WO2015192340A1 - Palette-based image coding method, device and image processing device - Google Patents

Abstract

Provided in an embodiment of the present invention are a palette-based image coding method, device and image processing device, the image coding method comprising: determining a palette corresponding to an image area to be coded, and determining a corresponding pixel index for pixels in palette mode; and after conducting bit stream coding on the information of the pixel index, conducting bit stream coding on the information of the palette to determine the size of the palette according to the information of the pixel index when decoding. The embodiment of the present invention further improves the coding compression ratio to obtain a smaller bit cost without compiling the information of the palette size.

Description

 Palette-based image encoding method, device and image processing device

 The present invention relates to the field of graphic image technology, and in particular, to a palette-based image encoding method, apparatus, and image processing apparatus.

Background technique

 Palette-based coding is widely used in graphic image technology (especially video coding technology). In the encoding process, for the image area to be encoded, for example, a coding unit (CU), including a plurality of pixels having color values (for example, RGB mode, having 24 bits of true color); The storage capacity of the image, usually pointing the pixel to the data index of the palette. During the decoding process, the color value of each output pixel can be determined by looking up the palette with the corresponding data index.

The palette is a set of pixel values. For pixels whose pixel values are in the palette, only the corresponding pixel index (pixel inde _X ) of the pixel value in the palette is used. Thereby, only the palette and the index corresponding to the pixels in the coding unit can be bit-stream encoded, and the bit cost of the encoding can be reduced.

 The following is a list of documents useful for understanding the present invention and conventional techniques, which are incorporated herein by reference as if fully set forth herein.

 [Non-Patent Document 1]: JCTVC-O0182. Xun Guo, etc, Microsoft, Major-color-based screen content coding.

 [Non-Patent Document 2]: JCTVC-N0249. Liwei Guo, etc, Qualcomm, Modified Palette Mode for Screen Content Coding.

 It should be noted that the above description of the technical background is only for the purpose of facilitating the clear and complete description of the technical solutions of the present invention, and is convenient for understanding by those skilled in the art. The above technical solutions are not considered to be well known to those skilled in the art simply because these solutions are set forth in the background section of the present invention.

Summary of the invention

Currently, when performing bit stream encoding, the information of the palette is first encoded into the bit stream, and then the pixel index is Information is programmed into the bitstream. It is necessary to program the palette size information and the value of the palette (including prediction information in some scenarios) into the bitstream. However, the inventor found that: the size information of the palette needs to occupy a large number of bits, which is not conducive to improving the coding compression ratio.

 Embodiments of the present invention provide an image encoding method, apparatus, and image processing apparatus. By first encoding the pixel index information into the bit stream and then grouping the palette information into the bit stream, it is possible to increase the coding compression ratio without coding the size information of the palette.

 According to a first aspect of the embodiments of the present invention, a palette-based image encoding method is provided, the image encoding method comprising:

 Determining a palette corresponding to the image region to be encoded, and determining a corresponding pixel index for pixels adopting the palette mode;

 After performing bitstream encoding on the information of the pixel index, the information of the palette is bitstream-encoded so that the size of the palette is determined according to the information of the pixel index at the time of decoding.

 According to a second aspect of the embodiments of the present invention, a palette-based image encoding apparatus is provided, the image encoding apparatus comprising:

 An information determining unit, determining a color palette corresponding to the image area to be encoded, and determining a corresponding pixel index for the pixel adopting the palette mode;

 a stream coding unit, after performing bitstream coding on the information of the pixel index, performing bitstream encoding on the information of the palette, so that the size of the palette is determined according to information of the pixel index at the time of decoding .

 According to a third aspect of the embodiments of the present invention, a palette-based image decoding method is provided, where the image decoding method includes:

 Decoding a bitstream to obtain information of a pixel index corresponding to a pixel in a palette mode; determining a size of the palette according to information of the pixel index, and decoding the bitstream to obtain the tone Swatch information;

 An image of the image region to be encoded is obtained based on the information of the palette and the information of the pixel index. According to a fourth aspect of the embodiments of the present invention, there is provided a palette-based image decoding apparatus, the image decoding apparatus comprising:

 An index decoding unit that decodes the bitstream to obtain information of a pixel index corresponding to a pixel in a palette mode;

a palette decoding unit, determining a size of the palette according to the information of the pixel index, and Decoding the bitstream to obtain information of the palette;

 The image obtaining unit obtains an image of the image region to be encoded based on the information of the palette and the information of the pixel index.

