Wavelet transform coding technique
First Claim
1. A method of compressing a digitized image, comprising the steps of:
- segmenting the image into a plurality of blocks of data;
transforming each of the plurality of blocks of data into a corresponding block of subband coefficients;
quantizing the subband coefficients; and
coding the quantized subband coefficients.
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Abstract
A wavelet transform coding technique is provided, which may be part of TROBIC or may be used independently in a wide variety of compression applications. The wavelet coding technique is carried out by a simple block codec with wavelets (SBCW) that uses wavelet filters to transform 32×2 image blocks into subband coefficients organized in a tree structure. These coefficients are then encoded using a novel entropy coding technique with precise rate control. The Two Row Buffer Image Compression (TROBIC) technique operates on 32×2 blocks of pixels and uses a block-based coding scheme to provide alternative coding modes for image blocks containing different types of image data. The TROBIC algorithm automatically evaluates the image presented to determine regions containing text, graphics, synthetic images and natural images along with determining the most effective combination of global-index coding, local-index coding, lossless coding and wavelet coding to use to guarantee the desired compression ratio and high quality.
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Citations
17 Claims
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1. A method of compressing a digitized image, comprising the steps of:
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segmenting the image into a plurality of blocks of data;
transforming each of the plurality of blocks of data into a corresponding block of subband coefficients;
quantizing the subband coefficients; and
coding the quantized subband coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An encoder/decoder system for compressing and decompressing a digitized image, comprising:
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an encoder comprising;
means for transforming each of a plurality of blocks of pixel data into a corresponding block of subband coefficients;
a quantizer for quantizing the subband coefficients;
an entropy-encoder for coding the quantized subband coefficients and generating a bit stream of coded data;
a decoder comprising;
an entropy decoder for decoding the bit stream of coded data and generating a plurality of blocks of coefficients;
a dequantizer for dequantizing the coefficients; and
means for inverse transforming each of the plurality of blocks of dequantized coefficients into a corresponding block of pixel data.
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9. An encoder for compressing a digitized image, comprising:
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means for transforming each of a plurality of blocks of pixel data into a corresponding block of subband coefficients;
a quantizer for quantizing the subband coefficients; and
an entropy-encoder for coding the quantized subband coefficients and generating a bit stream of coded data.
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10. A decoder for decompressing a compressed image represented by a bit stream of coded data, comprising:
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an entropy decoder for decoding the bit stream of coded data and generating a plurality of blocks of coefficients;
a dequantizer for dequantizing the coefficients; and
means for inverse transforming each of the plurality of blocks of dequantized coefficients into a corresponding block of pixel data.
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11. A article of manufacture having embodying a program of instructions executable by a device for performing a method of compressing a digitized image, said program of instructions comprising:
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instructions for segmenting the image into a plurality of blocks of data;
instructions for transforming each of the plurality of blocks of data into a corresponding block of subband coefficients;
instructions for quantizing the subband coefficients; and
instructions for coding the quantized subband coefficients. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification