[comp.graphics] Diagonal GIF files

ART100@PSUVM.BITNET (Andy Tefft) (03/07/89)

Thanks to those who sent me the list of FTP sites that was apparently
recently posted on here.

Now for a new question: what would make a GIF file appear slanted? For example,
suppose the picture is supposed to be a box:

   +---------+
   |         |
   |         |
   |         |
   +---------+

but it comes out thus:

      +----------+
                //
              //
            //
      -----++----

Actually the effect is more pronounced than that, but that's the idea.
None of the image is lost, but it's wrapped around!

Any ideas, or fixes?

Andy

art100@psuvm.bitnet / a1t@ecl.psu.edu

gandalf@csli.STANFORD.EDU (Juergen Wagner) (03/07/89)

In article <74425ART100@PSUVM> ART100@PSUVM.BITNET (Andy Tefft) writes:
>...
>Now for a new question: what would make a GIF file appear slanted?

Assuming it is a problem with the decoding program, somewhere it is eating
at least one pixel per line. Hard to say without seeing the source of your
program, and without knowing if the image itself is correct.

-- 
Juergen Wagner		   			gandalf@csli.stanford.edu
						 wagner@arisia.xerox.com

teittinen@cc.helsinki.fi (03/07/89)

In article <74425ART100@PSUVM>, ART100@PSUVM.BITNET (Andy Tefft) writes:
> Now for a new question: what would make a GIF file appear slanted? For
> example, suppose the picture is supposed to be a box:
>    +---------+
>    |         |
>    |         |
>    |         |
>    +---------+
> but it comes out thus:
>       +----------+
>                 //
>               //
>             //
>       -----++----
> Actually the effect is more pronounced than that, but that's the idea.
> None of the image is lost, but it's wrapped around!
> 
> Any ideas, or fixes?
>
This is just a guess, but maybe the value in the image width entry in
the GIF-file is off by one or two. Unfortunately I don't remember the
format to tell you its position in file, but perhaps some one could tell
it. To correct that fault just decrease the image width entry by one or
two using a disk editor.
-- 
EARN: teittinen@finuh
Internet: teittinen@cc.helsinki.fi
Marko Teittinen, student of computer science

ART100@PSUVM.BITNET (Andy Tefft) (03/08/89)

Now for a new question: what would make a GIF file appear slanted? For example,
suppose the picture is supposed to be a box:

   +---------+
   |         |
   |         |
   |         |
   +---------+

but it comes out thus:

      +----------+
                //
              //
            //
      -----++----

Actually the effect is more pronounced than that, but that's the idea.
None of the image is lost, but it's wrapped around!

It only happens with a FEW gif's, maybe 3 I've seen so far,
and these are all from different sites but the rest from
those places came out ok.

I'm using gif2ras to convert gif's to sun rasterfiles, then using
screenload to view the files. I don't think it's a problem with the
raster files since the border is square, just the information
in the actual gif file is diagonal!

Any ideas, or fixes?

Andy

art100@psuvm.bitnet / a1t@ecl.psu.edu