APNG bug

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

Moderators: XnTriq, xnview

Post Reply

APNG bug

Post by guest2008 » Thu Feb 21, 2008 2:33 am

XnView incorrectly displays this APNG file:


The file works fine in Firefox 3.

User avatar
Posts: 4441
Joined: Sun Oct 17, 2004 4:57 am
Location: Bordeaux, France

Threads and …

Post by Clo » Thu Feb 21, 2008 4:56 am

:arrow: guest 2008

:) Hello !

• There are already three main threads about APNG :

1. http://newsgroup.xnview.com/viewtopic.p ... light=apng
2. http://newsgroup.xnview.com/viewtopic.p ... light=apng
3. http://newsgroup.xnview.com/viewtopic.p ... light=apng

• Your sample works partially in XnView, one frame is not displayed, but the ones working give a different colour
for each displayed character (red, blue…).
• The whole animation works in Firefox, but all characters have the same colour (Yellow-green).
- The animation seems optimized, it should be intersting to test that file as non-optimized…
- Finally, here I have Maxthon¦IE6 browser which doesn't support APNG, but the needed #1 frame
normally planned in such a case telling “Your browser doesn't support APNG blah blah…” is missing…
… or not enabled.

:mrgreen: KR
Old user ON SELECTIVE STRIKE till further notice


Post by guest2008 » Thu Feb 21, 2008 9:21 am

Yes, it is optimized.

frame #1 is 192x72 (that's what you see in IE or old Firefox)
frames #2...#7 are 32x40 (highlighted letters)

I think the problem is that frames shift is calculated as 32x4 bytes, but it should be 32x3 bytes, because this image is 24 bit.

P.S. I don't think every APNG image should have “Your browser doesn't support APNG" message. It this case it's just "MATRIX" without animation.


Post by guest2008 » Fri Feb 29, 2008 8:57 am

The colors are fine in 1.93.b1, thanks for fixing that!

But there is still a small problem. The letters should be highlighted one at a time, that's how Firefox displays it.
Maybe this instruction for frames 2-7 is processed incorrectly:


Also, I found this webpage with lots of APNG examples:

I saved them all in one directory, and when I go from one image to another using PgUp/PgDn, sometimes they're displayed correctly, and sometimes they are not. It's somewhat unpredictable.

Posts: 559
Joined: Sat Sep 04, 2004 5:09 pm

Post by Danny » Fri Feb 29, 2008 3:12 pm

Where did APNG come from? I was under the impression that animated PNGs are MNGs, and they've existed since 2001.
Get the bugs fixed, THEN start adding features. It sucks, but someone has to do it.


Post by guest2008 » Tue Mar 04, 2008 8:18 pm

Everything works fine in v1.93 Beta 2. Thank you!

Post Reply