which shows the function and structure of the image forming apparatus which concerns on 3rd Embodiment of this invention.

  An image forming apparatus 10 according to a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the image forming apparatus 10 includes an image input device 100, an image processing device 200, an image output device 300, and a control unit 400.

  The image input apparatus 100 is a scanner that reads an image from a document. The image input device 100 outputs an image read from the document to the image processing device 200.

  The image processing apparatus 200 performs image processing for reproducing an image input from the image input apparatus 100 in consideration of the input characteristics of the image input apparatus 100 and the output characteristics of the image output apparatus 300. The processed image is output to the image output device 300. The image output apparatus 300 includes an image forming unit (not shown) that forms an image input from the image processing apparatus 200 on a sheet, and discharges the sheet on which the image is formed.

  The image processing apparatus 200 includes a storage unit 211, an A / D conversion unit 201, a shading correction unit 202, a document type automatic determination unit 203, an input tone correction unit 204, and an area separation processing unit (corresponding to a separation unit of the present invention). ) 205, an area area detection unit (corresponding to the detection unit of the present invention) 206, a color correction processing unit 207, a spatial filter processing unit 208, an output gradation correction unit 209, and a gradation reproduction processing unit 210. Each of these functional units is controlled by the control unit 400. The spatial filter processing unit 208, the output tone correction unit 209, and the tone reproduction processing unit 210 correspond to the image processing unit of the present invention, and reproduce the output tone of the image.

  The storage unit 211 stores threshold information 21 and optimization information 22.

  As an example, the threshold information 21 indicates a threshold for each object used when classifying the area for each region of the object included in the image for each size, as shown in FIG. There are a plurality of types of objects such as photographs / halftone dots, characters / thin lines, graphics, etc. Each of the characters / thin lines and graphics consists of an edge area around the characters / thin lines and the figure and an inner coating area. The first threshold value is smaller than the second threshold value.

  In the threshold information 21, different first and second threshold values are set for each object type. However, the threshold information may be uniformly set regardless of the object type. In addition, although two-stage thresholds such as the first threshold and the second threshold are provided, the present invention is not limited to this. Further, a threshold value may be provided for photographs and halftone dots.

  As shown in FIG. 3 as an example, the optimization information 22 is used to reproduce the output gradation of an image according to the type of the object and the classification of the area size (small area, medium area, large area). Image processing is shown. The image processing is spatial filter processing, output tone correction, and tone reproduction processing. The type of object is represented by a region identification signal D indicating which region each pixel belongs to, and the area of the object is represented by an area area signal E indicating the classification of the size of the area of each region.

  The A / D conversion unit 201 converts an image input from the image input device 100 from an analog signal to a digital signal.

  The shading correction unit 202 removes luminance unevenness due to the characteristics of the optical system and the imaging system in the image input apparatus 100 from the digital signal input from the A / D conversion unit 201, and corrects the image to have a uniform brightness. To do. The shading correction unit 202 outputs the corrected digital signal to the document type automatic determination unit 203.

  The automatic document type determination unit 203 converts the corrected digital signal input from the shading correction unit 202 into a signal (for example, a density signal) that is easy to handle for the image processing system employed in the image processing apparatus 200. At the same time, the type of the image is determined, such as whether the image is a photograph / halftone dot, a character / thin line, a figure, or a combination of them. The document type automatic determination unit 203 outputs a converted signal (for example, a density signal) to the input tone correction unit 204.

  The input tone correction unit 204 adjusts the color balance of the signal input from the document type automatic determination unit 203, and simultaneously performs image quality adjustment processing such as background density removal and contrast, and the processed signal is converted into a region separation processing unit. Output to 205.

  Based on the processed signal input from the input tone correction unit 204, the region separation processing unit 205 is configured such that each pixel of the image is a photo / halftone dot region, an edge region around a character / thin line, a character / thin line It is determined which one of the painted area inside, the edge area around the figure, and the filled area inside the figure belongs, and is separated for each area. For example, the region separation processing unit 205 separates the region shown in FIG. 4A from the image shown in FIG. 4B.

  The region separation processing unit 205 outputs the region identification signal D of each pixel to the area area detection unit 206, the spatial filter processing unit 208, the output gradation correction unit 209, and the gradation reproduction processing unit 210. The area separation processing unit 205 outputs the signal input from the input tone correction unit 204 to the area area detection unit 206 as it is.

