Convert GIF 89 to 87a ???

DoctorIt

This is a rather off-the-wall question, but does anyone know of a way to convert a gif 89 into the older 87a? I'm using an old software routine here in the lab (an optical velocimetry scheme) that will only accept and run images in gif 87a. Major PITA since all the new cameras and DV aquisition boards we have automatically save in the newer format.

I have found all sorts of descriptions of the file format, but I don't know enough about the code I'm using (someone else wrote it, in MATLAB) to try to alter it to accept the newer GIF. It seems that the newer versions of Photoshop have totally done away with the old format... either that, or I just can't find it.

Even a simple image converter would be fine.

Anyone??? Thanks!

patch29

Did you try a search at Versiontracker? That would be my first place to look.

Do you have an older version of photoshop, maybe it will save to the older format, not sure if that helps to convert new files?

DoctorIt

i did find a bunch of image converters (shareware) at Tucows.com already... i tried versiontracker.com and they had most of the same ones. The trouble with all these is that their description never mentions this miniscule detail. I've actually downloaded a couple already that appeared to specialize in GIF conversion, but none of them so far has had any settings that would specify GIF 89 or the older 87a.

cmr164

DoctorIt wrote:

This is a rather off-the-wall question, but does anyone know of a way to convert a gif 89 into the older 87a? I'm using an old software routine here in the lab (an optical velocimetry scheme) that will only accept and run images in gif 87a. Major PITA since all the new cameras and DV aquisition boards we have automatically save in the newer format.

I have found all sorts of descriptions of the file format, but I don't know enough about the code I'm using (someone else wrote it, in MATLAB) to try to alter it to accept the newer GIF. It seems that the newer versions of Photoshop have totally done away with the old format... either that, or I just can't find it.

Even a simple image converter would be fine.

Anyone??? Thanks!

Looking at the content of a GIF, I see that the "GIF89a" is right in the very first bytes. You might try using a binary editor to change that to look like the earlier version. Or you might write (or pay someone to write) some code to make a utility to make the changes. I don't have a GIF87 to look at so I can only show you what the GIF89a looks like.

$ od -c ne_nau.gif
0000000 G I F 8 9 a % \0 017 \0 221 003 \0 377 377 377
0000020 377 377 \0 \0 \0 \0 377 377 377 ! 377 013 N E T S
0000040 C A P E 2 . 0 003 001 \0 \0 \0 ! 371 004 \t
0000060 2 \0 003 \0 , \0 \0 \0 \0 % \0 017 \0 \0 002 ^
0000100 234 217 9 302 254 017 # 013 224 272 210 237 250 334 346 o
0000120 l 326 6 y 340 ! ( 242 \0 220 255 211 244 R 262 002
0000140 / 373 006 2 252 6 { 250 k M 032 7 232 / t D
0000160 272 032 : 306 355 262 H 372 v 251 025 323 347 241 & i
0000200 241 E 347 233 355 ~ 252 300 \n 323 334 375 e . " 235
0000220 031 035 = i 300 0 271 244 = 262 237 246 366 002 \0 !
0000240 371 004 005 F \0 003 \0 , \0 \0 \0 \0 % \0 017 \0
0000260 \0 002 ^ 234 217 9 302 254 017 # 013 224 272 210 237 250
0000300 334 f } 4 [ 7 Z M 210 \t 350 B 002 245 272 254
0000320 210 \b 307 245 005 270 301 244 326 264 361 003 262 * \r 235
0000340 300 325 013 211 200 K 341 255 270 Y 372 232 \t X 217 324
0000360 330 E c 334 L 362 326 341 | ? J ` X 273 ] 324
0000400 310 \ 360 N , d k 316 036 271 027 | 261 177 202 354
0000420 002 \0 ;
0000423

jimf

cmr164 wrote:

Looking at the content of a GIF, I see that the "GIF89a" is right in the very first bytes. You might try using a binary editor to change that to look like the earlier version. Or you might write (or pay someone to write) some code to make a utility to make the changes. I don't have a GIF87 to look at so I can only show you what the GIF89a looks like.

Charles is right, probably you could just change the ID tag. In fact, that's how I made a "GIF89a" reader out of a "GIF87a" reader with xloadimage all those years ago.

That was cheating, actually, since GIF89a supports a bunch of new modes and options that GIF87a didn't (like overlays and slideshows IIRC) ... but in practice those features are almost never used.

So if you want to do a quick and dirty conversion attempt, just change the fifth byte in the file from a 9 to a 7 and see how it goes. Odds are good that it'll work.

DoctorIt

I'm not too good at coding myself - all I really know is writing routines in MATLAB (which is cop out coding) - but I do have a colleague that should be able to write something based on what you've given me.

Thanks very much!

Bodwick

Amiga
Another option might be to look at Commodore Amiga emulation software .
87a rings a bell from way back....

If you get realy stuck I still have an Amiga3000 gathering dust which may well have convertors suitable to save to a 3.5 floppy on it's hard drive. I could dust it down and see if it still works if you are unable to sort this another way.

You could buy an old Amiga for very little or I'll post you a A500 for free if you want. I used to sell these back in around 89 and for some reason still have a few sitting around.

Let me know if you want to follow this route....


Paul

DoctorIt wrote:

I'm not too good at coding myself - all I really know is writing routines in MATLAB (which is cop out coding) - but I do have a colleague that should be able to write something based on what you've given me.

Thanks very much!