An patch to support semi-transparent PNG8

张挺 <[email protected]> Tue, 19 Oct 2010 10:13:18 +0000

Newsgroups	gmane.comp.python.image
Message-ID	<[email protected]>

according to PNG Specification, png8 images(with type 3) should support semi transparent images, with tRNS chunk, but current version of PIL does not handle it correctly

two simple patch can make PIL read this type of file correctly.

I've attached the patch file.

more efforts are needed to support saving png of this type.

PS: is there a bug tracing system for PIL?

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Image-SIG maillist  -  [email protected]
http://mail.python.org/mailman/listinfo/image-sig

Image.py.patch (application/octet-stream, 403 B)

615c615,620
<                 self.im.putpalettealpha(self.info["transparency"], 0)
---
>                 trans = self.info["transparency"]
>                 if type(trans) is int:
>                     self.im.putpalettealpha(self.info["transparency"], 0)
>                 else:
>                     for i, a in enumerate(trans):
>                         self.im.putpalettealpha(i, ord(a))

PngImagePlugin.py.patch (application/octet-stream, 313 B)

246,248c246,249
<             i = string.find(s, chr(0))
<             if i >= 0:
<                 self.im_info["transparency"] = i
---
>             #i = string.find(s, chr(0))
>             #if i >= 0:
>             #    self.im_info["transparency"] = i
>             self.im_info["transparency"] = s