JPH05274429A - Picture quality improving device - Google Patents

Abstract

PURPOSE:To remove a noise and shading while holding the edge of an image by setting the density difference between adjacent variation points to zero when the density difference is less than a specific value, and reproducing the image according to the updated difference in density. CONSTITUTION:A variation point detecting circuit 1 finds the position and density of the point where the variation tendency of image density varies and stores them in a variation point position and density memory 2. A deviation detecting circuit 3 finds the difference in density between the adjacent variation point. A comparing circuit 4 sets the difference in density between the adjacent variation points to zero when the absolute value of the difference is less than the specific value, but outputs its value as it is when the difference is larger than the specific value and stores it in the variation point position and density deviation memory 5. A variation point adjusting circuit 6 adjusts the position of the variation point to either of the positions of the adjacent variation points or to between the adjacent variation points and stores it in a variation point position and density deviation memory 7. A reproducing circuit 8 reproduces the image by integrating the deviation in density according to the position of the variation point and the density deviation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image quality improving apparatus for removing noise and shading contained in an image such as a grayscale image taken in from an image pickup device or the like to obtain an image with improved image quality.

[0002]

2. Description of the Related Art Conventionally, smoothing filters, median filters and the like have been used as means for removing noise contained in images. The smoothing filter uses the average value of the density values of neighboring pixels as the density value and can remove noise to some extent, but has the drawback of blurring the edges of the image. The median filter uses the median value of the density values of neighboring pixels as the density value.The edge of the image is less blurred than the smoothing filter, but it is unavoidable that the edge becomes blurred compared to the original image. Has the drawback of taking too long. In addition, shading cannot be removed with the above filter,
Therefore, for an image with shading, there is a problem that the shape extraction of the image by binarization is not successful and the shape analysis cannot be performed.

[0003]

In view of the above problems, an object of the present invention is to improve the image quality by removing noise and shading contained in the image while keeping the edges of the image. To provide the device.

[0004]

SUMMARY OF THE INVENTION The present invention for achieving the above object is an image quality improving apparatus for improving the image quality of an image, wherein the density of each scanning line is balanced from increase to balance and decrease from balance to balance. A means (A) for obtaining the position and density of a changing point that changes from increase to decrease, an equilibrium to increasing, an equilibrium to decreasing, and a decreasing to increasing, and means (B) for obtaining a difference in density between adjacent changing points. , When the difference between the densities of the adjacent change points is less than a predetermined value, the means (C) for making the difference zero and the difference between the densities of the adjacent change points updated by the means, An image quality improving apparatus characterized by having at least a means (D) for reproducing an image, and in the apparatus, the difference in density at the changing points where the adjacent changing points have a predetermined value or more. Either of the change points Position, or, at a location between the now each other change point, which is the image quality improving apparatus having a means for generating.

The above-mentioned means of the present invention represents a basic unidirectional means, and when the pixels of an image are arranged in the horizontal and vertical directions, the above-mentioned means are provided for each horizontal direction. , May be executed arbitrarily for each vertical direction,
It may also be executed in both directions.

The present invention will be described with reference to the drawings. FIG. 1- (a) shows the density of the image in one scanning line, N is noise, A is shading, and G is an image. An image has the property that the density changes sharply at the edge portion of the image and the amount of change is large as compared with noise and shading. The present invention utilizes this property to remove noise and shading.

In FIG. 1- (a), a point marked with a circle is a change point where the concentration changes from increase to equilibrium, decrease to equilibrium, increase to decrease, equilibrium to increase, equilibrium to decrease, and decrease to increase. Indicates. That is, it represents a point where the tendency of change in density changes. Obtains such a change point, and the position _{y 1, y 2 ... y i} -1, y i, y i + 1, ... and, respectively the density at that _{location, x 1, x 2, ...} , x i _-1 , x _i ,
x _{i + 1} , ... Next, the difference between the adjacent change points is obtained, and when the absolute value of the difference is less than the predetermined value THL, the difference is set to zero, and when the absolute value is equal to or larger than the predetermined value THL, it is left as it is. That is, when Δx _i = x _{i + 1} −x _i (i = 1, 2, ...) (1) │Δx _i │ <THL, Δx _i = 0 (2) │Δx _i │ ≧ THL Time Δx _i = x _{i + 1} −x _i (3) (where THL is a constant).

