1XV also supports the GIF 'aspect ratio' extension that was discussed on 2comp.graphics. Here's the description: 3---------------------------------------------------------------------------- 4 5There was quite a discussion in comp.graphics a few weeks ago, with a 6lot of people complaining about GIF images coming with many different 7aspect ratios, but no indication what the initial aspect ratio was. 8 9Several suggestions were made, the best of which was Chris Schoeneman 10(i think) suggesting the following extension block be added to specify 11the aspect ratio: 12# 7 6 5 4 3 2 1 0 Byte # 13# +---------------+ 14# |0 0 1 0 0 0 0 1| 1 '!' - GIF extension block introducer 15# +---------------+ 16# |0 1 0 1 0 0 1 0| 2 'R' - For 'aspect Ratio' 17# +---------------+ 18# |0 0 0 0 0 0 1 0| 3 2 - Two bytes in block 19# +---------------+ 20# | pixel width | 4 - First part of ratio (numerator) 21# +---------------+ 22# | pixel height | 5 - Second part of ratio (denominator) 23# +---------------+ 24# |0 0 0 0 0 0 0 0| 6 0 - extension block end code 25# +---------------+ 26# 27#Let byte four equal 'x' and byte five equal 'y' Then x:y is the _pixel_ 28#aspect ratio. 'x' and 'y' should be relatively prime (ie they should 29#have no common divisor except one), but they don't have to be. 30 31Jef Paskanzer [of PBMPLUS fame] modified his 32gif decoder to recognize this. I also modified my own, not that I count :-) 33Jef and I cross-checked ours and these diffs are compatible with both. 34 35This code, by the way, isn't terrible robust, and will only skip extensions 36found BEFORE the image separator, but it is a lot better than nothing. 37 38Since then, there has been a seemingly official announcement about a GIF89a 39standard from CompuServe, and the possibility of both GIF's becoming outlawed 40because of the Unisys LZW patent, etc. etc. etc. oh, well... life goes on. 41 42anyway... I hope this is of some help. you are welcome to post these patches 43to wherever is appropriate (i didnt do a patch on patchlevel.h, b.t.w.), or 44incorporate them into your new program, or whatever. I relinquish all claims, 45etc. etc. 46 47-steve 48-------------------------------------------------------+"Come, Watson, come!" 49 Steve Swales (716) 275-0265,-3857,-5101| he cried. "The game is 50 steve@bat.lle.rochester.edu (128.151.32.111)| afoot. Not a word! 51 {decvax,harvard,ames,rutgers}!rochester!ur-laser!steve| Into your clothes and 52 University of Rochester 250 East River Road| come!" S.H. 53 Laboratory for Laser Energetics Rochester, NY 14623| 'The Abbey Grange' 54 55