检测SDWebImage有没有缓存图片 IOS 获取网络图片大小

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];
            }

IOS 获取网络图片大小

/**  
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;
        }
    }
}