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【ObjC】 IOS 获取网络图片大小

作者:宝清 / 发布于2014/11/17/ 2963

/**
获取网络图片的Size, 先通过文件头来获取图片大小
如果失败会下载完整的图片Data 来计算大小所以最好别放在主线程
如果你有使用SDWebImage就会先看下 SDWebImage有缓存过改图片没有
支持文件头大小的格式 png、gif、jpg http://www.cocoachina.com/bbs/read.php?tid=165823
*/
+(CGSize)downloadImageSizeWithURL:(id)imageURL;


	//讨厌警告
	-(id)diskImageDataBySearchingAllPathsForKey:(id)key{return nil;}
	+(CGSize)downloadImageSizeWithURL:(id)imageURL
	{
	 NSURL* URL = nil;
	 if([imageURL isKindOfClass:[NSURL class]]){
	 URL = imageURL;
	 }
	 if([imageURL isKindOfClass:[NSString class]]){
	 URL = [NSURL URLWithString:imageURL];
	 }
	 if(URL == nil)
	 return CGSizeZero;
	
	 NSString* absoluteString = URL.absoluteString;
	
	#ifdef dispatch_main_sync_safe
	 if([[SDImageCache sharedImageCache] diskImageExistsWithKey:absoluteString])
	 {
	 UIImage* image = [[SDImageCache sharedImageCache] imageFromMemoryCacheForKey:absoluteString];
	 if(!image)
	 {
	 NSData* data = [[SDImageCache sharedImageCache] performSelector:@selector(diskImageDataBySearchingAllPathsForKey:) withObject:URL.absoluteString];
	 image = [UIImage imageWithData:data];
	 }
	 if(!image)
	 {
	 return image.size;
	 }
	 }
	#endif
	
	 NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:URL];
	 NSString* pathExtendsion = [URL.pathExtension lowercaseString];
	
	 CGSize size = CGSizeZero;
	 if([pathExtendsion isEqualToString:@"png"]){
	 size = [self downloadPNGImageSizeWithRequest:request];
	 }
	 else if([pathExtendsion isEqual:@"gif"])
	 {
	 size = [self downloadGIFImageSizeWithRequest:request];
	 }
	 else{
	 size = [self downloadJPGImageSizeWithRequest:request];
	 }
	 if(CGSizeEqualToSize(CGSizeZero, size))
	 {
	 NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];
	 UIImage* image = [UIImage imageWithData:data];
	 if(image)
	 {
	#ifdef dispatch_main_sync_safe
	 [[SDImageCache sharedImageCache] storeImage:image recalculateFromImage:YES imageData:data forKey:URL.absoluteString toDisk:YES];
	#endif
	 size = image.size;
	 }
	 }
	 return size;
	}
	+(CGSize)downloadPNGImageSizeWithRequest:(NSMutableURLRequest*)request
	{
	 [request setValue:@"bytes=16-23" forHTTPHeaderField:@"Range"];
	 NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
	 if(data.length == 8)
	 {
	 int w1 = 0, w2 = 0, w3 = 0, w4 = 0;
	 [data getBytes:&w1; range:NSMakeRange(0, 1)];
	 [data getBytes:&w2; range:NSMakeRange(1, 1)];
	 [data getBytes:&w3; range:NSMakeRange(2, 1)];
	 [data getBytes:&w4; range:NSMakeRange(3, 1)];
	 int w = (w1 << 24) + (w2 << 16) + (w3 << 8) + w4;
	 int h1 = 0, h2 = 0, h3 = 0, h4 = 0;
	 [data getBytes:&h1; range:NSMakeRange(4, 1)];
	 [data getBytes:&h2; range:NSMakeRange(5, 1)];
	 [data getBytes:&h3; range:NSMakeRange(6, 1)];
	 [data getBytes:&h4; range:NSMakeRange(7, 1)];
	 int h = (h1 << 24) + (h2 << 16) + (h3 << 8) + h4;
	 return CGSizeMake(w, h);
	 }
	 return CGSizeZero;
	}
	+(CGSize)downloadGIFImageSizeWithRequest:(NSMutableURLRequest*)request
	{
	 [request setValue:@"bytes=6-9" forHTTPHeaderField:@"Range"];
	 NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
	 if(data.length == 4)
	 {
	 short w1 = 0, w2 = 0;
	 [data getBytes:&w1; range:NSMakeRange(0, 1)];
	 [data getBytes:&w2; range:NSMakeRange(1, 1)];
	 short w = w1 + (w2 << 8);
	 short h1 = 0, h2 = 0;
	 [data getBytes:&h1; range:NSMakeRange(2, 1)];
	 [data getBytes:&h2; range:NSMakeRange(3, 1)];
	 short h = h1 + (h2 << 8);
	 return CGSizeMake(w, h);
	 }
	 return CGSizeZero;
	}
	+(CGSize)downloadJPGImageSizeWithRequest:(NSMutableURLRequest*)request
	{
	 [request setValue:@"bytes=0-209" forHTTPHeaderField:@"Range"];
	 NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
	
	 if ([data length] <= 0x58) {
	 return CGSizeZero;
	 }
	
	 if ([data length] < 210) {// 肯定只有一个DQT字段
	 short w1 = 0, w2 = 0;
	 [data getBytes:&w1; range:NSMakeRange(0x60, 0x1)];
	 [data getBytes:&w2; range:NSMakeRange(0x61, 0x1)];
	 short w = (w1 << 8) + w2;
	 short h1 = 0, h2 = 0;
	 [data getBytes:&h1; range:NSMakeRange(0x5e, 0x1)];
	 [data getBytes:&h2; range:NSMakeRange(0x5f, 0x1)];
	 short h = (h1 << 8) + h2;
	 return CGSizeMake(w, h);
	 } else {
	 short word = 0x0;
	 [data getBytes:&word; range:NSMakeRange(0x15, 0x1)];
	 if (word == 0xdb) {
	 [data getBytes:&word; range:NSMakeRange(0x5a, 0x1)];
	 if (word == 0xdb) {// 两个DQT字段
	 short w1 = 0, w2 = 0;
	 [data getBytes:&w1; range:NSMakeRange(0xa5, 0x1)];
	 [data getBytes:&w2; range:NSMakeRange(0xa6, 0x1)];
	 short w = (w1 << 8) + w2;
	 short h1 = 0, h2 = 0;
	 [data getBytes:&h1; range:NSMakeRange(0xa3, 0x1)];
	 [data getBytes:&h2; range:NSMakeRange(0xa4, 0x1)];
	 short h = (h1 << 8) + h2;
	 return CGSizeMake(w, h);
	 } else {// 一个DQT字段
	 short w1 = 0, w2 = 0;
	 [data getBytes:&w1; range:NSMakeRange(0x60, 0x1)];
	 [data getBytes:&w2; range:NSMakeRange(0x61, 0x1)];
	 short w = (w1 << 8) + w2;
	 short h1 = 0, h2 = 0;
	 [data getBytes:&h1; range:NSMakeRange(0x5e, 0x1)];
	 [data getBytes:&h2; range:NSMakeRange(0x5f, 0x1)];
	 short h = (h1 << 8) + h2;
	 return CGSizeMake(w, h);
	 }
	 } else {
	 return CGSizeZero;
	 }
	 }
	}

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