Image processing device, image processing method, and program

Abstract

To provide an image processing device, an image processing method, and a program that can suppress deterioration of image quality.SOLUTION: A Image processing device that detects the background density of a document and performs background correction includes a tint generation processing portion, a hue comparison portion, and a background correction portion. The tint generation processing portion generates image data indicating an image that is predicted to be output when input image data is corrected according to the detected background density. The hue comparison portion compares the hue of the input image data and the image data generated by the tint generation processing portion. The background correction portion performs background correction according to the comparison result by the hue comparison portion.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image processing apparatus, an image processing method, and a program.

Background Art

[0002] Generally, there are various types of originals handled by image scanners, facsimiles, digital copiers, etc., and the density of the paper used for the original, that is, the background density, also ranges over a wide range. On the other hand, as the output image of these devices, it is desired that the color of the background portion (the portion of the paper itself) is "white". If the output is at the density of the background of the original as it is read, it will be regarded as being dirty and the image quality will deteriorate (the evaluation of the image quality will decrease). For this reason, conventionally, a technique for correcting input image data (for example, a process of erasing portions below the background density) according to the background of the original is known.

[0003] For example, Patent Document 1 discloses a technique for detecting the background existing in an original and correcting input image data based on the detected background density.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique disclosed in Patent Document 1, for example, when the background density cannot be accurately detected, the corrected image data will change color to a color different from the original. For this reason, there has been a problem that the image quality deteriorates.

[0005] The present invention has been made in view of the above, and an object thereof is to provide an image processing apparatus, an image processing method, and a program capable of suppressing a decrease in image quality.

Means for Solving the Problems

[0006] To solve the above-mentioned problems and achieve the objective, the present invention provides an image processing apparatus that detects the scalp density of a document and performs scalp correction, comprising: a color generation processing unit that generates image data showing an image that is expected to be output when the input image data is corrected according to the detected scalp density; a hue comparison unit that compares the hue of the input image data with the image data generated by the color generation processing unit; and a scalp correction unit that performs the scalp correction according to the comparison result by the hue comparison unit. If the hue of the input image data differs from the hue of the image data generated by the color generation processing unit, the scalp correction unit performs the scalp correction without using the detected scalp density. . [Effects of the Invention]

[0007] According to the present invention, the degradation of image quality can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows an example of the schematic configuration of the mechanical parts in the digital color copier of the embodiment. [Figure 2] Figure 2 is a flowchart showing an example of the operation of the electrical components in the digital color copier of the embodiment. [Figure 3] Figure 3 shows an example of the configuration of a background removal circuit installed in the electronics section of a digital color copier according to the embodiment. [Figure 4] Figure 4 is a diagram illustrating an example of correction by the scalp density correction circuit of the embodiment. [Figure 5] Figure 5 is a flowchart showing an example of the operation of the scalp removal circuit in the embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the image processing apparatus, image processing method, and program according to the present invention will be described in detail with reference to the attached drawings.

[0010] Figure 1 shows an example of the schematic configuration of the mechanism in the digital color copier of the embodiment. As shown in Figure 1, the mechanism of the digital copier is mainly divided into a scanner unit 101 that reads the original document and a printer unit 102 that records the image on recording paper.

[0011] In the scanner unit 101, the original document 103 is placed in a predetermined position on the platen 104 and illuminated by xenon lamps 105-1 and 105-2. The reflected light from the original document passes through the first mirror 106, the second mirror 107, the third mirror 108, and the lens 109, and is imaged onto the CCD 110, which is a 3-line color line image sensor, and is photoelectrically converted into an image signal by the CCD 110.

[0012] The xenon lamps 105-1 and 105-2 and the first mirror 106 are mounted on a first carriage (not shown), and the second mirror 107 and the third mirror 108 are mounted on a second carriage (not shown). During document scanning, the first and second carriages move from left to right at a speed ratio of 2:1 by carriage drive motors (not shown). This ensures that the entire surface of the document 103 placed on the platen 104 is scanned while maintaining a constant optical path length between the document and the lens.

