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Re: Several suggestions for image support
From: |
YAMAMOTO Mitsuharu |
Subject: |
Re: Several suggestions for image support |
Date: |
Fri, 16 Apr 2004 18:29:05 +0900 |
User-agent: |
Wanderlust/2.10.1 (Watching The Wheels) SEMI/1.14.5 (Awara-Onsen) FLIM/1.14.5 (Demachiyanagi) APEL/10.6 Emacs/21.3.50 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI) |
>>>>> On 16 Apr 2004 02:21:11 +0200, David Kastrup <address@hidden> said:
> PNG images support transparency. Emacs can't make use of it. You
> can only have Emacs declare a particular color as transparent. This
> is dissatisfactory. It should tell the PNG decoding routines Emacs'
> background color for the purpose of transparency.
As for PNG transparency, there was one thing that I noticed (and I've
been forgotten to tell about it) while I was porting image support to
Carbon Emacs.
In png_load (image.c):
user_bg.red = color.red >> PNG_BG_COLOR_SHIFT;
user_bg.green = color.green >> PNG_BG_COLOR_SHIFT;
user_bg.blue = color.blue >> PNG_BG_COLOR_SHIFT;
fn_png_set_background (png_ptr, &user_bg,
PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
I think the background color should be specified in 8-bit depth here
(thus PNG_BG_COLOR_SHIFT should be 8 for all the platforms) because
the 4th argument (aka need_expand) for fn_png_set_background is 0 and
the image data has been normalized in 8-bit depth at this stage. You
can observe the difference using
http://www.w3.org/Graphics/PNG/alphatest.png. The same thing is also
applied to the other place (in png_load) where fn_png_set_background
is called with its 4th argument 0.
YAMAMOTO Mitsuharu
address@hidden
- Re: Several suggestions for image support, (continued)
- Re: Several suggestions for image support, Jason Rumney, 2004/04/16
- Re: Several suggestions for image support, David Kastrup, 2004/04/16
- Re: Several suggestions for image support, Kim F. Storm, 2004/04/16
- Re: Several suggestions for image support, Jason Rumney, 2004/04/16
- Re: Several suggestions for image support, David Kastrup, 2004/04/16
- Re: Several suggestions for image support, Jason Rumney, 2004/04/16
- Re: Several suggestions for image support, David Kastrup, 2004/04/16
- Re: Several suggestions for image support, Kim F. Storm, 2004/04/16
- Re: Several suggestions for image support, Stefan Monnier, 2004/04/16
- Re: Several suggestions for image support, David Kastrup, 2004/04/16
Re: Several suggestions for image support,
YAMAMOTO Mitsuharu <=
Re: Several suggestions for image support, Richard Stallman, 2004/04/17