JP2002354254A - Image processor, image processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a base without generating a false contour. SOLUTION: A base area in input image data is discriminated from a non- base area (S2). The image data of respective pixels included in the base area are set up at a base level (S2). The image data of pixels included in a boundary area between the base area set up at the base level and the non-base area are smoothed (S6). An image is reproduced so that a false contour is not caused in the boundary area on the basis of the smoothed image data and the original input image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, an image processing method, and a program for removing a background.

[0002] In this specification, "background removal" means that the brightness (tone value) of each pixel data in a background region (a region where a paper background appears if an image is printed on paper) is expressed in white. Means to convert to the maximum value corresponding to

[0003]

2. Description of the Related Art Conventionally, as a background removal process performed by an image processing apparatus, a histogram of lightness (gradation value) represented by each pixel data in an input image is created as shown in FIG. Is obtained, and a region having a higher brightness than the gradation level m (this is referred to as a “background region”)
Consider ), It is known that brightness data L is converted into a maximum value (255) corresponding to white as shown in FIG. 6C (Japanese Patent Laid-Open No. 2000-253250).
Alternatively, as shown in FIG.
Is converted to the maximum value (255), and in a region having the gradation level m or less (this is referred to as a “non-background region”), the background is not removed so that the converted lightness L ′ is continuous. It is known that a linear conversion is performed with a gradient α2 larger than the gradient α1 (= 1) in the case. FIG. 6B shows a form of linear conversion in a case where background removal is not performed.

[0004]

However, FIG.
According to the method (c), after the background is removed, the brightness L ′ is discontinuous at the boundary between the background region and the non-background region (represented by K1).
Therefore, there is a problem that a pseudo contour which does not exist in the original input image is generated at the boundary. FIG. 6 (d)
According to the method of (1), although the lightness L 'is continuous at the boundary between the background area and the non-base area, the gradation level (gradient α1
) To the gradation level of the straight line having the gradient α2, there is a problem that the image quality differs from that of the original image after the background is removed.

An object of the present invention is to provide an image processing apparatus, an image processing method, and an image processing method capable of removing a background without causing the generation of a false contour and without changing the image quality of an original image. To provide a program for executing the program.

[0006]

According to another aspect of the present invention, there is provided an image processing apparatus comprising: an area determining unit that determines a background area and a non-background area in input image data; Background level setting means for setting the image data of each pixel included in the background area determined by the means to the background level, and including the image data in the boundary area between the background area after setting the background level and the non-background area A smoothing means for performing a smoothing process on the image data of the extracted pixels, and an image for preventing a pseudo contour from being generated in the boundary area based on the image data smoothed by the smoothing means and the original input image data. And reproducing means for reproducing the data.

In the image processing apparatus according to the first aspect, first,
The area determining means determines a background area and a non-background area in the input image data. Next, the background level setting means sets the image data of each pixel included in the background area determined by the area determination means to the background level. next,
The smoothing means performs a smoothing process on the image data of the pixels included in the boundary region between the background region and the non-background region set at the background level. Then, the reproducing means reproduces the image based on the image data smoothed by the smoothing means and the original input image data so that a pseudo contour does not occur in the boundary area.

As described above, in this image processing apparatus, based on the image data subjected to the smoothing processing and the original input image data, a pseudo contour is not generated in a boundary region between a background region and a non-background region. Since the image is reproduced at the same time, the background can be removed without causing the generation of the pseudo contour. Further, since the smoothing process is only performed on the image data of the image included in the boundary area, the image quality of the non-base area, that is, the image quality of the original image does not change.

According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the image data of each pixel included in the non-base area is replaced with a specific level before the smoothing processing. The image processing apparatus further includes a background level setting unit, wherein the smoothing unit performs a smoothing process on the image data of the pixels included in the boundary area so that the background level and the specific level are continuous.

In the image processing apparatus according to the second aspect, before the smoothing process, the non-background level setting means replaces the image data of each pixel included in the non-background area with a specific level. The smoothing means performs a smoothing process on the image data of the pixels included in the boundary area so that the background level and the specific level are continuous. In the image data after the smoothing process, the background area is set to the background level and the non-base area is set to the specific level, and the image is continuous at the boundary area between the base area and the non-base area. Therefore, when, for example, the image data after the smoothing process is added to the original input image data, a pseudo contour does not occur in the boundary area. In the case of simple addition, the gradation level of the original input image data (original image) is maintained, and the image is reproduced without changing the image quality of the original image.

