利用ImageIo读取图片的元数据

- ( void)readXMPForImageWithURL:( NSURL *)url 

{ 

  CGImageSourceRef imageSourceRef = CGImageSourceCreateWithURL((__bridge CFURLRef)url, NULL);                  CGImageMetadataRef metadataRef = CGImageSourceCopyMetadataAtIndex(imageSourceRef, 0, NULL);

  if ( NULL == metadataRef) { return; } 

  NSLog( @"metadata = \n%@", metadataRef);

 }

- ( void)readXMPForImageWithData:( NSData  *)data

{ 

    CGImageSourceRef imageSourceRef =  CGImageSourceCreateWithData (( __bridge CFDataRef )data, NULL ) ;       

   CGImageMetadataRef  metadataRef =  CGImageSourceCopyMetadataAtIndex (imageSourceRef,  0 ,  NULL );

    if ( NULL == metadataRef) {   return; } 

    NSLog( @"metadata = \n%@", metadataRef);

 }