KR0125127B1 - Image encoder using contour - Google Patents

Abstract

The apparatus reduces false contour occurred at boundary of contour line caused by difference of grey level. When recovering image picture by compensating closed contour with arbitrary grey level, rapid changing part of grey level does not perform low pass filtering, otherwise, it is performed after determining the grey levels of two segments.

Description

Image coding device using contour

1 is a block diagram showing a conventional picture coding apparatus using contour lines;

2 is a block diagram showing a picture coding apparatus according to the present invention using an outline;

3 is a detailed block diagram of the dispersion calculation and comparison unit in FIG.

* Explanation of symbols for main parts of the drawings

11: contour construction unit 12: contour charging unit

13 dispersion calculation and comparison unit 14 low pass filter

15: multiplexer 21: local part calculation unit

22: comparator 23: endgate

The present invention relates to a picture coding apparatus using contours, and more particularly, to a picture coding apparatus capable of reducing false contours generated when restoring an image encoded using the outlines.

In general, the performance of picture coding is evaluated according to the number of bits representing the picture signal and the degree of distortion of the picture reconstructed from those bits. One of the attempts to achieve a high compression rate while the distortion of the picture is not noticeably noticeable is region division picture coding.

As is well known in the art, region division image coding divides an image into regions having similar values of pixels, and then separates the contours representing the boundaries from the contents and the information about the interior of the regions. It is a method of encoding. However, since the contour and the content are completely different information, the encoding method is independent of each other.

Here, as shown in FIG. 1, the image encoding using the contour lines is performed by extracting the edge portion of the image by using the contour information in the outline constructing unit 1, and dividing the image into several closed contours. In this case, the contour filling unit 2 uses the content information to fill the closed contour. At this time, the content information indicates the texture of the image. However, when there is a change in the gray level, the content information is usually replaced with an average gray level in the closed outline because another closed outline is formed.

In this case, the contour image (a) and the image (b) filled with the contours shown in FIG. 1 show that the gray level gradually changes on the hat or the shoulder, but after contour coding, the contour image (a) As the gray level changes, it is divided into several segments. After that, when the contour is filled, the false contour appears as shown in the image (b) in which the contour is filled.

Accordingly, the present invention is to solve the above-described problems of the prior art, when the gray level of the two segments are rapidly compared when the image is restored by filling one closed contour with an arbitrary gray level. It is an object of the present invention to provide an image encoding apparatus capable of reducing false contours generated at contour boundaries due to differences in gray levels by performing low pass filtering on a portion that does not change, and performing low pass filtering on a portion that does not.

In order to achieve the above object, the present invention provides an outline construction unit for constructing an outline image of an original image using outline information, an outline charging unit for charging the outline image constructed in the outline construction unit using content information; A low pass filter for low pass filtering the decoded image output from the contour filling unit, a local partial mountain of the decoded image output from the contour filling unit is calculated using the contour information, and then compared with a predetermined threshold A dispersion calculation and comparison unit for outputting a result as a selection signal, and for selectively outputting an image output from the contour filling unit and an image output from the low pass filter according to the selection signal output from the dispersion calculation and comparison unit Provided is an image encoding apparatus using an outline formed of a switching unit.

Further, in the picture coding apparatus of the present invention having the above-described configuration, the dispersion calculating and comparing section calculates a local partial calculation of the local partial of the decoded image output from the contour filling section using the contour information, and calculates the local partial calculation. And a comparator for comparing the obtained local partial mountain with a predetermined threshold and an AND gate for performing a logical product on predetermined masking information of the output signal of the comparator.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram of an image encoding apparatus using contours according to a preferred embodiment of the present invention.

As shown in the drawing, the image coding apparatus of the present invention uses the contour construction unit 11 for constructing the contour image of the original image using the contour information, and the contour image constructed in the contour construction unit 11. The contour filling unit 12 for charging by using the content information, the low pass filter 14 for low pass filtering the decoded image output from the contour filling unit 12, and the decoded output from the contour filling unit 12 A dispersion calculation and comparison section 13 for obtaining a local partial calculation of an image using contour information, and then comparing the result with a predetermined threshold and outputting the result as a selection signal, and a selection output from the dispersion calculation and comparison section 13. And a switching unit for selectively outputting the image output from the contour filling unit 12 and the image output from the low pass filter 14 according to the signal, that is, a multiplexer (MUX) 15.

