CN103533371B - A kind of based on image conversion and the data compression transmission method of image watermark - Google Patents

Abstract

The invention discloses a data compression transmission method based on image transformation and image watermark. By first decomposing the image and setting the index threshold, sub-images meeting the index are not transformed; The degree becomes flatter, the two sub-images are merged to form a complete image, watermark and function type are embedded in it, and the image with watermark is compressed and transmitted. The receiving end extracts the watermark from the watermarked image through decompression, restores the original transformed sub-image, and then obtains the original image through inverse transformation. The invention guarantees that the quality of the restored image under the given compression ratio meets the specified requirements, and is obviously better than the result of direct data compression. At the same time, the present invention embeds the watermark information of the image into the image for transmission without affecting the quality of image compression and recovery and without increasing the amount of transmitted data, thereby improving the efficiency of image transmission and providing convenience for image application.

Description

A Data Compression Transmission Method Based on Image Transformation and Image Watermark

technical field

The invention relates to a data compression method based on image transformation and image watermark, belonging to the technical field of image processing.

Background technique

Data transmission and image processing are important research topics in the field of communication at present. With the development of science and technology, people's demand for high-resolution images is increasing, and data compression is imperative.

Data compression is divided into lossy compression and lossless compression methods. The lossy compression method has a relatively large compression ratio, but there is a certain amount of information loss between the restored image and the original image after compression. As long as the subjective and objective evaluation indicators meet the requirements, it does not have much application in practice. influences. There is no loss of information between the restored image and the original image after compression by the lossless compression method, but the compression ratio is very small, generally about 2 times, and the application occasions are limited, which is not convenient for data transmission. Most of the compression methods used in high-speed data transmission systems are lossy compression methods, and the compression ratio is generally about 4 times. For images, the general peak signal-to-noise ratio (PSNR) is more than 35dB, and the effect is more ideal if it is more than 40dB.

There are many image data compression methods at present, the representative ones are JPEG and JPEG2000. Since the compression standard algorithm has many functions, and the algorithm is related to the characteristics of the image itself, the existing image compression methods are not ideal for some images such as aviation and space remote sensing. In practice, satisfactory image quality can only be obtained by reducing the compression ratio. The existing method does not distinguish the image content, and uses the same compression method for all images, and the compression effect for images with complex textures and poor pixel continuity is very unsatisfactory. Therefore, there is an urgent need to study an image data compression method to further improve the image compression recovery quality of image data transmission.

Contents of the invention

The problem solved by the technology of the present invention is: to overcome the deficiencies of the prior art, to provide a data compression method based on image transformation and image watermark, which improves the quality of image compression and restoration of image data transmission, and at the same time does not affect the quality of image compression and restoration 1. Without increasing the amount of transmitted data, the efficiency of image transmission is improved through the image watermark method, which provides convenience for the application of images.

Technical solution of the present invention is:

A data compression transmission method based on image transformation, comprising the following steps:

(1) Decomposing the original carrier image into multiple original carrier sub-images, the multiple original carrier sub-images are non-overlapping blocks of the original image, keeping the total image data volume unchanged;

(2) Determine the objective index threshold, compress the original carrier sub-image in step (1) according to a given compression ratio, calculate the objective index of the decompressed and restored sub-image and the sub-image before compression, and sub-images smaller than the objective index threshold Perform function transformation to obtain a new sub-image and enter step (3); the original carrier sub-image higher than the objective index threshold directly enters step (4);

(3) Compress the new sub-image obtained in step (2) with the same compression ratio as in step (2), perform the inverse transformation of the function transformation in step (2) on the decompressed sub-image, and calculate the inverse transformation The objective index of the sub-image and the original carrier sub-image, if the objective index is higher than the objective index before the function transformation in step (2), use the new sub-image obtained in step (2) to replace the original carrier sub-image for compressed transmission, And enter step (4); if the objective index is lower than or equal to the objective index before the function transformation in step (2), still use the original carrier sub-image compression transmission that is less than the objective index threshold in step (2) to enter step (4)