When equations (1) to (3) are applied to FIG. 1- (a) and reproduced, FIG. 1- (b) is obtained. Figure 1- (b)
Noise and shading are removed from the image of Fig. 1- (a), and the original image (Fig. 1- (a))
It becomes a very clear image in which the edge information of is stored. The image of FIG. 1- (c) is a change point that is close to that of the image of FIG. 1- (b) and is a change point that satisfies | Δx _i | ≧ THL (in FIG. 1- (b), y _i y _{i + 1} ), the position between the adjacent change points (y ₁ and y in FIG. 1- (c))
_{At i + 1} , y _j and the center of y _{j + 1} ), the density difference (FIG. 1- (b))
Then, Δx _i , Δx _j ) are generated. The image (FIG. 1- (c)) thus obtained is shown in FIG.
Compared to (b), the image is sharp with the edges emphasized.

<Embodiment> An embodiment will be described with reference to FIG. The image signal is sent to the change point detection circuit (1), and the change point at which the change tendency of the density of the image changes ((○ in FIG. 1- (a)).
The position of the mark) and the density are obtained and stored in the change point position and density memory (2). The position of the change point and the density thereof are stored in the change point position / density memory (2), and the information is sent to the deviation detection circuit (3). In the deviation detection circuit (3), the difference in the density of the change points which have become different based on the equation (1) is obtained and sent to the comparison circuit (4). In the comparison circuit (4), when the absolute value of the difference between the densities of the adjacent change points is less than the predetermined value THL, the difference is set to zero, and when the absolute value is more than the predetermined value THL, the value is output as it is. That is, the expressions (2) to (3) are executed. The density deviation and its position output from the comparison circuit (4) are stored in the change point position and density deviation memory (5).

The change point position and the information stored in the density deviation memory (5) are sent to the change point adjusting circuit (6), and the change point position is either one of the adjacent change points, or It is adjusted to the position between the adjacent change points. The adjusted position of the changing point is sent to and stored in the changing point position / density deviation memory (7). The information of the changing point position and the density deviation memory (7) is sent to the reproducing circuit (8), and the image is reproduced by integrating the density deviation based on the position of the changing point and the density deviation. Reproduction circuit (8)
The image output from is a very clear image with noise and shading removed and edges emphasized from the original image.
When the edge emphasis is not necessary, the change point adjusting circuit (6), the change point position, and the density deviation memory (7) in FIG. 2 are unnecessary.

[0011]

EFFECTS OF THE INVENTION By using the present invention, noise and shading contained in an image can be removed, and an image with improved image quality can be obtained.

[Brief description of drawings]

FIG. 1 shows an image or processed image to illustrate the means of the invention.

FIG. 2 shows an outline of image processing in the embodiment.

Claims (2)

[Claims] 1. An image quality improving apparatus for improving the image quality of an image, wherein the density is changed from increase to equilibrium, decrease to equilibrium, increase to decrease, equilibrium to increase, equilibrium to decrease, and decrease to increase for each scanning line. Means for obtaining the position and density of each change point, and means for obtaining the difference in density between adjacent change points, and when the difference in density between adjacent change points is less than a predetermined value, the difference is set to zero. An image quality improving apparatus comprising at least a means and a means for reproducing an image based on a difference in density of change points which have been updated by the means. 2. The difference between the density at a change point that is equal to or more than a predetermined value at the change point that is the adjacent change point, 2. The image quality improving device according to claim 1, further comprising means for generating at a position between them.