CN112801922A - Color image-gray image-color image conversion method - Google Patents
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Abstract
The invention discloses a color image-gray image-color image conversion method, which comprises the following steps: performing color space conversion from RGB to Ycbcr on an original color image to obtain a brightness plane and two chrominance planes, compressing the two chrominance planes to obtain a compressed chrominance plane, and embedding a binary code stream of the compressed chrominance plane into the brightness plane as watermark information to obtain a watermark gray image; gray image reconstruction color image decoding process: extracting a binary code stream of the compressed chrominance plane from the gray level image embedded with the watermark information, recovering two chrominance planes according to the binary code stream, and carrying out Ycbcr-to-RGB color space conversion on the luminance plane and the two chrominance planes to reconstruct a color image. The invention saves more color information, can obtain a brightness plane with little distortion or no distortion when reconstructing, and can obtain a high-quality gray image and a high-quality reconstructed color image.
Description
Technical Field
The invention relates to the technical field of image processing, in particular to a conversion method for generating a gray image from a color image and then effectively recovering the color image from the gray image.
Background
The conventional color map-gray map-color map conversion method can be divided into two types, the first type is based on an edge information embedding algorithm, and the second type is based on a vector quantization algorithm.
The side information embedding algorithm is based on that wavelet transformation, discrete cosine transformation or wavelet packet transformation and the like are adopted to carry out frequency domain transformation on the brightness plane of the color image, down sampling is carried out on the chrominance plane and the chrominance plane is embedded into a high frequency band of the brightness plane, and then frequency domain transformation is carried out on the brightness plane to obtain a gray level image. During reconstruction, frequency domain transformation is carried out on the gray level image, color information is extracted and up-sampled, high-frequency components of the brightness plane are replaced by 0 and frequency domain transformation is carried out, and a color image can be reconstructed. This method can lose high frequency information of the luminance plane and lose a large amount of color information, resulting in severe noise and blurring of the obtained grayscale image and the reconstructed color image.
Queiro et al proposed in IEEE TIP 2006 to perform frequency domain transformation on the luminance plane of a color image by using wavelet transformation, down-sampling two chrominance planes and replacing the high-frequency component of the luminance plane, then performing wavelet transformation on the luminance plane to obtain a gray image, and performing an inverse process to reconstruct the color image. In this method, both high-band information of the luminance plane is lost entirely, and only one-fourth of the color information is retained. The resulting grayscale image is blurred because of the loss of high frequency information. When a color image is reconstructed, excessive loss of color information and loss of high-frequency information of a brightness plane cause blurring and poor quality of the reconstructed color image.
Ko et al propose at J IMAGING SCI TECHN 2008 to compensate for color saturation by wavelet packet transformation and using pseudo random codes. In this method, the saturation of the color is compensated, and the quality of the reconstructed color image is improved to some extent, but due to the loss of high frequency information of the luminance plane and the excessive loss of color information, the obtained grayscale image has serious noise, and the edge of the reconstructed color image also has noise.
Horiuchi et al propose to efficiently embed color information into the primary wavelet sub-bands at the PATTERN RECOGN let 2010 to preserve chrominance and spatial resolution. In the method, the chrominance component is divided into a positive plane and a negative plane to respectively replace the high-frequency component of the luminance plane, so that the quality of a reconstructed color image is improved to a certain extent, but the information is lost too much, and the obtained gray-scale image and the reconstructed color image still become fuzzy.
In the algorithm based on vector quantization, an original color image is decomposed into a gray image and a color palette, a luminance plane and a chrominance plane are not in an orthogonal relation, the luminance plane changes along with the change of the color palette, the change of the luminance plane also causes the change of pixel values of a reconstructed color image, and the quality of the reconstructed color image depends on the design of the color palette. The design of the palette is essentially to quantize the brightness and the chromaticity, and is limited to that the gray image has only 256 gray levels, and when the color image is reconstructed, the corresponding chromaticity needs to be searched according to the brightness value, and the palette finally obtains 256 brightness and 256 chromaticity. And embedding the palette into the quantized luminance plane to obtain a gray image. And during reconstruction, extracting the palette, searching corresponding chromaticity according to the pixel value of the gray image, and reconstructing a color image. The gray level image obtained by the method has serious false contour artifacts. The embedding process generally adopts LSB digital watermark embedding, the gray level image can not be recovered in a lossless manner, and after the color palette is extracted, the pixel value of the gray level image can be changed. Since the gray image is not orthogonal to the color palette based on the vector quantization algorithm, the pixel value of the gray image is changed to search for an incorrect chrominance value, resulting in the generation of color shift.
Chaumont et al propose to generate a palette based on fuzzy C-means clustering in J SystSoftw 2013, and embed the palette by using a least significant bit replacement (LSB) digital watermark technology to obtain a gray level image. In this method, the original color image is quantized into 256 luminances and 256 chromaticities using a clustering algorithm using the similarity of colors. However, since the entire color image is represented by only 256 colors, both the resulting grayscale image and the reconstructed color image have severe false contour artifacts.
XU et al use halftone techniques in Signal Process Image Commun 2016 to enhance the visual effect of an Image. In the method, a halftone technique is used to perform certain error compensation on the color information, so that a reconstructed color image with good visual effect can be obtained. However, since the luminance and the chrominance are quantized into 256, much information is lost, and the color shift of the reconstructed color image is easy to occur.
