CN101448163A - Down-sampling method based on sub-pel and device therefor - Google Patents
Down-sampling method based on sub-pel and device therefor Download PDFInfo
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- CN101448163A CN101448163A CN 200810185885 CN200810185885A CN101448163A CN 101448163 A CN101448163 A CN 101448163A CN 200810185885 CN200810185885 CN 200810185885 CN 200810185885 A CN200810185885 A CN 200810185885A CN 101448163 A CN101448163 A CN 101448163A
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Abstract
The invention relates to a down-sampling method based on sub-pel and a device therefor. Based on edge detection, the invention adopts a self-adapting filtering wave 140 which can remove color overlapping caused by the down-sampling of the sub-pel and effectively maintain image definition.
Description
Related application
[0001] there is not application related to the present invention.
Technical field
[0002] the present invention relates generally to picture signal and handle, particularly image demonstration and image of down-sampling (down-sampling) are to meet less demonstration, software application, transmission or customer requirements.More particularly, the objective of the invention is to be used for the down-sampling that RGB shows based on sub-pix (subpixel).
Summary of the invention
[0003] image is to be made of pixel.It is possible that the mode of the number of pixels by reducing presentation video reduces size of images.Reducing number of pixels is to be undertaken by a down-sampling process.
[0004] in the down-sampling stage, all pixels that are not initial pictures can both obtain keeping, and only keep its partial pixel, can cause like this producing serious aliased distortion (aliasing artifact) in high spatial frequency (spatial frequency) zone, because fine rule fracture/and discontinuous and destroy shape information (shape information) and edge, thus scalariform distortion (staircase artifact) shown.
[0005] each pixel of common color LCD display is actually by single addressable red, green and blue sub-pix striped (sub-pixel stripe) and forms.Use can improve the apparent resolution (apparent resolution) of display image based on the demonstration of sub-pix.Because the sub-pix number is bigger three times than number of pixels, uses demonstration can reduce the scalariform distortion effectively, and rebuild shape information more faithfully based on sub-pix.So, be possible to strengthen visual quality by down-sampling based on sub-pix.But, will perceive color distortion (color fringing artifact) to some pixels, because not all red, green, blue sub-pix all is retained in the image of down-sampling.
[0006] and, employed anti-aliased low pass filter (low-pass filtering) can be paid image blurring cost though can alleviate color distortion in the down-sampling based on pixel.
[0007], and designs a filter to minimize this error metrics by deriving filter factor in order to reduce initial pictures and, can in frequency domain (frequency domain), to define an error metrics with the difference between the sub-pix mode display image.But, the down-sampling of these methods on only can the processing horizontal direction.If consider vertical down-sampling simultaneously, performance will significantly reduce.
[0008] the present invention relates to a kind of Downsapling method based on sub-pix.Downsapling method based on sub-pix can alleviate color distortion and fuzzy according to rim detection by an adaptive-filtering.Downsapling method based on sub-pix provides an optimum cut-off frequency (cutoff frequency) to give adaptive-filtering to keep image detail information as much as possible.Allow at one or more directions rather than the down-sampling on a horizontal direction only based on the Downsapling method of sub-pix, this did not occur before this disclosure.This can guarantee that the shape details on all directions obtains keeping.
[0009] an object of the present invention is to remove color distortion.Existing method only allow in the horizontal direction based on the sub-pix down-sampling, otherwise visual quality will significantly reduce.But, if shown in marginal existence is arranged in the image, may produce color distortion, if and be 255 o'clock at the numerical value of the RGB of edge left pixel sub-pix, i.e. display white, and when the numerical value at the RGB of edge right pixel sub-pix is 0, promptly show black, situation also is like this.The horizontal direction that only adopts left side R sub-pix and right side G and B sub-pix based on the sub-pix down-sampling after, will produce the pixel of a RGB numerical value for (255,0,0), promptly show redness.In initial pictures, there is not this color, thereby produces color distortion.Because CONSIDERING EDGE of the present invention, and use anti-aliasing filter (anti-aliasing filter) in different directions adaptively based on edge detection results, can remove or reduce color distortion at least,, can keep the more images detailed information as far as possible at least if remove fully.