According to a third aspect of the present invention, in the image processing apparatus of the second aspect, the non-background level setting means can arbitrarily set the specific level.

In the image processing apparatus according to the third aspect, the non-background level setting means can arbitrarily set the specific level. For example, when the non-background level setting unit sets the specific level to zero level, for example, when the image data after the smoothing process and the original input image data are added, for example, each of the pixels included in the non-background region is added. The image data does not shift. Therefore, an image equivalent to shifting only the image of the background region while maintaining the image of the non-background region of the original input image data faithfully is obtained.

According to a fourth aspect of the present invention, in the image processing apparatus of the first, second or third aspect, the reproduction means shifts the level of the image data after the smoothing processing by a predetermined value. Means for adding the shifted image data and the original input image data.

In the image processing apparatus according to the present invention, the reproducing means shifts the level of the image data after the smoothing processing by a predetermined value by the offset means, and thereafter, the shifted image data and the original input image The data and the data are added by adding means. Therefore, by setting the shift amount by the offset means according to the user's preference, for example, an image according to the user's preference is reproduced.

According to a fifth aspect of the present invention, in the image processing method, a background area and a non-background area in the input image data are determined, and the image data of each pixel included in the background area is set to a background level. Performing a smoothing process on the image data of the pixels included in the boundary region between the background region and the non-background region after setting the background level, and the image data subjected to the smoothing process and the original image data. Reproducing an image based on the input image data such that a pseudo contour does not occur in the boundary area.

In the image processing method according to the fifth aspect, first,
A background area and a non-background area in the input image data are determined. Next, the image data of each pixel included in the background area is set to the background level. Next, a smoothing process is performed on the image data of the pixels included in the boundary region between the background region and the non-background region set at the background level. Then, an image is reproduced based on the smoothed image data and the original input image data so that a pseudo contour does not occur in the boundary area.

As described above, in this image processing method, based on the image data subjected to the smoothing process and the original input image data, a pseudo contour is not generated in the boundary region between the base region and the non-base region. Since the image is reproduced at the same time, the background can be removed without causing the generation of the pseudo contour.

A program according to a sixth aspect of the present invention comprises the steps of: determining a background area and a non-background area in input image data; and setting image data of each pixel included in the background area to a background level. Performing a smoothing process on the image data of the pixels included in the boundary region between the background region and the non-background region after setting the background level; and performing the smoothing process on the image data and the original input image. A step of reproducing an image based on the data so that a pseudo contour does not occur in the boundary area.

According to the program of claim 6, the computer can execute the image processing method of claim 5.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows a block configuration of an image reading apparatus 300 according to an embodiment of the present invention.

The image reading apparatus 300 includes an operation panel 100 for a user to receive various settings and inputs, and a CPU (central processing unit) 200 for controlling the entire apparatus.
And a ROM (Read Only Memory) storing a program to be executed by the CPU 200. The image reading apparatus 300 includes a CCD sensor 111 for obtaining image data from a document, an A / D conversion unit 310 for performing image processing on the image data, a shading correction unit 320, a scaling / movement control unit. 330, Lab conversion section 340, background level adjustment section 350, inverse Lab conversion section 3
60, a LOG correction unit 370A, a color correction processing unit 370B,
An area determination unit 390 and an MTF correction processing unit 380 are provided.

The original surface is illuminated by an exposure lamp (not shown), and the reflected light from the original surface is guided by the optical system and enters the CCD sensor 111. The analog signal obtained by the photoelectric conversion of the CCD sensor 111 is converted by the A / D converter 310 into multi-value digital image data of R (red), G (green), and B (blue). That RG
The B image data is processed by the shading corrector 320
After being corrected so as to eliminate variations in reading caused by unevenness in density between pixels in the D sensor 111 and uneven light distribution of the exposure lamp, the output is output to the scaling / movement control unit 330.

The input RGB image data is subjected to processing for changing the magnification or moving the position of the image in advance by the scaling / movement control unit 330 to the magnification designated by the operator. Output to Lab conversion section 340.

