CN101316320A - Image processing method for image processing system and related image processing device - Google Patents

Abstract

An image processing method for an image processing system for improving the quality of an image subjected to sharpness processing comprises receiving a plurality of original image data; sharpening the plurality of original image data to generate a plurality of sharpened image data; adjusting the plurality of sharpened image data according to the plurality of original image data; and outputting the adjusted plurality of sharpened image data.

Description

Image processing method for image processing system and related image processing device

technical field

The present invention relates to an image processing method used in an image processing system and its related image processing device, in particular to an image processing method and its related image processing device which can effectively suppress excessive upscaling and background noise.

Background technique

In known digital image processing systems, the image processor may perform interlaced to progressive scan conversion (for interlaced type signals), image scaling processing, displacement and edge detection and interpolation, and color space conversion of the digital image signal etc. Some of these image processing operations require the use of low-pass interpolation filters, resulting in reduced image sharpness. For example, in a television broadcast signal display system of the NTSC standard, image data is displayed in an interlaced scanning method. The interlaced scanning method is produced in response to the operating characteristics of the traditional cathode ray tube (CRT). It is used to scan the display screen twice during the display of each picture. The working principle is to divide an image picture into two fields, one of which is One field consists of odd scan lines, while the other field consists of even scan lines. As for the conversion from interlaced scanning to progressive scanning, since low-pass filtering is used in the conversion process, the sharpness of the image after progressive scanning will be reduced. In addition, the image scaling process will also result in a reduction in image sharpness. Image scaling is the process of enlarging or reducing an image in one format to fit another format. For example, a standard NTSC image with an aspect ratio of 4:3 must be scaled horizontally and vertically to be displayed on a display with an aspect ratio of 16:9. That is, the signal received by the TV must be scaled to produce image data in the format to be displayed. This operation process also includes a low-pass interpolation process, which also causes the problem of reduced sharpness of the scaled image.

Generally speaking, any image processing process that includes low-pass interpolation filtering will result in the loss of some image details. Therefore, the known technology usually adds a step of controlling the sharpness of the image in some links of the image data processing process. A common method is to use peaking (Peaking) processing to sharpen the edge parts in the image, so as to enhance the visual effect of the edge of the image. However, the known peaking process often results in an undesired situation of overshooting at the edge of the image, thus degrading the quality of the image.

Please refer to FIG. 1 , which is a block diagram of a known sharpening control unit 10 . The sharpening control unit 10 includes a high-pass filter 100 , a coring operation unit 102 , a multiplier 104 and an adder 106 . The high-pass filter 100 performs high-pass filtering on the input image signal. Next, the coring calculation unit 102 performs a nonlinear coring function calculation on the filtered image signal, and its corresponding input and output relationship is shown in FIG. 2 . It can be seen from Figure 2 that only the data on both sides of the noise level (represented by the threshold Th) will be used to eliminate the noise in the data and reduce the data below the threshold to 0. Next, the multiplier 104 multiplies the operation result of the coring operation unit 102 by a scaling factor (Scaling Factor, also called a gain) SF to increase or decrease the signal value, and then combine it with the original image.

In the sharpening control unit 10, the high-frequency information will pass through the high-pass filter 100, so the aforementioned sharpness adjustment procedure will strengthen the higher-frequency edges in the image, that is, only the parts of dots and diagonal lines will have Enhanced effect. In other words, the sharpening control unit 10 can greatly enhance the sharpness of hard edges (Hard Edge), but has a very limited effect on the sharpness enhancement of soft edges (Soft Edge). The soft edge referred to here refers to an edge that is not particularly noticeable visually, such as a blurred edge in an image or an image edge formed by slight brightness changes. Hard edges refer to visually very obvious and clearly visible edges, such as image edges formed by strong contrast or drastic brightness changes. The sharpening control unit 100 in FIG. 1 uses the multiplier 104 to adjust the gain of the image signal. Since the component corresponding to the soft edge in the image signal filtered by the high-pass filter 100 has a very small value, even if the gain is adjusted, the image sharpness of the soft edge part can only be enhanced to a limited extent. On the contrary, the component corresponding to the hard edge in the filtered image signal has a very large value, and after the gain is adjusted, the image sharpness of the hard edge part can be significantly enhanced. But this is not an ideal situation, because the hard edge is by definition the edge that is very clearly visible in the original image, so the part that should be emphasized is actually the part of the soft edge. However, if the scaling factor SF is increased to a level sufficient to effectively enhance the soft edges, it will result in overshooting of the hard edge portion of the image and background noise will also be amplified. Therefore, in order to avoid the undesired result of excessive upscaling of the hard edge portion of the image, the known sharpening control unit 100 can only provide a relatively limited sharpness enhancement effect on the soft edge.

