检测SDWebImage有没有缓存图片 IOS 获取网络图片大小

判断图片是否缓存
NSURL *url = [NSURL URLWithString:[model.content objectForKey:@"image"]];//请求网络地址数据的同步方法//因为这个方法在子线程(全局队列)中执行,所以不需要考虑死线程的问题SDWebImageManager *manager = [SDWebImageManager sharedManager];[manager diskImageExistsForURL:url];if ([manager diskImageExistsForURL:url]) {LOG(@"11111")self.speakImage = [[manager imageCache] imageFromDiskCacheForKey:url.absoluteString];}else{LOG(@"3333333")NSData *data = [NSData dataWithContentsOfURL:url];self.speakImage = [UIImage imageWithData:data];}

/**  
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_safeif([[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;}}
#endifNSMutableURLRequest *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];
#endifsize = 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;}}
}