Chan et al propose in IEEE TIP 2020 that using convex hull to generate color palette, in combination with halftone technique, the image quality is improved. In the method, an original color image is divided into a plurality of regions according to brightness so as to quantize the brightness, each region quantizes the chroma into a plurality of chroma by using a convex hull algorithm, and the chroma is quantized into 256 brightness and 256 chroma in total, so that the quality of the reconstructed color image is improved. The resulting grayscale image may see some halftone artifacts and the reconstructed color image has slight low frequency noise.
In the current research, there is still a great development space for image processing technology of color image-grayscale image-color image conversion, and obtaining high-quality grayscale images and reconstructed high-quality color images is still the focus of the current research, wherein obtaining high-quality color images is the central focus of the research. The current method mainly has the following three defects: firstly, the traditional side information-based embedding method loses high-frequency information of an image, color information is lost too much, the quality of the obtained gray-scale image and the color image is not high, and the image becomes fuzzy; and secondly, the brightness and the chroma are quantized into 256 colors based on a vector quantization method, the obtained color image generally has the problems of color deviation and false contour, and the color image depends on the design of a color palette. And thirdly, the gray image and the color palette are not in an orthogonal relation, and the change of the pixel value of the gray image can cause the searching of the corresponding chromatic value and the generation of color shift.
Disclosure of Invention
The invention provides a color image-gray image-color image conversion method in order to overcome the defects and shortcomings of the prior art, well combines an image compression technology and a large-capacity digital watermarking technology, is a brand new thought different from the traditional method, fully utilizes an efficient image compression technology, and can retain more color information under the condition of requiring a certain compression ratio. The advantages of a large-capacity digital watermarking algorithm are fully utilized, and a gray image with small distortion can be obtained under the condition of requiring a certain embedding amount. When the color image is reconstructed, a brightness plane with little distortion or even a brightness plane without distortion can be obtained, so that the problem of larger distortion of the color image reconstructed by the previous method is effectively solved. The invention can not only obtain high-quality gray images, but also obtain high-quality color images.
A second object of the present invention is to provide a color image-grayscale image-color image conversion system.
A third object of the present invention is to provide a storage medium.
It is a fourth object of the invention to provide a computing device.
In order to achieve the purpose, the invention adopts the following technical scheme:
a color image-gray image-color image conversion method comprises the following steps:
color image conversion grayscale image encoding process:
reading the original color image, and calculating the data amount of the original color imageM*N*C*8The calculated binary representation valueM*N*C*8Minimum number of bits requiredwFor subsequent use inwRecording the size of the compressed chroma plane by a binary code stream of bits;
performing color space conversion from RGB to Ycbcr on the original color image to obtain a brightness plane, a chromaticity plane cb and a chromaticity plane cr;
respectively compressing the chrominance plane cb and the chrominance plane cr to obtain a compressed chrominance plane cb _ jp2 and a compressed chrominance plane cr _ jp 2;
reading in the compressed chroma planes cb _ jp2 and cr _ jp2, calculating the image sizes of the compressed chroma planes cb _ jp2 and cr _ jp2, i.e. the lengths of the corresponding binary code streams to obtain d1 and d2, and using the d1 and d2wBinary numbers w1, w2 of bits represent d1 and d2, respectively, for recording the sizes of the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, w1 and w2 as the first part of the embedded informationwatermark1Binary code streams of compressed chrominance planes cb _ jp2 and cr _ jp2 as embedded informationThe second partwatermark2；
A first part of the information to be embeddedwatermark1And a second part of the embedded informationwatermark2Embedding into brightness plane by digital watermarking technology, wherein 2 × w pixels in front of the brightness plane are fixed for embeddingwatermark1Obtaining a gray level image of the embedded information, and completing the conversion from the color image to the gray level image;
gray image reconstruction color image decoding process:
reading the gray scale image of the embedded information, and extracting the first part of the embedded information by using a digital watermarking technologywatermark1Extracting image sizes w1 and w2 of two chromaticity planes, and converting the image sizes into decimal numbers d1 and d 2;
extracting a second part of the embedded information by digital watermarking based on the decimal numbers d1 and d2watermark2Based on the second part of the embedded informationwatermark2Recovering the chrominance plane cb _ jp2 and the chrominance plane cr _ jp 2;
and carrying out Ycbcr-to-RGB color space conversion on the luminance plane, the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 to reconstruct a color image and complete the reconstruction from a gray image to the color image.
As a preferred technical solution, the color space conversion from RGB to Ycbcr is performed on the original color image, which is specifically expressed as:
wherein R, G, B is three channels of RGB of original color image, Y,cb、crFor the luminance plane Y, chrominance plane obtained after color space conversioncbAnd the chrominance planecr。
As a preferred technical solution, the chroma plane cb and the chroma plane cr are compressed separately, specifically by 16 times of JPEG2000 or JPEG compression.
Preferably, the first part of the information is embeddedwatermark1And a second part of the embedded informationwatermark2Embedding into luminance levels with digital watermarking techniquesIn the surface, information embedding is performed by using an LSB digital watermarking technology, which is specifically expressed as:
extracting a first part of embedded information by adopting a digital watermarking technologywatermark1And extracting a second part of the embedded information by using the digital watermarking technologywatermark2And information extraction is carried out by adopting an LSB digital watermarking technology, which is specifically expressed as follows:
where x denotes the pixel value of the original luminance plane and info denotes the first part of the embedded informationwatermark1And a second part of the embedded informationwatermark2，
Representing the pixel values of the luminance plane after embedding the information.
