SDWebImageDecoder.m
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/*
* This file is part of the SDWebImage package.
* (c) Olivier Poitrey <rs@dailymotion.com>
*
* Created by james <https://github.com/mystcolor> on 9/28/11.
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
#import "SDWebImageDecoder.h"
@implementation UIImage (ForceDecode)
+ (UIImage *)decodedImageWithImage:(UIImage *)image {
// while downloading huge amount of images
// autorelease the bitmap context
// and all vars to help system to free memory
// when there are memory warning.
// on iOS7, do not forget to call
// [[SDImageCache sharedImageCache] clearMemory];
@autoreleasepool{
// do not decode animated images
if (image.images) { return image; }
CGImageRef imageRef = image.CGImage;
CGImageAlphaInfo alpha = CGImageGetAlphaInfo(imageRef);
BOOL anyAlpha = (alpha == kCGImageAlphaFirst ||
alpha == kCGImageAlphaLast ||
alpha == kCGImageAlphaPremultipliedFirst ||
alpha == kCGImageAlphaPremultipliedLast);
if (anyAlpha) { return image; }
// current
CGColorSpaceModel imageColorSpaceModel = CGColorSpaceGetModel(CGImageGetColorSpace(imageRef));
CGColorSpaceRef colorspaceRef = CGImageGetColorSpace(imageRef);
bool unsupportedColorSpace = (imageColorSpaceModel == 0 || imageColorSpaceModel == -1 || imageColorSpaceModel == kCGColorSpaceModelCMYK || imageColorSpaceModel == kCGColorSpaceModelIndexed);
if (unsupportedColorSpace)
colorspaceRef = CGColorSpaceCreateDeviceRGB();
size_t width = CGImageGetWidth(imageRef);
size_t height = CGImageGetHeight(imageRef);
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(NULL,
width,
height,
bitsPerComponent,
bytesPerRow,
colorspaceRef,
kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
// Draw the image into the context and retrieve the new image, which will now have an alpha layer
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGImageRef imageRefWithAlpha = CGBitmapContextCreateImage(context);
UIImage *imageWithAlpha = [UIImage imageWithCGImage:imageRefWithAlpha scale:image.scale orientation:image.imageOrientation];
if (unsupportedColorSpace)
CGColorSpaceRelease(colorspaceRef);
CGContextRelease(context);
CGImageRelease(imageRefWithAlpha);
return imageWithAlpha;
}
}
@end