Contents of the invention

Therefore, the main objective of the present invention is to provide an image processing method for an image processing system and a related image processing device.

The present invention discloses an image processing method used in an image processing system to improve the quality of a sharpened image, including receiving a plurality of original image data; performing sharpening processing on the plurality of original image data, to generate a plurality of sharpened image data; adjust the plurality of sharpened image data according to the plurality of original image data; and output the adjusted plurality of sharpened image data.

The present invention also discloses an image processing device used in an image processing system to improve the quality of the sharpened image, including a receiving end for receiving a plurality of original image data; a sharpening control unit, coupled to the receiving end, for sharpening the plurality of original image data to generate a plurality of sharpened image data; a sharpening compensation unit, coupled to the receiving end and the sharpening control unit, for adjusting the plurality of sharpened image data according to the plurality of original image data; and an output terminal coupled to the sharpening compensation unit for outputting the adjusted sharpened image data.

Description of drawings

FIG. 1 is a block diagram of a known sharpening control unit.

FIG. 2 is a schematic diagram of the relationship between input and output corresponding to the operation of the nonlinear kernelization function.

FIG. 3 is a schematic diagram of an image processing flow for an image processing system according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of an image processing device used in an image processing system according to an embodiment of the present invention.

Description of reference symbols

10 Sharpening control unit

100 High Pass Filter

102 Coreized operation unit

104 Multiplier

106 Adder

30 Image processing flow

300, 302, 304, 306, 308, 310 steps

40 Image processing device

400 Receiver

402 Sharpening control unit

404 Sharpening compensation unit

406 output terminal

IN(m)～IN(n) Raw image data

IN_S(m)～IN_S(n) Sharpen image data

OUT Adjustment result

Detailed ways

Please refer to FIG. 3 , which is a schematic diagram of an image processing flow 30 for an image processing system according to an embodiment of the present invention. The image processing flow 30 can improve the quality of the sharpened image, which includes the following steps:

Step 300: start.

Step 302: Receive a plurality of original image data.

Step 304: Perform sharpening processing on the plurality of original image data to generate a plurality of sharpened image data.

Step 306: Adjust the sharpened image data according to the original image data.

Step 308: Output the adjusted sharpened image data.

Step 310: end.

According to the image processing flow 30 , the present invention adjusts the sharpened image data according to the value of the original image data after the original image data is sharpened. In other words, when the original image data is sharpened, the present invention adjusts the sharpened image data according to the original image data to avoid excessive upscaling and prevent background noise from being amplified.

In the image processing flow 30, step 304 performs sharpening processing on the original image data, which can be implemented in any sharpening processing flow, such as first performing high-pass filtering and coring operations on the original image data, and then multiplying the result of the coring operations A gain value is added to the original image data to generate sharpened image data. In addition, preferably, step 306 adjusts the sharpened image data according to the maximum and minimum values of the original image data. For example, if the value of a sharpened image data is greater than the maximum value of multiple original image data, the value of the sharpened image data can be set as the maximum value of the multiple original image data or the sharpened image data The value of is divided by a default value to attenuate the value of the sharpened image data. Conversely, if the value of a sharpened image data is less than the minimum value of multiple original image data, then the value of the sharpened image data can be set to the minimum value of the multiple original image data or the sharpened image data The value of is multiplied by a default value to amplify the value of the sharpened image data. In this way, the problems of excessive upscaling and amplification of background noise can be avoided.

In the known technology, when the soft edge is enhanced by increasing the scaling factor (ie, the gain value), the hard edge part of the image will be over-scaled, and the background noise will also be amplified, resulting in image quality degradation. In contrast, the present invention moderately adjusts the sharpened data according to the extremum of the original image data. Therefore, when the intensity of the soft-edge image is increased, the present invention can suppress the phenomenon of over-amplification of the image of the hard-edge, and prevent the background noise from being amplified.

