Re: Compression of very large images

This one time, at band camp, compression_apprentice wrote: 
        If I have a satelit image and I want to compress it, what is
the best way to do it? I know allmost all the important compressions:
ECW, JPEG2000, Mr. Sid. I even tried PWCM, with good result but it took
8 hours to compress. The problem is that it took almost the same time
to decrompress.  Can I have the same compression ratio with much faster
decompression time?  Compression speed is not an issue.


I've been testing image compression options on a CMYK TIFF;

(hope this lines up with your tab-stops)

61612_009351.tif Original file 43,112 CMYK/Original 61612_009351_TIFF.zip Original file zipped 35,810 CMYK/Lossless 61612_009351_LZW.tif LZW Compressed TIFF 35,179 CMYK/Lossless 61612_009351_LZW.7z LZW TIFF 7zipped 34,306 CMYK/Lossless
61612_009351_TIFF.sitx Original file Stuffited 32,337 CMYK/Lossless
61612_009351_RGB.tif Uncompressed RGB TIFF 32,315 RGB/Lossless
61612_009351_TIFF.7z Original file 7zipped 29,058 CMYK/Lossless
61612_009351_TIFF.rar Original file Rarred 26,734 CMYK/Lossless
61612_009351_LZWRGB.tif LZW Compressed RGB TIFF 22,924 RGB/Lossless
61612_009351.PWCM.rk Original file WinRKed 21,864 CMYK/Lossless
61612_009351_RGB.rar RGB TIFF Rarred 19,728 RGB/Lossless
61612_009351.png PNG version 18,613 RGB/Lossless
61612_009351_pngout.png PNG optimised (slow) 18,414 RGB/Lossless
61612_009351_RGB.jp2 JPEG2000 (LuraWave) 17,598 RGB/Lossless
61612_009351.j2c JPEG2000 (Kakadu) 16,000 RGB/Lossless
61612_009351_RGB.tif.rk RGB TIFF WinRKed 14,127 RGB/Lossless
61612_009351_CMYK.JPG CMYK JPEG ("High" Qual) 8,825 CMYK/Lossy
61612_009351_CMYK_o.JPG CMYK JPEG (High opt.) 8,429 CMYK/Lossy
61612_009351_100.jpg RGB JPEG (100% Quality) 7,601 RGB/Lossy
61612_009351_100.sitx RGB JPEG 100% Stuffit 7,041 RGB/Lossy
61612_009351_100.jp2 JPEG2000 LuraWave, 100% 4,691 RGB/Lossy
61612_009351_75.jp2 JPEG2000 LuraWave, 75% 1,997 RGB/Lossy
61612_009351_75.jpg RGB JPEG (75% Quality) 832 RGB/Lossy
61612_009351_50.jp2 JPEG2000 LuraWave, 50% 548 RGB/Lossy
61612_009351_50.jpg RGB JPEG (50% Quality) 462 RGB/Lossy
61612_009351_25.jpg RGB JPEG (25% Quality) 269 RGB/Lossy
61612_009351_5.jpg RGB JPEG (5% Quality) 120 RGB/Lossy

You're right though, the best lossless compression is WinRK (using the PAQ engine with PWCM) but it takes *hours* to both pack *and* unpack. Have you tried the "ROLZ" option specifically listed as having fast decoding? I haven't myself, but I haven't been testing for speed, only size.

RAR has some nice optimisations for images, and is much faster than PAQ. If ROLZ doesn't give you what you want, you could try RAR.

HTH.
.

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