LZW commpression not applied to TIFF

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dosdan
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LZW commpression not applied to TIFF

Post by dosdan » Wed Jan 07, 2009 11:38 pm

XnView 1.95.4.

When saving a TIFF, LZW compression is not used in "SaveAs" or "Export" even if it's ticked. I tested the same image in FastStone and it did work and the TIFF was about 25% smaller.

Dan.

marsh
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Post by marsh » Thu Jan 08, 2009 1:11 am

It looks like many programs use LZW + Predict, and not just LZW. I found a command line program (tiffcp) which produces comparable results for each option.

dosdan
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Post by dosdan » Thu Jan 08, 2009 1:20 am

That may be the case, but XnView has a bug. The file info indates that no compression was used, even though it was selected in the JPG saving options.

By the way, typically how much extra gain is there from adding prediction to LZW when compressing photos?

marsh
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Post by marsh » Thu Jan 08, 2009 1:26 am

dosdan wrote: By the way, typically how much extra gain is there from adding prediction to LZW when compressing photos?
I see 40%+ difference with a handful of samples.

siepict
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Joined: Fri Nov 14, 2008 6:25 pm

no compression

Post by siepict » Tue Jan 27, 2009 8:29 pm

Hi dosdan,
just to confirm but
[quote="dosdan"]The file info indates that no compression was used, /quote]
a bit different with me:
- file lzw compressed (by different software): 20.4 Mb
open that file and saved as by xnview lzw checked on: filesize 28.2 Mb, xnview shows image properties - compression : lzw
-
opening an uncompressed tiff by xnview and saved as compressed: nearly no differene in filesize but compression indicator shows lzw.
horst

Guest

Re: no compression

Post by Guest » Tue Jan 27, 2009 10:53 pm

siepict wrote:opening an uncompressed tiff by xnview and saved as compressed: nearly no differene in filesize but compression indicator shows lzw.
horst
Take the same uncompressed TIFF & save it as a LZW-compressed TIFF in another freeware package such as as FastStone, ans see how much it drops.

The compressability of a TIFF will depend on the content. Here are some test sizes on a 1500x1000 TIFF file using "true" KB (1,024 bytes). Actual filesize is 4,508,248 bytes. The slightly greater size then the calculated 4,500,000 bytes is due to the overhead of the TIFF file header.

Code: Select all

TIF             4,403KB  100%
TIF/LZW         3,120KB   71%
JPG 100%        1,190KB   27%
JPG  95%          617KB   14%
JPG  90%          435KB   10%
JPG  80%          297KB    7%
JPG  70%          237KB    5%
I had to redo this test in FastStone after first attempting it in XnView.

<Moderator's note: Double post has been deleted.>.

siepict
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?

Post by siepict » Wed Jan 28, 2009 6:12 am

Hi Guest,
please, what do you want to tell? I don't understand what the listing has to do with the prolem that is dicussed here?
horst

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xnview
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Re: LZW commpression not applied to TIFF

Post by xnview » Wed Jan 28, 2009 8:01 am

Could you send me a sample used to convert in LZW TIFF?
Pierre.

siepict
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Re: LZW commpression not applied to TIFF

Post by siepict » Wed Jan 28, 2009 4:27 pm

Pierre,
sure, but I will try to create a file a bit smaller then my 30 Mb files ;-).
Which e-mail adress ( <removed> ? )
horst

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Dreamer
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Re: LZW commpression not applied to TIFF

Post by Dreamer » Thu Jan 29, 2009 1:09 am

siepict wrote:Which e-mail adress ( <removed> ? )
How to contact the author
Dreamer

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Re: LZW commpression not applied to TIFF

Post by xnview » Thu Jan 29, 2009 7:54 am

siepict wrote:Pierre,
sure, but I will try to create a file a bit smaller then my 30 Mb files ;-).
Which e-mail adress ( <removed> ? )
horst
Ok, you can try LZW+Predict, and the result is smaller
Pierre.

siepict
Posts: 29
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confirmation?

Post by siepict » Thu Jan 29, 2009 8:49 am

Pierre, have you got my PM? horst
edit: I've just tried 'predict' option, and must confess, that works fine.
I've never read about that, always and only 'LZW', that was the reason, why I haven't tried.
Maybe a litle hint in the space of that dialog box will help to select the 'correct' compression mode?
horst

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