Image compressing apparatus, image compressing method and program

• US 8,320,684 B2
• Filed: 03/12/2007
• Issued: 11/27/2012
• Est. Priority Date: 03/15/2006
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Son, Sho
• Primary Examiner(s): Ahmed, Samir
• Application Number:
  US11/716,590
• Publication Number:
  US 20070217698A1
• Time in Patent Office: 2,087 Days
• Field of Search: None
• US Class Current: 382/232
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/146 Data rate or code amount at the encoder output
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/645 by grouping of coefficients into blocks after the transform

Abstract

An image compressing apparatus carrying out code amount control upon JPEG2000 coding, in which the number of coding passes and a code amount for each code block generated by a MQ (arithmetic) coder are input, and the number of coding passes and the code amount are determined based on a first code amount control standard and a second code amount control standard given for each code block. For a specific code block, the second code amount control standard is used to determine the number of coding passes and the code amount, while, for the other code blocks, the first code amount control standard is used to determine the number of coding passes and the code amount.

Claims

1. An image compressing apparatus carrying out code amount control upon JPEG2000 coding, in which a number of coding passes and a code amount for each code block generated by a MQ (arithmetic) coder are input, and a number of coding passes and a code amount are determined based on a first code amount control standard and a second code amount control standard given for each code block, comprising:

a part using, for a specific code block in a designated region, the second code amount control standard to determine the number of coding passes and the code amount, and using, for code blocks not in the designated region, the first code amount control standard to determine the number of coding passes and the code amount; and

wherein, according to a truncation table selected from among a plurality of truncation tables, the truncation table describes a truncation amount for each color component and for each sub-band of each level, truncation is carried out, and a total code amount is calculated;

each time the calculated total code amount is compared with a target code amount; and

selection of a truncation table is repeated until the calculated total code amount reaches the target code amount; and

wherein the apparatus is configured to select a truncation table from a memory based on a table address, and, for each code block not in the designated region, a truncation table value is subtracted from a corresponding coding passes number, and for the code block in the designated region, a truncation table value is not subtracted from a coding passes number, a coding amount is obtained for the obtained coding passes number, the process is repeated for all the code blocks to obtain the total code amount, it is determined whether the total code amount reaches the target code amount, the process starting from selection of a truncation table is repeated when the total code amount does not reach the target code amount, and the currently selected truncation table is finally selected when the total code amount reaches the target code amount.

2. The image compressing apparatus as claimed in claim 1, wherein:

the first code amount control standard is such that the predetermined number of coding passes to discard is used as it is for each coding block.

3. The image compressing apparatus as claimed in claim 1, wherein:

the second code amount control standard is such that the number of coding passes to discard is zero, and thus, no code generated by the MQ coder is discarded for a code block belonging to a designated spatial region.

4. The image compressing apparatus as claimed in claim 1, wherein:

the code blocks to use the second code amount control standard are determined by a predetermined spatial coordinate position.

5. The image compressing apparatus as claimed in claim 4, wherein:

the code blocks to use the second code amount control standard are determined by a frame to process.

6. An image compressing method for carrying out code amount control upon JPEG2000 coding, in which a number of coding passes and a code amount for each code block generated by a MQ (arithmetic) coder are input, and a number of coding passes and a code amount are determined based on a first code amount control standard and a second code amount control standard given for each code block;

comprising the steps of;

a) using, for a specific code block in a designated region, the second code amount control standard to determine the number of coding passes and the code amount; and

b) using, for code blocks not in the designated region, the first code amount control standard to determine the number of coding passes and the code amount; and

wherein, according to a truncation table selected from among a plurality of truncation tables, the truncation table describing a truncation amount for each color component and for each sub-band of each level, truncation is carried out, and a total code amount is calculated;

each time the calculated total code amount is compared with a target code amount; and

selection of a truncation table is repeated until the calculated total code amount reaches the target code amount; and

wherein the method includes the step of selecting a truncation table from a memory based on a table address, and wherein, for each code block not in the designated region, a truncation table value is subtracted from a corresponding coding passes number, and for the code block in the designated region, a truncation table value is not subtracted from a coding passes number, a coding amount is obtained for the obtained coding passes number, the process is repeated for all the code blocks to obtain the total code amount, it is determined whether the total code amount reaches the target code amount, the process starting from selection of a truncation table is repeated when the total code amount does not reach the target code amount, and the currently selected truncation table is finally selected when the total code amount reaches the target code amount.

7. The image compressing method as claimed in claim 6, wherein:

the first code amount control standard is such that the predetermined number of coding passes to discard is used as it is for each coding block.

8. The image compressing method as claimed in claim 6, wherein:

the second code amount control standard is such that the number of coding passes to discard is zero, and thus, no code generated by the MQ coder is discarded for a code block belonging to a designated spatial region.

9. The image compressing method as claimed in claim 6, wherein:

the code blocks to use the second code amount control standard are determined by a predetermined spatial coordinate position.

10. The image compressing method as claimed in claim 9, wherein:

the code blocks to use the second code amount control standard are determined by a frame to process.

11. A non-transitory computer-readable medium having embodied therein a program for image compressing comprising instructions to cause a computer to carry out code amount control upon JPEG2000 coding, in which a number of coding passes and a code amount for each code block generated by a MQ (arithmetic) coder are input, and a number of coding passes and a code amount are determined based on a first code amount control standard and a second code amount control standard given for each code block, said program further comprising instructions to cause the computer to:

use, for a specific code block in a designated region, the second code amount control standard to determine the number of coding passes and the code amount; and

use, for code blocks not in the designated region, the first code amount control standard to determine the number of coding passes and the code amount; and

wherein, according to a truncation table selected from among a plurality of truncation tables, the truncation table describing a truncation amount for each color component and for each sub-band of each level, truncation is carried out, and a total code amount is calculated;

each time the calculated total code amount is compared with a target code amount; and

selection of a truncation table is repeated until the calculated total code amount reaches the target code amount; and

wherein said program further comprises instructions to cause the computer to select a truncation table from a memory based on a table address, and wherein, for each code block not in the designated region, a truncation table value is subtracted from a corresponding coding passes number, and for the code block in the designated region, a truncation table value is not subtracted from a coding passes number, a coding amount is obtained for the obtained coding passes number, the process is repeated for all the code blocks to obtain the total code amount, it is determined whether the total code amount reaches the target code amount, the process starting from selection of a truncation table is repeated when the total code amount does not reach the target code amount, and the currently selected truncation table is finally selected when the total code amount reaches the target code amount.