Question

I’m trying to flatten some images I get from a server down to 40 x 40 thumbnails, so I can save them in /Library/Caches and use those instead with UITableViewCell’s UIImage.

So far, I know how bake / flatten an image like so:

 UIImage *newThumbnail = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:imageURL]]];

  UIGraphicsBeginImageContext(CGSizeMake(40, 40));
  [newThumbnail drawInRect:CGRectMake(0, 0, 40, 40)];
  newThumbnail = UIGraphicsGetImageFromCurrentImageContext();      
  UIGraphicsEndImageContext();

  [UIImagePNGRepresentation(newThumbnail) writeToFile:imageCachePath atomically:YES];

I’d also like to include rounded corners in the flattened image. But right now, I create the rounded corners by manipulating the layer of the UIImageView that hosts the UIIMage. Like so:

  imageView.layer.cornerRadius = 7.0;
  imageView.layer.masksToBounds = YES;
  imageView.layer.borderColor = [UIColor blackColor].CGColor;
  imageView.layer.borderWidth = 1.0;

So how do I include the above layer modifications into the whole UIGraphicsBeginImageContext mechanism? Or is there any better way of doing it?

Answer 1

Option (1), which involves more learning and more work, but is more flexible:

Take a look through the CGContextRef docs.

Figure how to draw a rounded corner path. (There’s a bunch of sample code floating around the internets using the CTM.)

To simulate cornerRadius and masksToBounds, use that path to set a clipping path before drawing your image.

To simulate the borderColor plus borderWidth, set an appropriate stroke color and width and then stroke that path.

Option (2):

Try rendering your UIImageView.layer into your context with renderInContext:.