TW201812697A - Clustering method with a two-stage local binary pattern and an iterative image testing system thereof - Google Patents

Abstract

A clustering method with a two-stage local binary pattern includes generating a gradient direction value according to a center sub-block and neighbor sub-blocks of a patch of an image; quantizing the gradient direction value, thereby generating a quantized gradient direction value; generating a gradient magnitude value according to the gradient direction value; quantizing the gradient magnitude value, thereby generating a quantized gradient magnitude value; concatenating the quantized gradient direction value and the quantized gradient magnitude value to generate a two-stage local binary pattern (2SLBP) value; and performing clustering of super-resolution imaging by using the 2SLBP value as an index.

Description

Grouping method using second-order region binary graph and iterative image testing system

The present invention relates to super-resolution (SR) techniques, and more particularly to a grouping method and an iterative image testing system using a two-stage local binary pattern (2SLBP).

High-resolution displays are rapidly evolving, however, many image capture devices (such as surveillance devices) produce low-resolution images. In order to fill the gap between the two, a super-resolution (SR) technique was proposed. Sample-based super resolution is a kind of super-resolution technology. It searches for a high-resolution (HR) patch in a patch database and uses the obtained high-resolution patch. The low resolution sub-block of the low resolution (LR) input image is replaced, thus predicting a high resolution image.

In the present specification, "high resolution" and "low resolution" are relative terms. Therefore, the resolution of high-resolution images is higher than that of low-resolution images.

In order to reduce the size of the patch database, the regression function is usually used to store the coefficients or descriptors of the mapping function in the patch database instead of directly storing the high-resolution patch itself.

The Area Binary Map (LBP) is a commonly used descriptor that describes the regional geometry of the patch blocks in the patch database to group the patches of the same or similar visual characteristics together. However, traditional regional binary maps produce many rare clusters (eg, usage rates less than 0.001% of total), resulting in wasted storage. Therefore, there is a need to propose a novel method to improve the shortcomings of grouping.

In view of the above, one of the objects of the embodiments of the present invention is to provide a grouping method using a second-order region binary map (2SLBP) and an iterative image testing system, which is used to reduce clusters that rarely occur, thereby avoiding waste of storage and enhancing super-resolution. The intensity of image processing.

According to an embodiment of the invention, an image is divided into a plurality of patches. The gradient sub-block is generated according to the central sub-block and the adjacent sub-block of the patch; and the gradient direction value is quantized to generate a quantized gradient direction value. A gradient intensity value is generated based on the gradient direction value; and the gradient intensity value is quantized to generate a quantized gradient intensity value. The quantized gradient direction value and the quantized gradient intensity value are serially connected to generate a second-order region binary graph value, which is used as an index to perform clustering of super-resolution image processing.

According to another embodiment of the present invention, an iterative image testing system based on a second-order region binary image for super-resolution image processing includes an interpolation device that receives a low-resolution input image to generate an interpolation pixel for the input image. In the block; the grouping device generates the second-order region binary graph value as an index; the mapping device stores the complex function table, each function table includes a complex mapping function, according to the index to obtain one of the mapping functions; and the prediction device, according to the obtained The mapping function maps the interpolated pixels to the enhanced pixels to produce a high resolution output image. In addition, the patch containing the enhancement pixels is fed back to the grouping device, the mapping device, and the prediction device at least once to generate updated enhancement pixels, thereby improving the output image.

The flowchart of the first figure shows a grouping method 100 using a two-stage local binary pattern (2SLBP) according to an embodiment of the present invention. The grouping method 100 can perform image processing (eg, training and testing) on image signals of super-resolution (eg, sample-based super-resolution). The steps of the grouping method 100 can be performed by an electronic circuit, such as a digital image processor, and the super-resolution image processing can be implemented using hardware, software, or a combination thereof.

In step 11, the image to be grouped is divided into patches of a preset size (for example, 7x7). The second A diagram illustrates a patch of size 7x7. The second A diagram also shows a central sub-block 21 (e.g., 3x3 in size) with its center pixel 211 in the center of the patch.

