UIImage with rounded corners

UIImage+RoundedCorners.m

// This could be done using CALayer cornerRadius property
// This is an example of how would be done without that :-)

@interface UIImage (RoundedCorners)

- (UIImage *)roundedImageWithCornerRadius:(CGFloat)cornerRadius;

@end

@implementation UIImage (RoundedCorners)

- (UIImage *)roundedImageWithCornerRadius:(CGFloat)cornerRadius
{
  // Negative radius means no rounded borders
  if (cornerRadius <= 0) {
    return self;
  }

  // Make sure the rounded corner fits in the image
  const CGFloat maxCornerSize = MIN(self.size.width, self.size.height) * 0.5;
  cornerRadius *= self.scale;
  if (cornerRadius > maxCornerSize) {
    cornerRadius = maxCornerSize;
  }

  // Get the closest posible alpha info for our context
  CGImageRef image = self.CGImage;
  const CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(image);
  CGImageAlphaInfo alphaInfo = (bitmapInfo & kCGBitmapAlphaInfoMask);
  switch (alphaInfo) {
    case kCGImageAlphaNone:
    case kCGImageAlphaNoneSkipFirst: alphaInfo = kCGImageAlphaPremultipliedFirst; break;
    case kCGImageAlphaNoneSkipLast: alphaInfo = kCGImageAlphaPremultipliedLast; break;
    default: break;
  }

  // Make a transparent (with Alpha) context that resembles the most to original image.
  const CGFloat h = self.size.height * self.scale;
  const CGFloat w = self.size.width * self.scale;
  CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
  CGContextRef context = CGBitmapContextCreate(NULL, w, h,
                                               CGImageGetBitsPerComponent(image),
                                               CGImageGetBitsPerComponent(image) * 4 * w,
                                               colorSpace,
                                               (bitmapInfo & ~kCGBitmapAlphaInfoMask) | alphaInfo);
  CGColorSpaceRelease(colorSpace);

  // Create a clipping path with rounded corners
  const CGFloat r = cornerRadius;
  CGContextBeginPath(context);
  CGContextMoveToPoint(context, 0, r);
  CGContextAddArcToPoint(context, 0, h, r, h, r);
  CGContextAddArcToPoint(context, w, h, w, h-r, r);
  CGContextAddArcToPoint(context, w, 0, w-r, 0, r);
  CGContextAddArcToPoint(context, 0, 0, 0, r, r);
  CGContextClosePath(context);
  CGContextClip(context);

  // Draw the image to the context; everything outside the clipping path will become transparent
  CGContextDrawImage(context, CGRectMake(0, 0, w, h), image);

  // Create a CGImage from the context and an UIImage from it.
  CGImageRef clippedImage = CGBitmapContextCreateImage(context);
  CGContextRelease(context);
  UIImage *roundedImage = [UIImage imageWithCGImage:clippedImage];
  CGImageRelease(clippedImage);
  return roundedImage;
}

@end