(4) Synthesize the original carrier sub-image obtained in step (2) which is higher than the threshold of the objective index and part of which is smaller than the threshold of the objective index with the new sub-image after the function transformation obtained in step (3), and use the image watermarking method in wherein the watermark is embedded and the transformation parameters of the function transformation described in step (2) form a watermarked image;

(5) Compress and transmit the watermarked image;

(6) The receiving end receives the data compressed in step (5) and decompresses it to obtain the watermarked image data, extracts the watermark and function transformation parameters from the watermarked image data, and obtains the original carrier subimage and the new subimage after function transformation , and perform function inverse transformation on the new sub-image transformed by the function to obtain the sub-image before the function transformation;

(7) Synthesize the sub-image before function transformation in step (6) and the original carrier sub-image to obtain the original carrier image.

In the step (2), the specific form of performing function transformation on sub-images smaller than the index threshold is any one of the following three functions:

a) Y=Y1*LOG10 (1+X), 0≤Y≤Ymax;

b) Y=Y2*Sqrt(X^p), 0≤Y≤Ymax;

c) Y=Y3/[1+exp(-X)], 0≤Y≤Ymax.

Where X represents the pixel value of the original image, Y represents the pixel value of the image transformed by the function, Ymax is the maximum value allowed by the transformed pixel value Y, and the transformed Y is adjusted by parameters Y1, Y2, Y3, p The range of values, where Y1, Y2, Y3, and p are all real numbers greater than 0.

In the step (2), the objective index threshold is set according to the compatibility index. When the objective index threshold is set to 0, the method uses the original sub-image to directly compress. When the index threshold is set to infinity, the method completely adopts function transformation for compression.

In the step (6), the function is inversely transformed into an inverse function of the function used in the step (3).

The objective index in the step (2) refers to PSNR.

The image watermark in the step (4) refers to data such as copyright information of the image, image compression parameters, shooting time, and shooting location; the image watermark method in the step (4) refers to image compression after the watermark is embedded in the image. , Decompression can also correctly extract the watermark, and can correctly restore the digital watermark method or information hiding method of the image.

The beneficial effect of the present invention compared with prior art is:

(1) Through the setting of the index threshold, the present invention selectively transforms sub-images that do not satisfy the index and then compresses and transmits them, thereby ensuring the quality of the restored image after image compression.

(2) The present invention first decomposes the original carrier image, selects some sub-images for function transformation, avoids the complexity of data processing for large images; at the same time selects some sub-images for watermark embedding through image decomposition, saving hidden capacity , only some of the sub-images are embedded with information, so the quality of the image is guaranteed.

(3) The present invention uses the function transformation of the original sub-image to change the characteristics of the sub-image. In an image, areas with complex textures and a large range of image pixel changes often make it difficult to compress the image. The present invention performs function transformation on these areas, By transforming the pixel values into a more compressible space, better restoration quality can be obtained under the same compression ratio, which avoids the limitation of poor image restoration quality of the original method.

(4) The present invention can use different functions for grayscale transformation, and embed the parameters of the function calculation formula into the sub-image through a robust information hiding method, so that the information will not be lost after data compression, thereby ensuring the quality of data compression. At the same time, the present invention When performing function transformation, multiple functions are applicable, which has strong versatility and very good compatibility.

(5) The present invention cannot directly obtain a complete image during the transmission process, which enhances the concealment of data transmission of sub-images and improves the security of data transmission.

(6) The present invention has higher restored image quality under the same compression ratio, or has a larger compression ratio under certain conditions of restored image quality. At the same time, the method has the practical characteristics of breaking into parts, small amount of single sub-image processing, low complexity, less resource occupation, and good compression effect, so it has more practical value in spacecraft engineering.

(7) The present invention can work in different states by setting the index threshold. The index threshold can be selected according to the characteristics of the input original image. For the case where the entire image is smooth, the index threshold is set to 0. For the entire image with complex texture and drastic pixel changes In some cases, the index threshold is set to a relatively large value, so that each sub-image of the entire image is in a "substandard" state. For an image with both smooth content and violent pixel changes, an appropriate index threshold value can be set. For better image recovery quality.

(8) The present invention can embed relevant image information such as copyright information, image compression parameters, shooting time and shooting location into the image for transmission without affecting the quality of image compression and recovery and without increasing the amount of transmitted data. It improves the efficiency of image transmission and facilitates the application of images.