[0010] another object of the present invention is to reduce fuzzy and the reservation image information.Defined the anti-aliasing filter cut-off frequency of an optimum in the present invention, it is novel and is higher than known cut-off frequency.Anti-aliasing filter of the present invention not only can be removed most color aliasing, and a traditional anti-aliasing filter of ratio result more clearly can be provided.
[0011] others of the present invention also will be in following disclosure.
Description of drawings
[0012] with reference to the following drawings, will describe other purpose of the present invention, aspect and embodiment subsequently in detail, wherein:
[0013] Fig. 1 shows the flow chart of an embodiment of the invention;
[0014] Fig. 2 shows a up-sampling and down-sampling embodiment;
[0015] Fig. 3 shows a rim detection embodiment;
[0016] Fig. 4 shows the embodiment of an adaptive anti-aliasing filter;
[0017] Fig. 5 shows a down-sampling embodiment based on sub-pix;
[0018] Fig. 6 shows a structural representation of implementing device of the present invention.
Detailed Description Of The Invention
[0019] Fig. 1 is presented at flow chart how to carry out the down-sampling based on sub-pix of the present invention in the described embodiment.In an embodiment, the desired size of image is
M pixel promptly arranged in the horizontal direction, N pixel arranged in vertical direction.The original dimension of image is
Wherein x and y are real numbers, cause multiple or the mark of M and N.
[0020] in an embodiment,, imports a high-definition picture at input step 110.Subsequently, in sampling step 120, have concurrently by up-sampling or down-sampling or both and to handle
Image produces one
Image wherein can be introduced the anti-aliased low pass filter based on pixel.Alternately or in the equal foreseeable embodiment, can adopt slightly different size equally, as (3M+1) x (3M+1), or (3M+2) x (3M+2), or even (3M+1) x (3M-2).In edge detecting step 130, identification is determined
Edge of image can be used maybe and needn't use gradient calculation, and edge direction also is determined simultaneously.In adaptive-filtering step 140, use different filtering according to edge direction.In sub-pix down-sampling step 150, R-sub-pix, G-sub-pix and B-sub-pix respectively from
Pick out in three pixels in the image, to provide
The RGB information of pixel in the image.In output step 160, output
Image.
[0021] Fig. 2 (a) and 2 (b) show the embodiment of a sampling step, and wherein up-sampling is to finish by interpolation (interpolation).In Fig. 2 (a) schematic diagram, along each initial pixel 210,220 of every row, fill up a additional pixels 230,240 with same intensity value, double to make picture size in the horizontal direction.Can add any amount of additional pixels in any direction.In an embodiment, down-sampling is to finish by sampling.At Fig. 2 (b), only every on the sampling image
The pixel 250 of the left hand corner of square is to produce a new images.All other remaining pixels 260,270,280 will be dropped.Like this, image in the horizontal direction with vertical direction on by down-sampling half.Usually, select in some way, in the down-sampling process, can introduce anti-aliased low pass filter, to keep picture quality with being added each intensity values of pixels that maybe will be sampled.
[0022] Fig. 3 shows the embodiment of an edge detecting step, in the illustrative example of edge detecting step, and each pixel in an image (i, j) 350 brightness Y
I, jBe used to determine marginal information, by relatively its in (i-1, j-1) 310, (i-1, j) 320, (i-1, j+1) 330, (i, j-1) 340, (i, j+1) 360, (i+1, j-1) 370, (i+1, j) 380 and (i+1, j+1) brightness of the neighbor on 390.The definition four direction, it comprises level, vertical, left diagonal (left diagonal) and right diagonal (rightdiagonal).In equation (1) definition gradient along horizontal direction:
[0023] in the gradient of equation (2) definition along vertical direction:
[0024] in the gradient of equation (3) definition along left diagonal:
[0025] in the gradient of equation (4) definition along right diagonal:
[0026] represents the rate of change of brightness on this specific direction along the gradient of each direction.Gradient along a specific direction is big more, and is obvious more along the edge of this specific direction.In described embodiment, by relatively along the Grad of different directions and find out have greatest gradient that direction to determine edge direction.The direction perpendicular quadrature (90 →) of edge direction and greatest gradient.(i, j) 350 gradient can adopt various gradient operators, comprises Roberts operator, Prewitt operator and Sobel operator, and many other operators are determining that the gradient on the different directions also is suitable for for calculating pixel.