Preferably, the first part of the information is embeddedwatermark1And a second part of the embedded informationwatermark2Embedding a digital watermark technology into a luminance plane, and embedding information by adopting a reversible watermark technology based on prediction error expansion, wherein the reversible watermark technology is specifically represented as follows:
extracting a first part of embedded information by adopting a digital watermarking technologywatermark1And extracting a second part of the embedded information by using the digital watermarking technologywatermark2The information is extracted by adopting a reversible watermarking technology based on prediction error expansion, which is specifically expressed as：
Wherein,
representing pixel values of a luminance plane after embedding information, x representing pixel values of an original luminance plane, and info representing a first part of the embedded informationwatermark1And a second part of the embedded informationwatermark2，
Representing x adjacent 4 pixels x1、x2、x3、x4The predicted value of (2).
As a preferred technical solution, the compressed chrominance planes cb _ jp2 and cr _ jp2 are read in a binary manner, and the compressed chrominance planes cb _ jp2 and cr _ jp2 are represented as a binary code stream for storing information of the chrominance planes.
As a preferred technical solution, the color space conversion from Ycbcr to RGB is performed on the luminance plane, the chrominance planes cb _ jp2 and cr _ jp2 to reconstruct a color image, which is specifically represented as:
wherein,
is a plane of brightness that is,
and
representing the two chrominance planes after compression.
In order to achieve the second object, the invention adopts the following technical scheme:
a color map-grayscale map-color map conversion system comprising: the system comprises a color image conversion gray level image coding module and a gray level image reconstruction color image decoding module;
the color image conversion grayscale image encoding module includes: the device comprises an original color image data amount calculation module, a color space conversion module, a chromaticity plane compression module, an image size calculation module and an information embedding module;
the gray scale image reconstruction color image decoding module comprises: the device comprises a chrominance plane image size extraction module, a color information extraction module and a reconstruction module;
the original color image data volume calculating module is used for reading the original color image and calculating the data volume of the original color image to obtainM*N*C*8The calculated binary representation valueM*N*C*8Minimum number of bits requiredwFor subsequent use inwRecording the size of the compressed chroma plane by a binary code stream of bits;
the color space conversion module is used for performing color space conversion from RGB to Ycbcr on the original color image to obtain a brightness plane, a chromaticity plane cb and a chromaticity plane cr;
the chrominance plane compression module is used for respectively compressing the chrominance plane cb and the chrominance plane cr to obtain a compressed chrominance plane cb _ jp2 and a compressed chrominance plane cr _ jp 2;
the image size calculating module is used for reading in the compressed chrominance planes cb _ jp2 and cr _ jp2, calculating the image sizes of the compressed chrominance planes cb _ jp2 and cr _ jp2 respectively, namely the lengths of binary code streams corresponding to the image sizes to obtain d1 and d2, and adopting the methodwBinary numbers w1, w2 of bits indicate d1 and d2, respectively, for recording the sizes of the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, and w1 and w2 as embedded informationThe first partwatermark1The binary code streams of the compressed chrominance planes cb _ jp2 and cr _ jp2 are color information as the second part of the embedded informationwatermark2；
The information embedding module is used for embedding a first part of informationwatermark1And a second part of the embedded informationwatermark2Embedding the digital watermark technology into a brightness plane to obtain a gray level image of the embedded information;
the chrominance plane image size extraction module is used for reading a gray level image of embedded information and extracting a first part of the embedded information by adopting a digital watermarking technologywatermark1I.e. w1 and w2, and converted to decimal numbers d1 and d 2;
the color information extraction module is used for extracting the binary code stream of the color information according to d1 and d2watermark2And restoring the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 according to the color information;
the reconstruction module is used for carrying out Ycbcr-to-RGB color space conversion on the luminance plane, the chrominance plane cb _ jp2 and cr _ jp2 to reconstruct a color image.
In order to achieve the third object, the invention adopts the following technical scheme:
a storage medium stores a program which, when executed by a processor, implements the color-to-grayscale-to-color conversion method as described above.
In order to achieve the fourth object, the invention adopts the following technical scheme:
a computing device comprises a processor and a memory for storing processor executable programs, wherein the processor executes the programs stored in the memory to realize the color image-gray image-color image conversion method.
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the invention provides an efficient color image-gray image-color image conversion method, which is a brand new thought, fully utilizes the advantages of an efficient image compression technology and a high-capacity digital watermarking technology, can not only store more color information of an original image, but also retain more brightness information of the original image, even retain a non-distorted brightness plane, solves the problem of large image distortion in the traditional method, and can obtain a gray image and a color image with better visual quality.
(2) The invention is based on high-efficiency image compression technology and high-capacity digital watermarking, fully utilizes JPEG2000 image compression technology, can reserve more color information of the original image under the condition of requiring a certain compression rate, and solves the problem of excessive color information loss in the traditional method.
(3) The invention fully utilizes the advantages of large-capacity digital watermarking, adopts the LSB digital watermarking technology, and has smaller influence on the brightness plane under the condition of requiring a certain embedding amount, the brightness plane loses the lowest-order information at most, and the brightness information can be better preserved, thereby obtaining a high-quality gray image; and a large-capacity reversible watermarking technology is adopted, the brightness plane can be recovered in a lossless manner under the condition of requiring a certain embedding amount, and the quality of the reconstructed color image is higher because the brightness plane can be reserved without any distortion. The problem that the information of the brightness plane is lost too much in the traditional method is solved.
