使用PHAsset来获取图像以及视频文件的大小

对于图片资源

[[PHImageManager defaultManager]
 requestImageDataForAsset:asset 
 options:nil 
 resultHandler:^(NSData *imageData, NSString *dataUTI, UIImageOrientation orientation, NSDictionary *info) { 
   float imageSize = imageData.length; //convert to Megabytes
   imageSize = imageSize/(1024*1024.0); 
   NSLog(@"%f",imageSize); 
}];

对于视频资源

PHVideoRequestOptions *options = [[PHVideoRequestOptions alloc] init];
options.version = PHVideoRequestOptionsVersionOriginal;
[[PHImageManager defaultManager]
 requestAVAssetForVideo:asset 
 options:options 
 resultHandler:^(AVAsset *asset, AVAudioMix *audioMix, NSDictionary *info) { 
   if ([asset isKindOfClass:[AVURLAsset class]]) {
   AVURLAsset* urlAsset = (AVURLAsset*)asset;
   NSNumber *size; 
   [urlAsset.URL getResourceValue:&size forKey:NSURLFileSizeKey error:nil]; 
   NSLog(@"size is %f",[size floatValue]/(1024.0*1024.0)); //size is 43.703005 
}}];