JP2011188489A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus in which a ground portion is detected through one time scanning and post-processing is properly performed in accordance with a detection result. <P>SOLUTION: The image processing apparatus includes: a first image-processing unit for processing an image signal input from an image input unit; a ground level-detecting unit for detecting a ground level within a preset range, in the image signal from the image input unit, and generating a ground detecting signal; a page memory for holding the image signal from the first image-processing unit and the ground detecting signal in the unit of a page; a second image-processing unit for processing an image signal outputted from the page memory while using the ground detecting signal as a control parameter; and an image output unit for outputting the image signal processed by the second image-processing unit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  Embodiments described herein relate generally to an image processing apparatus and an image processing method that detect a background level of an image input from an image input unit, perform post-processing of an image signal based on the detection result, and output the image signal to an image output unit.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus includes an image processing apparatus that detects background data of an image input from an image input unit (scanner) and removes a background using the detected data value. There is something. For example, if the image information read by the scanner has a background part or a thin part of the text, it automatically adjusts the density to match the original so that the base part is removed or the thin text is darkened. I have to.

  However, when real-time processing is performed, the background distribution for one page of the target document can only be obtained up to the point where the processing has progressed, and depending on the configuration of the document, it cannot be corrected satisfactorily. May occur. On the other hand, if it is necessary to accurately grasp the background distribution for one page of the document and remove the background, it is necessary to scan the document once to grasp the background portion and then perform the main scan, which slows down the processing. There is a problem.

Japanese Patent No. 3779400 Japanese Patent No. 32007067

  The problem to be solved by the invention is to provide an image processing apparatus and an image processing method for detecting a background portion in one scan and appropriately performing post-processing according to the detection result.

  An image processing apparatus according to an embodiment includes a first image processing unit that processes an image signal input from an image input unit, and a background level that falls within a preset range among the image signals from the image input unit. A background level detection unit that detects and generates a background detection signal; a page memory that holds the image signal from the first image processing unit and the background detection signal in units of pages; and the background detection signal as a control parameter. A second image processing unit that processes the image signal output from the page memory; and an image output unit that outputs the image signal processed by the second image processing unit.

1 is a configuration diagram showing the inside of an image forming apparatus according to an embodiment. 1 is a block diagram illustrating a configuration of a control system of an image forming apparatus according to an embodiment. 1 is a block diagram illustrating a configuration of an image processing apparatus according to an embodiment. 1 is a block diagram illustrating a configuration of a post-processing unit of an image processing apparatus according to an embodiment. 6 is a flowchart showing an operation of a background level detection unit of the image processing apparatus according to the embodiment. Explanatory drawing which shows signal distribution when input image data is a white background in one Embodiment. Explanatory drawing which shows the operation | movement of the histogram preparation of the base level detection part in one Embodiment. 10 is a flowchart illustrating an operation of a ground level detection unit according to the second embodiment.

  Embodiments for carrying out the invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected about the same location.

(First embodiment)
FIG. 1 is a configuration diagram of an image forming apparatus including an image processing apparatus according to an embodiment. In FIG. 1, an image forming apparatus 100 is, for example, a multifunction peripheral (MFP), a printer, a copier, or the like. In the following description, an MFP will be described as an example. An upper part of the main body 11 of the MFP 100 has a document table, and an automatic document feeder (ADF) 12 is provided on the document table so as to be opened and closed. An operation panel 13 is provided on the upper portion of the main body 11. The operation panel 13 includes an operation unit 14 composed of various keys and a touch panel type display unit 15.

  A scanner unit 16 is provided below the ADF 12 in the main body 11. The scanner unit 16 reads a document sent by the ADF 12 or a document placed on a document table and generates image data. Further, a printer unit 17 is provided at the center of the main body 11, and a plurality of cassettes 18 for storing various sizes of paper are provided at the bottom of the main body 11. The printer unit 17 includes a photosensitive drum, a laser, and the like. The printer unit 17 processes image data read by the scanner unit 16 or image data created by a PC (Personal Computer) or the like to fix an image on a sheet as a recording medium. . The paper on which the image is fixed by the printer unit 17 is discharged to the paper discharge unit 40.