 According to a fifth aspect of the embodiments of the present invention, an image processing apparatus is provided, including:

 An image encoding device as described above;

 An image decoding device as described above.

 According to still another aspect of an embodiment of the present invention, a computer readable program is provided, wherein when the program is executed in an image processing apparatus, the program causes a computer to perform a tone-based adjustment as described above in the image processing apparatus An image encoding method of a swatch, or a palette-based image decoding method as described above.

 According to still another aspect of an embodiment of the present invention, a storage medium storing a computer readable program, wherein the computer readable program causes a computer to perform a palette based image encoding method as described above in an image processing device Or perform a palette-based image decoding method as described above.

 An advantageous effect of the embodiment of the present invention is that after bit stream coding is performed on the information of the pixel index, the information of the color palette is bit-stream encoded, so that the size of the color palette is determined according to the information of the pixel index at the time of decoding. Thus, it is not necessary to program the size information of the palette, and the coding compression ratio can be further increased to obtain a smaller bit cost.

 Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, which illustrate the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the invention are not limited in scope. The embodiments of the present invention include many variations, modifications, and equivalents within the spirit and scope of the appended claims.

 Features described and/or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, in combination with, or in place of, features in other embodiments. .

 It should be emphasized that the term "comprising" or "comprising" is used to mean the presence of a feature, component, step or component, but does not exclude the presence or addition of one or more other features, components, steps or components. DRAWINGS

Many aspects of the invention can be better understood with reference to the following drawings. The components in the figures are not drawn to scale, but only to illustrate the principles of the invention. In order to facilitate the illustration and description of some parts of the invention, the corresponding parts in the figures may be enlarged or reduced. Elements and features described in one of the figures or one embodiment of the invention may be combined with elements and features illustrated in one or more other figures or embodiments. In the accompanying drawings, like reference numerals refer to the

 1 is a schematic flow chart of an image encoding method according to an embodiment of the present invention;

 2 is another schematic flowchart of an image encoding method according to an embodiment of the present invention;

 3 is a schematic structural diagram of an encoding apparatus according to an embodiment of the present invention;

 4 is a schematic flowchart of an image decoding method according to an embodiment of the present invention;

 FIG. 5 is another schematic flowchart of an image decoding method according to an embodiment of the present invention; FIG.

 6 is a schematic structural diagram of a decoding apparatus according to an embodiment of the present invention;

 Fig. 7 is a block diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention.

detailed description

 The foregoing and other features of the invention will be apparent from the The specific embodiments of the present invention are disclosed in the specification and the drawings, which are illustrated in the embodiments of the invention The invention includes all modifications, variations and equivalents falling within the scope of the appended claims.

 In the current palette-based image encoding method, the information of the palette needs to be encoded into the bit stream, and then the information of the pixel index is compiled into the bit stream. The following is a pseudo code example of the current palette encoding: Palette coding unit (nCbS) // nCbS * nCbS is the size of coding unit, e.g. 8x8, 16x16, 32x32, 64x64

{

 numPredPreviousPalette = 0

 For( i = 0; i < previousPaletteSize; i++ ) {

 Previous palette entry _flag[ i ]

 If ( revious_palette entry flag[ i ] ) {

 numPredPreviousPalette++

 }

 }

 Palette num signalled entries

 For( i = 0; i < palette num signalled entries; i++ )

 Palette_entrie[ numPredPreviousPalette + i ]

 Palette size = numPredPreviousPalette + palette num signalled entries

Pixel index infomation ( ); As shown above, for example, the prediction information (previous^palette_ entry_flag[ i ]), the size of the value in the palette that needs to be explicitly expressed in addition to the prediction information (palette_num_signal_entry), toning The value of the board (palette_entrie[ numPredPreviousPalette + i ] ) is programmed into the bitstream, and then the pixel information is programmed into the bitstream; this results in more information to be programmed into the bitstream.