Regarding the hardware implementation of the image processing process 30 , please refer to FIG. 4 , which is a schematic diagram of an image processing device 40 used in an image processing system according to an embodiment of the present invention. The image processing device 40 can improve the quality of the sharpened image, and includes a receiving end 400 , a sharpening control unit 402 , a sharpening compensation unit 404 and an output end 406 . In the image processing device 40, the sharpening control unit 402 is used to perform sharpening processing on the original image data IN(m)-IN(n) received by the receiving end 400 to generate sharpened image data IN_S(m)-IN_S (n), and the sharpening compensation unit 404 adjusts the sharpened image data IN_S(m)˜IN_S(n) according to the original image data IN(m)˜IN(n), and outputs the adjustment result OUT through the output terminal 406 . Therefore, when the original image data IN(m)-IN(n) is sharpened by the sharpening control unit 402, the sharpening compensation unit 404 adjusts the sharpened value according to the original image data IN(m)-IN(n). The image data IN_S(m)～IN_S(n) of the image to avoid excessive upscaling and prevent background noise from being amplified.

In FIG. 4 , the sharpening control unit 402 may be any circuit or device capable of implementing sharpening operations, such as the sharpening control unit 10 in FIG. 1 . On the other hand, preferably, the sharpening compensation unit 404 adjusts the sharpened image data IN_S(m)˜IN_S(n) according to the maximum and minimum values of the original image data IN(m)˜IN(n). For example, if the value of a sharpened image data IN_S(i) is greater than a maximum value MAX of the original image data IN(m)˜IN(n), the value of the sharpened image data IN_S(i) can be set to The maximum value MAX is used to attenuate and sharpen the value of the image data IN_S(i); on the contrary, if the value of the sharpened image data IN_S(i) is smaller than the minimum value MIN of the original image data IN(m) ~ IN(n), Then, the value of the sharpened image data IN_S(i) can be set as the minimum value MIN to amplify the value of the sharpened image data. In this case, the sharpening compensation unit 404 can be implemented with the following program codes (related functional operations are known in the industry and will not be described in detail):

MAX=max(IN(m), IN(m+1), ...IN(n-1), IN(n))

MIN=min(IN(m), IN(m+1),...IN(n-1), IN(n))

if(IN_S(i)＞MAX)

OUT=MAX;

else if(IN_S(i)<MIN)

OUT=MIN;

else

OUT=IN_S(i);

end

In addition, when the value of the sharpened image data IN_S(i) is greater than the maximum value MAX, the value of the sharpened image data IN_S(i) can be divided by a default value, and when the value of the sharpened image data IN_S(i) ) is smaller than the minimum value MIN, multiply the value of the sharpened image data IN_S(i) by the default value, and the corresponding program code is as follows:

MAX=max(IN(m), IN(m+1), ... IN(n-1), IN(n))

MIN=min(IN(m), IN(m+1),...IN(n-1), IN(n))

if(IN_S(i)＞MAX)

OUT＝IN_S(i)/A;

else if(IN_S(i)<MIN)

OUT＝IN_S(i)*B;

else

OUT=IN_S(i);

end

Among them, A and B represent default values.

It should be noted that the above program code is only an embodiment for implementing the sharpening compensation unit 404 , and those skilled in the art can design circuits and program codes that meet requirements, and are not limited thereto.

To sum up, the present invention moderately adjusts the sharpened data according to the extreme value of the original image data. Therefore, when the intensity of the soft-edge image is increased, the present invention can effectively suppress the phenomenon that the hard-edge image is over-upgraded, and prevent background noise from being amplified.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (18)

