RE: Seemingly Random: Gifs print reversed

[David Williams <DavidW@xxxxxxxx>]

[ Dropped Frameusers@frameusers.com list because I'm not subscribed. ]

Bart Windrum [mailto:bart.windrum@DiogenesInc.com] wrote (at 06 June 2002
21:59)
> I've got a handful of GIF images among dozens that print reversed. For
> Black/white it's a simple reverse; for white lettering on 
> various shades of gray backgrounds (each pix only 2 colors) 
> the letter is black and the backgrounds drop out to white.
> 
> I tried resaving the gifs at 256 levels rather than 2 just in 
> case but that didn't change the result. I also isolated the 
> culprits into their own one-page file but no change.

GIF files (and other formats) have headers and tags in addition to 
pixel by pixel information. These parts of the files define things like 
color tables, picture size, and interlacing. It is possible for applications
to set or read these parts incorrectly. One effect can be pictures in
negative, as you describe.

I saw something similar to what you describe with two-color TIFF files in 
FM v5.x on UNIX, but I believe that bug has been fixed and may never have 
existed on other platforms.

-

Possible workaround:

If you have a suitable graphics application, you might try adding
a third color that is unlikely to be noticed, say RGB=0,0,1 or 255,255,254
and applying that to a single pixel of an affected file. Then save the
file and see if that graphic file looks correct in FM. If yes, you have 
forced the GIF out of the 2-color / 2-level problem area (which can persist
otherwise, even when you save in 256 levels).

-

If you want solid confirmation of what is causing your problem, please post
again to identify the graphics application producing the graphics, the 
version of FM that you are using, and the platform (PC, Mac, UNIX variant).

I'm sure somebody has seen the same thing.

Regards,
David
-- 
David Williams. Writing personally. Working in Cambridge UK.


** To unsubscribe, send a message to majordomo@omsys.com **
** with "unsubscribe framers" (no quotes) in the body.   **