1、获取本地图片宽高

    /**
     *  本地图片宽高的获取
     */
    UIImage *img = [UIImage imageNamed:@"test.jpg"];
    UIImageView *imgView = [[UIImageView alloc]initWithImage:img];
    imgView.frame = CGRectMake(0, 0, img.size.width, img.size.height);
    [self.view addSubview:imgView];
    NSLog(@"===%f===%f",img.size.width,img.size.width);

2、加载互联网图片

• SDWebImage下载图片,图片被缓存到本地获取本地图片的宽高。

 /**
     *  sdwebimage获取图片宽高
     */
    UIImageView * sdImgView = [UIImageView new];
    [self.view addSubview:sdImgView];
    NSURL * url = [NSURL URLWithString:@"http://appceshi.ywsoftware.com/OneCarAPI/rechargeCard/logo/C9100.jpg"];
    [sdImgView sd_setImageWithURL:url completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
        NSLog(@"%f==%f",image.size.height,image.size.width);
        sdImgView.frame = CGRectMake(0, CGRectGetMaxY(imgView.frame)+20, image.size.width, image.size.height);
    }];

• 网络框架加载:先通过文件头获取图片大小(没什么卵用)，如果获取失败，则下载完整的图片data，然后计算大小

-(CGSize)getImageSizeWithURL:(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;                  // url不正确返回CGSizeZero
    
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:URL];
    NSString* pathExtendsion = [URL.pathExtension lowercaseString];
    
    CGSize size = CGSizeZero;
    if([pathExtendsion isEqualToString:@"png"]){
        size =  [self getPNGImageSizeWithRequest:request];
    }
    else if([pathExtendsion isEqual:@"gif"])
    {
        size =  [self getGIFImageSizeWithRequest:request];
    }
    else{
        size = [self getJPGImageSizeWithRequest:request];
    }
    if(CGSizeEqualToSize(CGSizeZero, size))                    // 如果获取文件头信息失败,发送异步请求请求原图
    {
        
        NSData* data = [NSURLConnection sendSynchronousRequest:[NSURLRequest requestWithURL:URL] returningResponse:nil error:nil];

        UIImage* image = [UIImage imageWithData:data];
        if(image)
        {
            size = image.size;
        }
    }
    return size;
}
//  获取PNG图片的大小
-(CGSize)getPNGImageSizeWithRequest:(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;
}
//  获取gif图片的大小
-(CGSize)getGIFImageSizeWithRequest:(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;
}
//  获取jpg图片的大小
-(CGSize)getJPGImageSizeWithRequest:(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;
        }
    }
}