 The embodiments of the present invention are described in detail below. Example 1

 Embodiments of the present invention provide a palette-based image encoding method. FIG. 1 is a schematic flowchart of an image encoding method according to an embodiment of the present invention. As shown in FIG. 1, the image encoding method includes:

 Step 101: Determine a color palette corresponding to the image area to be encoded, and determine a corresponding pixel index for the pixel adopting the palette mode;

 Step 102: Perform bitstream encoding on the information of the pixel index, and then perform bitstream encoding on the information of the palette, so that the size of the palette is determined according to the information of the pixel index at the time of decoding.

 In this embodiment, the image area to be encoded may be a coding unit (CU), but the invention is not limited thereto, and may be, for example, a Large Coding Unit (LCU) or the like. The present invention will be described below by taking only the CU as an example.

 In this embodiment, step 101 determines that the palette and the pixel index can be associated with any of the methods. You can use only the palette mode, or a combination of palette mode and non-palette mode (such as escape mode). The present invention is not limited thereto, and the present invention can be applied as long as a palette mode exists.

 In step 102, the information of the palette is first encoded into the bit stream, and then the information of the pixel index is encoded into the bit stream. In this embodiment, the information of the pixel index is first bit stream encoded, and then The bitstream information is then bitstream encoded. This eliminates the need to program the size information of the palette, which can increase the coding compression ratio.

 In an embodiment, before performing bitstream encoding on the information of the pixel index, the image encoding method may further include: performing bitstream encoding on the bitwidth information occupied by the pixel index, so that the bit width information is The information of the pixel index is decoded.

For example, the bit width information (index_bit_depth) occupied by the pixel index is, for example, 3 bits, and the information can be encoded into the bit stream, whereby the information of the pixel index can be accurately decoded. However, the invention is not limited to this, For example, the bit width information occupied by the pixel index can also be agreed in advance.

 In another embodiment, the image encoding method may further include: determining prediction information in the palette; and performing bitstream encoding on the information of the pixel index, and then predicting information of the palette and the palette The value is bitstream encoded.

 In this embodiment, the value of the palette may be predicted by a value that has occurred in the previous one or several CUs, and may be represented by an identifier (e.g., previous_palette_entry_flag). For details on the prediction information, refer to the related art.

 In this embodiment, determining the size of the palette according to the information of the pixel index may specifically include: adding a maximum value of the pixel index (maxjndex) to 1 to obtain a size of the palette (palette_size).

 FIG. 2 is another schematic flowchart of an image encoding method according to an embodiment of the present invention. As shown in FIG. 2, the image encoding method includes:

 Step 201: Determine a color palette corresponding to an image area to be encoded.

 Step 202: Determine a corresponding pixel index for a pixel adopting a palette mode.

 Step 203: Determine prediction information in a palette.

 Step 204: Perform bitstream encoding on the bit width information occupied by the pixel index.

 Step 205: Perform bitstream encoding on the information of the pixel index, so that the size of the palette is determined according to the information of the pixel index at the time of decoding;

 Step 206: Perform bitstream encoding on the prediction information of the palette.

 Step 207: Perform bitstream encoding on the value of the palette.

 It is to be noted that only the steps related to the present invention are given in Figs. 1 and 2, and other steps in the image encoding process can be referred to the related art. Further, the order of execution between the steps in Fig. 2 is not limited to this, and a specific manner can be determined according to actual conditions.

 In this embodiment, the image encoding method of the embodiment may be represented by the following pseudo code:

Palette coding unit (nCbS) // nCbS * nCbS is the size of coding unit, e.g. 8x8, 16x16, 32x32, 64x64

{

 Index bit depth

 Pixel index infomation ( );

 Palette size = max index + 1; numPredPreviousP alette = 0

 For( i = 0; i < previousPaletteSize; i++ ) {

Previous palette entry _flag[ i ] If ( revious_palette entry flag[ i ] ) {

 numPredPreviousPalette++

 }

 }

 Palette num signalled entries = palette size - numPredPreviousPalette;

 For( i = 0; i < palette num signalled entries; i++ )

 Palette_entrie[ numPredPreviousPalette + i ]

As shown above, for example, the size of the palette is 32, palette_size=32 _{; the} corresponding pixel index is {0, 1, 2, ······, 31 }, then each pixel index can be represented by 5 bits. Index_bit_depth=5. Therefore, in the embodiment of the present invention, it is only necessary to encode the address_bit_depth=5 (represented by 3 bits) into the bit stream, which is required to be encoded in the bit stream. CU can save 2bit.

