Compression - Compression of very large images

Author

Compression of very large images

compression_apprentice

2005-08-17, 4:59 pm

Hi group

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.

thanks for your help.

Phil Frisbie, Jr.

2005-08-17, 4:59 pm

compression_apprentice wrote:

> Hi group
>
> 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.

What is the native format of that image? Mono, RGB, how many bits per channel,
what are the image dimensions, etc.

Also, tell us what 'best' means to you.

--
Phil Frisbie, Jr.
Hawk Software
http://www.hawksoft.com

Chris Johnson

2005-08-17, 9:59 pm

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.

Thomas Richter

2005-08-18, 4:00 am

Hi,

> 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.

The important question here is whether you need to decompress the image
completely every time. That is, is it really necessary to reconstruct
the image fully? Or, rather, would you like to browse through the image
at the decompressor side and reconstruct only the part of the image you
need? In the latter case, JPEG2000 would be a good choice for you, and
for the browsing problem, I would recommend to look at JPEG2000 part 9,
JPIP, which was especially designed for this application type in mind.

So long,
Thomas

compression_apprentice

2005-08-18, 5:55 pm

thank you all for your resposes

I would like to specify that i need to decompress all the image
completely every time. What I mean is that I am kinda familiar with
PAQ code and that i'm not really a newbie in compression. I'm open to
either lossless or lossy compression. I read about a lot of lossless
image compressors (bmf,calic,etc) but these are old (it could be also
that my sources aren't good). So I was wondering if it is possible to
have a better compression than JPEG2000 using, I don't know, maybe a
PAQ specific adaption algorithm. That can take time to compress but
that is faster to decompress and I mean a lot faster. I know about the
AnalogModel(for audio,bmp,etc) in PAQ but I'm not sure how it works.

Thomas Richter

2005-08-18, 5:55 pm

Hi,

> I would like to specify that i need to decompress all the image
> completely every time. What I mean is that I am kinda familiar with
> PAQ code and that i'm not really a newbie in compression. I'm open to
> either lossless or lossy compression. I read about a lot of lossless
> image compressors (bmf,calic,etc) but these are old (it could be also
> that my sources aren't good). So I was wondering if it is possible to
> have a better compression than JPEG2000 using, I don't know, maybe a
> PAQ specific adaption algorithm. That can take time to compress but
> that is faster to decompress and I mean a lot faster. I know about the
> AnalogModel(for audio,bmp,etc) in PAQ but I'm not sure how it works.

If lossless is fine for you, and you really need to compress and decompress
all of the image, and it must be really, really fast, then my answer
would be JPEG-LS. It is a very simple algorithm, is stunningly fast, and,
for lossless, performs better than JPEG2000.

So long,
Thomas

Jim Leonard

2005-08-18, 5:55 pm

Thomas Richter wrote:
> If lossless is fine for you, and you really need to compress and decompress
> all of the image, and it must be really, really fast, then my answer
> would be JPEG-LS. It is a very simple algorithm, is stunningly fast, and,
> for lossless, performs better than JPEG2000.

I'm interesting in implementing this -- where can I find algorithm
details on JPEG-LS? A google search didn't turn up anything easily
parsable.

Pete Fraser

2005-08-18, 5:55 pm

"Jim Leonard" <MobyGamer@gmail.com> wrote in message
news:1124384773.688361.24170@g44g2000cwa.googlegroups.com...

> I'm interesting in implementing this -- where can I find algorithm
> details on JPEG-LS? A google search didn't turn up anything easily
> parsable.

There are a couple of papers and some source here:

http://www.hpl.hp.com/research/info_theory/loco/

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