Method of detection and smoothing of stepped edges in television image

FIELD: physics, processing of images.

SUBSTANCE: invention is related to methods of television image processing, namely, to methods of detection and smoothing of stepped edges on image. Method consists in the fact that pixels intensity values (PIV) of image are recorded in memory; for every line: PIV of the current line is extracted; PIV of line that follows the current line is extracted; dependence of pixel intensity difference module dependence (PIDMD) is calculated for the mentioned lines that correspond to single column; PIDMD is processed with threshold function for prevention of noise; "hill" areas are determined in PIDMD; single steps are defined out of "hill" areas; PIV of line that is next nearest to the current line is extracted; for current line and line next nearest to the current line operations of "hill" areas definition are repeated; for every part of image line that is defined as single step, availability of stepped area is checked in image in higher line, if so, these two stepped areas are defined as double stepped area (DSA); parts of DSA lines are shifted in respect to each other, and DSA is divided into two single steps; values of line pixels intensity are extracted for the line that is located in two lines from the current line, and operations of "hill" areas definition are repeated; single steps are smoothened by averaging of pixel intensity values.

EFFECT: improvement of quality of image stepped edges correction.

2 dwg

 

The invention relates to a method of processing television images, and in particular to methods for detecting and smoothing jagged edges in the image.

Jagged edges are one of the distortions that often occur in the image. Step edges is called the speed lines on the edges of objects in the image, where there should be smooth contours.

To remove jagged edges, you first need to find them and then smooth.

There are various ways of detecting and smoothing jagged edges of the image.

In U.S. patent No. 5151787 [1] described a method for the correction of the edges of objects in the image, which processes the signal of the Y channel of the YCrCb representation of the digital image, determines the blurred area contour on the image, then override the color of the pixels in the image areas, to make the borders more sharp.

The disadvantage of this method is that it changes the entire image, not just the field of jagged edges, which usually distorts the image: small parts are lubricated and disrupted texture image.

Graphic television display system described in U.S. patent No. 6339451 [2], provides a way of smoothing out the edges, which determines whether to smooth or round found the edge or not. The pixel image is s represented in the form of four sub-pixels, and the color of each subpixel is determined in accordance with the color of neighboring pixels. Then the value of cubicle determine the overall color of the pixel.

One disadvantage of this method is that it works with a palette of sixteen colors. In addition, the algorithm uses a threshold to determine the difference between neighboring pixels. Therefore, the boundaries between objects close colors can be found. The algorithm corrects all of the edges and not just speed, for example, vertical and horizontal lines that do not need correction, it leads to quality deterioration correction.

Closest to the claimed invention is a method of determining the jagged edges and smoothing described in U.S. patent No. 5293579 [3]. In this way the image is processed in the horizontal direction. The edge is determined by sequential scanning two rows or two columns of the image. Determine the color change. Preset table to determine whether this type of color change to take over the edge. If changing the color matches one of the types shown in the table, then the average value of neighboring pixels, By using the method of distribution of colors. This method is chosen as the prototype of the claimed invention.

The main disadvantage of this method is the prototype thresholds the condition, which are used to determine the color changes, as in the case of the application of the threshold conditions will not be defined border between similar color regions. If you increase the resolution of the image (e.g., bicubic interpolation) to determine the edges, this method will be many false paths, as defined in table color scheme assumes that the paths have a width of one pixel. Furthermore, the method smoothes found all edges regardless of speed or not, because of what can be lost in the small details of the image. That is, this method adjusts the picture isn't of high quality.

Objective of the claimed invention is a method of smoothing jagged edges of the image, which allows to improve the quality correction step the edges of the image and can operate in real time.

