UITableViewCell with UIImage scaling performance

The UITableViewCell has UIImage to be displayed within it.

Images are obtained from the server, and stored in NSDictionary as NSData.

This image is resized for non-retina devices using UIImageGraphicsBeginImageContext as listed below.

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {

static NSString *cellID=@”Cell”;
UITableViewCell *cell=[tableView dequeueReusableCellWithIdentifier:cellID];
NSDictionary *myDictionary=[self.tableObject objectAtIndex:indexPath.row];
NSData *imgData=[myDictionary objectForKey:@"icon"];
UIImage *img=[UIImage imageWithData:imgData];
if(isRetina]){
cell.iconImageView.image=img;
}else{
CGRect imgRect=CGRectMake(0, 0, img.size.width/2.0, img.size.height/2.0);
UIGraphicsBeginImageContext(imgRect.size);
[img drawInRect:imgRect];
UIImage *newImg=UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
cell.iconImageView.image=newImg;
}
}

Would it be better approach and less memory intensive or should store it in the disk, and then access the image from it and assign it to cell.iconImageView.image;