Description of drawings

Fig. 1 is the flow chart of the present invention.

detailed description

Specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The invention utilizes technologies such as image decomposition, index threshold setting, and image watermarking to perform function transformation on sub-images whose PSNR does not meet the standard, and embeds watermarks and transformation functions into transformed images for transmission. The receiving end can correctly extract the watermark and transformation function from the image, and perform inverse transformation to restore the original image data. Without affecting the quality of image compression and recovery and without increasing the amount of image data, an image compression method with superior compression performance is provided, and the compression effect of the existing data compression method is obviously improved. The method of the present invention also protects the original image, so that others can only directly obtain part of the sub-image, and cannot directly obtain the complete image, which enhances the concealment of data transmission of some sub-images and improves the security of data transmission.

As shown in Figure 1, the steps of the present invention are as follows:

(1) Decomposing the original carrier image into multiple original carrier sub-images, the multiple original carrier sub-images are non-overlapping blocks of the original image, keeping the total image data volume unchanged;

(2) Determine the objective index threshold, compress the original carrier sub-image in step (1) according to a given compression ratio, and calculate the objective index of the sub-image after decompression and restoration and the sub-image before compression (the objective index refers to PSNR) , sub-images smaller than the objective index threshold are subjected to function transformation to obtain a new sub-image and enter step (3); original carrier sub-images higher than the objective index threshold directly enter step (4); the objective index threshold is set according to the compatibility index, When the objective index threshold is set to 0, then this method uses the original sub-image to directly compress, when the index threshold is set to infinity, then this method completely uses function transformation to compress, and the situation of the remaining index thresholds is the general working state of the present invention .

(3) Compress the new sub-image obtained in step (2) with the same compression ratio as in step (2), perform the inverse transformation of the function transformation in step (2) on the decompressed sub-image, and calculate the inverse transformation The objective index of the sub-image and the original carrier sub-image, if the objective index is higher than the objective index before the function transformation in step (2), use the new sub-image obtained in step (2) to replace the original carrier sub-image for compressed transmission, And enter step (4); if the objective index is lower than or equal to the objective index before the function transformation in step (2), then still use the original carrier sub-image compression transmission in step (2) to enter step (4); for example, after The objective index of part of the new sub-image in the judgment step (2) is higher than the objective index before image transformation, then this part of the new sub-image replaces the original carrier image for compressed transmission, and the rest of the remaining sub-images still use the original carrier image. image transmission;

(4) For the original carrier sub-images obtained in step (2) that are higher than the objective index threshold and partially smaller than the objective index threshold (the part of the original carrier sub-image that is smaller than the objective index threshold refers to the objective index that still remains after the function transformation in step (3). The original carrier sub-image that does not meet the standard, in this case, the original carrier sub-image before the function transformation is still used for compression transmission) and the new sub-image after the function transformation obtained in step (3) is synthesized, and the image watermarking method is used in the wherein the watermark is embedded and the transformation parameters of the function transformation described in step (2) form a watermarked image;

(5) Compress and transmit the watermarked image;

(6) The receiving end receives the data compressed in step (5) and decompresses it to obtain the watermarked image data, extracts the watermark and function transformation parameters from the watermarked image data, and obtains the original carrier subimage and the new subimage after function transformation , and perform function inverse transformation on the new sub-image transformed by the function to obtain the sub-image before the function transformation;

(7) Synthesize the sub-image before function transformation in step (6) and the original carrier sub-image to obtain the original carrier image.

In the step (2), the specific form of performing function transformation on sub-images smaller than the index threshold is any one of the following three functions:

a) Y=Y1*LOG10 (1+X), 0≤Y≤Ymax;

b) Y=Y2*Sqrt(X^p), 0≤Y≤Ymax;

c) Y=Y3/[1+exp(-X)], 0≤Y≤Ymax.

Where X represents the pixel value of the original image, Y represents the pixel value of the image transformed by the function, Ymax is the maximum value allowed by the transformed pixel value Y, and the transformed Y is adjusted by parameters Y1, Y2, Y3, p The range of values, where Y1, Y2, Y3, and p are all real numbers greater than 0.