  The area area detection unit 206 detects the classification of the area size of each region based on the region identification signal D of each pixel. Specifically, first, the area area detection unit 206 detects the area of each region by counting the number of pixels of each pixel in the same region. Then, the area area detection unit 206 refers to the threshold information 21 stored in the storage unit 211, compares the detected area of each region with the threshold value, and detects the classification of the size of the area. The size of the area is classified as small when the detected area is less than the first threshold, medium when the detected area is greater than or equal to the first threshold and less than the second threshold, and large when the detected area is greater than or equal to the second threshold. To do.

  The area area detection unit 206 transmits an area area signal E (small area, medium area, large area) for each region to the spatial filter processing unit 208, the output gradation correction unit 209, and the gradation reproduction processing unit 210. The area area detection unit 206 outputs the signal input from the region separation processing unit 205 to the color correction processing unit 207 as it is.

  The color correction processing unit 207 converts the RGB signal into a CMYK four-color signal in order to faithfully reproduce the color of the signal (RGB signal) input from the area area detection unit 206. Specifically, the color correction processing unit 207 removes the color turbidity based on the spectral characteristics of the CMY color material including unnecessary absorption components, and converts the color chromaticity into a CMY three-color signal. Then, the color correction processing unit 207 generates a K signal from the three color signals of CMY, and generates a new CMY signal obtained by subtracting the K signal obtained by the black generation process from the original CMY signal. The color correction processing unit 207 outputs the converted CMYK four-color signals to the spatial filter processing unit 208.

  The spatial filter processing unit 208 refers to the optimization information 22 in the storage unit 211 and uses the digital filter corresponding to the region identification signal D and the area area signal E to perform post-conversion input from the color correction processing unit 207. For the four color signals of CMYK, smoothing processing for smoothing the change in light and shade of the object or edge enhancement processing for clearly reproducing the object included in the image is performed. The spatial filter processing unit 208 outputs the processed CMYK four-color signals to the output tone correction unit 209.

  In the spatial filter processing unit 208, since the photographic / halftone area is subjected to smoothing processing, importance is placed on gradation, and the halftone period of the original read by the image input apparatus 100, the scan scanning period, and the output time Interference and moire with the dithering cycle of the image can be prevented. In addition, the edge area of the character / thin line and the edge area of the figure can be improved by performing edge emphasis processing using a filter that emphasizes more strongly as the area becomes smaller. It is also possible to discriminate between extremely small letters and fine lines.

  The output tone correction unit 209 refers to the optimization information 22 in the storage unit 211, and performs CMYK 4 after processing input from the spatial filter processing unit 208 according to the region identification signal D and the area area signal E. Adjust the intermediate density gradation of the color signal. The output tone correction unit 209 outputs the adjusted four color signals of CMYK to the tone reproduction processing unit 210.

  Specifically, by setting the intermediate density of the character / thin line edge area higher and setting the intermediate density of the character / thin line intermediate area lower, the toner consumption remains high while the character / thin line discrimination is high. The amount can be reduced.

  The gradation reproduction processing unit 210 refers to the optimization information 22 in the storage unit 211, and is input from the output gradation correction unit 209 using a dither pattern corresponding to the region identification signal D and the area area signal E. For the four color signals of CMYK after adjustment, gradation reproduction processing (halftone generation) is performed so that the image is separated into pixels and each gradation can be reproduced. The gradation reproduction processing unit 210 outputs the processed CMYK four-color signals to the image output apparatus 300.

  In the gradation reproduction processing unit 210, the gradation of the photograph / halftone area can be emphasized by performing gradation conversion with a halftone dither pattern having a relatively large halftone dot size in which the dot gain is stable. . In the edge region of characters / thin lines, sharpness can be emphasized rather than gradation by performing a high-definition dither pattern or error diffusion processing.

  As described above, the image processing apparatus 200 performs image processing according to the type of object and the classification of the area size for each object region included in one image, and is included in one image. Image processing suitable for each object can be performed. As a result, the object can be faithfully reproduced regardless of the type and size of the object included in one image.

  The storage unit 211 of the image forming apparatus according to the second embodiment of the present invention is different from the image forming apparatus 10 according to the first embodiment in that the threshold information 21 is not stored and only the optimization information 22 is stored. . Only the differences will be described below.

