Method and apparatus for image data compression with low memory requirement
US6678422B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 30, 2000 |
| Grant date | Jan 13, 2004 |
| Priority date | — |
| Expiry date | Jul 12, 2022 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N19/63
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for performing a multi-stage wavelet transform on a block of image data, using a smaller memory than would be required to implement an equivalent conventional multi-stage wavelet transform on the same block, and a method and apparatus for performing compression on a block of image data by performing a multi-stage wavelet transform on the block, quantizing coefficients resulting from the multi-stage wavelet transform, and performing entropy encoding on the quantized coefficients. Typically, the input image data is generated by a document scanner, and is compressed in a manner allowing fast decompression (by employing simple entropy encoding) and imposing low memory requirements. The data is compressed by operating a first circuit to perform at least two consecutive horizontal wavelet transform stages on a block of the image data, quantizing and entropy encoding at least a first block of the resulting coefficients indicative of relatively high spatial frequency information (“high frequency coefficients”) and writing to a memory a second block of the resulting coefficients indicative of relatively low spatial frequency information (“low frequen…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.