Method for processing a digital image and image representation format
View Patent ↗An image representation format for representing a digital image comprises: image information stored as a bitstream representing sequential image blocks, each block comprising one or more components, each component comprising one or more data units and each data unit being represented as a Huffman-coded stream of coefficients of basis functions, wherein a zeroth order coefficient is represented as a difference to the previous zeroth order coefficient of the corresponding component, and a block information table, which comprises: indicators to the first coefficient of a specified order of each image block in said bitstream, information indicating the number of bits in the bitstream between adjacent coefficients of said specified order of the image block, and the zeroth order coefficient of at least the first data unit of each component, said zeroth order coefficient being represented in a non-differential form.
1. A method for encoding raw image data into a compressed digital image representation, said method comprising:
in arbitrary order reading image blocks of a specified size of the raw image data, and for each image block:
transforming the image block into one or more data units of one or more components, said transforming creating a representation of each data unit as coefficients of basis functions,
calculating a quantized approximation of said coefficients,
representing at least some of the quantized coefficients as a stream of coefficients of sequential image blocks,
Huffman-coding said stream of coefficients, wherein a zeroth order coefficient is represented as a difference to a previous zeroth order coefficient of the corresponding component,
storing said Huffman-coded stream of coefficients in a bitstream,
storing in a block information table indicators to one zeroth order or first order coefficient of each image block in the bitstream,
storing in the block information table information indicating the number of bits in the bitstream between coefficients of zeroth or first order in adjacent data units of the image block, and
storing in the block information table the zeroth order coefficient of at least one data unit of each component, said zeroth order coefficient being represented in a non-differential form.
2. The method according to claim 1 , wherein the indicators in the block information table are stored as indicators of the bit offset to the coefficient from a static location.
3. The method according to claim 1 , wherein the indicators in the block information table are stored as indicators of the bit offset to the coefficient from a bitstream landmark and the image representation format further comprises a list providing information of in which image block each bitstream landmark is located.
4. The method according to claim 1 , wherein the zeroth order coefficient is stored represented in a non-differential form for each zeroth order coefficient that is represented in the bitstream as a difference to a zeroth order coefficient of a previous image block.
5. The method according to claim 1 , wherein each zeroth order coefficient is stored represented in a non-differential form.
6. The method according to claim 1 , wherein the bitstream represents the digital image in the JPEG-format.
7. A method for encoding raw image data into a compressed digital image representation, said method comprising:
in arbitrary order reading image blocks of a specified size of the raw image data, and for each image block:
transforming the image block into one or more data units of one or more components, said transforming creating a representation of each data unit as coefficients of basis functions,
calculating a quantized approximation of said coefficients,
representing at least some of the quantized coefficients as a stream of coefficients of sequential image blocks,
Huffman-coding said stream of coefficients, wherein a zeroth order coefficient is represented as a difference to a previous zeroth order coefficient of the corresponding component,
storing said Huffman-coded stream of coefficients in a bitstream
storing in a block information table indicators to one zeroth order or first order coefficient of each image block in the bitstream, and
storing in the block information table the zeroth order coefficient of at least one data unit of each component, said zeroth order coefficient being represented in a non-differential form.
8. The method according to claim 7 , further comprising storing in the block information table information indicating the number of bits in the bitstream between coefficients of zeroth or first order in adjacent data units of the image block.
9. The method according to claim 7 , wherein the indicators in the block information table are stored as indicators of the bit offset to the coefficient from a static location.
10. The method according to claim 7 , wherein the indicators in the block information table are stored as indicators of the bit offset to the coefficient from a bitstream landmark and the image representation format further comprises a list providing information of in which image block each bitstream landmark is located.
11. The method according to claim 7 , wherein the zeroth order coefficient is stored represented in a non-differential form for each zeroth order coefficient that is represented in the bitstream as a difference to a zeroth order coefficient of a previous image block.
12. The method according to claim 7 , wherein each zeroth order coefficient is stored represented in a non-differential form.
13. The method according to claim 7 , wherein the bitstream represents the digital image in the JPEG-format.