CN117812266A

CN117812266A - Color library coding method, code stream pre-allocation method, image compression method and device

Info

Publication number: CN117812266A
Application number: CN202311575518.3A
Authority: CN
Inventors: 魏晓帆; 胡本川
Original assignee: Beijing Eswin Computing Technology Co Ltd; Haining Eswin IC Design Co Ltd
Current assignee: Beijing Eswin Computing Technology Co Ltd; Haining Eswin IC Design Co Ltd
Priority date: 2023-11-23
Filing date: 2023-11-23
Publication date: 2024-04-02

Abstract

The application provides a color library coding method, a code stream pre-allocation method, an image compression method and a device, when an image pixel packet is coded based on a color library, if a pixel with a matching color does not exist in the color library when the matching color of each pixel in the image pixel packet is searched in the color library, the color library is updated by utilizing the color of the part of pixels, so that the color library coding of the part of pixels can be realized in a mode of transmitting the color of the part of pixels and an index corresponding to the color of the part of pixels in the updated color library into the code stream. Based on the color library coding method considering the actual color condition in the pixel packet of the image to be coded, the use condition of the color library coding in the image compression process is reduced, so that the compression rate of the image and the image reconstruction quality are greatly improved.

Description

Color library coding method, code stream pre-allocation method, image compression method and device

Technical Field

The present invention relates to the field of image processing technologies, and in particular, to a color library coding method, a code stream pre-allocation method, an image compression method and an image compression device.

Background

Video is a continuous sequence of images, consisting of successive frames, one frame being an image. In practical applications, in order to reduce the amount of data stored or transmitted, it is generally necessary to compress each frame of image in a video.

One type of compression method that is currently mainstream is image compression using a combination of predictive coding and color library coding. The color library coding can greatly save code streams and has higher image reconstruction quality, but the traditional color library coding method has very harsh use conditions and cannot be used in many cases.

Disclosure of Invention

In order to solve the technical problems, the application provides a color library coding method, a code stream pre-allocation method, an image compression method and an image compression device, which can improve the compression rate of images and the image reconstruction quality.

According to a first aspect of the present application, there is provided a color library encoding method for implementing image compression, including:

determining a color library corresponding to an image pixel packet to be coded currently, and searching a matching color of each pixel in the image pixel packet in the color library, wherein the image pixel packet comprises M pixels, the color library comprises N colors, and M and N are positive integers;

Transmitting the index corresponding to the matching color of each pixel in the image pixel packet in the color library into a code stream,

for the pixel with the matching color found in the color library, transmitting an index corresponding to the matching color of the pixel in the color library into a code stream;

and for the pixel with the matching color not found in the color library, updating the color library by using the color of the pixel, and transmitting the color of the pixel and the index corresponding to the color in the updated color library into a code stream.

Optionally, determining the color library corresponding to the current image pixel packet to be encoded includes:

judging whether N is a positive integer power of 2;

and under the condition that N is the positive integer power of 2, eliminating x colors of which the correlation with the current image pixel packet does not meet the requirement from N colors of the color library, determining the color library with the x colors eliminated as the color library corresponding to the current image pixel packet to be encoded, wherein x is a positive integer less than M.

Optionally, the step of transmitting the index input code stream corresponding to the matching color of each pixel in the image pixel packet in the color library includes:

counting the number K of pixels in the image pixel packet of which the matching color is found in the color library, wherein K is a non-negative integer;

If K is equal to M, transmitting indexes corresponding to the matching colors of each pixel in the image pixel packet in the color library into a code stream;

if K is smaller than M, counting the number J of the colors of the pixels with the matching colors which are not found in the color library, updating the color library by utilizing the J colors under the condition that J is smaller than or equal to x, transmitting the J colors and indexes corresponding to the matching colors of each pixel in the image pixel packet in the updated color library into a code stream, wherein J is a positive integer,

the color number represents the kind number of the color, and the color number J is smaller than or equal to the number of pixels in the color library, for which no matching color is found.

Optionally, the color library includes a colors from the current row of pixels and b colors from the previous row of pixels, where a and b are positive integers;

and eliminating x colors which are not required by the correlation with the current image pixel packet in the N colors of the color library, wherein the x colors comprise:

and eliminating x colors of which the correlation with the current image pixel packet does not meet the requirement from a colors of the current row of pixels.

Optionally, determining whether each of the a colors meets a correlation requirement with the current image pixel packet based on a position of each of the a colors relative to the current image pixel packet,

Wherein the color of the pixel at a position further apart from the current image pixel packet in the pixel address is less correlated with the current image pixel packet.

Optionally, searching the color library for a matching color of each pixel in the image pixel packet, including:

and determining whether a color with a difference value smaller than a preset threshold value from the pixel value of the pixel to be coded currently exists in the color library, and if so, determining the color as a matching color of the pixel to be coded currently.

