| Re: what is an efficient lossless compression way to store a gray-scale image [message #36120] |
Tue, 26 August 2003 09:35 |
Wolfgang Funk
Messages: 3
Registered: June 2003
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Junior Member |
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Hi Julia,
the PNG format provides a lossless compression scheme (in fact it was
defined as a replacement for GIF).
Depending on your IDL version the WRITE_PNG routine is available (as far
as I remember PNG support starts with version 5.3). I'm running IDL 5.4
and WRITE_PNG compresses the good old "Lenna" image (512 by 512 grey
scale) from 256K into a 146K PNG file.
Hope it helps.
Wolfgang
> Hi, there,
>
> For a gray-scale image, I haven't found a good way to store it yet. It
> seems that there is no way to store gray-scale images in IDL
> efficiently. If so, that will be too bad, because all the satellite
> images we processed are very large and occupy a lot of space.
>
> I tried 'tiff' format with Packbits compression, but it does not help
> for gray-scale image. Sometimes the file size of the compressed image
> is even larger than the original raw data!!!
>
> Can anyone give me some hint? Thank you very much!
>
> Regards,
>
> Julia
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