Inverse discrete wavelet transforms for data decompression
AssigneeCanon Kabushiki Kaisha
InventorJames Philip Andrew
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Abstract
A method inverse discrete wavelet transforms subband data in segments and maintains a state between segments. The method selects one of a plurality of different computational procedures for performing the inverse DWT by testing the state and the subset of the current segment of subband data to determine if a current segment can be inverse transformed with a reduced computation procedure. If the test is positive the method performs the inverse DWT using the reduced computation procedure; otherwise the method performs the inverse DWT of the segment using another procedure.
Claims46
A method of inverse discrete wavelet transforming subband data in segments, wherein a plurality of different computational procedures for performing the inverse DWT may be used, and wherein a current state is maintained between a current and previous segments of subband data, the method comprising the steps of:
- testing the current state and a subset of the current segment of subband data to determine if the current segment can be inverse transformed with a reduced computational procedure;
- if the test is positive, performing the inverse DWT using the reduced computational procedure;
- otherwise performing the inverse DWT of the segment using another computational procedure.
A method of performing a two-dimensional inverse discrete wavelet transform on blocks of LL, LH, HL and HH subband coefficients, utilizing a non-AC and AC lifting state between adjacent vertical and horizontal blocks, the method comprising the step of:
- generating a current output block of pixels corresponding to a current set of LL, HL, LH, and HH blocks, wherein if the HL, LH and HH blocks contain all zero valued coefficients, and the AC lifting state corresponding to the current block of pixels is zero, performing an inverse block-based DWT using the LL block and non-AC lifting state to generate the current block of pixels.
A method of two-dimensional inverse discrete wavelet transforming subband data, wherein the subband data comprises a plurality of blocks of subband data and the blocks each comprise at least one quadruplet of LL, HL, LH and HH subband coefficients, and wherein the method utilizes a non-AC and AC lifting state between adjacent vertical and horizontal blocks, the method comprising the step of:
- generating a current output block of pixels corresponding to a current set of LL, HL, LH, and HH blocks, wherein if the HL, LH and HH blocks contain all zero valued coefficients, and the AC lifting state corresponding to the current block of pixels is zero, performing an inverse block-based DWT using the LL block and a non-AC lifting state to generate the current block of pixels.
An apparatus for inverse discrete wavelet transforming subband data in segments, wherein a plurality of different computational procedures for performing the inverse DWT may be used, and wherein a current state is maintained between a current and previous segments of subband data, said apparatus comprising:
- means for testing the current state and a subset of the current segment of subband data to determine if the current segment can be inverse transformed with a reduced computational procedure;
- means for performing, if the test is positive, the inverse DWT using the reduced computational procedure;
- and
- means for performing, if the test is negative, the inverse DWT of the segment using another computational procedure.
An apparatus for performing a two-dimensional inverse discrete wavelet transform on blocks of LL, LH, HL and HH subband coefficients, utilizing a non-AC and AC lifting state between adjacent vertical and horizontal blocks, said apparatus comprising:
- means for testing whether the HL, LH and HH blocks contain all zero valued coefficients and the AC lifting state corresponding to a current block of pixels is zero;
- and
- means for performing, if said means for testing returns in the affirmative, an inverse block-based DWT using the LL block and non-AC lifting state to generate the current block of pixels.
An apparatus for two-dimensional inverse discrete wavelet transforming subband data, wherein the subband data comprises a plurality of blocks of subband data and the blocks each comprise at least one quadruplet of LL, HL, LH and HH subband coefficients, the apparatus utilizing a non-AC and AC lifting state between adjacent vertical and horizontal blocks, the apparatus comprising:
- means for testing whether the HL, LH and HH blocks contain all zero valued coefficients and the AC lifting state corresponding to a current block of pixels is zero;
- and
- means for performing, if said means for testing returns in the affirmative, an inverse block-based DWT using the LL block and a non-AC lifting state to generate the current block of pixels.
A computer program stored in a computer-readable storage medium which, when executed, performs a method for inverse discrete wavelet transforming subband data in segments, wherein a plurality of different computational procedures for performing the inverse DWT may be used, and wherein a current state is maintained between current and previous segments of subband data, the program comprising:
- code for testing the current state and a subset of the current segment of subband data to determine if the current segment can be inverse transformed with a reduced computational procedure;
- code for performing, if the test is positive, the inverse DWT using the reduced computational procedure;
- and
- code for performing, if the test is negative, the inverse DWT of the segment using another computational procedure.
A computer program stored in a computer-readable storage medium which, when executed, performs a method for performing a two-dimensional inverse discrete wavelet transform on blocks of LL, LH, HL and HH subband coefficients, utilizing a non-AC and AC lifting state between adjacent vertical and horizontal blocks, the computer program comprising:
- code for testing whether the HL, LH and HH blocks contain all zero valued coefficients and the AC lifting state corresponding to a current block of pixels is zero;
- and
- code for performing, if said code for testing returns in the affirmative, an inverse block-based DWT using the LL block and non-AC lifting state to generate the current block of pixels.
A computer program stored in a computer-readable storage medium which, when executed, performs a method for two-dimensional inverse discrete wavelet transforming subband data, wherein the subband data comprises a plurality of blocks of subband data and the blocks each comprise at least one quadruplet of LL, HL, LH and HH subband coefficients, the apparatus utilizing a non-AC and AC lifting state between adjacent vertical and horizontal blocks, the computer program comprising:
- code for testing whether the HL, LH and HH blocks contain all zero valued coefficients and the AC lifting state corresponding to a current block of pixels is zero;
- and
- code for performing, if said code for testing returns in the affirmative, an inverse block-based DWT using the LL block and a non-AC lifting state to generate the current block of pixels.
Dependencies are inferred from the claim text.