Optionally, after the index corresponding to the matching color of each pixel in the image pixel packet in the color library is transferred into the code stream, the method further includes:

and updating the color library by using the colors of M pixels in the current image pixel packet to be encoded, so as to take the updated color library as a color library corresponding to the next image pixel packet to be encoded.

According to a second aspect of the present application, there is provided a code stream pre-allocation method, including:

constructing a color library of the current line of pixels to be encoded based on the colors of at least part of the pixels in the previous line of pixels, wherein the color library comprises b colors from the pixels in the previous line;

Determining, based on the color library, T image pixel packets encoded by the color library encoding method according to any embodiment of the present application, where W and T are positive integers, from W image pixel packets of a current row of pixels, and calculating a code stream space required by the T image pixel packets when performing color library encoding;

determining a reassignable code stream space according to the total code stream space distributed by the current line of pixels and the code stream space required by the determined T image pixel packets capable of being subjected to color library coding, evenly distributing the reassignable code stream space into W image pixel packets, wherein the image pixel packets except for the T image pixel packets,

wherein, in the case that b is a positive integer power of 2, it further comprises: and eliminating x colors of which the correlation with the pixels of the current row does not meet the requirement from the b colors of the color library.

According to a third aspect of the present application, there is provided an image compression method, including:

dividing each row of pixels of an image to be encoded into a plurality of image pixel packets;

under the condition that the current image pixel packet to be encoded meets the color library encoding condition, the bit number and the reconstruction error of the current image pixel packet to be encoded during predictive encoding and color library encoding are estimated respectively;

Judging according to the estimated bit number and the reconstruction error, and determining an optimal coding mode of the current image pixel packet to be coded;

coding the current image pixel packet to be coded according to the determined optimal coding mode, outputting a corresponding code stream,

when the determined optimal coding mode is color library coding, the color library coding method according to any embodiment of the application is adopted to code the current image pixel packet to be coded.

Optionally, the step of determining whether the current image pixel packet to be encoded meets the color library encoding condition includes:

determining a color library corresponding to an image pixel packet to be coded currently, and searching a matching color of each pixel in the image pixel packet to be coded currently in the color library, wherein the image pixel packet contains M pixels, the color library contains N-x colors, M is a positive integer, N is a positive integer power of 2, and x is a positive integer smaller than M;

if K is equal to M, judging that the current image pixel packet to be coded meets the coding condition of the color library;

If K is smaller than M, counting the number J of the colors of pixels which are not found to be matched with the colors in the color library, if J is smaller than or equal to x, judging that the current image pixel packet to be coded meets the color library coding condition, and if J is larger than x, judging that the current image pixel packet to be coded does not meet the color library coding condition.

Optionally, under the condition that the current image pixel packet to be coded does not meet the coding condition of the color library, the prediction coding mode is adopted to code the current image pixel packet to be coded.

Optionally, before determining the optimal coding mode of each image pixel packet in the current line of pixels and coding the current line of pixels, the method further comprises:

and performing code stream pre-allocation on a plurality of image pixel packets corresponding to the pixels of the current row.

According to a fourth aspect of the present application, there is provided an image processing apparatus, comprising:

an encoder for executing the image compression method according to any embodiment of the present application, and outputting a corresponding code stream;

and the decoder is connected with the encoder and used for decoding the code stream so as to reconstruct the image.

According to a fifth aspect of the present application, there is provided an electronic device, comprising: a processor, a memory, and a program stored on the memory and executable on the processor, which when executed by the processor, performs the steps of at least one of the methods of:

A color library encoding method as described in any of the embodiments herein;

the code stream allocation method according to any embodiment of the present application;

an image compression method as in any of the embodiments herein.

According to a sixth aspect of the present application, there is provided a storage medium having stored thereon a computer program or instructions which, when executed by a processor, perform the steps of at least one of the following methods:

a color library encoding method as described in any of the embodiments herein;

an image compression method as in any of the embodiments herein.

By adopting the technical scheme disclosed by the embodiment of the application, the compression rate and the image reconstruction quality of the image can be improved, the complexity is low, and the implementation is easy.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.

Drawings

Fig. 1 shows a flow diagram of an image compression method according to an embodiment of the present application;

FIG. 2 shows a flowchart of a color library encoding method according to an embodiment of the present application;

FIG. 3 is a schematic flow chart of encoding each pixel in an image pixel packet into a code stream according to an embodiment of the present application;

fig. 4 shows a flow chart of a code stream pre-allocation method according to an embodiment of the present application;

fig. 5 shows a block diagram of the structure of an image processing apparatus provided according to an embodiment of the present application;

fig. 6 shows a block diagram of an electronic device according to an embodiment of the present application.

Detailed Description

In order to facilitate an understanding of the present application, a more complete description of the present application will now be provided with reference to the relevant figures. Preferred embodiments of the present application are shown in the accompanying drawings. This application may, however, be embodied in different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Reference in the specification to "one embodiment" or "some embodiments" or the like means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.

In the description of the present application, words such as "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments. "and/or" herein is a description of an association relationship of an associated object, meaning that there may be three relationships, e.g., a and/or B, which may represent: a exists alone, A and B exist together, and B exists alone. "plurality" means two or more than two.

In the field of image coding (also referred to as the field of video coding, CODEC), the terms "picture", "frame" or "picture" may be used as synonyms. The image encoding and decoding comprises two parts of image encoding and image decoding. Image encoding is performed on the source side, typically involving processing (e.g., compressing) the original image to reduce the amount of data needed to represent the image (and thus more efficiently store and/or transmit). Image decoding is performed on the destination side, typically involving an inverse process with respect to the encoder to reconstruct the video image.

Fig. 1 shows a flowchart of an image compression method according to an embodiment of the present application, as shown in fig. 1, where the image compression method includes the following steps:

In step 110, each row of pixels of the image to be encoded is divided into a plurality of image pixel packets.

In this step, the image to be encoded may be a single picture, or may be any image sequence in a video sequence. Each row of pixels of the image to be encoded is divided into a plurality of image pixel packets, that is, a single row of pixels of the image to be processed is divided into packets (packets) according to actual requirements, and each row of pixels can be divided into a plurality of image pixel packets, wherein the width of each image pixel packet is M, that is, each image pixel packet contains M pixels, and M is a positive integer.

In step 120, under the condition that the current image pixel packet to be encoded meets the color library encoding condition, the bit number and the reconstruction error of the current image pixel packet to be encoded during the prediction encoding and the color library encoding are estimated respectively.

It should be noted that, the color library coding in this step refers to the new color library coding method disclosed in this application, and the specific details thereof are described below. On the basis, the step of judging whether the current image pixel packet to be coded meets the coding conditions of the color library comprises the following steps:

determining a color library corresponding to the current image pixel packet to be encoded, and searching the matching color of each pixel in the current image pixel packet to be encoded in the color library, wherein the color library comprises N-x colors, N is a positive integer, N is the power of N of 2, N is a positive integer, and x is a positive integer smaller than M; counting the number K of pixels in an image pixel packet of which the matching color is found in a color library, wherein K is a non-negative integer; if K is equal to M, judging that the current image pixel packet to be coded meets the coding condition of the color library; if K is smaller than M, counting the number J of the colors of pixels which are not found to match colors in the color library, if J is smaller than or equal to x, judging that the current image pixel packet to be encoded meets the color library encoding condition, and if J is larger than x, judging that the current image pixel packet to be encoded does not meet the color library encoding condition.

In the color library, each color corresponds to an index (index), and the index may be represented by a number of bits with a bit width of N, and in the case of N determination, N colors may be represented by at most N powers of 2. For example, assuming that N is equal to 5, the index described by the 5-bit number has at most 32 (2 is 5 times equal to 32) variations from "00000" to "11111", that is, the range of values of the index in the color library is [0, 31], and n=32 colors can be represented by the index at most in the color library.

In this embodiment, when setting a color library for color library encoding, if the color library initially set includes N colors, x colors having the worst correlation with corresponding image pixel packets need to be removed from the N colors, so that when performing color library encoding on each image pixel packet, on the basis of not increasing the bit width of the index of the color, a certain blank space can exist in the color library corresponding to the image pixel packet to facilitate new color addition, so that the color library encoding method disclosed in the application can be applied to the color library encoding method; of course, if the number of colors included in the color library initially set is less than N (it can be understood that, at this time, the number of colors in the color library may also be represented by n—x, where x corresponds to different values according to practical situations), that is, is not a positive integer power of 2, it indicates that a certain blank space naturally exists in the color library initially set, and at this time, no color rejection operation may be performed. In particular, the novel color library encoding methods disclosed in the present application may be described with reference to the following.

When counting the number K of pixels in an image pixel packet with the matched color in a color library, if the pixel in the current image pixel packet is found in the determined corresponding color library, namely the color with the difference value of the pixel being smaller than a preset threshold value, the pixel can be considered to find the corresponding matched color in the color library, and the pixel should be counted in the K; otherwise, if the color closest to the pixel is not found in the determined corresponding color library, that is, the difference value between the pixel value of each color in the color library and the pixel value of the pixel is greater than or equal to the preset threshold value, the pixel can be determined that the corresponding matching color cannot be found in the color library, and the statistics should be performed in J.

After the matching color searching task in the color library is executed for each pixel in the image pixel packet, whether the current image pixel packet to be encoded meets the color library encoding condition can be judged according to the counted K value and J value:

if K is equal to M, each pixel in the image pixel packet to be coded currently finds a corresponding matching color in a color library, and the image pixel packet can be judged to meet the condition of executing the color library coding;

If K is smaller than M and J is smaller than x, the fact that the corresponding matching color cannot be found in the color library by pixels in the image pixel packet to be coded currently is indicated, but the color library coding method disclosed by the application can be used for carrying out color library coding, namely, the color library can be updated by adding the J colors into the color library, so that each pixel in the image pixel packet to be coded currently can find the corresponding matching color in the color library, and at the moment, the image pixel packet can also be judged to meet the condition of executing the color library coding;

if K is smaller than M and J is larger than x, the fact that the corresponding matching color cannot be found in the color library by pixels in the image pixel packet to be coded currently is indicated, and meanwhile, under the condition that the bit number n corresponding to the index of the color in the color library is unchanged, the J colors cannot be added into the color library completely, and at the moment, it can be determined that the image pixel packet does not meet the condition of executing color library coding.

