Editing palette of transparent GIFs

Bugs found in XnView Classic. Please report only one bug per topic!

Moderators: XnTriq, xnview

Post Reply
User avatar
XnTriq
Moderator & Librarian
Posts: 5602
Joined: Sun Sep 25, 2005 3:00 am
Location: Ref Desk

Editing palette of transparent GIFs

Post by XnTriq » Thu Aug 18, 2011 8:45 pm

  • Download and open 28jkub6.gif.
  • Go to Image » Edit Palette... and double-click the third color (Index: 2).
  • Change the value from R0/G170/B238 to any other color in the color picker and click OK.
  • Image colors are all mixed up :bug:

marsh
XnThusiast
Posts: 2443
Joined: Sun May 15, 2005 6:31 am

Re: Editing palette of transparent GIFs

Post by marsh » Tue Aug 23, 2011 3:07 pm

Confirmed.

User avatar
DOS386
Posts: 291
Joined: Sun Jun 11, 2006 2:43 pm

Re: Editing palette of transparent GIFs

Post by DOS386 » Sat Sep 03, 2011 8:28 am

XnTriq wrote:[*]Image colors are all mixed up :bug:
FYI:

[1] The GIF is transparent, 3bpp (!!!), 3 unique colours from 8 (badly optimized), trans index ZERO, colour white ($FF,$FF,$FF)
[2] The GIF has a faulty ratio of 49 :shock:
[3] Nothing is "mixed up", just the view is "broken", and only if transparency in XN is ON
There is indeed no WinZIP under my rock.

User avatar
XnTriq
Moderator & Librarian
Posts: 5602
Joined: Sun Sep 25, 2005 3:00 am
Location: Ref Desk

Re: Editing palette of transparent GIFs

Post by XnTriq » Sun Sep 04, 2011 7:00 am

DOS386 wrote:FYI:

[1] The GIF is transparent, 3bpp (!!!), 3 unique colours from 8 (badly optimized), trans index ZERO, colour white ($FF,$FF,$FF)
[2] The GIF has a faulty ratio of 49 :shock:
[3] Nothing is "mixed up", just the view is "broken", and only if transparency in XN is ON
FYI: Post #97684 is of tangential (!!!) if not ZERO relevance “in this” context :shock:

I know perfectly well how to optimize my GIFs.
XnTriq ([url=http://newsgroup.xnview.com/viewtopic.php?p=97287#p97287]Transparency color when converting ICO -> PNG[/url]) wrote:
  • Image 32-bit (16m truecolor + alpha channel) PNG
    vs. Image 2-bit (4 color palette) GIF
28jkub6.gif is the result of an experiment and was saved with XnView, which doesn't provide export to 2bpp.

The bug is reproducible at any color depth.

User avatar
DOS386
Posts: 291
Joined: Sun Jun 11, 2006 2:43 pm

Re: Editing palette of transparent GIFs

Post by DOS386 » Sun Sep 04, 2011 2:59 pm

> Image colors are all mixed up

NO. Just the transparent index points to the color edited last time. How to fix? Remember the transparent index before editing the palette and set it back where it used to be.

> The bug is reproducible at any color depth.

Right. I had suspected the GIF to be "strange" ... but it's same for any transparent indexed color images, also PNG.

The problem is always there, but it's visible only if "view transparency" is ON.

PS: GIF ratio 49 is just a silly way to say "1" ... see formula in spec :bug:
There is indeed no WinZIP under my rock.

Post Reply