[0013] The image signal converted photoelectrically by the CCD 110 is processed in various ways by the image processing unit 111, etc., and then input to an LD (laser diode) (not shown) in the printer unit 102, where it is converted into laser light.

[0014] Focusing on the printer unit 102, the laser light emitted from the LD is reflected by the polygon mirror 112, passes through the fθ lens 113 and the fourth mirror 114, and is projected onto the surface of the photoreceptor drum 115, which is rotating counterclockwise. Here, the polygon mirror 112 is fixed to the rotation axis of the polygon motor 116, and the polygon motor 116 rotates at a constant speed to rotate the polygon mirror 112. Furthermore, the rotation of this polygon mirror 112 causes the aforementioned laser light to be scanned in a direction perpendicular to the rotational movement direction of the photoreceptor drum 115, that is, in a direction along the drum axis.

[0015] The surface of the photoreceptor drum 115 is pre-charged to a uniform positive potential by a charging charger 117 connected to a high-voltage generator (not shown). When laser light is shone on the photoreceptor drum 115, the surface charge is discharged to the drum's ground via photoconductivity. Here, the LD is dimly lit for areas with light document density and brightly lit for areas with dark document density. As a result, an electrostatic latent image corresponding to the density of the document is formed on the surface of the photoreceptor drum 115 by the main scan by the polygon mirror 112 and the sub-scan by the rotation of the photoreceptor drum 115.

[0016] The developing unit 118 has developing sections K, C, M, and Y, which house positively charged toners of black, cyan, magenta, and yellow, respectively, and one of these developing sections is selected. The selected developing section is biased to a predetermined positive potential by a high-voltage generator (not shown), develops the electrostatic latent image, and forms a toner image on the surface of the photoreceptor drum 115 according to the density of the original document.

[0017] The transfer belt 119 is biased to a predetermined negative potential by a high-voltage generator (not shown) and rotates clockwise at the same speed as the photoreceptor drum 115. The toner image is attracted by the bias as the photoreceptor drum 115 and the transfer belt 119 approach each other and transferred to the surface of the transfer belt 119.

[0018] The formation of the electrostatic latent image, the formation of the toner image, and the transfer operation of the toner image are repeated the necessary number of times. That is, in the case of each mode of full color, original color, and registered color, it is performed 4 times. The developing units are selected in the order of K, C, M, and Y, respectively. The formed toner image is transferred to the surface of the transfer belt 119 after alignment. In the case of each mode of black, cyan, magenta, and yellow, it is performed only once, and the developing units K, C, M, and Y are selected respectively. In the case of each mode of red, green, and blue, it is performed 2 times. The developing units are selected in the order of M and Y, C and Y, and C and M, respectively. The formed toner image is transferred to the surface of the transfer belt 119 after alignment.

[0019] On the other hand, the recording papers 121-1 and 121-2 are respectively stored in the paper feed cassettes 120-1 and 120-2, and one of the paper feed cassettes is selected. The recording paper 121-1 in the selected paper feed cassette, for example, the paper feed cassette 120-1, is fed out by the paper feed operation of the paper feed roller 122-1 and reaches the registration rollers 123-1 and 123-2. The registration rollers 123-1 and 123-2 are initially stopped and start rotating at a predetermined timing according to the position of the toner image on the rotating transfer belt 119 to send out the recording paper.

[0020] The transfer charger 124 is connected to a high-voltage generator with a negative voltage not shown. The toner image on the transfer belt 119 is re-transferred to the fed-out recording paper by the action of the transfer charger 124. Incidentally, when re-transferring the toner image to the recording paper, the bias of the transfer belt 119 is released to promote re-transfer.