(4) The invention has the advantages that the luminance plane and the chrominance plane are in an orthogonal relation, the luminance plane and the chrominance plane can be independently processed, the problem of the dependency relation between the luminance plane and the chrominance plane in a vector quantization method is solved, the gray level plane is well stored in the orthogonal relation, and the lossy compression on the chrominance plane can be more efficient.
(5) The invention well combines the image compression technology and the high-capacity digital watermarking technology, solves the technical problem of complicated palette design in the traditional method, has clear and simple overall algorithm flow and low complexity and has good practical application scene.
Drawings
FIG. 1 is a schematic diagram of an encoding process in a color image-grayscale image-color image conversion method based on an image compression technique and a digital watermarking technique according to the present invention;
FIG. 2 is a schematic diagram of a decoding process in a color image-grayscale image-color image conversion method based on an image compression technique and a digital watermarking technique according to the present invention;
fig. 3 is a schematic diagram illustrating distribution of pixel value information embedding conditions of an image in the reversible watermarking technology of the present invention.
FIG. 4(a) is an original gray scale of the present invention;
FIG. 4(b) is a grayscale image obtained by the Queiorz method;
FIG. 4(c) is a grayscale image obtained by the method of Chan;
fig. 4(d) is a gray scale image obtained by LSB _ CWCI _ JPEG 20000.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Examples a Kodak dataset and McMaster dataset were used as test subjects, wherein there were 24 pictures in the Kodak dataset, the pictures being in png format, the pictures having a size of 512 x 768 or 768 x 512. There were 18 pictures in the McMaster dataset, in tif format, with a picture size of 500 x 500. The pictures contained in the two data sets have different characteristics, and some pictures have flat blocks, clear and fine lines, gradually-changed light and shadow, color depth layers and the like; some pictures have sharp outlines and are bright and dark; some pictures have characteristics such as continuous pixel values and smooth edges. Compared with the Kodak data set, the McMaster data set contains pictures with less spectral correlation, higher color saturation and larger color scale. Various pictures in daily life have the characteristics, so that the experimental result can be popularized by adopting the two data sets as test objects.
The present example employs general image quality evaluation indicators including peak signal-to-noise ratio (PSNR), Structural Similarity (SSIM), Feature Similarity (FSIM), and gradient magnitude similarity bias (GMSD). The larger the PSNR, SSIM and FSIM values are, the better the quality of the representative image is, the better the visual quality of the image is, and the smaller the GMSD value is, the smaller the distortion of the representative image is.
Example 1
The embodiment provides a color image-gray image-color image conversion method based on an image compression technology and a digital watermarking technology, wherein the digital watermarking technology adopts a large-capacity LSB digital watermarking technology, and comprises the following steps:
as shown in fig. 1, the color image conversion grayscale image encoding process:
a) reading original color imagesICalculatingIIs obtained byM*N*C(ii) a Binary representation of values for calculationsM*N*C*8Minimum number of bits requiredwWhereinM*N*Crepresenting how many pixels of the image are, each pixel being represented by an 8-bit binary number,M*N*C*8is to calculate the amount of data of the color image,wfor the subsequent usewRecording the size of the compressed chroma plane by a binary code stream of bits;
b) the original color image is processedIPerforming RGB to Ycbcr color space conversion, luminance planeYAnd the chrominance planes cb, cr are processed separately;
the RGB to Ycbcr color space conversion is specifically as follows:
wherein R, G, B is three channels of RGB of original color image, Y,cb、crFor the luminance plane Y, chrominance plane obtained after color space conversioncbAnd the chrominance planecr。
c) JPEG2000 or JPEG compression of 16 times of the chrominance planes cb and cr respectively to obtain compressed chrominance planes cb _ jp2 and cr _ jp 2;
d) the compressed chroma planes cb _ jp2 and cr _ jp2 are read in a binary mode, the image sizes of the compressed chroma planes cb _ jp2 and cr _ jp2, namely the lengths of corresponding binary code streams, are respectively calculated to obtain d1 and d2, and the d1 and the d2 are usedwBinary numbers w1, w2 of bits represent d1 and d2, respectively, for recording image sizes of cb _ jp2 and cr _ jp 2; w1 and w2 as the first part of the embedded informationwatermark1(binary code stream length for recording color information)) Compressed chroma planes cb _ jp2 and cr _ jp2 as the second part of the embedded informationwatermark2(as color information) for subsequent restoration of the color image;
e) handlewatermark1Andwatermark2embedding in luminance plane with LSB digital watermarking techniqueYIn the embedding, 2 × w pixels in front of the luminance plane are used for embeddingwatermark1Obtaining a gray scale image of the embedded information
And completing the conversion from the color image to the gray image.