R output from scaling / movement control section 330
The color conversion system of the GB image data is converted into L (lightness data) and a and b (chromaticity data) by a Lab conversion unit 340. The Lab image data obtained by this conversion is output to the background level adjustment unit 350.

The background level adjustment unit 350 receives the input L
The background adjustment is performed on the ab image data to prevent show-through of the document and background fog.

The Lab image data after the background adjustment is inverse La
The image data is again converted into RGB image data by the b conversion unit 360,
Output to LOG correction section 370A and color correction processing section 370B.

The LOG correction unit 370A converts the input RGB image data, which is the luminance data, into a Y color corresponding to the toner color.
(Yellow), M (magenta) and C (cyan). On the other hand, the color correction processing unit 370B generates K (black) density data from the YMC density data by UCR (under color removal) processing or inking (BP) processing. The density data is expressed in 256 (0 to 255) gradations.

CMYK image data, which is density data,
After performing edge processing in the MTF correction processing unit 380,
Output to a printer (not shown).

On the other hand, the RGB image data output from the inverse Lab conversion section 360 is also input to the area determination section 390. The area determination unit 390 determines whether or not the corresponding pixel is an edge part based on the input RGB image data.

FIG. 2 shows the block configuration of the background level adjustment unit 350. This background level adjustment unit 350
Includes a multiplying unit 351, a white region discriminating unit 352, an edge discriminating unit 353, a smoothing processing unit 354, and an offset adjusting unit 355, which sequentially perform a predetermined process on the brightness data L of the input Lab image data. And an image synthesizing unit 356 for adding the brightness data output from the offset adjusting unit 355 and the original brightness data.

The operation of the background level adjustment section 350 is C
It is controlled by the PU 200 (FIG. 2) according to the flow shown in FIG. Hereinafter, the operation of the background level adjustment unit 350 will be described.
This will be described with reference to the flow of FIG. 3, the image data (represented by a bitmap image) and the brightness profile illustrated in FIGS. 4 (a) to 5 (f). FIG.
5A to 5F, the upper row represents the image data in the process of being processed, and the lower row represents the brightness profile of the corresponding image data along the center line C.

FIG. 4A illustrates input image data (original image). The input image data includes a background area 1 as a background and a donut-shaped non-base area 3. The brightness data is L = 200 in the background area 1 and L ≒ 120 in the non-base area 3.

First, the multiplication unit 351 multiplies the L data in the input image data by a predetermined constant a (where a> 1) (S1 in FIG. 3). By this multiplication, image data as shown in FIG. 4B is obtained. Note that the region where the L data exceeds 255 is uniformly represented as L = 255 for convenience of setting the background level described below.

Next, the white area discriminating section 352 functions as an area discriminating means, and the area in which the L data is 255 after multiplication is the base area (white area) 1,
Is determined (S2 in FIG. 3). At the same time, the white area determination unit 352 functions as a background level setting unit,
For the area where the data exceeds 255, the excess is cut and L = 255 is uniformly set as the background level.

Next, the edge determining section 353 determines whether or not each pixel included in the image data is an edge (S
3). If it is an edge, the L data of the pixel is L = 25
5 and included in the white area (S4). Thereby, blurring and bleeding of the edge can be prevented.

Next, as shown in FIG. 4C, the smoothing processing section 354 operates as a non-background level setting means to set the L data of each pixel included in the non-background area 3 to a zero level as a specific level. (S5 in FIG. 3).

Then, as shown in FIG. 5 (d), the smoothing processing unit 354 compares the background area 1 after the background level L = 255 and the non-background area 3 after the zero level L = 0. The smoothing process is performed on the L data of the pixels included in the boundary region 2 between S and S so that the background level L = 255 and the zero level L = 0 are continuous (S6 in FIG. 3).

Next, as shown in FIG. 5E, the offset adjusting section 355 works as an offset means to shift the L data after the smoothing processing by a predetermined value (S7 in FIG. 3). This shift amount is obtained by adding the L data of the base region 1 to the target base level L = 25 in the addition process described below.
Set to 5 In this example, the L data of each pixel after the smoothing process is uniformly reduced by 200. The L data after the offset adjustment is applied to the background area 1
L = 55, L = 0 in the non-base area 3, and L = 55 from the base area 1 to the non-base area 3 in the boundary area 2, continuously changing from L = 55 to L = 0.

