UIImageの合成

/*
UIImageの合成
http://iphone-dev.g.hatena.ne.jp/horigood/20090702/1246547603
*/
 
//バンドル画像からUIImageを2つ作成
UIImage *imgA = [UIImage iamgeNamed:@"hogeA"];
UIImage *imgB = [UIImage iamgeNamed:@"hogeB"];
 
int widthA = CGImageGetWidth(imgA.CGImage);
int widthB = CGImageGetWidth(imgB.CGImage);
int height = CGImageGetHeight(imgA.CGImage);
 
//CGContextを作成
int widthC = widthA + widthB;
unsigned char *bitmap = malloc(widthC * height * sizeof(unsigned char) * 4);
CGContextRef bitmapContext = CGBitmapContextCreate(bitmap,
							width,
							height,
							8,
							width * 4,
							CGColorSpaceCreateDeviceRGB(),
							kCGImageAlphaPremultipliedFirst);
 
//imgAをbitmapContextに描画
CGContextDrawImage(bitmapContext, CGRectMake(0, 0, widthA, height), imgA.CGImage);
 
//imgBをimgAの隣に描画
CGContextDrawImage(bitmapContext, CGRectMake(widthA, 0, widthB, height), imgB.CGImage);
 
 
//CGContextからCGImageを作成
CGImageRef imgRef = CGBitmapContextCreateImage (bitmapContext);
 
//CGImageからUIImageを作成
UIImage *imgC = [UIImage imageWithCGImage:imgRef];
 
//bitmapを解放（paellaさんのコメントを受けて追記）
free(bitmap);