543674 - (apng) Implement graceful error handling for APNG

Status: NEW

(Core :: Graphics: ImageLib, defect)

Description

[Max Stepin]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; ru; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4 WebMoney Advisor
Build Identifier: Trunk

Actual: Currently all errors in acTL, fcTL, fDAT chunks result in png_error().
So Firefox won't display anything, while IE will display the first frame.

Expected: Any single error in any single apng chunk should cause Firefox to throw away all information from all apng chunks, and display the file as a static PNG image (first frame).


Reproducible: Always

Comment 1

[Glenn Randers-Pehrson]

Test case at http://www.simplesystems.org/users/glennrp/santa

Compare santa_bad_fctl.png (bad fctl chunk at the very end of the
datastream) with santaj.png (OK)

Comment 2

[[e-mail]]

Max originally brought up this issue in bug 257197 with reference to the APNG specs: 

https://wiki.mozilla.org/APNG_Specification#Error_Handling

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee didn't login in Bugzilla in the last 7 months.
:aosmond, could you have a look please?
For more information, please visit auto_nag documentation.

Comment 4

[chris]

PNG WG has started to discuss APNG error handling here:

https://github.com/w3c/PNG-spec/issues/360

Contributions from Mozillians would be very welcome!

Comment 5

[chris]

Expected: Any single error in any single apng chunk should cause Firefox to throw away all information from all apng chunks, and display the file as a static PNG image (first frame).

Absolutely! The whole point of APNG was graceful fallback to the static image. For implementations that don't support animation, but also in the case of errors in the animation itself.