The image watermark in the step (4) refers to data such as copyright information of the image, image compression parameters, shooting time, and shooting location; the image watermark method in the step (4) refers to image compression after the watermark is embedded in the image. , Decompression can also correctly extract the watermark, and can correctly restore the digital watermark method or information hiding method of the image.

The contents not described in detail in the description of the present invention belong to the well-known technology of those skilled in the art.

Claims (6)

1. A data compression transmission method based on image transformation and image watermarking, characterized in that the steps are as follows: (1) Decomposing the original carrier image into multiple original carrier sub-images, the multiple original carrier sub-images are non-overlapping sub-blocks of the original image, keeping the total image data volume constant; (2) Determine the objective index threshold, compress the original carrier sub-image in step (1) by a given compression ratio, calculate the objective index of the decompressed and restored sub-image and the sub-image before compression, and sub-images smaller than the objective index threshold Perform function transformation to obtain a new sub-image and enter step (3); the original carrier sub-image higher than the objective index threshold directly enters step (4); (3) Compress the new sub-image obtained in step (2) with the same compression ratio as in step (2), perform the inverse transformation of the function transformation in step (2) on the decompressed and restored sub-image, and calculate the inverse transformation The objective index of the sub-image and the original carrier sub-image, if the objective index is higher than the objective index before the function transformation in step (2), then use the new sub-image obtained in step (2) to replace the original carrier sub-image for compressed transmission, And enter step (4); if the objective index is lower than or equal to the objective index before the function transformation in step (2), then still use the original carrier sub-image smaller than the objective index threshold in step (2) to carry out compressed transmission, and enter step (4); (4) The original carrier sub-image obtained in step (2) is higher than the objective index threshold and the objective index is still not up to standard after the function transformation in step (3), and the new sub-image obtained in step (3) after function transformation Carry out synthesis, adopt the image watermarking method to embed watermark wherein and the transformation parameter of the function transformation described in step (2) form watermarked image; (5) Compress and transmit the watermarked image; (6) The receiving end receives the data compressed in step (5) and decompresses it to obtain watermarked image data, extracts the watermark and function transformation parameters from the watermarked image data, and obtains the original carrier subimage and the new subimage after function transformation , and perform function inverse transformation on the new sub-image transformed by the function to obtain the sub-image before the function transformation; (7) Combining the sub-image before function transformation in step (6) and the original carrier sub-image to obtain the original carrier image. 2. A kind of data compression transmission method based on image conversion and image watermarking according to claim 1, it is characterized in that: in the described step (2), the specific form that the function conversion is carried out to the sub-image that is less than index threshold is following three Any of these functions: a) Y=Y1*LOG10(1+X), 0≤Y≤Ymax; b) Y=Y2*Sqrt(X^p), 0≤Y≤Ymax; c) Y=Y3/[1+exp(-X)], 0≤Y≤Ymax; Where X represents the pixel value of the original image, Y represents the pixel value of the image transformed by the function, Ymax is the maximum value allowed by the transformed pixel value Y, and the transformed Y is adjusted by parameters Y1, Y2, Y3, p The range of values, where Y1, Y2, Y3, and p are all real numbers greater than 0. 3. a kind of data compression transmission method based on image transformation and image watermark according to claim 1, it is characterized in that: in described step (2), objective index threshold is set according to compatibility index, when objective index threshold is set to 0, this method uses the original sub-image to directly compress, and when the index threshold is set to infinity, this method completely uses function transformation to perform compression. 4. A data compression transmission method based on image transformation and image watermarking according to claim 1, characterized in that: in the step (6), the inverse function is transformed into the inverse function of the function used in the step (3). 5. A data compression transmission method based on image transformation and image watermarking according to claim 1, characterized in that: the objective index in the step (2) refers to PSNR. 6. A kind of data compression transmission method based on image transformation and image watermark according to claim 1, it is characterized in that: the image watermark in the described step (4) refers to the copyright information of the image, image compression parameters, shooting All data of the time and shooting location; the image watermarking method in the step (4) refers to a digital watermarking method or an information hiding method that can correctly extract the watermark after the watermark is embedded in the image, decompress the image, and correctly restore the image .