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    // 获取图片的size
            CGSize size = [UIImage imageNamed:@"20170609.png"].size;

     获取网络图片的尺寸:

     
    // 根据图片url获取图片尺寸
    +(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;
            }
        }
    }
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  • 原文地址:https://www.cnblogs.com/gongyuhonglou/p/6972274.html
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