Under the condition that the current image pixel packet to be encoded meets the color library encoding condition, respectively carrying out predictive encoding and color library encoding on the current image pixel packet to be encoded, and accordingly calculating the number of bits and reconstruction errors required to be consumed by the current image pixel packet to be encoded in the two encoding modes according to the encoding result, and completing prediction.

In step 130, the optimal coding mode of the current image pixel packet to be coded is determined according to the estimated bit number and the reconstruction error.

In some embodiments, if the number of bits and the reconstruction error required to be consumed by the current image pixel packet to be encoded in the prediction encoding manner are smaller than the number of bits and the reconstruction error required to be consumed by the current image pixel packet to be encoded in the color library encoding manner, selecting the prediction encoding as an optimal encoding mode of the current image pixel packet to be encoded; and if the bit number and the reconstruction error required to be consumed by the current image pixel packet to be encoded in the color library encoding mode are smaller than the bit number and the reconstruction error required to be consumed by the current image pixel packet to be encoded in the prediction encoding mode, selecting the color library encoding mode as the optimal encoding mode of the current image pixel packet to be encoded.

In other embodiments, corresponding weights may be set for two discriminant criteria, i.e., the number of bits to be consumed and the reconstruction error, so as to comprehensively compare the number of bits and the reconstruction error of the current image pixel packet to be encoded under the prediction encoding and the color library encoding according to the weights, and determine the optimal encoding mode of the current image pixel packet to be encoded according to the comparison result.

It can be understood that, under the condition that the current image pixel packet to be encoded does not meet the color library encoding condition, the prediction encoding mode is directly adopted to encode the current image pixel packet to be encoded.

It should be noted that, in the above embodiments of the present application, only the selection of the image pixel packet in two coding modes (prediction coding and color library coding) is listed, but in other embodiments of the present application, a conventional coding mode such as conventional variable length coding and/or RAW coding may be used as an option for determining the optimal coding mode of the image pixel packet to be currently encoded, and the selection method is the same as the selection method disclosed in step 120 and step 130 of the present application, and of course, other conventional coding mode selection methods may also be used, which is not strictly limited in this application.

In step 140, the current image pixel packet to be encoded is encoded according to the determined optimal encoding mode, and a corresponding code stream is output.

When the determined optimal coding mode is predictive coding, an existing predictive coding method may be used to code the current image pixel packet to be coded, and specific details of the predictive coding may be understood with reference to the prior art, which is not described in detail in this application. When the determined optimal coding mode is color library coding, the image pixel packet to be currently coded can be coded by adopting a color library coding method as shown in fig. 2.

It should be noted that, in the conventional color-library encoding method, recently appeared pixels are stored in a color library. If each pixel in the current image pixel packet to be encoded can find a corresponding close color in the color library (i.e. the difference between the two is smaller than a preset threshold), the color in the color library can be used as the reconstruction value of the current pixel. When the code stream is transmitted, only the index of the code stream in the color library is transmitted.

However, this does not take into account the color in the current image pixel packet to be encoded, and thus when the color in the image pixel packet is relatively single, but such color is not stored in the color library, the color library cannot be used for encoding. In this case, only the predictive coding method is used, and the quantization is required, so that the quality of the image reconstruction is poor. For example: assuming that the colors in the pixel packet of the current image are black and white alternation, wherein white can be found in a color library, and black cannot be found in the color library, the traditional color library coding cannot be applied, and only predictive coding can be used instead, but the effect of the predictive coding is very poor due to the fact that black and white alternation is adopted in the packet, so that the code stream space cannot be saved, and the reconstruction quality of the image is very poor.

In view of this problem, the embodiment of the application discloses a new color library coding method for image compression, which considers the situation in the current pixel packet, reduces the use conditions of color library coding in the image compression process, greatly improves the compression rate and the image reconstruction quality, and can greatly improve the reconstruction effect of images on certain image contents. Referring to fig. 2, the color library encoding method includes performing the steps of:

in step 210, a color library corresponding to the current image pixel packet to be encoded is determined, and a matching color of each pixel in the image pixel packet is searched in the color library, wherein the image pixel packet contains M pixels, the color library contains N colors, and M and N are positive integers.

In this step, searching the color library for the matching color of each pixel in the image pixel packet includes: and determining whether a color with a difference value smaller than a preset threshold value from the pixel value of the pixel to be coded currently exists in the color library, and if so, determining the color as a matching color of the pixel to be coded currently.

