iOS 獲取網絡圖片尺寸的處理方式

之前有個需求是根據用戶上傳的圖片鏈接按顯示比例鋪滿排版
常見的處理方式是解析圖片的header信息內容格式(png、jpg、gif等)來獲取圖片尺寸(網上很多就不列舉了) 但有問題是不夠準確 經常會計算錯誤 導致排版異常 下面這種方式可以準確的獲取圖片的寬高尺寸

/**
 *  根據圖片url獲取圖片尺寸
 */
+ (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 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);
}