  The printer unit 17 is, for example, a tandem color laser printer, which scans a photosensitive member with a laser beam from a laser exposure device 19 to generate an image. The printer unit 17 generates black (K), yellow (Y), magenta (M ) And cyan (C) image forming units 20K, 20Y, 20M, and 20C. The image forming units 20K, 20Y, 20M, and 20C are arranged below the transfer belt 21 in parallel from upstream to downstream.

  Since the image forming units 20K, 20Y, 20M, and 20C have the same configuration, the image forming unit 20K will be described as a representative. The image forming unit 20K includes a photosensitive drum 22K, and a charging charger 23K, a developing device 24K, a transfer roller 25K, a cleaner 26K, and the like are disposed around the photosensitive drum 22K. Above the image forming units 20K, 20Y, 20M, and 20C, a developer cartridge 28 that supplies the developer to the developing devices 24K, 24Y, 24M, and 24C is provided. The developer cartridge 28 is adjacent to black (K), yellow (Y), magenta (M), cyan (C) developer cartridges 28K, 28Y, 28M, and 28C.

  The intermediate transfer belt 21 moves cyclically, and for example, semiconductive polyimide is used from the viewpoint of heat resistance and wear resistance. The intermediate transfer belt 21 is stretched around a driving roller 29 and driven rollers 30, 31 and 32. The intermediate transfer belt 21 can be opposed to and contact the photosensitive drum 22K. A primary transfer voltage is applied to the position of the intermediate transfer belt 21 facing the photosensitive drum 22K by the transfer roller 25K, and the toner image on the photosensitive drum 22K is primarily transferred to the intermediate transfer belt 21.

  Further, a secondary transfer roller 33 is disposed opposite to the drive roller 29 that stretches the intermediate transfer belt 21. When the sheet S passes between the driving roller 29 and the secondary transfer roller 33, a secondary transfer voltage is applied by the secondary transfer roller 33, and the toner image on the intermediate transfer belt 21 is secondarily transferred to the sheet S. . A belt cleaner 34 is provided near the driven roller 32 of the intermediate transfer belt 21.

  The exposure position of the photosensitive drum 22K is irradiated with a black laser beam from the laser exposure device 19 to form a latent image on the photosensitive drum 22K. The charging charger 23K uniformly charges the entire surface of the photosensitive drum 22K. The developing device 24K supplies a two-component developer composed of toner and carrier of each color to the photosensitive drum 22K by a developing roller. The cleaner 26K removes residual toner on the surface of the photosensitive drum 22K using a blade.

  The laser exposure device 19 scans the laser beam emitted from the semiconductor laser element in the axial direction of the photosensitive drum 22K, and includes a polygon mirror 19A, an imaging lens system 19B, a mirror 19C, and the like.

  Further, a separation roller 35, a transport roller 36, and a registration roller 37 for taking out the paper S in the paper feed cassette 18 are provided between the paper feed cassette 18 and the secondary transfer roller 33. A fixing device 38 is provided downstream. A paper discharge roller 39 is provided downstream of the fixing device 38 to discharge the paper S to the paper discharge unit 40. A reverse conveyance path 41 is also provided. The reverse conveyance path 41 has a plurality of rollers 42 and reverses the paper S and guides it in the direction of the secondary transfer roller 33, and is used when performing duplex printing. The paper S that has passed through the fixing device 38 is guided to the paper discharge unit 40 or the reverse conveyance path 41 by the sorting gate 43.

  The operation of the image forming apparatus 100 will be briefly described. When image information is input from a scanner, a personal computer terminal, or the like, black (K), yellow (Y), magenta (M), and cyan (C) toner images are formed by the image forming units 20K to 20C. Black (K), yellow (Y), magenta (M), and cyan (C) toner images are multiplex-transferred at the same position on the transfer belt 21 where the toner image is formed, and a full-color toner image is obtained.