In step 220, an index corresponding to a matching color of each pixel in the image pixel packet in the color library is transmitted into the code stream, wherein for the pixel with the matching color found in the color library, the index corresponding to the matching color of the pixel in the color library is transmitted into the code stream; and for the pixel with the matching color not found in the color library, updating the color library by using the color of the pixel, and transmitting the color of the pixel and the index corresponding to the color in the updated color library into the code stream.

Taking M equal to 3, that is, each image pixel packet contains 3 pixels (a 1, a2, a 3) as an example, assuming that a matching color of the pixel a1 is found in the color library (for example, denoted as is_hit=1), when the pixel a1 is color-library encoded, an index of a matching color pair of the pixel a1 in the color library is directly transmitted into the code stream; assuming that the matching color of the pixels a2 and a3 is not found in the color library (e.g., denoted as is_hit=0), the colors of the pixels a2 and a3 are added to the color library, and corresponding indexes are set for the colors of the pixels a2 and a3 in the color library, respectively, and when the pixels a2 and a3 are color-library encoded, in addition to the index set in the color library for the colors of the pixels a2 and a3 being transferred into the code stream, the colors of the pixels a2 and a3 are also transferred into the code stream, so that the color library at the decoding end is synchronously updated.

According to the color library coding method disclosed by the embodiment of the application, when the matching color of a certain pixel in the current image pixel packet to be coded does not exist in the color library, the color of the pixel is added into the color library to update the color library, so that each pixel of the current image pixel packet to be coded can find the corresponding matching color in the updated corresponding color library, namely, the updated corresponding color library can be used for carrying out color library coding on the pixel of the current image pixel packet to be coded no matter how the pixel color of the current image pixel packet to be coded is, the use condition of the color library coding is reduced, and the image reconstruction effect can be greatly improved.

In a specific embodiment, determining a color library corresponding to the current image pixel packet to be encoded includes: judging whether N is a positive integer power of 2; under the condition that N is the positive integer power of 2, eliminating x colors of which the correlation with the current image pixel packet does not meet the requirement from N colors of a color library, determining the color library with the x colors eliminated as the color library corresponding to the current image pixel packet to be encoded, wherein x is a positive integer less than M; in case N is not a positive integer power of 2, the color bin is directly determined as the corresponding color bin of the image pixel packet currently to be encoded.

In some examples, it is assumed that when a row of pixels is processed, the initial color library constructed for it contains a positive integer power of 2 (e.g., 32) colors, i.e., N is 32, equal to the power of 2 to 5, and the index of each color in the color library needs a number of 5 bits to represent. At this time, when the color library coding is performed on the line of pixels based on the initial color library, x colors in the color library, which do not meet the requirements on the correlation with the current image pixel packet, need to be removed in advance (in the color library, the color of the pixel at the position most different from the current image pixel packet in the pixel address can be considered as the worst correlation with the current image pixel packet), so that when the color library coding is performed on each image pixel packet in the line of pixels later, the number of colors actually contained in the color library corresponding to each image pixel packet is 32-x, and a certain blank space exists, and at this time, even if the corresponding matching color is not found in the color library corresponding to a pixel in a certain image pixel packet, and the color of the pixel needs to be added into the color library to update the color library, the total number of colors in the updated color library does not exceed 32, the index of 5 bits can still be used to represent each color in the updated color library, the number of bits of the index of each color library is not increased, and the bit stream of bits of the color in the updated color library is still not increased, and the coding condition is not reduced when the bit stream coding is completed.

The N colors included in the initial color library include a colors from the current line of pixels and b colors from the previous line of pixels, where a and b are positive integers, when x colors, which are not related to the current image pixel packet, of the N colors in the initial color library need to be removed, x colors, which are not related to the current image pixel packet, of the a colors from the current line of pixels need to be removed, that is, when the color library needs to be updated, a plurality of colors, which are related to the current image pixel packet, of the color library, are updated, so that the situation in the current packet can be effectively considered when each image pixel packet of a line of pixels is subjected to color library coding. Further, determining whether each of the a colors from the current row of pixels meets a correlation requirement with the current image pixel packet according to a position of each of the a colors from the current row of pixels relative to the current image pixel packet, wherein the color of a pixel at a position further apart in pixel address from the current image pixel packet has a lower correlation with the current image pixel packet.

In some examples, it is assumed that when a certain row of pixels is processed, the number of colors contained in an initial color library constructed for the initial color library is not a positive integer power of 2, for example, 28 colors, that is, N is 28, and at this time, although the index of each color in the color library still needs to be represented by 5 bits, the color library itself has a certain blank space, and similarly, when the row of pixels is encoded based on the initial color library, no color reject operation needs to be performed, and at this time, even when a pixel in a certain image pixel packet is detected that the corresponding matching color is not found in the color library corresponding to the pixel, and the color of the pixel needs to be added into the color library to update the color library, the total number of colors in the updated color library does not exceed 32, and the index of each color in the updated color library can still be represented by the index of 5 bits, without increasing the bit width of the index of each color in the updated color library, which does not cause an increase in the required bit number when the code stream is transmitted after the encoding is completed, and the color encoding condition is well used.