At step 12, a gradient direction value is generated. In one embodiment, the average difference between the adjacent sub-blocks and the central sub-block 21 is generated to represent the gradient direction between the adjacent sub-blocks and the central sub-block 21. First, the average value of the adjacent sub-blocks is calculated, and the average value of the center sub-blocks 21 is calculated. Next, the average of the adjacent sub-blocks is subtracted from the average of the central sub-blocks 21 to produce an average difference. In one embodiment, a weighted average difference between adjacent sub-blocks and central sub-block 21 is generated.

The second B-picture further shows the adjacent sub-block 22 (which is 3x3 in size) with its center pixel 221 located above the center sub-block 21. The average difference between the adjacent sub-block 22 and the central sub-block 21 is indicated by an arrow to indicate the gradient direction between the secondary blocks 22 and 21.

For other directions (eg, upper right, right, lower right, lower middle, lower left, left, and upper left), the foregoing step 22 is repeated until all directions or predetermined directions have been reached (step 13). The second C-picture further shows the adjacent sub-block 23 (which is 3x3 in size) with its center pixel 231 located at the upper right of the center sub-block 21. The average difference between the adjacent sub-block 23 and the central sub-block 21 is indicated by an arrow to indicate the gradient direction between the secondary blocks 23 and 21.

In step 14, the average difference generated in step 12 is quantized to generate a local multi-gradient level pattern (LMGP) value, or a quantized gradient direction value. For example, the average difference between eight adjacent sub-blocks and the central sub-block 21 is quantized, thus producing an octet value. In one embodiment, the average difference is quantized to one of three quantization levels of 0, 1, or 2, thus forming a ternary value. The average difference and its quantification can be expressed as follows: Where w _o , w _c and w _i are weights, P _o is the pixel value of the adjacent sub-block 22/23, P _c is the pixel value of the central sub-block 21, and θ is a preset critical value.

The third A diagram illustrates the average difference between the central sub-block 21 and the adjacent sub-block 22/23. The third B graph shows the corresponding average difference for each gradient, where the critical value θ is 30. The third C plot shows the corresponding quantized mean difference for each gradient. The resulting regional multi-gradient level map (LMGP) value can be expressed as a trigonometric value of 01200100, which corresponds to a decimal value of 1224.

At step 15, a gradient magnitude value is generated to represent the gradient strength between the adjacent sub-block 22/23 and the central sub-block 21. In one embodiment, the root mean square (RMS) value of the average difference is generated, that is, the mathematical mean of the square of the mean difference is calculated and the square root is taken. .

In step 16, the root mean square (RMS) value (i.e., the gradient intensity value) of the average difference obtained in step 15 is quantized to produce a quantized gradient intensity value. In an embodiment, the root mean square (RMS) value of the mean difference and its quantification can be expressed as follows: Where p _k is the average of the adjacent sub-blocks 22/23, p _c is the average of the central sub-blocks 21, and Ψ ₁ , Ψ ₂ , and Ψ _T-1 are preset threshold values.

In step 17, the regional multi-gradient level map (LMGP) value generated in step 14 (ie, the first stage) and the quantized gradient intensity value (C _M ) generated in step 16 (ie, the second stage) are obtained. Concatenate or join to generate a two-stage local binary pattern (2SLBP) value. In an embodiment, the bits of the quantized gradient intensity value (C _M ) have a higher significance than the bits of the regional multi-gradient level map (LMGP) value. The second-order region binary map (2SLBP) value generated in step 17 can be used as an index when performing grouping (step 18) of super-resolution (SR) image processing (for example, training and testing).

According to the foregoing clustering method 100, since the gradient direction and the gradient intensity are respectively generated and quantized, when the generated index is used to perform grouping, it is stronger than the conventional method. For example, compared to the conventional method, the clustering method 100 of the present embodiment generates a rare cluster (for example, the usage rate is less than 0.001%), which can be effectively reduced, thereby avoiding waste of storage and enhancing the intensity of super-resolution image processing. .

