不加载完整图片就获取图片属性

引用：

#import <ImageIO/ImageIO.h>

代码：

NSString* path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"back-btn.png"];

NSURL* imageFileURL = [NSURL fileURLWithPath:path];

CGImageSourceRef imageSource = CGImageSourceCreateWithURL((__bridge CFURLRef)imageFileURL, NULL);

if(imageSource) {

   NSDictionary* options = @{(NSString*)kCGImageSourceShouldCache:@NO};

   CFDictionaryRef imageProperties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, (__bridge CFDictionaryRef)options);

   if(imageProperties) {

      NSLog( @"properties: %@", imageProperties);

      CFRelease(imageProperties);

   }

} else{

   NSLog(@" Error loading image");

}