  The full color toner image on the intermediate transfer belt 21 is secondarily transferred onto the sheet S by the secondary transfer roller 31 at once. The sheet S is fed from the sheet feeding unit 18 to the position of the secondary transfer roller 33. The sheet S on which the toner image is secondarily transferred is sent to the fixing device 38 and the toner image is fixed on the sheet S. On the other hand, the intermediate transfer belt 21 is cleaned of residual toner by the belt cleaner 32 after the completion of the secondary transfer. The photosensitive drum 22 primarily transfers the toner image to the intermediate transfer belt 21, and then the residual toner is removed by the cleaner 26, so that the next image can be formed.

  FIG. 2 is a block diagram illustrating a configuration of a control system of the image forming apparatus (MFP) 100 according to the embodiment. In FIG. 2, the MFP 100 includes a main control unit 50, an operation panel 13, a scanner unit 16, and a printer unit 17. The control system of the MFP 100 includes a plurality of CPUs including a main CPU 500 in the main control unit 50, a panel CPU 130 of the operation panel 13, a scanner CPU 160 of the scanner unit 16, and a printer CPU 170 of the printer unit 17.

  The main control unit 50 includes a main CPU 500, ROM 501, RAM 502, NVRAM 503, shared RAM 504, page memory control unit 505, page memory 506, HDD 507 as a storage device, network controller 508, and image processing unit 60. Reference numeral 101 denotes an image data bus.

  The main CPU 500 controls the overall operation of the MFP 100 and controls the ADF 12. The ROM 501 stores a control program and the like. The RAM 502 temporarily stores data. The NVRAM 503 is a non-volatile memory and retains stored data even when the power is turned off. The shared RAM 504 is used for bidirectional communication between the main CPU 500 and the printer CPU 170.

  The image processing unit 60 controls the page memory control unit 505 to control the storage and reading of image data in the page memory 506 or a memory such as a line memory (not shown). Thereby, image conversion processing such as enlargement / reduction of image information is performed. The image processing unit 60 detects a background level based on the image data scanned by the scanner unit 30, and uses a detection signal of the background level to perform a post-processing unit (for example, a color conversion unit, a spatial filter unit, a density conversion unit, an identification unit, Control).

  The page memory 506 has an area capable of storing image information for a plurality of pages, and can store image information from the scanner unit 16 for each page. The network controller 508 is connected to a network, and the MFP 100 can be connected to an external device such as a server or a PC (Personal Computer) via the network controller 508.

  The HDD 507 compresses and stores image data read by the scanner unit 16 and image data (document data, drawing image data, etc.) from the PC. The image data stored in the HDD 507 is input to the image processing unit 60, subjected to various image processing, and printed on paper by the printer unit 17.

  The operation panel 13 includes a panel CPU 130 connected to the main CPU 500, a display unit 15 including various operation keys 14 and liquid crystal, and the operation key 14 includes a numeric keypad for instructing the number of copies to be printed. The display unit 15 has a touch panel function, and can input various instructions such as paper size and printing magnification, and can perform various settings such as image point adjustment by operating the display 15.

  The scanner unit 16 includes a scanner CPU 160, an image correction unit 161, a CCD driver 162 that drives an image sensor, and the like. The CCD driver 162 drives the image sensor to read an image of the document and converts it into image data. The image correction unit 161 converts the R, G, and B analog signals output from the image sensor into digital signals, the shading correction circuit, and the corrected digital signal from the shading correction circuit, respectively. It is composed of a line memory and the like for storing once.

  The printer unit 17 includes a printer CPU 170, a laser driver 171 that drives the laser of the laser exposure device 19, a transport control unit 172 that controls transport of the paper P, and a control unit 173 that controls the charger, the developing device, the transfer device, and the like. Have.