The block diagram of the fourth diagram shows an iterative image testing system 400 for performing super-resolution (SR) image processing based on a second-order region binary map (2SLBP) in accordance with an embodiment of the present invention. The blocks of the iterative image testing system 400 can be implemented using hardware, software, or a combination thereof.

In this embodiment, the iterative image testing system 400 can include an interpolation device 41 that receives a low resolution (LR) input image to produce interpolated pixels in a patch (eg, 7x7 in size). The interpolation device 41 can use a suitable interpolation method such as bicubic interpolation. Next, the grouping device 42 performs the steps shown in the first figure on the patch including the interpolated pixels based on the second-order region binary map (2SLBP) to generate an index.

In one embodiment, the grouping device 42 normalizes the patch containing the interpolated pixels prior to grouping. For example, the pixel value of the patch is subtracted from the patch average to perform luminance normalization.

The iterative image testing system 400 can also include mapping means 43, which includes a complex function table, each function table including a complex mapping function, which is typically stored in the memory device of the mapping device 43 in the form of matrix coefficients. It is worth noting that the mapping function is provided by an image training system (not shown in the figure) based on a second-order region binary map (2SLBP). The image training system can be implemented by conventional techniques and therefore will not be described. One of the provided complex mapping functions is obtained based on the index generated by the grouping device 42.

The iterative image testing system 400 may further include a prediction device 44 that maps the interpolated pixels (generated by the interpolation device 41) to the enhancement pixels in accordance with the mapping function obtained by the mapping device 43. Therefore, the enhanced pixels and other pixels of the patch form a high resolution (HR) output image. It should be noted that, according to the present embodiment, the pixels to be grouped are pre-interpolated by the interpolation device 41, so the image quality of the interpolated pixels is enhanced by the prediction device 44 instead of Scaled up.

If the patch is normalized before the grouping (for example, brightness normalization), the patch of the high-resolution (HR) output image must be de-normalized, that is, the normalized reverse action. For example, the patch average is added to the pixel value of the patch of the high resolution (HR) output image.

In accordance with features of the present embodiment, patches containing enhancement pixels may be repeatedly (or iteratively) processed by an image training system (not shown) to provide an update function table containing complex mapping functions. As shown in the fourth figure, the patches containing the enhancement pixels are fed back to the grouping device 42, the mapping device 43, and the prediction device 44 to produce updated enhancement pixels, thereby improving the high resolution (HR) output image. In this embodiment, the preset number of times can be repeatedly executed, and each time there is an improved update function table. In practice, since the image training system is usually an offline job, the iterative image testing system 400 is an online job, and the update function tables may be stored in the memory device of the mapping device 43 as a whole. Use the corresponding update function table for each iteration.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the invention should be included in the following Within the scope of the patent application.

100‧‧‧ group method

11‧‧‧Division of images as patches

12‧‧‧ average difference

13‧‧‧View all directions have been reached

14‧‧‧Quantitative mean difference to generate regional multi-gradient level map values

15‧‧‧The root mean square value of the mean difference

16‧‧‧Quantitative rms value

17‧‧‧ Generate second-order regional binary graph values

18‧‧‧Performance grouping

21‧‧‧ Central sub-block

211‧‧‧Center pixel

22‧‧‧ adjacent subblocks

221‧‧‧Center pixel

23‧‧‧ adjacent subblocks

231‧‧‧Center pixel

400‧‧‧Overlay image test system

41‧‧‧Interpolation device

42‧‧‧Group device

43‧‧‧ Mapping device

44‧‧‧ forecasting device

The flowchart of the first figure shows a grouping method using a second-order region binary map (2SLBP) according to an embodiment of the present invention. The second to second C diagrams show an average difference between the adjacent sub-block and the central sub-block. The third A diagram illustrates the average difference between the central sub-block and the adjacent sub-block. The third B plot shows the corresponding average difference for each gradient. The third C plot shows the corresponding quantized mean difference for each gradient. The block diagram of the fourth figure shows an iterative image testing system based on a second-order region binary map (2SLBP) for performing super-resolution (SR) image processing according to an embodiment of the present invention.