The specific formula for embedding the LSB digital watermarking technology is as follows:
where x is the original luminance planeYThe pixel value of (1), info is the first part of the embedded informationwatermark1And a second part of the embedded informationwatermark2，
Is the luminance plane after embedding information
The value of the pixel of (a) is,
as shown in fig. 2, the gray image reconstruction color image decoding process:
f) reading information embedded grayscale images
Image sizes w1 and w2 for two chrominance planes are extracted using LSB digital watermarking (2 × w pixels in front of the luminance plane for embedding)watermark1，May be extracted first) and converted into decimal numbers d1 and d 2;
the specific formula for extracting the LSB technology is as follows:
g) extracting color information according to d1 and d2 (the binary code stream lengths of two chroma planes are known only by d1 and d2, and further the position of the pixel is known to extract information)watermark2。The extracted color information is a binary code stream, the binary code stream records information of the colorfulness plane, and the chrominance planes cb _ jp2 and cr _ jp2 can be recovered according to the binary code stream;
h) obtaining a luminance plane
(i.e., the information-embedded grayscale image described above
) The chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 perform Ycbcr to RGB color space conversion to reconstruct a high-quality color imageI rec And finishing the reconstruction from the gray image to the color image.
The Ycbcr to RGB color space conversion is specifically as follows:
wherein,
is a luminance plane (i.e. a gray scale image of the embedded information
），
And
are the two chroma planes after compression. The invention well combines JPEG2000 image compression technology and large capacity LSB digital watermark technology, because JPEG2000 is high efficiency image compression technologyIn the case where a certain compression rate is required, the color information of the original image can be more preserved, so that
And
can be as close as possible to the chrominance plane of the original image. Moreover, the LSB digital watermarking technique is a high-capacity digital watermarking technique, and can embed enough color information and lose only the lowest order information at most, so that a high-quality gray image can be obtained after embedding chrominance information into a gray plane. Based on the LSB method, the data is encoded in the LSB method,
can be as close as possible to the luminance plane Y of the original color image. With less pass distortion
、
And
a high quality reconstructed color image can be obtained.
In this embodiment, the luminance plane and the chrominance plane are orthogonal, and the luminance plane and the chrominance plane can be processed independently, and the changes of the luminance plane and the chrominance plane cannot affect each other. This orthogonal relationship preserves the gray plane well and also makes lossy compression of the chrominance plane more efficient.
As shown in table 1 below, the test results of the color map-grayscale map-color map conversion method based on the JPEG2000 image compression technique and the LSB digital watermarking technique on the Kodak data set and the McMaster data set are obtained, and the results show that the excellent results can be obtained on both data sets in this example 1.
TABLE 1 conversion result table based on JPEG2000 image compression technique and LSB digital watermarking technique
As shown in table 2 below, according to the image conversion method of this embodiment 1, a comparison table of the test results of the color map-grayscale map-color map conversion method based on the JPEG2000 image compression technique and the LSB digital watermarking technique (LSB _ CCPCI _ JPEG 2000) and the test results of the existing advanced algorithm is obtained. For the gray image with embedded information, the PSNR value of the gray image obtained by the method is about 10dB higher than the best effect of the existing advanced algorithm, the average value of the index SSIM in a kodak data set can reach 0.9991, and the average value of the index GMSD is only 0.005, which is also the best effect of the existing method. For a reconstructed color image, the PSNR value of the reconstructed color image obtained by the method is about 11dB higher than the best effect of the current advanced algorithm, the index FSIM is also the best at present, the index FSIM is superior to the current advanced algorithm, and the performance is greatly improved.
Table 2 comparison table of effect between image conversion method and conventional conversion method in embodiment 1
As shown in fig. 4(a) -4 (d), the gray image obtained by the method of queeiorz has serious noise, the gray image obtained by the method of Chan et al can see some halftone artifacts, human eyes can feel that the gray image obtained by the method of Chan is brighter than the original gray image as a whole, and the gray image obtained by the image conversion method (LSB _ CCPCI _ JPEG 2000) of the present invention has the best effect. From data, the PSNR of the gray scale image obtained by the Queiorz method is 27.16dB, the PSNR of the gray scale image obtained by the Chan method is 42.05dB, and the PSNR of the gray scale image obtained by the LSB _ CWCCI _ JPEG20000 is 51.23 dB.
And the reconstructed color image obtained by the Queiorz method has noise at the edge, the PSNR is 39.43dB, the color image reconstructed by the Chan et al method has slight low-frequency noise, the PSNR is 36.61dB, and the quality of the reconstructed color image obtained by the method is optimal, and the PSNR is 49.81 dB.
Example 2
The embodiment provides a color image-gray image-color image conversion method based on an image compression technology and a reversible watermarking technology, which adopts a high-capacity reversible watermarking technology based on prediction error expansion of valiley and specifically comprises the following steps:
a) reading original color imagesICalculatingIIs obtained byM*N*C(ii) a Binary representation of values for calculationsM*N*C*8Minimum number of bits requiredw，wFor the subsequent usewRecording the size of the compressed chroma plane by a binary code stream of bits;
b) the original color image is processedIPerforming RGB to Ycbcr color space conversion, luminance planeYAnd the chrominance planes cb, cr are processed separately;
the RGB to Ycbcr color space conversion is specifically as follows:
wherein R, G, B is three channels of RGB of original color image, Y,cb、crFor the luminance plane Y, chrominance plane obtained after color space conversioncbAnd the chrominance planecr。
c) JPEG2000 or JPEG compression of 16 times of the chrominance planes cb and cr respectively to obtain compressed chrominance planes cb _ jp2 and cr _ jp 2;
d) the compressed chroma planes cb _ jp2 and cr _ jp2 are read in a binary mode, the sizes of the compressed chroma planes cb _ jp2 and cr _ jp2 are calculated respectively to obtain the lengths d1 and d2 of corresponding binary code streams, and the lengths d1 and d2 are usedwBinary numbers w1, w2 of bits represent d1 and d2, respectively, for recording the sizes of cb _ jp2 and cr _ jp2, w1 and w2 as the first part of the embedded informationwatermark1(ii) a Compressed binary code streams of the chrominance planes cb _ jp2 and cr _ jp2 as a second part of the embedded informationwatermark2；
e) Handlewatermark1(when embedding, 2 x w pixels in front of the luminance plane are used for embeddingwatermark1) Andwatermark2embedding into luminance plane using reversible watermarking techniqueYIn the method, a gray scale image with embedded information is obtained
And completing the conversion from the color image to the gray image.
