PNG transparency problems on Windows

[GoogleCodeExporter]

PNGs with partial transparency, particularly in color values close to 
white, do not display properly in Gargoyle on Windows (tested under XP). 
Instead, they display with a ragged, nontransparent gray edge.

The following samples compare what a white diagonal bar with antialiased 
edges with PNG transparency looks like under Zoom or Spatterlight with the 
appearance under Gargoyle. In both cases, the image is displayed over a 
white rectangle to indicate the issue with transparency.

Zoom/Spatterlight:
http://dl.dropbox.com/u/947038/PNG%20transparency%20-%20Zoom-
Spatterlight.png

Gargoyle:
http://dl.dropbox.com/u/947038/PNG%20transparency%20-%20Gargoyle.png

WinGit and WinGlulxe also exhibit similar behavior, so this could 
potentially be an issue with the PNG libraries used, rather than a 
Gargoyle-specific problem.

Original issue reported on code.google.com by Ek.Temple@gmail.com on 3 Mar 2010 at 9:13

[GoogleCodeExporter]

Can you attach a sample game file that demonstrates the issue?

Original comment by bcressey@gmail.com on 4 Mar 2010 at 11:29

• Changed state: Accepted

[GoogleCodeExporter]

Here's a sample game file (zipped):

http://dl.dropbox.com/u/947038/Basic%20Floorplan.gblorb.zip

The diagonal elements and some of the rougher elements are the main culprits.

Original comment by Ek.Temple@gmail.com on 5 Mar 2010 at 12:44

[GoogleCodeExporter]

The artifacts only appear when scaling an image with transparency by non-integer
multiples of the original.

Somehow, when synthesizing pixels, the alpha values are not being calculated or
applied correctly.

Original comment by bcressey@gmail.com on 15 Mar 2010 at 5:33

[GoogleCodeExporter]

Fixed in r334. Need to supply a build to Erik for testing.

Original comment by bcressey@gmail.com on 22 Mar 2010 at 6:55

[GoogleCodeExporter]

Original comment by bcressey@gmail.com on 22 Mar 2010 at 9:33

• Changed state: Fixed