In this embodiment, referring to fig. 3, the method for transmitting the index corresponding to the matching color of each pixel in the image pixel packet into the code stream in the color library includes the following steps:

In step 310, counting the number K of pixels in the image pixel packet of which the matching color is found in the color library, wherein K is a non-negative integer;

in step 320, determining the magnitude relation between K and M, if K is equal to M, executing step 330, and if K is less than M, executing step 340;

in step 330, the index corresponding to the matching color of each pixel in the image pixel packet in the color library is transmitted into the code stream;

in step 340, counting the number of colors J of pixels for which no matching color is found in the color library, J being a positive integer;

in step 350, determining the magnitude relation between J and x, if J is less than or equal to x, executing step 360;

in step 360, the color library is updated with the J colors, and the J colors and the index corresponding to the matching color of each pixel in the image pixel packet in the updated color library are transmitted into the code stream.

It can be understood that, in the present embodiment, when performing color library encoding, the color library encoding is performed by using an image pixel packet as a unit, and when performing color library encoding on a certain image pixel packet to be encoded, the pixel values of each color in the color library are respectively compared with the pixel values of each color in the image pixel packet, and the number K of pixels in the image pixel packet in which the matching color is found in the color library is counted. After obtaining the K value, comparing the size relation between K and M, if K is equal to M, indicating that each pixel in the current image pixel packet to be coded finds the corresponding matching color in the color library, and transmitting the index corresponding to the matching color of each pixel in the image pixel packet in the color library into the code stream to finish the color library coding of the image pixel packet; if K is smaller than M and J is smaller than x, the fact that the corresponding matching color cannot be found in the color library by pixels in the image pixel packet to be coded currently is indicated, the J colors are added into the color library to update the color library, indexes corresponding to the J colors and the matching colors of each pixel in the image pixel packet in the updated color library are transmitted into a code stream, and color library coding of the image pixel packet is completed.

It can be understood that the number of colors represents the number of types of colors, and in the case that pixels in the current image pixel packet to be encoded cannot find the corresponding matching color in the color library, the J value obtained by statistics is not necessarily equal to the number of pixels in the image pixel packet, in which no matching color is found in the color library, because in the partial pixels, in which no matching color is found in the color library, there may be two or more pixels whose pixel values are equal or very close to each other, where the pixels can be considered to belong to the same color, and the number of colors J is less than or equal to the number of pixels, in which no matching color is found in the color library.

According to the color library coding scheme disclosed by the application, the actual color condition in the current image pixel packet to be coded is fully considered, and even if the current image pixel packet to be coded has single color and the corresponding color library is not stored, the color library can be updated by adding the color into the color library, so that the color library coding is completed based on the updated color library, the use condition of the color library coding in the image compression process is reduced, and the compression rate and the image reconstruction quality of an image are greatly improved.

Further, after the index corresponding to the matching color of each pixel in the image pixel packet in the color library is transferred into the code stream, the method further comprises: and updating the color library by using the colors of M pixels in the current image pixel packet to be encoded, so that the updated color library is used as the color library corresponding to the next image pixel packet to be encoded.

It should be noted that, when x colors of N colors (specifically, a colors from the current row of pixels in the N colors) of the initial color library need to be removed, the removing action occurs before the current row of pixels are color-library coded, and at this time, the number of colors in the color library corresponding to each image pixel packet of the row of pixels is changed from N in the initial color library to N-x; when the pixel color in a certain image pixel packet needs to be added into a corresponding color library, the color library updating action occurs during the color library encoding of the image pixel packet, and the number of colors in the color library corresponding to the image pixel packet is temporarily changed from N-x to N so as to perform accurate encoding and decoding; when the color library is updated by using the colors of M pixels in the current image pixel packet to be encoded, the color library updating action occurs after the completion of the color library encoding of the image pixel packet, and the color library updating action of the time comprises: and on the basis of the color library updating action generated during the color library encoding of the current image pixel packet, eliminating x colors in the color library, the correlation of which with the next image pixel packet to be encoded does not meet the requirement, so as to restore the number of colors in the color library corresponding to the next image pixel packet from N to N-x. It will be appreciated that the color library at the decoding end is also configured to perform the same updating actions as the color library at the encoding end in order to achieve accurate decoding. It can be understood that, at the decoding end, if the decoded index is greater than N-x, the subsequently transmitted code stream is J colors newly added into the color library, so that the color library at the decoding end can be synchronously updated accordingly.

