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【ObjC】异步加载图片按钮

作者:Dezai.CN / 发布于2013/8/20/ 886


	@interface UIButton (AsyncImage)
	
	//size by point
	- (void)setImageFromURL:(NSString *)urlString adjustToSize:(CGSize)size completion:(void (^)(void))completion logo:(UIImage *)logoImage;
	
	@end
	
	
	@implementation UIButton (AsyncImage)
	
	- (void)setImageFromURL:(NSString *)urlString adjustToSize:(CGSize)size completion:(void (^)(void))completion logo:(UIImage *)logoImage
	{
	 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
	 UIImage *image = nil;
	 NSURL *url = [NSURL URLWithString:urlString];
	 NSData *data = [NSData dataWithContentsOfURL:url];
	 image = [UIImage imageWithData:data];
	
	 if (image) {
	 if (!CGSizeEqualToSize(size, CGSizeZero)) {
	 image = [UIImage imageWithCGImage:image.CGImage scale:[self scaleImage:image adjustToSize:size] orientation:image.imageOrientation];
	 }
	 if (logoImage) {
	 image = [self addLogoImage:logoImage toImage:image];
	 }
	
	 dispatch_async(dispatch_get_main_queue(), ^{
	 [self setImage:image forState:UIControlStateNormal];
	 completion();
	 });
	 }
	 else {
	 NSLog(@"async load error.");
	 }
	 });
	}
	
	// 缩放图片以适应按钮大小
	- (CGFloat)scaleImage:(UIImage *)image adjustToSize:(CGSize)size
	{
	 CGFloat xScale = size.width / image.size.width;
	 CGFloat yScale = size.height / image.size.height;
	
	 return 1.0 / MIN(xScale, yScale);
	}
	
	- (UIImage *)addLogoImage:(UIImage *)logo toImage:(UIImage *)img
	{
	 //get image width and height
	 CGFloat scale = [UIScreen mainScreen].scale;
	 int w = scale * img.size.width;
	 int h = scale * img.size.height;
	 int logoWidth = logo.scale * logo.size.width;
	 int logoHeight = logo.scale * logo.size.height;
	 CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
	
	 //create a graphic context with CGBitmapContextCreate
	 CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);
	 CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);
	 CGContextDrawImage(context, CGRectMake(w - logoWidth, 0, logoWidth, logoHeight), [logo CGImage]);
	 CGImageRef imageMasked = CGBitmapContextCreateImage(context);
	 CGContextRelease(context);
	 CGColorSpaceRelease(colorSpace);
	
	 return [UIImage imageWithCGImage:imageMasked scale:scale orientation:img.imageOrientation];
	}
	
	@end

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　异步加载图片按钮　

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