  The main CPU 500 performs bidirectional communication with the printer CPU 170 via a shared RAM (random access memory) 504, the main CPU 500 issues an operation instruction, and the printer CPU 170 returns a status status. The printer CPU 170 and the scanner CPU 160 perform serial communication, the printer CPU 170 issues an operation instruction, and the scanner CPU 160 returns a status status. Note that the image processing unit 60, the page memory 506, the network controller 508, the image correction unit 161, and the laser driver 171 are connected by the image data bus 101.

  FIG. 3 is a block diagram illustrating a configuration of an image processing apparatus that is a main part of the embodiment. In the image processing apparatus of FIG. 3, an image signal (image data) read by the image input unit (scanner unit 16) is input to the image processing unit 60, the image processing unit 60 processes the image data, and an image output unit (Printer unit 17).

  The image processing unit 60 includes a preprocessing unit 61 that preprocesses image data read by the scanner unit 16 and a background level detection unit 62 that detects the background level of the document. The image data from the preprocessing unit 61 and the background level detected by the background level detection unit 62 are respectively supplied to the page memory 506 and further stored in the HDD 507.

  The background level detection unit 62 is controlled by the main CPU 500, and the main CPU 500 controls the HDD 507 and controls each unit of the post-processing unit 70 according to the background detection signal from the HDD 507. That is, the image data read from the HDD 507 is delivered to the post-processing unit 70 after the page memory 506, but the main CPU 500 controls each unit of the post-processing unit 70 using the background detection signal stored in the HDD 507 as a control parameter. To do.

  FIG. 4 is a block diagram illustrating an example of the post-processing unit 70. The post-processing unit 70 includes, for example, a color conversion unit 71, a spatial filter 72, a density conversion unit 73, and an identification unit 74. The post-processing unit 70 includes a gradation processing unit and a screen processing unit.

  The color conversion unit 71 converts R, G, and B image data from the scanner unit 16 into yellow (Y), magenta (M), and cyan (C) data, and performs background removal and the like. The spatial filter 72 performs processing such as noise removal and edge enhancement on the Y, M, and C image data output from the color conversion unit. The density conversion unit 73 adjusts the density of each color of C, M, and Y. The identification unit 74 identifies areas such as characters, photographs, and halftone dots. After the density conversion, the C, M, and Y image data are subjected to black correction processing (inking), and Y, M, C, and K (black) image data are obtained.

  The operation of the image processing apparatus according to the embodiment will be described below. As shown in FIG. 3, the image processing unit 60 detects the background level of the image data input from the scanner unit 16 by the background level detection unit 62, and temporarily transmits the background detection signal and the image data to the HDD 507 via the page memory 506. Store. Then, it is read again from the HDD 507 at the time of printing, and as preprocessing, rotation, imposition (including a Nin1 function for arranging a plurality of pages in one page), etc. are performed on the page memory 506, and then sent to the post-processing unit 70.

  The post-processing unit 70 includes a color conversion unit 71, a spatial filter 72, a density conversion unit 73, an identification unit 74, and the like. Control using the detection signal.

  The color conversion unit 71 can perform processing so as to remove only the background level data as a reference and not affect other data. For example, when performing color copying, if the original is yellow, the background is removed. If the paper color is significant, such as pink, the background will not be removed because the color will disappear if the background is removed. Whether or not to remove the background is determined by setting a threshold value.

  The spatial filter 72 performs selective processing such as suppressing enhancement processing on background level data. Further, the density processing unit 73 performs processing when all the images below the preset density level are set to zero. Furthermore, since the background level is known, the identification unit 74 can identify areas such as characters, photographs, and halftone dots with higher accuracy.

  The post-processing unit 70 also includes a screen processing unit. The screen processing unit can perform adaptive processing for outputting the background level by setting the output signal to zero for the background. Further, a synergistic effect can be expected by combining a plurality of post-treatments as described above.

