From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 11 Oct 2013 09:52:43 +0000 (+0300)
Subject: Avoid the unpadding loop with kCGImageAlphaNoneSkipFirst
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgui.git;a=commitdiff_plain;h=03f5e11e6bcf9487e396403041f84009ff4eb900

Avoid the unpadding loop with kCGImageAlphaNoneSkipFirst

The data looks like this:

  X RGB X RGB X RGB X RGB ...

Ignoring the first padding byte allows treating it as RGBX.  The padding
bytes move to different RGB triplets, but they're going to get ignored
anyway.
---

diff --git a/source/graphics/quartz/quartzloader.cpp b/source/graphics/quartz/quartzloader.cpp
index 3447f5f..1fc93ad 100644
--- a/source/graphics/quartz/quartzloader.cpp
+++ b/source/graphics/quartz/quartzloader.cpp
@@ -104,9 +104,9 @@ void QuartzLoader::load(Image::Data &data)
 		{
 			if(alpha==kCGImageAlphaLast)
 				data.fmt = RGBA;
-			else if(alpha==kCGImageAlphaNoneSkipLast)
+			else if(alpha==kCGImageAlphaNoneSkipLast || alpha==kCGImageAlphaNoneSkipFirst)
 				data.fmt = RGBX;
-			else if(alpha==kCGImageAlphaNone || alpha==kCGImageAlphaNoneSkipFirst)
+			else if(alpha==kCGImageAlphaNone)
 				data.fmt = RGB;
 			else
 				throw unsupported_image_format("unknown alpha mode");
@@ -117,26 +117,12 @@ void QuartzLoader::load(Image::Data &data)
 		CGDataProviderRef dp = CGImageGetDataProvider(image);
 		CFDataRef image_data = CGDataProviderCopyData(dp);
 		data.data = new char[data.height*data.stride];
-		CFDataGetBytes(image_data, CFRangeMake(0, CFDataGetLength(image_data)), reinterpret_cast<UInt8 *>(data.data));
+		unsigned offset = (alpha==kCGImageAlphaNoneSkipFirst);
+		CFRange range = CFRangeMake(offset, CFDataGetLength(image_data)-offset);
+		CFDataGetBytes(image_data, range, reinterpret_cast<UInt8 *>(data.data));
 		CFRelease(image_data);
 
 		CFRelease(image);
-
-		if(alpha==kCGImageAlphaNoneSkipFirst)
-		{
-			const char *src = data.data;
-			if(alpha==kCGImageAlphaNoneSkipFirst)
-				++src;
-			char *dest = data.data;
-			for(unsigned y=0; y<data.height; ++y)
-				for(unsigned x=0; x<data.width; ++x)
-				{
-					for(unsigned i=0; i<3; ++i)
-						dest[i] = src[i];
-					dest += 3;
-					src += 4;
-				}
-		}
 	}
 	catch(...)
 	{