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LZW commpression not applied to TIFF
Posted: Wed Jan 07, 2009 11:38 pm
by dosdan
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.
Posted: Thu Jan 08, 2009 1:11 am
by marsh
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.
Posted: Thu Jan 08, 2009 1:20 am
by dosdan
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?
Posted: Thu Jan 08, 2009 1:26 am
by marsh
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.
no compression
Posted: Tue Jan 27, 2009 8:29 pm
by siepict
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
Re: no compression
Posted: Tue Jan 27, 2009 10:53 pm
by Guest
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.>.
?
Posted: Wed Jan 28, 2009 6:12 am
by siepict
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
Re: LZW commpression not applied to TIFF
Posted: Wed Jan 28, 2009 8:01 am
by xnview
Could you send me a sample used to convert in LZW TIFF?
Re: LZW commpression not applied to TIFF
Posted: Wed Jan 28, 2009 4:27 pm
by siepict
Pierre,
sure, but I will try to create a file a bit smaller then my 30 Mb files
.
Which e-mail adress (
<removed> ? )
horst
<Moderator's note: Mail address has been removed - please see Rules and Guidelines>
Re: LZW commpression not applied to TIFF
Posted: Thu Jan 29, 2009 1:09 am
by Dreamer
siepict wrote:Which e-mail adress ( <removed> ? )
How to contact the author
Re: LZW commpression not applied to TIFF
Posted: Thu Jan 29, 2009 7:54 am
by xnview
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
confirmation?
Posted: Thu Jan 29, 2009 8:49 am
by siepict
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