Next, as shown in FIG. 5 (f), the image synthesizing unit 356 works as an adding means to add the L data after the offset adjustment and the L data of the original input image (original image). (S8 in FIG. 3). The brightness data after the addition processing is the data L after the offset adjustment in the background area 1.
= 55 and L = 200 of the original image are added, and L = 255
become. That is, a state in which the background removal is appropriately performed is obtained. In the non-base area 3, since the data after the offset adjustment is L = 0, L ≒ 120 of the original image is maintained. Therefore, the original image can be faithfully reproduced without changing the image quality of the original image. In the boundary region 2, the brightness data continuously changes from L = 255 to L ≒ 200 from the base region 1 to the non-base region 3. Therefore, a pseudo contour does not occur in the boundary region 2.

In step S5 (non-background level setting process) in FIG. 3, the L data of each pixel included in the non-background area 3 is set to zero level. However, the present invention is not limited to this. Other levels may be set as desired. In this case, the brightness of the non-base area 3 after the addition processing (S8 in FIG. 3) can be changed according to the set level. Similarly, in step S7 (offset adjustment processing) in FIG. 3, the L data of the background region 1 is L =
The level may be set to a level other than 255. In this case, the brightness of the background region 1 after the addition processing (S8 in FIG. 3) can be changed according to the set level. In this way, an image according to the user's preference can be reproduced.

[0042]

As is clear from the above, according to the image processing apparatus of the present invention, the occurrence of a false contour can be prevented.
In addition, the background can be removed so as not to change the image quality of the original image.

According to the image processing method of the present invention, the background can be removed without causing the generation of a false contour.

According to the program of the present invention, the computer can execute the image processing method of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a block configuration of an image reading apparatus according to an embodiment of the present invention;

FIG. 2 is a diagram showing a block configuration of a base level adjustment unit 350.

FIG. 3 is a diagram showing an operation flow of a background level adjustment unit 350.

FIG. 4 is a diagram showing image data and a brightness profile in a processing process.

FIG. 5 is a diagram showing image data and a brightness profile in a processing process.

FIG. 6 is a diagram illustrating a conventional background removal process and its problems.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Background area 2 Boundary area 3 Non-background area 300 Image reading device 350 Background level adjustment unit

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 5B057 AA11 BA02 CA01 CA08 CA12 CA16 CB01 CB08 CB12 CB16 CE05 CE08 DA08 DB02 DB06 DB09 DC22 5C077 LL05 MP01 PP02 PP12 PP25 PP48 PQ12 PQ19 PQ20 SS01

Claims (6)

[Claims] 1. An area discriminating means for discriminating a background area and a non-background area in input image data, and setting image data of each pixel included in the background area discriminated by the area discriminating means to a background level. Background level setting means for performing, smoothing means for performing smoothing processing on image data of pixels included in a boundary area between the background area and the non-background area after setting the background level, and smoothing by the smoothing means. An image processing apparatus, comprising: reproduction means for reproducing an image based on processed image data and original input image data so that a pseudo contour does not occur in the boundary area. 2. The image processing apparatus according to claim 1, further comprising a non-background level setting unit that replaces image data of each pixel included in the non-background area with a specific level before the smoothing processing. The image processing apparatus, wherein the means performs a smoothing process on the image data of the pixels included in the boundary area so that the background level and the specific level are continuous. 3. The image processing apparatus according to claim 2, wherein said non-background level setting means can arbitrarily set said specific level. 4. The image processing apparatus according to claim 1, wherein said reproducing means shifts a level of the image data after the smoothing processing by a predetermined value, and
An image processing apparatus comprising: an adding unit that adds the shifted image data and the original input image data. 5. A step of determining a background area and a non-background area in input image data; setting image data of each pixel included in the background area to a background level; Performing a smoothing process on the image data of the pixels included in the boundary region between the background region and the non-background region, based on the smoothed image data and the original input image data, Reproducing the image so that a pseudo contour does not occur in the boundary area. 6. A step of determining a background area and a non-background area in the input image data; setting image data of each pixel included in the background area to a background level; Performing a smoothing process on the image data of the pixels included in the boundary region between the background region and the non-background region, based on the smoothed image data and the original input image data, Reproducing an image so that a pseudo contour does not occur in the boundary area.