Variable-Length Image Compression Encoding
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Solution Overview
Problem
Existing image compression methods face challenges in efficiently encoding image data values, particularly in tiled image processing systems with limited memory resources, where variable length encoding can lead to ambiguity during decoding and increased data length due to the need for explicit length information.
Innovation Solution
The Increasing Length Encoding (ILE) method represents each image data value using a palette value with a bit length that is either equal to or greater than the previous value, with offsets recording position changes in the data stream, ensuring minimal bit usage and eliminating the need for explicit length information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If variable length encoding is used to minimize bit usage, then compression ratio is improved, but decoding ambiguity increases
Solution Approach 1:
The patent applies dynamics by making the code length adaptive rather than fixed. The encoding system dynamically adjusts the number of bits used to represent palette values based on the actual number of distinct values encountered in the image data. This allows the system to use fewer bits when possible (improving compression) while maintaining enough bits to uniquely represent all values (maintaining decoding accuracy).
Solution Approach 2:
The patent uses preliminary action by first scanning the image data to count the number of distinct values before performing the actual encoding. This preliminary counting step allows the system to determine the optimal bit length needed for representation, ensuring that sufficient information is available to decode without ambiguity while minimizing the number of bits used.
2Reliability
If explicit length information is inserted in the bitstream to guide decompression, then decoding reliability is improved, but data length increases
Solution Approach 1:
The patent applies self-service by designing an encoding system where the bitstream structure itself contains all the information needed for decoding. The variable bit length is determined by the actual data characteristics, and the encoding scheme is self-descriptive - the decoder can determine the appropriate bit length by understanding the encoding structure and the range of values present, without needing separate length metadata.
3Reliability
If fixed length palette values are used to eliminate decoding ambiguity, then decoding reliability is improved, but compression ratio deteriorates
Solution Approach 1:
The patent applies parameter changes by varying the bit length parameter based on the actual number of distinct values in the data. Instead of using a fixed bit length for all palette values, the system changes the bit length parameter to match the minimum required for representing the observed values. This resolves the contradiction by making the parameter adaptive - using more bits only when necessary for accuracy, and fewer bits when possible for compression.
Data Source
AI summary
Disclosed is a variable-length image compression arrangement which represents successive distinct image data values (220, 221) of an image using corresponding non-decreasing Palette values (215, 222), and which incorporates (915, 1025) into the encoded data stream information recording the position in the encoded data stream at which each Palette value bit representation length increase occurs.