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DPChallenge Forums >> Hardware and Software >> Raw Images, TIFF files and Image Compression
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10/03/2004 12:56:42 AM · #1
When processing raw images, I always save the file as a tiff file and I choose None for Image Compression. A friend told me recently that selecting LZW is a better way since the file saved is a much smaller file but it's still lossless. I did a test of this saving the same photo using None image compression and LZW. The first one was 18.0MB and the LZW was 6.48MB. Quite a difference in file size. Hard to believe that the LZW did not lose any data compared to the first one.

Any thoughts on this? Just wanted to know how you go about this.
10/03/2004 01:24:03 AM · #2
cool if it actually works!
10/03/2004 02:04:07 AM · #3
Originally posted by kyebosh:

cool if it actually works!


I don't doubt that it works. Guess I'm trying to look for an explanation to the file size difference and when to use None and LZW. It makes sense to use LZW considering the savings in storage space but is it really the way to go? When do we use None then?
10/03/2004 05:11:31 AM · #4
It works fine, but from what I understand LZW tiffs are not universally recognized.

One of the more basic ways to reduce space, without loosing data, is to replace repeating sequences of data with a single token; such as the common words (and, or, but, etc.) or common parts of words (ing, less, etc.). The same can be done with the RGB data of an image file. There are other methods, and much more complex ways of finding reoccuring sequences, but I hope you get the idea.

As long as the programs you use tiff files with support LZW compression, there is little reason not to use it.

David
10/03/2004 05:15:42 AM · #5
LZW is actually a compression alogrothim (spelling?)... It is used widely in computers, just like a zip file! it used to be very popular when DOS (old PC language) was around. It does not compress the picture or take away data forever, it compresses the code, which is then rebuilt perfectly on uncompressing it.
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