System to adaptively compress raster image data

• US 6,337,747 B1
• Filed: 01/29/1998
• Issued: 01/08/2002
• Est. Priority Date: 01/29/1998
• Status: Expired due to Fees

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Rosenthal, Hanan
• Primary Examiner(s): Popovici, Dov
• Application Number:
  US09/015,346
• Time in Patent Office: 1,440 Days
• Field of Search: 395/112, 395/114, 395/115, 395/116, 358/261.2, 358/430, 358/261.4, 358/426, 358/261.1, 358/1.13, 358/1.15, 358/1.16, 358/1.17, 358/1.1, 382/239, 382/238, 382/244, 382/246, 382/232, 382/245, 382/247, 348/410, 348/409, 348/401, 348/410.1, 348/409.1, 348/401.1, 341/50, 341/51
• US Class Current: 358/1.15
• CPC Class Codes: G06K 15/02 using printers
• CPC Class Codes: G06K 2215/0014 Transforming the printer input data into internal codes
• CPC Class Codes: G06K 2215/0062 combining generic and host data, e.g. filling a raster
• CPC Class Codes: G06T 9/00 Image coding bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00
• CPC Class Codes: H04N 1/3333 during transmission, input or output of the picture signal; within a single document or page
• CPC Class Codes: H04N 2201/33357 Compression mode

Abstract

A system for compressing raster image data comprised of M (M>1) bands to a compression ratio of at least C:1, each band being comprised of a plurality of pixels each having a pixel value, which includes compression of N (1≦N<M) bands of the raster image data using a lossless compression technique, calculation of a compression ratio for the compressed N bands of raster image data, determination of whether the calculated compression ratio is at least C′:1, wherein C′ is less than C, and, following the compression of the N bands, compression of a remaining (M−N) bands of the raster image data using the lossless compression technique if it is determined that the calculated compression ratio is at least C′:1, wherein the remaining bands are rendered after the first compressing step and each band of raster image data is compressed prior to rendering a next band and, wherein if it is determined that the calculated compression ratio is less than the C′:1, the raster image data is compressed to a compression ratio of at least C:1 using a lossy compression technique.

Claims

1. A method for compressing raster image data comprised of M (M>

1) bands to a compression ratio of at least C′

;

1, each band being comprised of a plurality of pixels each having a pixel value, the method comprising;

a first compressing step of compressing N (1≦

N<

M) bands of the raster image data using a lossless compression technique;

calculating a compression ratio for the compressed N bands of raster image data;

a first determining step of determining whether the calculated compression ratio is at least C′

;

1, wherein C′

is less than C; and

a second compressing step of compressing a remaining (M−

N) bands of the raster image data using the lossless compression technique if it is determined that the calculated compression ratio is at least C′

;

1,

wherein the remaining bands are rendered after the first compressing step and each band of raster image data is compressed before rendering a next band, and wherein, if it is determined in said first determining step that the calculated compression ratio is less than the C′

;

1, the raster image data is compressed to a compression ratio of at least C;

1 using a lossy compression technique.

2. A method according to claim 1, wherein the second compressing step comprises:

compressing X, X<

(M−

N), bands of the raster image data using the lossless compression technique;

calculating a second compression ratio for the compressed N+X bands of raster image data;

a second determining step of determining whether the second compression ratio is at least C″

;

1, wherein C′

<

C″

<

C; and

compressing a remaining M−

(N+X) bands using the lossless compression technique if it is determined that the second compression ratio is at least C″

;

1.

3. A method according to claim 2, wherein, if it is determined in said second determining step that the calculated second compression ratio is less than C″

;

1, the raster image data is compressed at a compression ratio of at least C;

1 using the lossy compression technique.

4. An apparatus for compressing raster image data comprised of M (M>

1) bands to a compression ratio of at least C;

1, each band being comprised of a plurality of pixels each having a pixel value, comprising;

compressing means for compressing N (1≦

N<

M) bands of the raster image data using a lossless compression technique;

calculating means for calculating a compression ratio for the compressed N bands of raster image data; and

determining means for determining whether the calculated compression ratio is at least C′

;

1, wherein C′

is less than C,

wherein said compressing means compresses a remaining (M−

N) bands of the raster image data using the lossless compression technique if it is determined that the calculated compression ratio is at least C′

;

1,

wherein the remaining bands are rendered after the compressing means compresses the N bands and each band of raster image data is compressed before rendering a next band, and wherein, if it is determined by said determining means that the calculated compression ratio is less than the C′

;

1, the raster image data is compressed to a compression ratio of at least C;

1 using a lossy compression technique.