The specific formula for reversible watermark embedding is as follows:
wherein,
is a luminance plane after representing embedded information
X is the original luminance planeYPixel value of (1), info is information to be embeddedwatermark1Andwatermark2，
is 4 pixels (x) around x1、x2、x3、x4) As shown in fig. 3, the pixels marked as dots are used for embedding information, and the pixels marked as crosses are used for testing without embedding information. X being the pixel in which the information is to be embedded, X1、X2、X3、X4No information is embedded and the pixel values are unchanged.
Gray image reconstruction color image decoding process:
f) reading information embedded grayscale images
By usingThe reversible watermarking technique extracts the sizes w1 and w2 of the two chrominance planes (2 x w pixels in front of the luminance plane for embedding)watermark1，May be extracted first) and converted into decimal numbers d1 and d 2;
the reversible watermarking technique extracts the watermark as follows:
therefore, the embedded information info can be extracted, and the pixel value x of the original luminance plane is restored.
g) Extracting color information according to d1 and d2 (the binary code stream lengths of two chroma planes are known only by d1 and d2, and further the position of the pixel is known to extract information)watermark2And a non-distorted luminance planeY；
h) From a binary code streamwatermark2The chrominance planes cb _ jp2 and cr _ jp2 may be recovered;
i) combining the undistorted luminance plane Y, the chrominance planes cb _ jp2 and cr _ jp2 to perform Ycbcr-to-RGB color space conversion, and reconstructing a high-quality color imageI rec And finishing the reconstruction from the gray image to the color image.
The Ycbcr to RGB color space conversion is specifically as follows:
where Y is the original luminance plane (since with the reversible watermarking technique the carrier can be recovered without loss),
and
are the two chroma planes after compression.
The present embodiment employs a high-capacity reversible watermarking technique to incorporate JPEG2000 image compression. Since the reversible watermarking technique can recover the luminance plane Y without loss, the luminance plane can be made distortion-free when reconstructing the color image, i.e. through Y,
And
the quality of the reconstructed color image can be further improved.
In this embodiment, the luminance plane and the chrominance plane are orthogonal, and the luminance plane and the chrominance plane can be processed independently, and the changes of the luminance plane and the chrominance plane cannot affect each other. This orthogonal relationship preserves the gray plane well and also makes lossy compression of the chrominance plane more efficient.
Compared with the previous algorithm, the traditional algorithm loses too much information, such as based on a side information embedding algorithm, only one fourth of color information is kept, and high-frequency information of a brightness plane is discarded, so that the obtained gray-scale image and the reconstructed color image are blurred, and the obtained image quality is poor. If only one color palette is generated based on a vector quantization algorithm, limited to a gray image with 256 gray levels, which is equivalent to only 256 luminances and 256 chromaticities, the reconstructed color image has the problems of color shift and false contour. For the method of the invention, the chroma plane is compressed by 16 times (the compression by 16 times ensures that the size of the compressed color information can be embedded into the lowest bit of the gray image), the color information can be kept by more than one third, if the LSB watermarking technology is adopted, the luminance information is only lost at the lowest bit, and if the reversible watermarking technology is adopted, the luminance information can be completely kept. Therefore, the method can obtain the high-quality gray-scale image and the high-quality color image, and has good practical application scenes.
As shown in table 3 below, the same picture is used as a test object for comparison, and a comparison table of the test results of the color map-grayscale map-color map conversion method based on the LSB watermark technique and the JPEG2000 image compression technique (LSB _ CCPCI _ JPEG 2000) and the test results of the color map-grayscale map-color map conversion method based on the reversible watermark technique and the JPEG2000 image compression technique (RW _ CWCI _ JPEG 2000) is obtained;
table 3 effect of image conversion method of example 2 in comparison with example 1
In the present example, an embeddable picture in the Kodak dataset is employed as the test object. The reversible watermarking technology can recover the carrier in a lossless manner to obtain an original undistorted brightness plane, so that the color image-gray image-color image conversion method based on the reversible watermarking technology can obtain a reconstructed color image with better image quality.
In this embodiment, a reversible watermarking technology is used for embedding, and compared with the embodiment 1 that an LSB watermarking technology is used for embedding, the same picture is converted, and both technologies can correctly extract embedded information, that is, the size of the extracted chrominance plane and the extracted color information are the same and have no difference, but the gray level image of the finally obtained embedded information is different. The LSB watermarking technology cannot obtain a distortion-free brightness plane in the color image restoration stage, but the reversible watermarking technology can obtain the distortion-free brightness plane in the color image restoration stage, so that a reconstructed color image with better quality can be obtained.