  FIG. 5 is a flowchart showing the processing of the background level detection unit 61, and shows an example in which the image data input from the image input unit (scanner unit 16) is three-dimensional data. First, assuming that the operation A0 is a start step, the target pixel is moved in the operation A1. That is, since the scanner unit 16 sequentially reads the original, the target pixel moves sequentially. In operation A2, the data (RGB signal) input from the image input unit is converted into a signal of another dimension, for example, C (cyan), M (magenta), and Y (yellow). The converted data are Dc, Dm, and Dy, respectively.

  FIG. 6 shows a signal distribution when the input image data (RGB signal) is a white background. When the R, G, and B signals are represented by levels 0 to 255, when the original is a white background, the R, G, and B signals each have a frequency peak near the level 255. On the other hand, when the RGB signals are converted into C, M, and Y signals, when the original is a white background, the C, M, and Y signals show frequency peaks near the level 0. Therefore, the background portion can be determined by setting the threshold value and determining the levels of the C, M, and Y signals.

  In the operation A3 of FIG. 5, each data Dc, Dm, Dy is compared with preset threshold values Thc, THm, THy, an input image lower than the threshold values THc, THm, THy is determined, and attention is paid to a range regarded as a background. It is determined whether or not there is a pixel. In operation A4, a histogram is created using only data that falls within the range considered as the background. That is, since the signals handled in the operation A4 are C, M, and Y signals, a histogram is created when the C, M, and Y values of the target pixel are smaller than the threshold value. The histograms are created separately for C, M, and Y.

  For example, as shown in FIG. 7, when the levels of the C, M, and Y signals are represented by 0 to 255, when the C, M, and Y values of the pixel of interest are smaller than the threshold, the threshold is set for each level of 0 to 255. A histogram is created by counting up the number below. FIG. 7 illustrates one of the histograms (hist_C [Dc], hist_M [Dm], hist_Y [Dy]) of the C, M, and Y signals.

  When the above-described processing is performed for one page and one page is completed in the operation A5, in the operation A6, the feature amounts of the C, M, and Y signals at the background level are obtained from the histogram shape using the created histogram data. . The feature value is used as a background detection signal. Operation A7 is a background level detection end step.

  The detected background detection signal is output to the page memory 506 together with the image data, and further stored in the HDD 507. The HDD 507 is connected to the main CPU 500, and based on the background detection signal stored in the HDD 507, the main CPU 500 detects each part of the post-processing unit 70 (color conversion unit 71, spatial filter 72, density conversion unit 73, identification unit 74, etc. ) To control. Therefore, the background removal signal suitable for the input image can be realized by applying the background detection signal as a control parameter to the processing of the post-processing unit 70.

  As another processing plan, it is also possible to create up to the creation of a histogram by hardware, calculate the background level by the main CPU 500 based on the created data, and reflect it as a subsequent processing parameter.

(Second Embodiment)
FIG. 8 is a flowchart showing the processing of the ground level detection unit 61 according to the second embodiment. In FIG. 8, background level detection is performed based on R, G, and B signals input from the image input unit (scanner unit 16). First, assuming that the operation A10 is a start step, the pixel of interest is moved in the operation A11. In operation A12, the difference between the image data (R, G, B signals) input from the image input unit is calculated and compared with a preset threshold value.

  In other words, when the original is a white background, the R, G, B signal has a frequency peak at a portion close to the level 255 as shown in FIG. Therefore, the difference ([RG], [GB], [BR]) of each signal is close to zero. Then, a portion where each difference is lower than preset threshold values Th1, Th2, Th3 is determined as a background portion, and in operation A13, a histogram is created using only image data that falls within the range considered as the background. The histogram creates hist_R [R], hist_G [G], and hist_B [B] separately for R, G, and B.

  When the processing described above is performed for one page and one page is completed in operation A14, the feature data of the R, G, and B signals at the background level is obtained from the shape of the histogram using the generated histogram data in operation A15. The feature value is used as a background detection signal. The operation A16 is a background level detection end step.

