#324 GM returns MagickFail, when raw profile length is 0.

[alien]

When encouting a 'raw profile type' while reading a png file, the gm code always have a judgement that whether the profile length equals 0, if 0, return MagickFail. Howecer, if this profile is just a futile label, the gm could not process this file.

[alien]

I suggest that the gm could return MagickTrue in png_read_raw_profile function when encounting profile length 0, without set this image profile. For myself, I have ecncoutered some png image which hold this problem.

[Bob Friesenhahn]

The calling code is not checking the return status from png_read_raw_profile(). The error returned to the user is due to a CoderError exception being thrown at line 1150 of png.c. Perhaps it would work better if a warning was thrown instead. Unfortunately, the internal design of GM does not allow storing empty profiles.

[Bob Friesenhahn]

It would be very helpful if the problematic PNG was attached to this bug report, bundled up as a zip archive in order to prevent SourceForge from modifying it.

[alien]

The attachment is 3 problematic PNG images. These PNG have a 0 length profile. So, in 1150, GM throw a CoderError exception. All these images look right in browser or a system photo viewer. That's why I suggest that GM could just ignore this profile with 0 length.

[Glenn Randers-Pehrson]

I've pushed a fix to coders/png.c for Bob's review. GM will issue a warning about the profile and will then proceed to convert the image without copying the bad profile. The other profiles in the image are preserved.

[alien]

Thanks for your adoption of my suggestion. I have some other questions about GM, which I will open new tickets.

[Bob Friesenhahn]

I am satisfied with Glenn's fix. All seems good. Valgrind is happy.