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From: | Jason Rumney |
Subject: | Re: Several suggestions for image support |
Date: | Fri, 16 Apr 2004 13:50:22 +0100 |
User-agent: | Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6) Gecko/20040113 |
Kim F. Storm wrote:
You are right. Shifting 8 bits here as well on X fixes transparent bg. I will commit a fix for X shortly. However, on W32, it seems that it explicitly scales things to 16 bits in both cases. I cannot test this on W32, so I cannot say what's the right thing to do.
The W32 port scales to 16 bits in places because the native Windows COLORREF is 8 bits, while Emacs XColor is 16 bits. So in this case, 8 bits is right, but alpha is currently coming out wrong. I suspect the use of COLOREF instead of XColor that you considered a bug when merging the image code (see comment around that location) was in fact not a bug.
Here is an easy way to test it -- after downloading the image you mentioned: (insert-image (create-image "alphatest.png")) this should result in a light blue image with nice rounded edges; a darker blue with rough edges indicates a problem.
On Windows the image comes out with a black background and the image has rainbow colored stripes. Non-alpha PNGs look OK.
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