Claims (14)

A grouping method using a second-order region binary graph, comprising: dividing an image into a complex patch; generating a gradient direction value according to a central sub-block and an adjacent sub-block of the patch; and quantifying the gradient direction value to Generating a quantized gradient direction value; generating a gradient intensity value according to the gradient direction value; quantifying the gradient intensity value to generate a quantized gradient intensity value; concatenating the quantized gradient direction value and the quantized gradient intensity value to generate a second-order region 2 The meta-graph value; and the use of the second-order region binary graph value as an indicator to perform clustering of super-resolution image processing. A grouping method using a second-order region binary graph according to the first aspect of the patent application, wherein the generating of the gradient direction value comprises the following steps: generating an average difference between the central sub-block and an adjacent sub-block in one direction Value; and repeat the previous step in other directions to produce the average difference, respectively. A grouping method using a second-order region binary map as described in claim 2, wherein the average differences in all directions are respectively quantized to one of three quantization levels to produce a triple-digit value. A method of grouping using a second-order region binary graph according to claim 3, wherein the generating of the gradient intensity value comprises the steps of: generating a root mean square value of the average differences in all directions to form the gradient strength value. A grouping method using a second-order region binary map as described in claim 1 of the patent application, wherein the bit of the quantized gradient intensity value has higher validity than the bit of the quantized gradient direction value. An iterative image testing system using a second-order region binary image, comprising: an interpolation device that receives a low-resolution input image to generate interpolated pixels in a patch of the input image; and a grouping device, performs the following steps: a central sub-block of the patch and an adjacent sub-block to generate a gradient direction value; quantizing the gradient direction value to generate a quantized gradient direction value; generating a gradient intensity value according to the gradient direction value; and quantifying the gradient intensity a value to generate a quantized gradient intensity value; and concatenating the quantized gradient direction value and the quantized gradient intensity value to generate a second-order region binary graph value as an index; a mapping device storing a complex function table, each function table comprising The complex mapping function obtains one of the mapping functions according to the index; and the prediction device maps the interpolated pixel to the enhanced pixel according to the obtained mapping function, thereby generating a high-resolution output image. An iterative image testing system using a second-order region binary map as described in claim 6 of the patent application, wherein the generating of the gradient direction value comprises the steps of: generating between the central sub-block and an adjacent sub-block in one direction The average difference; and repeat the previous step in other directions to produce the average difference, respectively. An iterative image testing system using a second-order region binary map as described in claim 7 of the patent application, wherein the average differences in all directions are respectively quantized to one of three quantization levels to generate a triple-digit value . An iterative image testing system using a second-order region binary map as described in claim 8 wherein the generation of the gradient intensity value comprises the steps of: generating a root mean square value of the average differences in all directions to form The gradient intensity value. An iterative image testing system using a second-order region binary map as described in claim 6 of the patent application, wherein the bit of the quantized gradient intensity value has higher validity than the bit of the quantized gradient direction value. An iterative image testing system using a second-order region binary map as described in claim 6 of the patent application, wherein the grouping device normalizes the patch block before processing the patch block containing the interpolated pixel. An iterative image testing system using a second-order region binary map as described in claim 11 of the patent application, wherein the patch of the output image is denormalized. An iterative image testing system using a second-order region binary map as described in claim 6 wherein the patch containing the enhanced pixels is fed back to the grouping device, the mapping device and the predicting device at least once to generate an update Enhance the pixels, thus improving the output image. An iterative image testing system using a second-order region binary map according to claim 13 of the patent application, wherein the patch containing the enhanced pixels is fed back to the grouping device, the mapping device and the prediction device each time A corresponding update function table stored in the mapping device.