5. An apparatus according to claim 4, wherein said compressing means compresses X, X<

(M−

N), bands of the raster image data using the lossless compression technique, said calculating means calculates a second compression ratio for the compressed N+X bands of raster image data, said determining means determines whether the second compression ratio is at least C″

;

1, wherein C′

<

C″

<

C, and said compressing means compresses a remaining M−

(N+X) bands using the lossless compression technique if it is determined that the second compression ratio is at least C″

;

1.

6. An apparatus according to claim 5, wherein, if it is determined by said determining means that the calculated second compression ratio is less than C″

;

1, the raster image data is compressed at a compression ratio of at least C;

1 using the lossy compression technique.

7. A computer-readable medium storing computer-executable process steps to compress raster image data comprised of M (M>

1) bands to a compression ratio of at least C;

1, each band being comprised of a plurality of pixels each having a pixel value, the process steps comprising;

a first compressing step to compress N (1≦

N<

M) bands of the raster image data using a lossless compression technique;

a calculating step to calculate a compression ratio for the compressed N bands of raster image data;

a first determining step to determine whether the calculated compression ratio is at least C′

;

1, wherein C′

is less than C; and

.

a second compressing step to compress a remaining (M−

N) bands of the raster image data using the lossless compression technique if it is determined that the calculated compression ratio is at least C′

;

1,

wherein the remaining bands are rendered after the first compressing step and each band of raster image data is compressed before rendering a next band, and wherein, if it is determined in said first determining step that the calculated compression ratio is less than the C′

;

1, the raster image data is compressed to a compression ratio of at least C;

1 using a lossy compression technique.

8. A computer-readable medium storing computer-executable process steps according to claim 7, wherein the second compressing step comprises:

a compressing step to compress X, X<

(M−

N), bands of the raster image data using the lossless compression technique;

a calculating step to calculate a second compression ratio for the compressed N+X bands of raster image data;

a second determining step to determine whether the second compression ratio is at least C″

;

1, wherein C′

<

C″

<

C; and

a compressing step to compress a remaining M−

(N+X) bands using the lossless compression technique if it is determined that the second compression ratio is at least C′

;

1.

9. A computer-readable medium storing computer-executable process steps according to claim 8, wherein, if it is determined in said second determining step that the second calculated compression ratio is less than C″

;

1, the raster image data is compressed at a compression ratio of at least C;

1 using the lossy compression technique.

10. An apparatus for compressing raster image data comprised of M (M>

1) bands to a compression ratio of at least C;

1, each band being comprised of a plurality of pixels each having a pixel value, comprising;

a memory storing computer-executable process steps; and

a processor, wherein the processor executes the computer-executable process steps stored in the memory, the process steps comprising;

     1) a first compressing step to compress N (1≦

N<

M) bands of the raster image data using a lossless compression technique,

     2) a calculating step to calculate a compression ratio for the compressed N bands of raster image data,

     3) a first determining step to determine whether the calculated compression ratio is at least C′

;

1, wherein C′

is less than C; and

     4) a second compressing step to compress a remaining (M−

N) bands of the raster image data using the lossless compression technique if it is determined that the calculated compression ratio is at least C′

;

1,

wherein the remaining bands are rendered after the first compressing step and each band of raster image data is compressed before rendering a next band, and wherein, if it is determined in said first determining step that the calculated compression ratio is less than the C′

;

1, the raster image data is compressed to a compression ratio of at least C;

1 using a lossy compression technique.

11. An apparatus according to claim 10, wherein the step of compressing a remaining (M−

N) bands comprises;

a compressing step to compress X, X<

(M−

N), bands of the raster image data using the lossless compression technique;

a calculating step to calculate a second compression ratio for the compressed N+X bands of raster image data;

a second determining step to determine whether the second compression ratio is at least C″

;

1, wherein C′

<

C″

<

C; and

a compressing step to compress a remaining M−

(N+X) bands using the lossless compression technique if it is determined that the second compression ratio is at least C″

;

1.

12. An apparatus according to claim 11, wherein, if it is determined in said second determining step that the calculated second compression ratio is less than C″

;

1, the raster image data is compressed at a compression ratio of at least C;

1 using the lossy compression technique.