 It should be noted that the above pseudo code is only one embodiment of the embodiment of the present invention, but the embodiment of the present invention is not limited thereto. For example, the prediction information or the bit width information occupied by the pixel index may be used in advance, and a specific implementation manner may be determined according to actual conditions.

 It can be seen from the above embodiment that after bit stream coding is performed on the information of the pixel index, the information of the palette is bit-stream encoded so that the size of the palette is determined according to the information of the pixel index at the time of decoding. This eliminates the need to program the size information of the palette, and can further increase the coding compression ratio to obtain a smaller bit cost. Example 2

 An embodiment of the present invention provides an image encoding apparatus based on a palette, which corresponds to the image encoding method of Embodiment 1, and the same content will not be described again.

 Fig. 3 is a block diagram showing the structure of an encoding apparatus according to an embodiment of the present invention. It is to be noted that Figure 3 only schematically shows the components associated with the present invention, and is not shown for other components of the encoding device, reference may be made to the prior art.

As shown in FIG. 3, the image encoding device 300 includes: an information determining unit 301 and a stream encoding unit 302; the information determining unit 301 determines a palette corresponding to an image region to be encoded, and determines a corresponding pixel for the palette mode. Pixel index; stream encoding unit 302 performs bitstream encoding on the information of the pixel index, and then performs bitstream encoding on the information of the palette, so that the color of the palette is determined according to the information of the pixel index at the time of decoding. small.

 In an embodiment, the stream coding unit 302 may be further configured to perform bitstream encoding on the bit width information occupied by the pixel index before performing bitstream encoding on the information of the pixel index, so that the bit width information is used according to the bit width information during decoding. The information of the pixel index is decoded.

 In another embodiment, the information determining unit 301 is further configured to determine prediction information in the palette; and the stream encoding unit 302 performs bitstream encoding on the information of the pixel index, and then predicts the palette and adjusts the palette. The value of the swatch is bitstream encoded.

 It can be seen from the above embodiment that after bit stream coding is performed on the information of the pixel index, the information of the palette is bit-stream encoded so that the size of the palette is determined according to the information of the pixel index at the time of decoding. This eliminates the need to program the size information of the palette, and can further increase the coding compression ratio to obtain a smaller bit cost. Example 3

 An embodiment of the present invention provides a method for decoding an image based on a palette, which corresponds to the image encoding method of Embodiment 1, and the same content will not be described again.

 FIG. 4 is a schematic flowchart of an image decoding method according to an embodiment of the present invention. As shown in FIG. 4, the image decoding method includes:

 Step 401: Decode a bit stream to obtain an in-pixel index corresponding to a pixel in a palette mode.

 Step 402: Determine a size of the color palette according to the information of the pixel index, and decode the bit stream to obtain information of the color palette.

 Step 403: Obtain an image of the image area to be encoded based on the information of the palette and the information of the pixel index. In the present embodiment, the bit stream generated by the image encoding method described in Embodiment 1 can be decoded by the decoder. The size of the palette can be determined based on the information of the pixel index, whereby the image decoding of the image region to be encoded can be accurately performed even if the size information of the color palette is not included in the bit stream.

 In an embodiment, before the bit stream is decoded in step 401 to obtain information of a pixel index corresponding to a pixel of the palette mode, the image decoding method may further include: decoding the bit stream to obtain a pixel index. The bit width information occupied. Thereby, the information of the pixel index can be accurately decoded based on the bit width information in the bit stream.

In another embodiment, the step 402 of decoding the bitstream to obtain the information of the palette may include: In the case where the palette prediction information is not included in the bit stream, the value of the palette is obtained; or, in the case where the palette prediction information is included in the bit stream, the prediction information of the palette and the palette are obtained. Value.

