iOS根据图片url获取尺寸

可以在UIImage的分类中加入下面的代码,并且引入系统的ImageIO.framework

/**
 根据图片的url获取尺寸

 @param URL url
 @return CGSize
 */
+ (CGSize)getImageSizeWithURL:(id)URL;

/**
 *  根据图片url获取图片尺寸
 */
+ (CGSize)getImageSizeWithURL:(id)URL{
    NSURL * url = nil;
    if ([URL isKindOfClass:[NSURL class]]) {
        url = URL;
    }
    if ([URL isKindOfClass:[NSString class]]) {
        url = [NSURL URLWithString:URL];
    }
    if (!URL) {
        return CGSizeZero;
    }
    CGImageSourceRef imageSourceRef =     CGImageSourceCreateWithURL((CFURLRef)url, NULL);
    CGFloat width = 0, height = 0;
    if (imageSourceRef) {
        CFDictionaryRef imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSourceRef, 0, NULL);
        if (imageProperties != NULL) {
            CFNumberRef widthNumberRef = CFDictionaryGetValue(imageProperties, kCGImagePropertyPixelWidth);
            
//            if (widthNumberRef != NULL) {
//                CFNumberGetValue(widthNumberRef, kCFNumberFloat64Type, &width);
//            }
//            CFNumberRef heightNumberRef = CFDictionaryGetValue(imageProperties, kCGImagePropertyPixelHeight);
//            if (heightNumberRef != NULL) {
//                CFNumberGetValue(heightNumberRef, kCFNumberFloat64Type, &height);
//            }
            //判断设备是否为64位
#if defined(__LP64__) && __LP64__
            if (widthNumberRef != NULL) {
                CFNumberGetValue(widthNumberRef, kCFNumberFloat64Type, &width);
            }
            CFNumberRef heightNumberRef = CFDictionaryGetValue(imageProperties, kCGImagePropertyPixelHeight);
            if (heightNumberRef != NULL) {
                CFNumberGetValue(heightNumberRef, kCFNumberFloat64Type, &height);
            }
#else
            if (widthNumberRef != NULL) {
                CFNumberGetValue(widthNumberRef, kCFNumberFloat32Type, &width);
            }
            CFNumberRef heightNumberRef = CFDictionaryGetValue(imageProperties, kCGImagePropertyPixelHeight);
            if (heightNumberRef != NULL) {
                CFNumberGetValue(heightNumberRef, kCFNumberFloat32Type, &height);
            }
#endif
            
            CFRelease(imageProperties);
        }
        CFRelease(imageSourceRef);
    }
    return CGSizeMake(width, height);
}

实践证明,网上的另外一种方法是不可行存在问题的,贴上所示的图片url:http://xs3.op.xywy.com/club.xywy.com/doc/20181017/0fd2a51f9435a4.jpg

// 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;
        }
    }
}

源自:https://www.jianshu.com/p/9984c37f3f54