[0021] The recording paper onto which the toner image has been re-transferred is sent to the heat fixing units 125-1 and 125-2, where the toner image is fixed to the recording paper and discharged outside the machine. Incidentally, the toner remaining on the surface of the photosensitive drum 115 after transfer is removed by the cleaning unit 126, and the photosensitive drum 115 is prepared for the next operation. Also, the toner remaining on the surface of the transfer belt 119 after re-transfer is removed by the cleaning unit 127, and the transfer belt 119 is also prepared for the next operation.

[0022] In the electrical equipment unit (corresponding to an image processing apparatus) of the digital color copier according to this embodiment, the background density of the original is detected and background correction is performed. In this example, the background correction is a background removal process that dynamically detects the background density of the original and removes portions below the background density.

[0023] As shown in FIG. 2, when the background removal function is set to on (S1: Yes), the electrical equipment unit executes the background removal process (S2). The on / off of the background removal function may be switched, for example, by accepting a user operation, or may be in a form that automatically switches according to conditions. The detailed content of the background removal process will be described later.

[0024] FIG. 3 is a diagram showing an example of the configuration of a background removal circuit 200 mounted in the electrical equipment unit of the digital color copier according to this embodiment. As shown in FIG. 3, the background removal circuit 200 includes a background density detection circuit 401, a color prediction circuit 430, an input / output color ratio comparison circuit 440, and a background density correction circuit 450.

[0025] The background density detection circuit 401 detects the background density of the original image based on the input color image signal (input image data). As shown in FIG. 3, the background density detection circuit 401 includes a background density storage circuit 403, a background density prediction circuit 404, a representative value extraction circuit 405, a flatness determination circuit 406, an achromaticity determination circuit 407, a brightness determination circuit 408, a light-dark change evaluation circuit 409, a background portion determination circuit 410, a background density determination circuit 411, a background density holding circuit 412, and a background density correction circuit 413. The functions of each part may be the same as the configuration disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-262401.

[0026] The background density storage circuit 403 is a circuit that stores the color background density for each section when the main scanning direction of the image signal is divided into a plurality of sections, and inputs the stored background density to the background density prediction circuit 404 according to the position in the main scanning direction of the image signal input to the background density detection circuit 401.

[0027] The scalp density prediction circuit 404 is a circuit that predicts the scalp density of the area of ​​interest based at least on the stored scalp density corresponding to the surrounding areas of the area being processed by the representative value extraction circuit 405 and the flatness determination circuit 406, and outputs the predicted scalp density to the light / dark change evaluation circuit 409, the scalp area determination circuit 410, and the scalp density determination circuit 411. Various known techniques can be used for predicting scalp density, and for example, the technique disclosed in Japanese Patent Application Publication No. 2006-262401 can also be used.

[0028] The representative value extraction circuit 405 is a circuit that extracts and outputs image signal values ​​for each color component that represent the corresponding section, i.e., the section of interest, according to the position in the main scanning direction of the input image signal (input image data). The extracted representative values ​​are output to the achromaticity determination circuit 407, the brightness determination circuit 408, the brightness change evaluation circuit 409, and the skin area determination circuit 410, etc. Representative values ​​can be extracted by finding the average or median value of the image signals in the section of interest (the signal value located in the middle when the image signals are arranged in order of magnitude), or the average or median value of the image signals in the section of interest and its surroundings, and using these as representative values.

[0029] The flatness determination circuit 406 determines the flatness of the image signal in the section of interest and outputs the flatness determination result to the skin area determination circuit 410. The achromatic determination circuit 407 determines whether the image signal in the section of interest is nearly achromatic or not and outputs the achromaticity determination result to the skin area determination circuit 410. The brightness determination circuit 408 determines whether the image signal in the section of interest is bright or not and outputs the brightness determination result to the skin area determination circuit 410. The brightness change evaluation circuit 409 evaluates how the brightness of the image signal in the section of interest changes compared to the surrounding image signals and outputs the brightness change evaluation result to the skin area determination circuit 410.

