Compressing and Decompressing Image Data Using Compacted Region Transforms

• US 20190320209A1
• Filed: 06/25/2019
• Published: 10/17/2019
• Est. Priority Date: 05/03/2016
• Status: Active Grant

• Current Assignee: Imagination Technologies Limited (Imagination Technologies Group Ltd.)
• Original Assignee: Imagination Technologies Limited (Imagination Technologies Group Ltd.)
• Inventors: Fenney, Simon
• Granted Patent: US 11,122,301 B2
• Time in Patent Office: Days
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction
• CPC Class Codes: H03M 7/3068 Precoding preceding compression, e.g. Burrows-Wheeler transformation
• CPC Class Codes: H03M 7/3082 Vector coding for television signals, see H04N19/94
• CPC Class Codes: H04N 19/124 Quantisation
• CPC Class Codes: H04N 19/167 Position within a video image, e.g. region of interest [ROI]
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/196 being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters processing of motion vectors H04N19/513
• CPC Class Codes: H04N 19/426 using memory downsizing methods
• CPC Class Codes: H04N 19/46 Embedding additional information in the video signal during the compression process H04N19/517, H04N19/68, H04N19/70 take precedence
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/94 Vector quantisation

Abstract

A method of compressing image data comprising a set of image values each representing a position in image-value space so as to define an occupied region thereof. The method comprises selectively applying a series of compression transforms to subsets of the image data items to generate a transformed set of image data items occupying a compacted region of value space. The method further comprises identifying a set of one or more reference data items that quantizes the compacted region in value space. For each image data item in the set of image data items, a sequence of decompression transforms from a fixed set of decompression transforms is identified that generates an approximation of that image data item when applied to a selected one of the one or more reference data items. Each image data item in the set of image data items is encoded as a representation of the identified sequence of decompression transforms for that image data item. The encoded image data items, set of reference data items and the fixed set of decompression transforms are stored as compressed image data.

Claims

1. A data compressor configured to compress data to thereby determine compressed data, wherein the data comprises a set of data items each representing a position in value space, the compressor comprising:

an encoding block configured to, for each data item in the set of data items;

identify a sequence of decompression transforms from a fixed set of decompression transforms that generates an approximation of that data item when applied to a selected one of a set of one or more reference data items, and

encode the data item as a representation of the identified sequence of decompression transforms for that data item;

wherein the compressed data comprises the encoded data items, the set of one or more reference data items and the fixed set of decompression transforms.

2. The data compressor as claimed in claim 1, further comprising a compression transform block configured to selectively apply a series of compression transforms to subsets of the data items to generate a transformed set of data items occupying a compacted region of value space.

3. The data compressor as claimed in claim 2, further comprising a quantization unit configured to identify the set of one or more reference data items by quantizing the compacted region in value space.

4. The data compressor as claimed in claim 1, wherein the data compressor is configured to cause the compressed data to be stored.

5. The data compressor as claimed in claim 1, further comprising a memory configured to store the compressed data.

6. The data compressor as claimed in claim 1, wherein the data is image data.

7. The data compressor of claim 6, wherein the value space is a colour space, wherein each of the one or more reference data items represents a position in the colour space, and wherein the encoded data items encode data representing positions in the colour space.

8. A method of compressing data thereby determining compressed data, wherein the data comprises a set of data items each representing a position in value space, the method comprising:

identifying for each data item in the set of data items a sequence of decompression transforms from a fixed set of decompression transforms that generates an approximation of that data item when applied to a selected one of a set of one or more reference data items; and

encoding each data item in the set of data items as a representation of the identified sequence of decompression transforms for that data item;

wherein the compressed data comprises the encoded data items, the set of one or more reference data items and the fixed set of decompression transforms.

9. The method of claim 8, wherein the method further comprises selectively applying a series of compression transforms to subsets of the data items to generate a transformed set of data items occupying a compacted region of value space.

10. The method of claim 9, wherein the method further comprises identifying the set of one or more reference data items by quantizing the compacted region in value space.

11. The method of claim 8, further comprising storing the compressed data.

12. The method of claim 8, wherein the data is image data.

13. A method of decompressing compressed data comprising an item of encoded data, and a set of one or more reference data items, the encoded data item identifying a sequence of transforms from a predetermined set of transforms, the method comprising:

using the encoded data item to apply the sequence of transforms identified by that encoded data item to a reference data item selected from the set of one or more reference data items to thereby transform that reference data item to a decoded data item.

14. The method of claim 13, wherein the data is image data.

15. The method of claim 14, wherein the decoded data item represents a position in a colour space.

16. The method of claim 13, wherein the encoded data item is used to apply the sequence of transforms identified by that encoded data item to the reference data item to thereby transform that reference data item from an initial position in colour space to a position corresponding to a position encoded by that encoded data item.

17. The method of claim 13, further comprising loading the set of one or more reference data items and the set of predetermined transforms from a memory.

18. The method of claim 13, further comprising interpreting information contained in the encoded data item to select said reference data item from the set of one or more reference data items.

19. The method of claim 13, further comprising interpreting information contained in the encoded data item representing the selective application of each transform from the predetermined set of transforms to thereby identify the sequence of transforms to be applied to the selected reference data item.

20. The method of claim 13, wherein the compressed data comprises a plurality of encoded data items, and wherein the method further comprises, for each encoded data item, using the encoded data item to apply the sequence of transforms identified by that encoded data item to one of the reference data items selected from the set of one or more reference data items to thereby transform the reference data item to a decoded data item.