  In creating the histogram, the difference between at least two color signals among the R, G, and B signals of the image signal is calculated, the difference value is compared with a preset threshold value, and the histogram of pixel data lower than the threshold value is compared. You may make it create.

  The threshold values (Thc, Thm, Thy) in FIG. 5 and the threshold values (Th1, Th2, Th3) in FIG. 8 can be set in advance. The smaller the threshold value, the white background, and the higher the threshold value, the colored background. Can be determined. Therefore, by setting the threshold value, it is possible to remove the background when the document is yellowed, and not to remove the background when the document is meaningful in paper color such as pink. Become.

  According to the embodiment described above, it is possible to detect the background portion in one scan and perform appropriate background removal in accordance with the input image.

  In addition, although several embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

100: Image forming apparatus (MFP)
DESCRIPTION OF SYMBOLS 11 ... Image forming apparatus main body 13 ... Operation panel 16 ... Scanner part 17 ... Printer part 50 ... Main control part 60 ... Image processing part 61 ... Pre-processing part (1st image processing part)
62 ... Background level detection unit 63 ... Page memory 70 ... Post-processing unit (second image processing unit)
71 ... Color conversion unit 72 ... Spatial filter 73 ... Density conversion unit 74 ... Identification unit 500 ... Main CPU
507 ... Storage device (HDD)

Claims (10)

A first image processing unit that processes an image signal input from the image input unit;
A background level detection unit that detects a background level that falls within a preset range among the image signals from the image input unit and generates a background detection signal;
A page memory that holds the image signal from the first image processing unit and the background detection signal in units of pages;
A second image processing unit that processes the image signal output from the page memory using the background detection signal as a control parameter;
An image output unit for outputting an image signal processed by the second image processing unit;
An image processing apparatus comprising:   The background level detection unit converts the RGB signal of the input image signal into a signal of another color space, compares the converted signal with a preset threshold value, and generates a histogram of pixel data lower than the threshold value. The image processing apparatus according to claim 1, wherein the image processing apparatus creates and detects a background level from the shape of the histogram.   The background level detection unit calculates a difference between at least two color signals among the RGB signals of the input image signal, compares the difference value with a preset threshold, and a histogram of pixel data lower than the threshold The image processing apparatus according to claim 1, wherein a background level is detected from the shape of the histogram.   The image processing apparatus according to claim 1, wherein the background level detection unit counts up when a signal value of a target pixel satisfies a specific condition set in advance, creates a histogram, and detects a background level from the shape of the histogram.   5. The image processing apparatus according to claim 4, wherein when the histogram created by the background level detection means is created for each RGB signal, the specific condition is set separately for all of the RGB signals.   The image processing apparatus according to claim 1, wherein the second image processing unit includes a color conversion processing unit, and performs background removal according to the background detection signal.   The image processing apparatus according to claim 1, wherein the second image processing unit includes a spatial filter and suppresses enhancement processing of a background level signal according to the background detection signal. The image signal input from the image input unit is processed by the first image processing unit,
Among the image signals from the image input unit, a background level that falls within a preset range is detected to generate a background detection signal,
The image signal from the first image processing unit and the background detection signal are held in a page memory in units of pages,
Using the background detection signal as a control parameter, the image signal output from the page memory is processed by a second image processing unit,
An image processing method for outputting an image signal processed by the second image processing unit.   The detection of the background level is performed by converting the RGB signal of the input image signal into a signal in another color space, comparing the converted signal with a preset threshold value, and generating a histogram of pixel data lower than the threshold value. 9. The image processing method according to claim 8, wherein the image processing method is prepared and a ground level is detected from the shape of the histogram.   The background level is detected by calculating a difference between at least two color signals among the RGB signals of the input image signal, comparing the difference value with a preset threshold value, and a histogram of pixel data lower than the threshold value. The image processing method according to claim 8, wherein a background level is detected from the shape of the histogram.

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