  The optimization information 22 indicates image processing for reproducing an image according to the type and area (number of pixels) of the object. FIG. 5 shows an example of image processing for the edge region of characters / thin lines. The description of other areas is omitted.

  The area area detection unit 206 detects the area of each region based on the region identification signal D of each pixel. Specifically, the area area detection unit 206 detects the area of each region by counting the number of pixels in the same region. The area area detection unit 206 transmits an area area signal E1 indicating the area (number of pixels) of each region to the spatial filter processing unit 208, the output gradation correction unit 209, and the gradation reproduction processing unit 210. The area area detection unit 206 outputs the signal input from the region separation processing unit 205 to the color correction processing unit 207 as it is.

  The spatial filter processing unit 208, the output tone correction unit 209, and the tone reproduction processing unit 210 refer to the optimization information 22 in the storage unit 211, respectively, and perform processing according to the region identification signal D and the area area signal E1. I do. For example, as shown in FIG. 5A, the spatial filter processing unit 208 performs edge enhancement processing with an intensity corresponding to the area on the edge region of a character / thin line. Further, as shown in FIG. 5B, the output tone correction unit 209 adjusts the intermediate density according to the area of the edge region of the character / thin line. Further, as shown in FIG. 5C, normal gradation reproduction processing is performed on the edge region of the character / thin line regardless of the size of the area.

  As described above, the image processing apparatus 200 performs image processing according to the type and area of an object for each object area included in one image, and is suitable for each object included in one image. Image processing can be performed. As a result, the object can be faithfully reproduced regardless of the type and size of the object included in one image.

  The image forming apparatus 10A according to the third embodiment of the present invention is different from the image forming apparatuses according to the first and second embodiments in that the image forming apparatus 10A is connected to the image input apparatus 100A. Only the differences will be described below with reference to the drawings. As shown in FIG. 6, the image forming apparatus 10A includes at least an image processing apparatus 200, an image output apparatus 300, and a control unit 400, and is connected to the image input apparatus 100A.

  The image input device 100 </ b> A is a digital camera that has an image sensor and photographs a subject. The image input device 100A outputs an image captured by the image sensor to the image processing device 200. Note that the image input device 100A may output the captured image to the image processing device 200 via a recording medium such as a USB or an SD card.

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. A disk system including a card system such as an IC card / optical card other than an SD card, or a semiconductor memory system such as a mask ROM / EPROM / EEPROM / flash ROM can be used.

  Furthermore, MFP 100 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth (registered trademark) ), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, Long Term Evolution (LTE, Long Term Evolution) and the like.

  The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

  As described above, the image processing apparatus 200 also has an object type and an area size for each area of an object included in one image, even for an image input from the image input apparatus 100A connected to the outside. By performing image processing according to the classification, it is possible to perform image processing suitable for each object included in one image. As a result, the object can be faithfully reproduced regardless of the type and size of the object included in one image.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

200 ... Image processing device 205 ... Area separation processing unit 206 ... Area area detection unit 208 ... Spatial filter processing unit 209 ... Output tone correction unit 210 ... Tone reproduction processing unit 211 ... Storage unit

Claims (5)

A separation unit that separates an image into a plurality of regions for each of objects of photographs, figures, and characters included in the image;
A detection unit for detecting an area for each of the plurality of regions;
An image processing unit that performs image processing for reproducing the image according to the type of the object and the area detected by the detection unit for each of the plurality of regions separated by the separation unit. Image processing device.   The image processing apparatus according to claim 1, wherein the image processing unit performs at least a spatial filter process of a smoothing process or an edge enhancement process as the image process.   3. The image processing apparatus according to claim 1, wherein the character or the graphic area of the object includes an edge area around the character or the graphic and an internal paint area. 4. A storage unit that stores a threshold value used for detection of classification of the size of the area of the region;
The detection unit detects a classification of the size of the area according to a comparison result between the area and the threshold for each of the plurality of regions,
The image processing apparatus according to claim 1, wherein the image processing unit performs the image processing according to a type of the object and a classification of the size of the area detected by the detection unit. An image processing apparatus according to any one of claims 1 to 4,
An image forming apparatus comprising: an image forming unit that forms an image after the image processing by the image processing apparatus on a sheet.