[0027] Fig. 4 (a) shows the embodiment of an anti-aliasing filter (anti-aliasing filter), and it can be used channel element 410,420 adaptively, 430,440,450,460,470,480 and 490.Each direction channel all requires an anti-aliasing filter.In theory, (i.e., R=G=B=Y U=V=0), are the 1.5cy/ display pixels based on the sample rate of sub-pix down-sampling, and it is based on three times of pixel down-sampling 0.5cy/ display pixel to a monochrome image.Under condition R=G=B, use to keep all monochrome informations effectively based on the sub-pix down-sampling.But,, form by brightness and the sampling of colourity two parts usually: Y component and UV component a colored fully image.Because the aliasing that causes of UV component, on sample rate, can not reach 3 times lifting based on the sub-pix down-sampling.Be necessary between reservation luminance detail information and colourity aliasing, to make balance.Because human eyes are more responsive to the brightness chrominance, appreciable resolution is arranged in brightness usually.
[0028] traditionally, the down-sampling for 3 to 1,7./3 the filtering cut-off frequency of selection is.Based on the present invention and above analysis, in the present invention, approximately 7. cut-off frequency be lengthened to/3 and 7. between to obtain extra monochrome information, obvious colourity visible distortion can not take place simultaneously.5 7./12 best cut-off frequency is among the present invention.The embodiment of an anti-aliasing filter be an endless in spatial domain be the low pass filter of sinc function, its main lobe is taken as frequency overlapped-resistable filter usually.In another embodiment, the anti-aliasing filter of use is a 9-rank filter (9-tap filter).At Fig. 4 (b), show the response curve of various airspace filter devices 491,493,495 in frequency domain in the different embodiment.Do not need one at 5 sharp-pointed cut-off frequencies on 7./12, as filtering 493 and 495.Overshoot (overshoot) also might appear in anti-aliasing filter, as filtering 495.As long as they remain low-pass filtering, frequency domain response curve profile can be different in the different embodiment of anti-aliasing filter.
[0029] and, can use anti-aliasing filter adaptively based on rim detection.Anti-aliasing filter is embodied on the direction opposite with edge direction.For example,, be different from the sub-pixel values on right side fully, can use anti-aliasing filter in the horizontal direction so such as the sub-pixel values in left side if edge direction is vertical.Handle the red, green and blue channel respectively.
[0030] Fig. 5 shows an embodiment based on sub-pix down-sampling step of the present invention.(i j) is sub-pix by a 3M3N image in each pixel of a MN image
Form.For example, on (0,0) of MN image, the R sub-pix of pixel 500 equals the R sub-pix of pixel 510 on (0,0) position of 3M3N image on (0,0) position of MN image, and it equals R
0,0The G sub-pix of pixel 500 equals the G sub-pix of pixel 550 on (0,0) position of 3M3N image on (0,0) position of MN image, and it equals G
1,1The B sub-pix of pixel 500 equals the B sub-pix of pixel 590 on (0,0) position of 3M3N image on (0,0) position of MN image, and it equals B
2,2Like this, be on a diagonal, to carry out based on the sub-pix down-sampling.A variety of methods can be used for implementing based on sub-pix down-sampling step 150.Except those along the pixel of the diagonal of 3M3N image, also can use different pixels to obtain R sub-pix, G sub-pix and the B sub-pix of pixel 500 in the MN image.For example, the R sub-pix of pixel 500 is averages of the R sub-pix of pixel 520,540,560 and 580.Even used the pixel 510,550,590 of 3M3N image, also can select different sub-pixs to obtain R sub-pix, G sub-pix and the B sub-pix of pixel 500.For example, can select the B sub-pix from pixel 550, and select the G sub-pix from pixel 590.
