Bug 4096

Summary:	Speedup png reading
Product:	cairo	Reporter:	Billy Biggs <billy.biggs>
Component:	png functions	Assignee:	Carl Worth <cworth>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	minor
Priority:	high
Version:	0.9.3
Hardware:	x86 (IA32)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:
Attachments:	Patch

Description Billy Biggs 2005-08-14 19:29:31 UTC

The png code is very convenient, however it spends a long time performing
premultiplication of the input.  The attached patch speeds it up a fair bit for me.

I think alpha premultiplication is something useful enough to belong in
libpixman (I even have my own MMX implementation), however this patch is small
and straightforward so I think it's worth just putting in for now.

Comment 1 Billy Biggs 2005-08-14 19:29:49 UTC

Created attachment 2859 [details] [review]
Patch

Comment 2 Carl Worth 2005-08-18 10:57:28 UTC

The patch looks fairly good to me. Here are a few (very minor) comments:

Why does this use "__inline__" rather than the C99 "inline"? Or it could
be a macro similar to the other multiplication macro (macros?) we have
elsewhere in the implementation.

I don't like the single-letter ientifiers "a" and "r" if they're intended
to refer to specific things. Maybe alpha? and color?

But if the arguments are interchangable, then single-letter generic names
would be better. "a" and "b" ? And if so, perhaps "multiply_alpha" should
also have a more generic name.

Anyway, feel free to resolve those as you see fit, then commit.

Comment 3 Billy Biggs 2005-08-19 23:08:58 UTC

Released to HEAD with modifications.

I don't know what the correct thing is to do for asking the compiler to inline
things.  I would think that if it's OK to depend on C99, using that "inline"
would be a good thing.  However, since I am unsure, and since pixman uses
__inline__ for gcc, I used that for this commit (with a macro in cairoint.h). 
Hopefully someone who knows these things better can fix it in both cairo and
pixman if it's wrong.

Comment 4 Carl Worth 2005-08-22 17:15:24 UTC

Move bugs against "cvs" version to "0.9.3" so we can remove the "cvs" version.

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