From d30c2ae2095fdb6826d7c25351e2be0e25ef1940 Mon Sep 17 00:00:00 2001
From: Matej Bukovinski <matej@bukovinski.com>
Date: Fri, 16 Nov 2012 14:17:25 +0100
Subject: [PATCH] Improved background image decoding performance.

Tests on large images indicate an up to 4x improvement with regard to the time spent in decodedImageWithImage:.
---
 SDWebImage/SDWebImageDecoder.m | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/SDWebImage/SDWebImageDecoder.m b/SDWebImage/SDWebImageDecoder.m
index 20eaff10..318683e7 100644
--- a/SDWebImage/SDWebImageDecoder.m
+++ b/SDWebImage/SDWebImageDecoder.m
@@ -13,18 +13,26 @@
 @implementation UIImage (ForceDecode)
 
 + (UIImage *)decodedImageWithImage:(UIImage *)image
-{
-    CGImageAlphaInfo alphaInfo = CGImageGetAlphaInfo(image.CGImage);
-    BOOL imageHasAlphaInfo = (alphaInfo != kCGImageAlphaNone &&
-                              alphaInfo != kCGImageAlphaNoneSkipFirst &&
-                              alphaInfo != kCGImageAlphaNoneSkipLast);
-
-    UIGraphicsBeginImageContextWithOptions(image.size, !imageHasAlphaInfo, 0);
-    CGRect rect = (CGRect){.origin = CGPointZero, .size = image.size};
-    [image drawInRect:rect];
-    UIImage *decompressedImage = UIGraphicsGetImageFromCurrentImageContext();
-    UIGraphicsEndImageContext();
-
+{	
+    CGImageRef imageRef = image.CGImage;
+    CGSize imageSize = CGSizeMake(CGImageGetWidth(imageRef), CGImageGetHeight(imageRef));
+    CGRect imageRect = (CGRect){.origin = CGPointZero, .size = imageSize};
+	
+    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
+    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
+    CGContextRef context;
+    context = CGBitmapContextCreate(NULL, imageSize.width, imageSize.height, 8, imageSize.width * 4, colorSpace, bitmapInfo);
+    CGColorSpaceRelease(colorSpace);
+    
+    if (!context) return nil;
+	
+    CGContextDrawImage(context, imageRect, imageRef);
+    CGImageRef decompressedImageRef = CGBitmapContextCreateImage(context);
+	
+    CGContextRelease(context);
+	
+    UIImage *decompressedImage = [UIImage imageWithCGImage:decompressedImageRef];
+    CGImageRelease(decompressedImageRef);
     return decompressedImage;
 }