Example 3
A color map-grayscale map-color map conversion system comprising: the system comprises a color image conversion gray level image coding module and a gray level image reconstruction color image decoding module;
in this embodiment, the color image conversion grayscale image encoding module includes: the device comprises an original color image data amount calculation module, a color space conversion module, a chromaticity plane compression module, an image size calculation module and an information embedding module;
in this embodiment, the grayscale image reconstruction color image decoding module includes: the device comprises a chrominance plane image size extraction module, a color information extraction module and a reconstruction module;
in this embodiment, the original color image data amount calculating module is used for reading the original color image and calculating the data amount of the original color imageM*N*C*8The calculated binary representation valueM*N*C*8Minimum number of bits requiredwFor subsequent use inwRecording the size of the compressed chroma plane by a binary code stream of bits;
in this embodiment, the color space conversion module is configured to perform color space conversion from RGB to Ycbcr on an original color image to obtain a luminance plane, a chrominance plane cb, and a chrominance plane cr;
in this embodiment, the chroma plane compression module is configured to compress the chroma plane cb and the chroma plane cr, respectively, to obtain a compressed chroma plane cb _ jp2 and a compressed chroma plane cr _ jp 2;
in this embodiment, the image size calculating module is configured to read in the compressed chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, and calculate the image sizes of the compressed chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, that is, the lengths of the binary code streams corresponding to the image sizes, to obtain d1 and d2, and adopt the method of calculating the image sizeswBinary numbers w1, w2 of bits represent d1 and d2, respectively, for recording the sizes of the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, w1 and w2 as the first part of the embedded informationwatermark1The binary code streams of the compressed chrominance planes cb _ jp2 and cr _ jp2 are color information as the second part of the embedded informationwatermark2；
In this embodiment, the information embedding module is configured to embed a first portion of the informationwatermark1And a second part of the embedded informationwatermark2Embedding the digital watermark technology into a brightness plane to obtain a gray level image of the embedded information;
in this embodiment, the chrominance plane image size extraction module is configured to read a grayscale image of the embedded information, and extract a first portion of the embedded information by using a digital watermarking techniquewatermark1I.e., w1 and w2,and converted into decimal numbers d1 and d 2;
in the embodiment, the color information extraction module is used for extracting the binary code stream of the color information according to d1 and d2watermark2And restoring the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 according to the color information;
in this embodiment, the reconstruction module is configured to perform color space conversion from Ycbcr to RGB on the luminance plane, the chrominance planes cb _ jp2, and cr _ jp2 to reconstruct a color image.
Example 4
This embodiment provides a storage medium, which may be a storage medium such as a ROM, a RAM, a magnetic disk, an optical disk, etc., and the storage medium stores one or more programs, and when the programs are executed by a processor, the color image-grayscale image-color image conversion method of embodiment 1 is implemented.
Example 5
The embodiment provides a computing device, which may be a desktop computer, a notebook computer, a smart phone, a PDA handheld terminal, a tablet computer, or other terminal devices with a display function, where the computing device includes a processor and a memory, where the memory stores one or more programs, and when the processor executes the programs stored in the memory, the color-to-grayscale-to-color conversion method in embodiment 1 is implemented.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A color image-gray image-color image conversion method is characterized by comprising the following steps:
color image conversion grayscale image encoding process:
reading the original color image, and calculating the data amount of the original color imageM*N*C*8The calculated binary representation valueM*N*C*8Minimum number of bits requiredwFor subsequent use inwRecording the size of the compressed chroma plane by a binary code stream of bits;
performing color space conversion from RGB to Ycbcr on the original color image to obtain a brightness plane, a chromaticity plane cb and a chromaticity plane cr;
respectively compressing the chrominance plane cb and the chrominance plane cr to obtain a compressed chrominance plane cb _ jp2 and a compressed chrominance plane cr _ jp 2;
reading in the compressed chroma planes cb _ jp2 and cr _ jp2, calculating the image sizes of the compressed chroma planes cb _ jp2 and cr _ jp2, i.e. the lengths of the corresponding binary code streams to obtain d1 and d2, and using the d1 and d2wBinary numbers w1, w2 of bits represent d1 and d2, respectively, for recording the sizes of the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, w1 and w2 as the first part of the embedded informationwatermark1The binary code stream of the compressed chroma planes cb _ jp2 and cr _ jp2 as the second part of the embedded informationwatermark2；
A first part of the information to be embeddedwatermark1And a second part of the embedded informationwatermark2Embedding into brightness plane by digital watermarking technology, wherein 2 × w pixels in front of the brightness plane are fixed for embeddingwatermark1Obtaining a gray level image of the embedded information, and completing the conversion from the color image to the gray level image;
gray image reconstruction color image decoding process:
reading the gray scale image of the embedded information, and extracting the first part of the embedded information by using a digital watermarking technologywatermark1Extracting image sizes w1 and w2 of two chromaticity planes, and converting the image sizes into decimal numbers d1 and d 2;
extracting a second part of the embedded information by digital watermarking based on the decimal numbers d1 and d2watermark2Based on the second part of the embedded informationwatermark2Recovering the chrominance plane cb _ jp2 and the chrominance plane cr _ jp 2;
and carrying out Ycbcr-to-RGB color space conversion on the luminance plane, the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 to reconstruct a color image and complete the reconstruction from a gray image to the color image.