[0031] Fig. 6 shows a kind of structural representation of implementing device of the present invention.Device 600 is displays, and it may be an any kind in particular implementation, as LCD, and LED and OLED.Install 600 integrated processors, it utilizes an Xilinx fpga chip or a SoC asic chip in specific embodiment, aims at the video down-sampling and design in preliminary treatment and reprocessing.A high-definition picture 605 is inputs of device 600, and high-definition picture 605 is handled by a sampler 610 subsequently, carry out up-sampling and down-sampling with the resolution that obtains expectation so that carry out aforesaid further processing.After up-sampling and down-sampling, image is handled by an edge detector 620, with the edge in the recognition image, and discerns its direction by aforesaid edge detection method.Image is handled by a filtering 630 then, and its basis is method as mentioned above, carries out a self adaptation anti-aliasing filter based on edge detection results.After filtering, image is handled based on sub-pix sampler 640 by one again, and its execution is aforesaid based on the image 650 of sub-pix down-sampling to export a low resolution.
[0032] to those skilled in the art, the description of the preferred embodiment of the present invention is not limit, clearly can make any renewal or modification to it, so can be with reference to the claims that are used for determining the scope of the invention.
Commercial Application
[0033] the present invention is at low resolution handheld device such as portable media player (PMPs) Or has widely worker when the upper display of high resolution images of personal digital assistant (PDAs) or video content Industry is used. The present invention also can be used in RGB-wire LCD, LED, OLED or any its Its type of display. The present invention also is suitable in the application of various requirement image down sampling. In addition, The present invention may be implemented within the Xilinx that aims at the preliminary treatment of video down-sampling and post processing and design On fpga chip or the SoC asic chip.
Claims (12)
1. down-sampling xM
The method of yN image comprises:
With an xM
The yN image sampling becomes a 3M
The 3N image;
Detect 3M
One or more edges in the 3N image;
Based on rim detection, at 3M
Implement an adaptive-filtering on the 3N image; With
With 3M
The 3N image becomes a M based on the sub-pix down-sampling
The N image.
2. down-sampling xM according to claim 1
The method of yN image, wherein said filtering have one greater than 7./3 but less than 7. cut-off frequency.
3. down-sampling xM according to claim 1
The method of yN image, wherein said filtering have one 5 cut-off frequency 7./12.
4. down-sampling xM according to claim 1
The method of yN image, wherein said filtering are one 9 rank filtering.
5. down-sampling xM according to claim 1
The method of yN image is to carry out on a diagonal based on the sub-pix down-sampling wherein.
6. down-sampling xM according to claim 1
The method of yN image, wherein said filtering are embodied on the direction opposite with edge direction.
7. down-sampling xM
The device of yN image comprises:
A sampler is with an xM
The yN image sampling becomes a 3M
The 3N image;
An edge detector detects 3M
One or more edges in the 3N image;
A filter, based on rim detection to 3M
The ground filtering of 3N image adaptive; With
One based on the sub-pix down-sampler, based on sub-pix with 3M
The 3N image down sampling becomes a M
The N image.
8. down-sampling xM according to claim 7
The device of yN image, wherein said filtering have one greater than 7./3 but less than 7. cut-off frequency.
9. down-sampling xM according to claim 7
The device of yN image, wherein said filtering have one 5 cut-off frequency 7./12.
10. down-sampling xM according to claim 7
The device of yN image, wherein said filtering are a 9-rank filtering.
11. down-sampling xM according to claim 7
The device of yN image is wherein saidly carried out based on the sub-pix down-sampling on a diagonal based on the sub-pix sampler.
