Intrinsic size

gistfile1.txt

@property (assign, nonatomic) CGSize preferredMaxSize;

- (CGSize)intrinsicContentSize {
  CGSize imageSize = self.image.size;
  CGSize maxSize = self.preferredMaxSize;
        
  if (imageSize.height > maxSize.height) {
    imageSize.width *= maxSize.height / imageSize.height;
    imageSize.height = maxSize.height;
  }
  if (imageSize.width > maxSize.width) {
    imageSize.height *= maxSize.width / imageSize.width;
    imageSize.width = maxSize.width;
  }
  return imageSize;
}

- (void)setImage:(UIImage *)aImage {
  [super setImage:aImage];
  [self invalidateIntrinsicContentSize];
}

- (void)setPreferredMaxSize:(CGSize)size {
  _preferredMaxSize = size;
  [self invalidateIntrinsicContentSize];
}