The problem is solved by creating a method for identifying and smoothing jagged edges in the image, which includes the following operations:

step 1 - record the intensity values of image pixels in the block of memory;

for each line of pixels of the image perform the following operations:

step 2 - extract the intensity values of the pixels of the current line;

step 3 - extract the intensity values of pixelarray, following the current row.

step 4 - calculate the dependence of the modulus of the difference of the intensity of pixels of the current row and the next row after the current row corresponding to one column, the numbers in this column;

step 5 - process dependence of the modulus of the difference of pixel intensities from the column number of the threshold function to prevent noise;

step 6 - determine the dependence of the modulus of the difference intensity pixel region "hills", i.e. segments in which the dependence of the module of the difference between the first intensity monotonically increases and then monotonically decreases, and the ratio of the length of the growing part to the decreasing part of more than 0.5 but less than 2;

step 7 - determine which of the areas "hills" are single steps, while checking the values of intensities of pixels of the original image lines corresponding to the area of the "hill", the monotonous increase/decrease:

- determine the sign of the difference between the values of the intensities of the leftmost and rightmost pixels of the line image;

- determine the sign of the difference between the values of the intensities of the pixels in the column corresponding to the top of the "hill";

- calculated the signs of the differences is determined which areas of the selected sample should be tested for monotonic increment/decrement;

- check the ut region on the monotonous increase/decrease;

- if the field condition monotone ascending/descending order, then it is determined as a single step;

step 8 - remove the intensity values of the pixels of the next row through one from the current line;

step 9 - for the current row and the next row through one from the current line, perform an operation repeat steps 4-7;

step 10 for each part of the line image, which is defined as a single step, check whether the image in the row above the stepped region corresponding to columns with the same numbers, if Yes, then the two stepped area is defined as a double stepped region;

step 11 - hold shift parts of the double row staggered relatively to each other right and left, while the share of double stepped into two single steps;

step 12 - remove the intensity values of pixels in the line, the next two from the current line;

step 13 - for the current row and the next row in two from the current line, perform an operation repeat steps 4-7;

step 14 - smooth single steps by averaging the intensity values of the pixels.

The technical result of the claimed invention is to improve the quality correction step the edges of the image due to the precise definition of the areas of the image with stepped the edges and increase the speed correction step edges due to the fact, that method handles at the same time limited the number of pixels of the initial image.

For a better understanding of the present invention the following is a detailed description with the appropriate drawings.

Figure 1. Scheme step-by-step execution (algorithm) detection method and smoothing jagged edges in the image, made according to the invention.

Figure 2. The area of the image with stepped edges and the corresponding part according to B(i) - module of difference of the pixel intensity.

Let's step through the execution of the claimed method in the device definition and smoothing jagged edges in the image on the example (Figure 1). Each step is marked in the index from 101 (step 1) to 114 (step 14).

First record of the intensity values of the pixels of the image in the memory (step 1). Then, for the pixels of each row of the image perform the following operations. Retrieve from the memory of the intensity values of the pixels of the current row and the next row after the current (steps 2, 3). Calculate the dependence of B(i) of the modulus of the difference of the intensity of pixels of the current row and the next row after the current row corresponding to one column, from the number i of this column (step 4). If A1the top row and a2the lower, then the values of the elements according to B(i) is defined by the expression B(i)=|A1(i)A2(i)|, the de 1≤ i≤N-1, where N is the width of the line image. Process dependence of the modulus of the difference of pixel intensities from the column number of the threshold function to prevent noise (step 5). Determine the dependence of the modulus of the difference intensity pixel region "hills", i.e. segments in which the dependence of the modulus of the difference intensity first increases monotonically (Figure 2), and then monotonically decreases, and the ratio of the length of the growing part to the decreasing part of more than 0.5 but less than 2 (step 6). Determine which of the areas "hills" are single steps, while checking the values of intensities of pixels of the original image lines corresponding to the area of the "hill", the monotonous increase/decrease (step 7)to determine the sign of the difference between the values of the intensities of the leftmost and rightmost pixels of the line image; determine the sign of the difference between the values of the intensities of the pixels in the column corresponding to the top of the "hill"; on the calculated signs of the differences is determined which areas of the selected sample should be checked for the monotonous increase/decrease; check the field on the monotonous increase/decrease; if the field condition monotone ascending/descending order, then it is determined as a single step. Retrieve from the memory the values of the intensity p is xela line following through one from the current row (step 8). For the current row and the next row through one from the current line, perform step 9 (i.e. repeat steps 4-7). For each part of the line image, which is defined as a single step, check whether the image in the row above the stepped region corresponding to columns with the same numbers, if Yes, then the two stepped area is defined as a double speed region (step 10). Hold shift parts of the double row staggered relatively to each other right and left, while the share of double stepped into two single steps (step 11). Retrieve from the memory of the intensity values of pixels in the line, the next two from the current row (step 12). For the current row and the next row in two from the current line, perform step 13 (i.e. repeat steps 4-7). Smooth single steps by averaging the intensity values of the pixels (step 14).