2. The color-to-grayscale-to-color conversion method according to claim 1, wherein the color space conversion of RGB to Ycbcr is performed on the original color image, specifically expressed as:
wherein R, G, B is three channels of RGB of original color image, Y,cb、crFor the luminance plane Y, chrominance plane obtained after color space conversioncbAnd the chrominance planecr。
3. The color-to-gray-to-color conversion method according to claim 1, wherein the compression is performed on the chrominance plane cb and the chrominance plane cr, respectively, specifically by 16-fold JPEG2000 or JPEG compression.
4. The color-to-grayscale-to-color conversion method as set forth in claim 1, wherein the first portion of information to be embedded iswatermark1And a second part of the embedded informationwatermark2The digital watermarking technology is embedded into a brightness plane, and the LSB digital watermarking technology is adopted for information embedding, and the specific expression is as follows:
extracting a first part of embedded information by adopting a digital watermarking technologywatermark1And extracting a second part of the embedded information by using the digital watermarking technologywatermark2And information extraction is carried out by adopting an LSB digital watermarking technology, which is specifically expressed as follows:
wherein x represents the original luminancePixel value of plane, info represents first part of embedded informationwatermark1And a second part of the embedded informationwatermark2，
Representing the pixel values of the luminance plane after embedding the information.
5. The color-to-grayscale-to-color conversion method as set forth in claim 1, wherein the first portion of information to be embedded iswatermark1And a second part of the embedded informationwatermark2Embedding a digital watermark technology into a luminance plane, and embedding information by adopting a reversible watermark technology based on prediction error expansion, wherein the reversible watermark technology is specifically represented as follows:
extracting a first part of embedded information by adopting a digital watermarking technologywatermark1And extracting a second part of the embedded information by using the digital watermarking technologywatermark2The method adopts a reversible watermarking technology based on prediction error expansion to extract information, and is specifically represented as follows:
wherein,
representing pixel values of a luminance plane after embedding information, x representing pixel values of an original luminance plane, and info representing a first part of the embedded informationwatermark1And a second part of the embedded informationwatermark2，
Representing x adjacent 4 pixels x1、x2、x3、x4The predicted value of (2).
6. The color-to-grayscale-color conversion method according to claim 1, characterized in that the compressed chrominance planes cb _ jp2 and cr _ jp2 are read in a binary manner, and the compressed chrominance planes cb _ jp2 and cr _ jp2 are represented as a binary code stream for storing information of the chrominance planes.
7. The color-to-gray-to-color image conversion method according to claim 1, characterized in that said Ycbcr to RGB color space conversion of the luminance plane, the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 reconstructs a color image, specifically represented as:
wherein,
is a plane of brightness that is,
and
representing the two chrominance planes after compression.
8. A color-to-gray-to-color conversion system, comprising: the system comprises a color image conversion gray level image coding module and a gray level image reconstruction color image decoding module;
the color image conversion grayscale image encoding module includes: the device comprises an original color image data amount calculation module, a color space conversion module, a chromaticity plane compression module, an image size calculation module and an information embedding module;
the gray scale image reconstruction color image decoding module comprises: the device comprises a chrominance plane image size extraction module, a color information extraction module and a reconstruction module;
the original color image data volume calculating module is used for reading the original color image and calculating the data volume of the original color image to obtainM*N*C*8The calculated binary representation valueM*N*C*8Minimum number of bits requiredwFor subsequent use inwRecording the size of the compressed chroma plane by a binary code stream of bits;
the color space conversion module is used for performing color space conversion from RGB to Ycbcr on the original color image to obtain a brightness plane, a chromaticity plane cb and a chromaticity plane cr;
the chrominance plane compression module is used for respectively compressing the chrominance plane cb and the chrominance plane cr to obtain a compressed chrominance plane cb _ jp2 and a compressed chrominance plane cr _ jp 2;
the image size calculating module is used for reading in the compressed chrominance planes cb _ jp2 and cr _ jp2, calculating the image sizes of the compressed chrominance planes cb _ jp2 and cr _ jp2 respectively, namely the lengths of binary code streams corresponding to the image sizes to obtain d1 and d2, and adopting the methodwBinary numbers w1, w2 of bits represent d1 and d2, respectively, for recording the sizes of the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2, w1 and w2 as the first part of the embedded informationwatermark1The binary code streams of the compressed chrominance planes cb _ jp2 and cr _ jp2 are color information as the second part of the embedded informationwatermark2；
The information embedding module is used for embedding a first part of informationwatermark1And a second part of the embedded informationwatermark2Embedding the digital watermark technology into a brightness plane to obtain a gray level image of the embedded information;
the chrominance plane image size extraction module is used for reading a gray level image of embedded information and extracting a first part of the embedded information by adopting a digital watermarking technologywatermark1I.e. w1 and w2, and converted to decimal numbers d1 and d 2;
the color information extraction module is used for extracting the binary code stream of the color information according to d1 and d2watermark2And restoring the chrominance plane cb _ jp2 and the chrominance plane cr _ jp2 according to the color information;
the reconstruction module is used for carrying out Ycbcr-to-RGB color space conversion on the luminance plane, the chrominance plane cb _ jp2 and cr _ jp2 to reconstruct a color image.
9. A storage medium storing a program, wherein the program when executed by a processor implements the color-to-gray-to-color conversion method according to any one of claims 1 to 7.
10. A computing device comprising a processor and a memory for storing a processor-executable program, wherein the processor, when executing the program stored in the memory, implements the color-to-grayscale-to-color conversion method as recited in any one of claims 1-7.
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