It will be appreciated that the problem of pre-allocation of the code stream is always involved in the process of image compression, and in the conventional scheme, when the code stream is allocated, it is common practice to allocate the same amount of code stream space for each image pixel packet in a row of pixels, but this does not consider the difficulty and ease of distribution of the image. Since more code streams can be saved in the color library coding, when a line of pixels is processed, if it can be predicted in advance which image pixel packets can be coded by the color library, then some code streams can be allocated to the image pixel packets, and some code streams can be allocated to other image pixel packets, so that the image quality can be improved. Thus, in some preferred examples of the present application, the image compression method disclosed in the present application further includes, before determining the optimal coding mode of each image pixel packet in the current line of pixels and coding the current line of pixels: and performing code stream pre-allocation on a plurality of image pixel packets corresponding to the pixels of the current row.

Conventional color-library coding relies on pixels that have been reconstructed in the same row of pixels, so the complexity of the code-stream reassignment to the current row of pixels is very high. In view of this problem, the embodiment of the application discloses a new code stream pre-allocation method, as shown in fig. 4, which includes the following steps:

In step 410, a color library of pixels of the current row to be encoded is constructed based on the colors of at least some of the pixels in the previous row, the color library containing b colors from the pixels in the previous row. That is, the color library constructed when the pre-allocation of the code stream is performed includes only b colors in the pixels of the previous row.

Further, in the case where b is a positive integer power of 2, it further includes: and eliminating x colors of which the correlation with the pixels of the current row does not meet the requirement from the b colors of the color library. In this way, a certain blank interval can be reserved in the color library, so that the judgment of the encoded image pixel packet can be performed by applying the color library encoding method in each embodiment among the plurality of image pixel packets of the current line of pixels.

It will be appreciated that if an image pixel packet is capable of implementing the color library encoding described above based on the color library containing only the b colors of the previous row of pixels, then the image pixel packet must be capable of implementing the color library encoding described above based on the color library containing both the a colors of the present row of pixels and the b colors of the previous row of pixels.

In step 420, it is determined based on the color library that, of the W image pixel packets of the current line of pixels, T image pixel packets encoded by the color library encoding method in the foregoing embodiments can be applied, and the code stream space required for the T image pixel packets in performing the color library encoding is calculated, where W and T are both positive integers.

In this step, assuming that the current line pixel can be divided into W image pixel packets, determining that, among the W image pixel packets of the current line pixel, the image pixel packets that can be encoded by using the color library encoding method in the foregoing embodiments is substantially the same as the step of determining whether the image pixel packet currently to be encoded satisfies the color library encoding condition in the foregoing step 120, except that the respective adopted color libraries are different, specifically includes: counting the number K of pixels in a current image pixel packet of which the matching color is found in a color library, wherein K is a non-negative integer; if K is equal to M, judging that the current image pixel packet meets the color library coding condition; if K is smaller than M, counting the number J of the colors of pixels which are not found to match colors in the color library, if J is smaller than or equal to x, judging that the current image pixel packet meets the color library coding condition, and if J is larger than x, judging that the current image pixel packet does not meet the color library coding condition.

In step 430, a reassignable code stream space is determined according to the total code stream space assigned to the current row of pixels and the determined code stream space required for the T image pixel packets capable of color library encoding, and the reassignable code stream space is evenly assigned to the image pixel packets except for the T image pixel packets.

Assuming that the current line of pixels is divided into 50 image pixel packets (i.e., W is equal to 50), and the allocated total code stream space is m1, and it is confirmed through discrimination that 20 image pixel packets among the 50 image pixel packets can perform the color library encoding (i.e., T is equal to 20), and the code stream space required for the total of the 20 image pixel packets is m2, it can be understood that m1/50 is greater than m2/20. At this time, the code stream in which each of the image pixel packets capable of color library encoding described above can be pre-allocated is m2/20, and the code stream in which each of the image pixel packets not capable of color library encoding described above can be pre-allocated is (m 1-m 2)/30.

It can be understood that, the color library adopted in the code stream pre-allocation process does not contain the color of the reconstructed pixel of the current row, that is, the color library coding performed in the code stream pre-allocation process only depends on the reconstructed pixel of the previous row and the actual pixel of the current row, but does not depend on the reconstructed pixel of the current row, so that the complexity of the code stream pre-allocation process and the computing process can be greatly reduced in the code stream pre-allocation process and the computing process based on the color library, so that the code stream allocation is more reasonable, and the image reconstruction effect is further improved.

The embodiment of the application also discloses an image processing device, as shown in fig. 5, which comprises: an encoder 10 and a decoder 20.

Wherein the encoder 10 receives an image to be encoded, performs an image compression method according to any embodiment of the present application, and outputs a corresponding code stream; the decoder 20 is connected to the encoder 10 for decoding the code stream output from the encoder 10 to reconstruct the image.

It will be appreciated that the decoder 20 performs the inverse process of the encoder 10 and maintains an updated same color library in both the encoder 10 and the decoder 20, so that the image processing apparatus can perform image compression using the color library encoding method.