1. An image processing method for an image processing system, in order to improve the quality of the sharpened image, comprising: receiving a plurality of raw image data; performing sharpening processing on the plurality of original image data to generate a plurality of sharpened image data; adjusting the plurality of sharpened image data according to the plurality of original image data; and Outputting the adjusted sharpened image data. 2. The image processing method according to claim 1, wherein performing sharpening processing on the plurality of original image data to generate the plurality of sharpened image data comprises: performing a high-pass filtering operation on the plurality of original image data to generate a plurality of high-pass filtering operation results; performing a coring operation on the plurality of high-pass filtering operation results to generate a plurality of coring operation results; multiplying the plurality of coring operation results by a gain value to generate a plurality of edge enhancement data; and The plurality of edge enhancement data and the plurality of original image data are accumulated to generate the plurality of sharpened image data. 3. The image processing method according to claim 1, wherein the plurality of sharpened image data are adjusted according to the plurality of original image data, and the plurality of sharpened image data are adjusted according to the maximum value and the minimum value of the plurality of original image data. image data. 4. The image processing method as claimed in claim 3, wherein adjusting the plurality of sharpened image data according to the maximum and minimum values of the plurality of original image data, that is, a sharpened image in the plurality of sharpened image data When the value of the data is greater than the maximum value of the plurality of original image data, attenuate the value of the sharpened image data. 5. The image processing method as claimed in claim 4, wherein attenuating the value of the sharpened image data is setting the value of the sharpened image data to a maximum value of the plurality of original image data. 6. The image processing method as claimed in claim 4, wherein attenuating the value of the sharpened image data is dividing the value of the sharpened image data by a default value. 7. The image processing method as claimed in claim 3 , wherein the plurality of sharpened image data are adjusted according to the maximum value and the minimum value of the plurality of original image data, that is, a sharpened image in the plurality of sharpened image data When the value of the data is smaller than the minimum value of the plurality of original image data, the value of the sharpened image data is amplified. 8. The image processing method as claimed in claim 7, wherein enlarging the value of the sharpened image data is setting the value of the sharpened image data to a minimum value of the plurality of original image data. 9. The image processing method as claimed in claim 7, wherein enlarging the value of the sharpened image data is multiplying the value of the sharpened image data by a default value. 10. An image processing device for an image processing system, used to improve the quality of the sharpened image, comprising: A receiving end, used to receive a plurality of original image data; A sharpening control unit, coupled to the receiving end, used to perform sharpening processing on the plurality of original image data to generate a plurality of sharpened image data; a sharpening compensation unit, coupled to the receiving end and the sharpening control unit, for adjusting the plurality of sharpened image data according to the plurality of original image data; and An output terminal is coupled to the sharpening compensation unit for outputting the adjusted sharpened image data. 11. The image processing device as claimed in claim 10, wherein the sharpening control unit comprises: A high-pass filter, coupled to the receiving end, is used to perform high-pass filtering operation on the plurality of original image data to generate a plurality of high-pass filtering operation results; A coring operation unit, coupled to the high-pass filter, is used to perform coring operations on the multiple high-filtering calculation results to generate multiple coring calculation results; A multiplier, coupled to the coring operation unit, is used to multiply the plurality of coring operation results by a gain value to generate a plurality of edge enhancement data; and An adder, coupled to the multiplier and the receiving end, is used to accumulate the plurality of edge enhancement data and the plurality of original image data to generate the plurality of sharpened image data. 12. The image processing device as claimed in claim 10, wherein the sharpening compensation unit comprises: an extremum judging unit, coupled to the receiving end, for judging the maximum and minimum values of the plurality of original image data; and A limiter, coupled to the extreme value judging unit and the sharpening control unit, is used for adjusting the plurality of sharpened image data according to the maximum and minimum values of the plurality of original image data. 13. The image processing apparatus according to claim 12, wherein the limiter attenuates the sharpened image when a value of a sharpened image data of the plurality of sharpened image data is greater than a maximum value of the plurality of original image data The value of the data. 14. The image processing device according to claim 13 , wherein the limiter attenuates the value of the sharpened image data by setting the value of the sharpened image data to the maximum value of the plurality of original image data to attenuate the sharpness. value of the image data. 15. The image processing device as claimed in claim 13, wherein the limiter attenuates the value of the sharpened image data by dividing the value of the sharpened image data by a default value to attenuate the value of the sharpened image data. 16. The image processing apparatus as claimed in claim 12, wherein the limiter enlarges the sharpened image when a value of a sharpened image data of the plurality of sharpened image data is smaller than a minimum value of the plurality of original image data The value of the data. 17. The image processing apparatus as claimed in claim 16, wherein the limiter amplifies the value of the sharpening image data and sets the value of the sharpening image data to a minimum value of the plurality of original image data to amplify the sharpening The value of the image data. 18. The image processing device as claimed in claim 16, wherein the limiter amplifies the value of the sharpened image data by multiplying the value of the sharpened image data by a default value to amplify the value of the sharpened image data.

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