[0030] The scalp area determination circuit 410 is a circuit that extracts scalp density according to the image signal of the area of ​​interest. It determines whether the image signal of the area of ​​interest is a scalp area or a similar area, and outputs the determination result to the scalp density holding circuit 412. It also outputs the extracted scalp density according to the determination result to the scalp density holding circuit 412 and the scalp density correction circuit 413. The scalp density correction circuit 413 is a circuit that evaluates the reliability of the above-mentioned scalp density and makes corrections, and outputs the corrected scalp density to the scalp density determination circuit 411.

[0031] The scalp density determination circuit 411 is a circuit that determines the scalp density of the area of ​​interest based at least on the predicted scalp density and corrected scalp density described above, and outputs the determined scalp density to the scalp density memory circuit 403, the color prediction circuit 430, and the scalp density correction circuit 450.

[0032] The color prediction circuit 430 is an example of a "color generation processing unit," and based on the input image data and the detected scalp density, it generates image data that shows the image that is predicted to be output (for example, output from an output device such as a printer) when the input image data is corrected according to the detected scalp density. In this embodiment, the color prediction circuit 430 corrects the input image data according to the scalp density detected by the scalp density detection circuit 401 (scalp density determined by the scalp density determination circuit 411) (removes the portion below the scalp density). After that, the color prediction circuit 430 performs a color conversion on the corrected image data to match the output device (for example, CMYK conversion is also performed here in the case of a printer). This color-converted image data corresponds to the image data that shows the image that is predicted to be output when the input image data is corrected according to the detected scalp density. The color prediction circuit 430 outputs the image data generated in this manner to the input / output hue comparison circuit 440.

[0033] The input / output hue comparison circuit 440 is an example of a "hue comparison unit" and compares the hue of the input image data with the image data output from the color prediction circuit 430. In this embodiment, the input / output hue comparison circuit 440 performs hue division on a pixel-by-pixel basis for both the input image data and the image data output from the color prediction circuit 430.

[0034] For example, hue division can divide image data into eight hues: Red, Green, Blue, Cyan, Magenta, Yellow, Black, and White. Hue division can determine which hue each pixel in the image data belongs to. The input / output hue comparison circuit 440 compares the classified hues of each pixel in the input image data and the image data output from the color prediction circuit 430 to determine whether they are the same or not.

[0035] The scalp density correction circuit 450 is an example of a "scalp correction unit" and performs scalp correction according to the hue comparison result by the input / output hue comparison circuit 440. In this embodiment, if the hue of the input image data and the hue of the image data output from the color prediction circuit 430 are different, the scalp density correction circuit 450 performs scalp correction without using the detected scalp density.

[0036] More specifically, if the hue of the input image data differs from the hue of the image data output from the color prediction processing circuit 430, the scalp density correction circuit 450 performs a correction to uniformly lower the scalp density without using the detected scalp density. For example, as shown in Figure 4, if the hue of the scalp in the input image data is Green, but the scalp in the image data output from the color prediction circuit 430 is Yellow due to a false detection of scalp density, the scalp density correction circuit 450 performs a scalp removal process to uniformly lower the scalp density without using the detected scalp density. On the other hand, if the scalp in the image data output from the color prediction circuit 430 is Green, the scalp density correction circuit 450 performs scalp correction according to the detected scalp density (it removes the portion below the scalp density).

[0037] Figure 5 is a flowchart showing an example of the operation of the scalp removal circuit 200. In step S11, the scalp density detection circuit 401 detects the scalp density. In step S12, the color prediction circuit 430 generates image data that shows the image that is predicted to be output when the input image data is corrected according to the scalp density detected in step S11. In step S13, the input / output hue comparison circuit 440 performs a hue comparison process to compare the hue of the input image data with the image data output from the color prediction circuit 430. In step S14, the scalp density correction circuit 450 performs scalp correction according to the comparison result in step S13.