An embodiment of the present application further provides an electronic device, as shown in fig. 6, including a processor 40 and a memory 30 storing a computer program, where the processor 40 can implement at least one of a color library encoding method, a code stream allocation method, and an image compression method as described in any embodiment of the present application when executing the computer program. The electronic device may be an intelligent device with image encoding and decoding functions, such as a mobile phone, a tablet computer, a notebook computer, a palm computer, a mobile internet device (MID, mobile internet device), a wearable device, or the like, but may also be a sub-module that may be manufactured separately in the intelligent device.

In particular, any of the implementations described above with reference to flowcharts may be implemented as computer software programs in accordance with embodiments of the present disclosure. For example, embodiments disclosed herein include a computer program product comprising a computer program embodied on a computer readable medium, the computer program comprising program code for performing the method shown in the flowcharts. In such embodiments, the computer program may be downloaded and installed from a network via a communication portion, and/or installed from a removable medium. The above-described functions defined in the system of the present application are performed when the computer program is executed by a Central Processing Unit (CPU).

It should be noted that the computer readable medium shown in the present application may be a computer readable signal medium or a computer readable storage medium, or any combination of the two. The computer readable storage medium includes, for example, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or a combination of any of the foregoing. More specific examples of the computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. In the present application, however, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, with computer-readable program code embodied therein. Such a propagated data signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination of the foregoing. A computer readable signal medium may also be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wire, fiber optic cable, RF, etc., or any suitable combination of the foregoing.

The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams or flowchart illustration, and combinations of blocks in the block diagrams or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The units or modules described in the embodiments of the present application may be implemented by software, or may be implemented by hardware. The described units or modules may also be provided in a processor. Wherein the names of the units or modules do not in some cases constitute a limitation of the units or modules themselves.

As another aspect, the present application also provides a computer-readable medium that may be contained in the apparatus described in the above embodiments; or may be present alone without being fitted into the device. The computer readable medium carries one or more programs which, when executed by one of the apparatuses, implement at least one of the color library encoding method, the code stream allocation method, and the image compression method described in any of the embodiments of the present application.

It should be noted that, each numerical value listed in each embodiment of the present application is an exemplary description for describing the embodiment of the present application more simply and clearly, and should not be taken as limiting the protection scope of the present application.

Finally, it should be noted that: it is apparent that the above examples are only examples for clearly illustrating the present application and are not limiting to the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are intended to be within the scope of the present application.

Claims

1. A color library encoding method for implementing image compression, comprising:

2. The color library encoding method of claim 1, wherein determining the color library corresponding to the current image pixel packet to be encoded comprises:

judging whether N is a positive integer power of 2;

3. The color library encoding method of claim 2, wherein the entering the index corresponding to the matching color of each pixel in the image pixel packet in the color library into the code stream comprises:

4. The color library encoding method according to claim 2, wherein the color library comprises a colors from the pixels of the current row and b colors from the pixels of the previous row, and a and b are positive integers;

5. The color library encoding method of claim 4, wherein determining whether each of the a colors meets a correlation requirement with a current image pixel packet is based on a position of each of the a colors with respect to the current image pixel packet,

6. The color library encoding method of any one of claims 1-5, wherein finding a matching color for each pixel in the image pixel packet in the color library comprises:

7. The color library encoding method according to any one of claims 1-5, wherein after passing the index corresponding to the matching color in the color library for each pixel in the image pixel packet into a code stream, further comprising:

8. A code stream pre-allocation method, comprising:

determining, based on the color library, T image pixel packets that can be encoded by the color library encoding method according to any one of claims 1 to 7 from among W image pixel packets of a current line of pixels, and calculating a code stream space required by the T image pixel packets when performing color library encoding, where W and T are positive integers;

9. An image compression method, comprising:

wherein when the determined optimal coding mode is color library coding, the method for color library coding according to any one of claims 1-7 is used for coding the current image pixel packet to be coded.

10. The image compression method of claim 9, wherein the step of determining whether the current image pixel packet to be encoded satisfies the color library encoding condition comprises:

11. The image compression method according to claim 9 or 10, wherein the image pixel packet to be currently encoded is encoded using a predictive encoding mode in a case where it is determined that the image pixel packet to be currently encoded does not satisfy a color library encoding condition.

12. The image compression method according to any one of claims 9-11, wherein before determining an optimal coding mode for each image pixel packet in a current row of pixels and coding the current row of pixels, further comprising:

13. An image processing apparatus, comprising:

an encoder for performing the image compression method according to any one of claims 9-12 and outputting a corresponding code stream;

14. An electronic device, comprising: a processor, a memory, and a program stored on the memory and executable on the processor, which when executed by the processor, performs the steps of at least one of the methods of:

the color library encoding method of any one of claims 1 to 7;

the code stream allocation method according to claim 8;

an image compression method as claimed in any one of claims 9 to 13.

15. A storage medium having stored thereon a computer program or instructions which when executed by a processor perform the steps of at least one of the following methods:

the color library encoding method of any one of claims 1 to 7;

the code stream allocation method according to claim 8;

An image compression method as claimed in any one of claims 9 to 13.