12. down-sampling xM according to claim 7
The device of yN image, wherein said filtering are embodied on the direction opposite with edge direction.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200810185885 CN101448163A (en) | 2008-12-17 | 2008-12-17 | Down-sampling method based on sub-pel and device therefor |
| CN200910225724.5A CN101770759B (en) | 2008-12-17 | 2009-11-27 | Method and device for downsampling based on sub-pixel |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102044067A (en) * | 2009-10-13 | 2011-05-04 | 索尼公司 | Method and system for reducing ringing artifacts of image deconvolution |
| CN103338378A (en) * | 2013-07-24 | 2013-10-02 | 西安电子科技大学 | Two-dimensional sub-pixel sampling-based super-resolution display method and device |
| CN105206215A (en) * | 2015-10-13 | 2015-12-30 | 深圳市华星光电技术有限公司 | Display device and display method thereof |
| CN106341671A (en) * | 2015-07-13 | 2017-01-18 | 西安诺瓦电子科技有限公司 | Image display method based on sub-pixel downsampling |
| CN106358028A (en) * | 2015-07-13 | 2017-01-25 | 西安电子科技大学 | Image processing method based on subpixel downsampling |
| CN106470335A (en) * | 2015-08-17 | 2017-03-01 | 西安诺瓦电子科技有限公司 | Image processing method based on sub-pix sampling and method for displaying image |
| CN104658488B (en) * | 2013-11-18 | 2017-09-29 | 华为技术有限公司 | Downsapling method and device |
| CN108028909A (en) * | 2016-08-08 | 2018-05-11 | 深圳秦云网科技有限公司 | Wisdom monitors cloud transcoding platform |
| US10013908B2 (en) | 2015-10-13 | 2018-07-03 | Shenzhen China Star Optoelectronics Technology Co., Ltd | Display devices and displaying methods |
| CN110335198A (en) * | 2019-07-08 | 2019-10-15 | 威创集团股份有限公司 | A kind of image processing method and system |
| CN112188178A (en) * | 2020-09-30 | 2021-01-05 | Tcl华星光电技术有限公司 | Image display method and image display device |
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Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102044067A (en) * | 2009-10-13 | 2011-05-04 | 索尼公司 | Method and system for reducing ringing artifacts of image deconvolution |
| CN103338378A (en) * | 2013-07-24 | 2013-10-02 | 西安电子科技大学 | Two-dimensional sub-pixel sampling-based super-resolution display method and device |
| CN103338378B (en) * | 2013-07-24 | 2015-07-01 | 西安电子科技大学 | Two-dimensional sub-pixel sampling-based super-resolution display method and device |
| CN104658488B (en) * | 2013-11-18 | 2017-09-29 | 华为技术有限公司 | Downsapling method and device |
| CN106358028B (en) * | 2015-07-13 | 2018-06-01 | 西安电子科技大学 | Image processing method based on sub-pix down-sampling |
| CN106341671A (en) * | 2015-07-13 | 2017-01-18 | 西安诺瓦电子科技有限公司 | Image display method based on sub-pixel downsampling |
| CN106358028A (en) * | 2015-07-13 | 2017-01-25 | 西安电子科技大学 | Image processing method based on subpixel downsampling |
| CN106341671B (en) * | 2015-07-13 | 2018-04-06 | 西安诺瓦电子科技有限公司 | Method for displaying image based on sub-pix down-sampling |
| CN106470335B (en) * | 2015-08-17 | 2019-05-17 | 西安诺瓦电子科技有限公司 | Image processing method and image display method based on sub-pix sampling |
| CN106470335A (en) * | 2015-08-17 | 2017-03-01 | 西安诺瓦电子科技有限公司 | Image processing method based on sub-pix sampling and method for displaying image |
| CN105206215B (en) * | 2015-10-13 | 2017-12-15 | 深圳市华星光电技术有限公司 | Display device and its display methods |
| US10013908B2 (en) | 2015-10-13 | 2018-07-03 | Shenzhen China Star Optoelectronics Technology Co., Ltd | Display devices and displaying methods |
| CN105206215A (en) * | 2015-10-13 | 2015-12-30 | 深圳市华星光电技术有限公司 | Display device and display method thereof |
| CN108028909A (en) * | 2016-08-08 | 2018-05-11 | 深圳秦云网科技有限公司 | Wisdom monitors cloud transcoding platform |
| CN110335198A (en) * | 2019-07-08 | 2019-10-15 | 威创集团股份有限公司 | A kind of image processing method and system |
| CN112188178A (en) * | 2020-09-30 | 2021-01-05 | Tcl华星光电技术有限公司 | Image display method and image display device |
| CN112188178B (en) * | 2020-09-30 | 2022-02-22 | Tcl华星光电技术有限公司 | Image display method and image display device |
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