 In this embodiment, determining the size of the color palette according to the information of the pixel index may specifically include: adding a maximum value of the pixel index to 1 to obtain a size of the color palette.

 FIG. 5 is another schematic flowchart of an image decoding method according to an embodiment of the present invention. As shown in FIG. 5, the image decoding method includes:

 Step 501: Decode a bitstream to obtain bit width information occupied by a pixel index.

 Step 502: Obtain information about a pixel index corresponding to a pixel in a palette mode.

 Step 503: Determine a size of the color palette according to the information of the pixel index.

 Step 504: Decode the bit stream to obtain a value of the palette, or prediction information of the palette and a value of the palette;

 Step 505: Obtain an image of the image area to be encoded based on the information of the palette and the information of the pixel index. It is to be noted that only the steps related to the present invention are given in Figs. 4 and 5, and other steps in the image decoding process can be referred to the related art. Further, the order of execution between the steps in Fig. 5 is not limited to this, and a specific manner can be determined according to actual conditions.

 As is apparent from the above embodiment, the bit stream is decoded to obtain pixel index information, the size of the palette is determined based on the pixel index information, and the bit stream is decoded to obtain palette information. Thereby, even if the size information of the palette is not incorporated in the bit stream, the image decoding of the image area to be encoded can be accurately performed. Example 4

 The embodiment of the present invention provides a palette-based image decoding apparatus, which corresponds to the image decoding method of Embodiment 3, and the same content will not be described again.

 FIG. 6 is a block diagram showing a configuration of a decoding apparatus according to an embodiment of the present invention. It is to be noted that Figure 6 only schematically shows the components associated with the present invention, and is not shown for other components of the decoding device, reference may be made to the prior art.

As shown in FIG. 6, the image decoding device 600 includes an index decoding unit 601, a palette decoding unit 602, and an image obtaining unit 603; the index decoding unit 601 decodes the bit stream to obtain a pixel corresponding to the palette mode. Information of the pixel index; the palette decoding unit 602 determines the size of the palette based on the information of the pixel index, and decodes the bit stream to obtain information of the palette; the image obtaining unit 603 is based on the palette The information and the information of the pixel index obtain an image of the image area to be encoded.

 In an embodiment, the index decoding unit 601 may be further configured to decode the bit stream to obtain a pixel index before decoding the bit stream to obtain information of a pixel index corresponding to a pixel of the palette mode. Bit width information.

 In another embodiment, the palette decoding unit 602 can be configured to: obtain a value for the palette, or obtain prediction information for the palette and a value for the palette.

 In another embodiment, the palette decoding unit 602 can be configured to: add a maximum of 1 to the pixel index to obtain the size of the palette.

 As is apparent from the above embodiment, the bit stream is decoded to obtain pixel index information, the size of the palette is determined based on the pixel index information, and the bit stream is decoded to obtain palette information. Thereby, even if the size information of the palette is not incorporated in the bit stream, the image decoding of the image area to be encoded can be accurately performed. Example 5

 An embodiment of the present invention provides an image processing apparatus, the image processing apparatus comprising: the image encoding apparatus according to Embodiment 2; and the image decoding apparatus according to Embodiment 2.

 Fig. 7 is a block diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention. As shown in FIG. 7, the image processing apparatus 700 may include: a central processing unit (CPU) 100 and a memory 110; the memory 110 is coupled to the central processing unit 100. The memory 110 can store various data; in addition, a program for information processing is stored, and the program is executed under the control of the central processing unit 100.

 In one embodiment, the functions of image encoding device 300 or image decoding device 600 may be integrated into central processor 100. The central processing unit 100 may be configured to implement the image encoding method as described in Embodiment 1, or implement the image decoding method as described in Embodiment 3.

 In another embodiment, the image encoding device 300 or the image decoding device 600 may be configured separately from the central processing unit. For example, the image encoding device 300 or the image decoding device 600 may be configured as a chip connected to the central processing unit 100 through central processing. The control of the image is performed by the image encoding device 300 or the image decoding device 600.