[0038] In the above-described embodiment, the functions of the scalp density detection circuit 401, the color prediction circuit 430, the input / output hue comparison circuit 440, and the scalp density correction circuit 450 are each implemented by dedicated hardware circuits. However, the system is not limited to this, and may be implemented in software, for example. For example, the system may consist of a processor and non-volatile memory containing a program as the minimum hardware elements, and the processor may execute the program to realize all or part of the functions of the scalp density detection circuit 401, the color prediction circuit 430, the input / output hue comparison circuit 440, and the scalp density correction circuit 450.

[0039] As described above, in this embodiment, skin tone correction is performed according to the result of comparing the hue of the input image data with image data that shows the image that is expected to be output when the input image data is corrected according to the detected skin tone density (image data showing the predicted color). This makes it possible to suppress color changes that differ from the original.

[0040] More specifically, in this embodiment, if the hue of the input image data differs from the hue of the image data representing the predicted color (image data output from the color prediction circuit 430), a correction is performed to uniformly lower the scalp density without using the detected scalp density, thereby suppressing a color change to a different color. This has the advantageous effect of suppressing a decrease in image quality.

[0041] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the gist of the invention. Furthermore, various inventions can be formed by appropriate combinations of the multiple components disclosed in the embodiments described above. For example, some components may be deleted from all the components shown in the embodiments described above. [Explanation of symbols]

[0042] 200 Scalp Removal Circuit 401 Scalp density detection circuit 403 Scalp Concentration Memory Circuit 404 Scalp density prediction circuit 405 Representative Value Extraction Circuit 406 Flatness judgment circuit 407 Achromaticity determination circuit 408 Brightness detection circuit 409 Light / Dark Change Detection Circuit 410 Scalp Area Detection Circuit 411 Scalp density determination circuit 412 Scalp Concentration Retention Circuit 413 Scalp density correction circuit 440 Input / Output Hue Comparison Circuit 450 Scalp density correction circuit [Prior art documents] [Patent Documents]

[0043] [Patent Document 1] Japanese Patent Publication No. 2006-262401

Claims

1. An image processing device that detects the background density of a document and performs background correction, A color generation processing unit generates image data that shows the image expected to be output when the input image data is corrected according to the detected scalp density, and A hue comparison unit that compares the hue of the input image data with the image data generated by the color generation processing unit, The system includes a scalp correction unit that performs scalp correction according to the comparison results from the hue comparison unit, If the hue of the input image data differs from the hue of the image data generated by the color generation processing unit, the scalp correction unit performs the scalp correction without using the detected scalp density. Image processing device.

2. The hue comparison unit performs hue division, which divides the image data into eight hues, and performs a comparison for each hue. The image processing apparatus according to claim 1.

3. If the hue of the input image data differs from the hue of the image data generated by the color generation processing unit, the scalp correction unit performs a correction that uniformly lowers the scalp density without using the detected scalp density. The image processing apparatus according to claim 1 or 2.

4. An image processing method using an image processing device that detects the density of the background of a document and performs background correction, A color generation processing step that generates image data showing the image that is expected to be output when the input image data is corrected according to the detected scalp density, A hue comparison step that compares the hue of the input image data with the image data generated in the color generation processing step, The method includes a scalp correction step in which scalp correction is performed according to the comparison results obtained in the hue comparison step, In the scalp correction step, if the hue of the input image data and the hue of the image data generated in the color generation processing step are different, the scalp correction is performed without using the detected scalp density. Image processing methods.

5. An image processing device that detects the background density of a document and performs background correction, A color generation processing step that generates image data showing the image that is expected to be output when the input image data is corrected according to the detected scalp density, A hue comparison step that compares the hue of the input image data with the image data generated in the color generation processing step, Depending on the comparison result from the hue comparison step, the scalp correction step is performed, and In the scalp correction step, if the hue of the input image data and the hue of the image data generated in the color generation processing step are different, the scalp correction is performed without using the detected scalp density. program.

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