A Lossy Method for Compressing Raw CCD Images
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| Format: | Artículo científico |
| Langue: | en |
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Universidad Nacional Autónoma de México
2002
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| _version_ | 1876482178392522752 |
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| author | Alan M. Watson |
| author_facet | Alan M. Watson |
| contents | A Lossy Method for Compressing Raw CCD Images Alan M. Watson Física, Astronomía y Matemáticas TECHNIQUES: IMAGE PROCESSING This paper describes a lossy method for compressing raw images produced byCCDs or similar devices. The method is very simple: lossy quantization followedby lossless compression using general-purpose compression tools such as gzip andbzip2. A key feature of the method is that compressed images can be converted toFITS files simply by decompressing with gunzip or bunzip2, and this is a significantadvantage for distributing compressed files. The degree of quantization is chosento eliminate low-order bits that over-sample the noise, contain no information, andare difficult or impossible to compress. The method is lossy but gives guarantees onthe maximum absolute difference, the expected mean difference, and the expectedRMS difference between the compressed and original images; these guarantees makeit suitable for use on raw images. The method consistently compresses images toroughly 1/5 of their original size with a quantization such that no value changes bymore than 1/2 of a standard deviation in the background. This is a dramatic improvementon lossless compression. It appears that bzip2 compresses the quantizedimages to within a few tens of percent of the theoretical limit. 2002 artículo científico 0185-1101 https://www.redalyc.org/articulo.oa?id=57138212 en http://www.redalyc.org/revista.oa?id=571 Revista Mexicana de Astronomía y Astrofísica application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Astronomía y Astrofísica (México) Num.2 Vol.38 |
| format | Artículo científico |
| id | redalyc_57138212 |
| institution | Redalyc |
| language | en |
| publishDate | 2002 |
| publisher | Universidad Nacional Autónoma de México |
| spellingShingle | A Lossy Method for Compressing Raw CCD Images Alan M. Watson Física, Astronomía y Matemáticas TECHNIQUES: IMAGE PROCESSING A Lossy Method for Compressing Raw CCD Images Alan M. Watson Física, Astronomía y Matemáticas TECHNIQUES: IMAGE PROCESSING This paper describes a lossy method for compressing raw images produced byCCDs or similar devices. The method is very simple: lossy quantization followedby lossless compression using general-purpose compression tools such as gzip andbzip2. A key feature of the method is that compressed images can be converted toFITS files simply by decompressing with gunzip or bunzip2, and this is a significantadvantage for distributing compressed files. The degree of quantization is chosento eliminate low-order bits that over-sample the noise, contain no information, andare difficult or impossible to compress. The method is lossy but gives guarantees onthe maximum absolute difference, the expected mean difference, and the expectedRMS difference between the compressed and original images; these guarantees makeit suitable for use on raw images. The method consistently compresses images toroughly 1/5 of their original size with a quantization such that no value changes bymore than 1/2 of a standard deviation in the background. This is a dramatic improvementon lossless compression. It appears that bzip2 compresses the quantizedimages to within a few tens of percent of the theoretical limit. 2002 artículo científico 0185-1101 https://www.redalyc.org/articulo.oa?id=57138212 en http://www.redalyc.org/revista.oa?id=571 Revista Mexicana de Astronomía y Astrofísica application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Astronomía y Astrofísica (México) Num.2 Vol.38 |
| title | A Lossy Method for Compressing Raw CCD Images |
| topic | Física, Astronomía y Matemáticas TECHNIQUES: IMAGE PROCESSING |
| url | https://www.redalyc.org/articulo.oa?id=57138212 |