The claimed invention can be applied in industrial products, which are at the entrance of the image with low resolution.

First of all, we are talking about applications for digital television. The received signal should be displayed on the screen with a higher resolution. Thus, the input stream must be interpolated. But the input digital image typically contains the field with the effect of the imposition of the spectrum. And interpole the Oia causes speed effects. Thus, potential problem areas must be found and treated in a special way. The developed method can be applied for finding such areas.

The proposed method can also be applied to improve the quality of the displays of mobile devices. These displays usually have low resolution and speed of the effect can be quite significant.

Another important application is HDTV. To improve the perceptual quality of the stream HDTV using local contrast enhancement and methods of improving color. This leads to increased speed of the effect. The proposed method can be applied to detect such potentially bad areas to prevent the strengthening effect of aliasing.

Although the above embodiment of the invention has been set forth to illustrate the present invention, the experts it is clear that various modifications, additions and substitutions, without departing from the scope and meaning of the present invention, as claimed in the attached claims.

Method for identifying and smoothing jagged edges in the image, comprising the following operations:

step 1 - record the intensity values of the pixels of the image in the memory;

for each line of pixels of the image perform the following operations:

< num="52"> step 2 - extract the intensity values of the pixels of the current line;

step 3 - extract the intensity values of the pixels of the next row after the current row.

step 4 - calculate the dependence of the modulus of the difference of the intensity of pixels of the current row and the next row after the current row corresponding to one column, the numbers in this column;

step 5 - process dependence of the modulus of the difference of pixel intensities from the column number of the threshold function to prevent noise;

step 6 - determine the dependence of the modulus of the difference intensity pixel region "hills", i.e. segments in which the dependence of the module of the difference between the first intensity monotonically increases and then monotonically decreases, and the ratio of the length of the growing part to the decreasing part is greater than 0.5 but less than 2;

step 7 - determine which of the areas "hills" are single steps, while checking the values of intensities of pixels of the original image lines corresponding to the area of the "hill", the monotonous increase/decrease:

determine the sign of the difference between the values of the intensities of the leftmost and rightmost pixels of the line image;

determine the sign of the difference between the values of the intensities of the pixels in the column corresponding to the top of the "hill";

on the calculated signs of the differences is determined which areas of the selected sample should be tested for monotonic increment/decrement;

check the area on the monotonous increase/decrease;

if the field condition monotone ascending/descending order, then it is determined as a single step;

step 8 - remove the intensity values of the pixels of the next row through one from the current line;

step 9 - for the current row and the next row through one from the current line, perform an operation repeat steps 4-7;

step 10 for each part of the line image, which is defined as a single step checks whether the image in the row above the stepped region corresponding to columns with the same numbers, if Yes, then the two stepped area is defined as a double stepped region;

step 11 - hold shift parts of the double row staggered relatively to each other right and left, while the share of double stepped into two single steps;

step 12 - remove the intensity values of pixels in the line, the next two from the current line;

step 13 - for the current row and the next row in two from the current line, perform an operation repeat steps 4-7;

step 14 - smooth single stupen the key by averaging the intensity values of the pixels.



 

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