FIG. 3 is a detailed block diagram of the dispersion calculation and comparison unit 13 in FIG. 2, which calculates the local partial calculation of the decoded image output from the contour filling unit 12 using the contour information. ), An comparator 22 for comparing the local partial mountain obtained by the local partial calculation unit 21 with a predetermined threshold, and an AND gate for performing an AND function on the output signal of the comparator 22 and predetermined masking information. It consists of 23.

Next, the configuration as described above will be described in detail with respect to the operation of the present invention.

In FIG. 2, the outline constructing unit 11 and the outline filling unit 12 are the same components that perform substantially the same functions as the conventional coding apparatus shown in FIG. The description is omitted.

On the other hand, the dispersion calculation and comparison unit 13 uses the contour information to determine the local partial calculation of the decoded image output from the contour filling unit 12 in order to prepare a criterion for determining whether the edge portion or the false contour is with respect to the contour boundary. The result is then compared with a predetermined threshold, and the result is output to the multiplexer 15 as a selection signal.

More specifically, as can be seen from FIG. 3 showing the detailed block diagram, in the operation of the dispersion calculation and comparison section 13, the local calculation calculation section 21 decodes the output from the contour filling section 12. The local partial mountain of the obtained image is obtained by using the contour information and then output to the comparator 22.

Here, the comparator 22 is to compare the local partial mountain obtained by the local partial calculation unit 21 with a predetermined threshold. If the local partial mountain is smaller than the threshold, the comparator 22 classifies a false contour and outputs a 'high' logic level. If large, it sorts into edges and outputs a 'low' logic level.

In addition, the AND gate 23 is for performing an AND operation on the output signal of the comparator 22 and the predetermined masking information, wherein the masking information is information on the masked pixel and the contour pixel. That is, when the contour pixel is located at the center of n × n pixel units, a 'high' logic level is output.

On the other hand, the low pass filter 14 low pass filters the decoded image output from the contour filling unit 12 and outputs it to the multiplexer 15.

In addition, the multiplexer 15 selectively outputs the image output from the contour filling unit 12 and the image output from the low pass filter 14 in accordance with the selection signal output from the dispersion calculation and comparator 13. That is, the image output from the low pass filter 14 is selected and output only when the local partial acid is smaller than the threshold and the masking information is in the 'high' logic state.

At this time, when the masking information outputs a 'high' logic level even when the contour pixel does not come to the center, the low-pass filter 14 may be applied not only to the contour but also to pixels around the contour whose local portion is smaller than the threshold. By using the output value, a longer natural image can be obtained.

As described above, according to the present invention, when reconstructing an image by filling one closed outline to an arbitrary gray level, the portion where the gray level changes rapidly by comparing the gray levels of two segments is not subjected to low pass filtering. The low pass filtering of the part has the effect of reducing the false contours generated at the contour boundary due to the difference in the gray level.

Claims (5)

An outline construction unit for constructing an outline image of the original image using the outline information; An outline charging unit for charging an outline image constructed in the outline construction unit using content information; A low pass filter for low pass filtering the decoded image output from the contour filling unit; A dispersion calculator for comparing the local partial calculation of the decoded image output from the contour charging unit with the contour information, comparing the predetermined threshold with a predetermined threshold, and outputting the result as a selection signal; And a switching unit for selectively outputting the image output from the contour filling unit and the image output from the low pass filter according to the selection signal output from the dispersion calculation and comparison unit. 2. The apparatus of claim 1, wherein the variance calculator and comparer calculates a local variance of the decoded image output from the contour filler using the contour information, and a local partial calculator obtained by the local partial calculator. And a comparator for performing comparison with a threshold value of the comparator and an AND gate for performing a logical product on the output signal of the comparator and predetermined masking information. The image encoding apparatus according to claim 1, wherein the switching unit outputs an image output from the low pass filter only when the local partial acid is smaller than a threshold and the masking information is in a 'high' logic state. . The image encoding apparatus according to claim 3, wherein the masking information outputs a 'high' logic level only when the contour pixel is located at the center of n × n pixel units. 4. The image encoding apparatus according to claim 3, wherein the masking information outputs a 'high' logic level only when the contour pixel is located at the periphery instead of the center of n × n pixel units.