In addition, as shown in FIG. 7, the image processing apparatus 700 may further include: an input and output unit 120, a display unit 130, and the like; wherein the functions of the components are similar to those of the prior art, and details are not described herein again. It is to be noted that the image processing apparatus 700 does not necessarily have to include all the components shown in FIG. 7; further, the image processing apparatus 700 may also include components not shown in Figure 7, reference to the prior art.

 The embodiment of the present invention further provides a computer readable program, wherein when the program is executed in an image processing apparatus, the program causes a computer to execute the palette based method described in Embodiment 1 in the image processing apparatus The image encoding method, or the palette-based image decoding method described in Embodiment 3 is performed.

 An embodiment of the present invention further provides a storage medium storing a computer readable program, wherein the computer readable program causes a computer to execute the palette based image encoding method described in Embodiment 1 in an image processing device, or execute The palette-based image decoding method described in Embodiment 3.

 The above apparatus and method of the present invention may be implemented by hardware, or may be implemented by hardware in combination with software. The present invention relates to a computer readable program that, when executed by a logic component, enables the logic component to implement the apparatus or components described above, or to cause the logic component to implement the various methods described above Or steps. The present invention also relates to a storage medium for storing the above program, such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, or the like.

 One or more of the functional blocks described in the figures and/or one or more combinations of functional blocks may be implemented as a general purpose processor, digital signal processor (DSP) for performing the functions described herein. ), an application specific integrated circuit (AS), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, or any suitable combination thereof. One or more of the functional blocks described with respect to the figures and/or one or more combinations of functional blocks may also be implemented as a combination of computing devices, eg, a combination of a DSP and a microprocessor, multiple microprocessors One or more microprocessors in conjunction with DSP communication or any other such configuration.

 The present invention has been described in connection with the specific embodiments thereof, and it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention. A person skilled in the art can make various modifications and changes to the invention in accordance with the spirit and the principles of the invention, which are also within the scope of the invention.

Claims

Claim A palette-based image encoding method, the image encoding method comprising: determining a palette corresponding to an image region to be encoded, and determining a corresponding pixel index for a pixel adopting a palette mode ;  After performing bitstream encoding on the information of the pixel index, the information of the palette is bitstream-encoded so that the size of the palette is determined according to the information of the pixel index at the time of decoding.  2. The image encoding method according to claim 1, wherein the image encoding method further comprises: before performing bitstream encoding on the information of the pixel index, the image encoding method further comprises:  The bit width information occupied by the pixel index is bit-stream encoded such that the information of the pixel index is decoded according to the bit width information at the time of decoding.  3. The image encoding method according to claim 1, wherein the image encoding method further comprises: determining prediction information in the palette;  After bitstream coding the information of the pixel index, the prediction information of the palette and the value of the palette are bitstream encoded.  The image encoding method according to claim 1, wherein determining the size of the palette according to the information of the pixel index comprises: adding a maximum value of the pixel index to 1 to obtain the color palette the size of.  5. A palette-based image encoding apparatus, wherein the image encoding apparatus comprises: an information determining unit that determines a palette corresponding to an image region to be encoded, and determines a pixel using a palette mode Corresponding pixel index;  a stream coding unit, after performing bitstream coding on the information of the pixel index, performing bitstream encoding on the information of the palette, so that the size of the palette is determined according to information of the pixel index at the time of decoding .  The image encoding apparatus according to claim 5, wherein the stream encoding unit is further configured to perform bit bit information occupied by the pixel index by bit before encoding the information of the pixel index. The stream is encoded such that the information of the pixel index is decoded according to the bit width information at the time of decoding.  7. The image encoding apparatus according to claim 5, wherein the information determining unit is further configured to determine prediction information in the palette; The stream coding unit performs bitstream coding on the information of the pixel index, and then performs bitstream encoding on the prediction information of the palette and the value of the palette. 8. The image encoding apparatus according to claim 5, wherein determining the size of the palette according to the information of the pixel index comprises: adding a maximum value of the pixel index to 1 to obtain the color palette the size of.  9. An image processing apparatus, the image processing apparatus comprising:  An image encoding apparatus according to any one of claims 5 to 8;  A decoding device that decodes the bitstream to obtain an image.