improper blending method in anim

[GoogleCodeExporter]

What steps will reproduce the problem?

as reported on the mailing list:

1. link to source images: 
png=>webp with:
 cwebp.exe -m 6 -pass 10 -q 70 -sns 0 -f 50 -lossless "%%n" -o "%%n.webp"

webp=>animatedWebp 
webpmux.exe -frame C:/z/anim_0.webp +50 -frame C:/z/anim_1.webp +50 [...]  -o 
anim_container.webp

What is the expected output? What do you see instead?

attached is the result (glitchy_anim.webp) that doesn't display correctly on 
Chrome.

Original issue reported on code.google.com by pascal.m...@gmail.com on 31 Mar 2014 at 9:04

Attachments:

• correct_anim.webp
• glitchy_anim.webp

[GoogleCodeExporter]

the result is ok when i force the blending method to be "-b" for each frame:

webpmux  \
  -frame anim_0.webp +50+0+0+0-b \ 
  -frame anim_1.webp +50+0+0+0-b \ 
  -frame anim_2.webp +50+0+0+0-b \ 
  -frame anim_3.webp +50+0+0+0-b \ 
  -frame anim_4.webp +50+0+0+0-b \ 
  -frame anim_5.webp +50+0+0+0-b \ 
  ...
 -o anim_good.webp

(but compression suffers)

Original comment by pascal.m...@gmail.com on 31 Mar 2014 at 9:05

Attachments:

• anim_good.webp

[GoogleCodeExporter]

Hi Vlozer,
As you mentioned on the mailing list, for your case, either (i) no blend / 
dispose method = NONE, or (ii) with blend / dispose method = BACKGROUND would 
generate the expected output.

In general, though, the correct parameters depend on what your source animation 
uses.

In your case, what was the source image (was it a GIF, for example)?

Original comment by urv...@google.com on 2 Apr 2014 at 12:45