Memory issue in using UIImagePNGRepresentation

I found this module to be troublesome. I import more than 100 images from Photolibrary, save them in documents directory with a different name. As expected I had a memory issue in the unusual place. It seems UIImagePNGRepresenation is caching files. So when I run the below process for 300+ images, I see "Overall bytes" in the range of 3.00 GB and crashes due to Memory (tested in allocations tool). I have pasted the code below. Is there any alternative for this code

-(void)something
{
   NSData *data=nil;
   for (int i=0; i<numberOfImages; i++) {
    
    @autoreleasepool {
        
        UIImage *image=[UIImage imageNamed:[NSString stringWithFormat:@"image%d.png",i]];
        NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
        
        NSString *documentsDirectory = [[paths objectAtIndex:0] stringByAppendingString:@"directoryname"];
        
        NSString *fullPath = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"image%d.png",i]];
        
        //convert image into .png format
        data=UIImagePNGRepresentation(image);
        [data writeToURL:[NSURL URLWithString:fullPath] atomically:NO];
      }
   }
   data=nil;
}

I mailed this issue to Apple and they asked me to introduce sleep cycles between every allocation. Add sleep before allocation.