How to draw a rounded NSImage

Question

I am trying to create a NSImage or NSImageCell with rounded corners inside a NSTableView. I can't get anything to work. Here is the best I have so far inside my custom NSCell:

- (void)drawInteriorWithFrame:(NSRect)frame inView:(NSView *)controlView { 
  if (thumbnailLink) {
    NSURL *url = [NSURL URLWithString:thumbnailLink];
    if (url) {
        NSRect imageFrame = [self _imageFrameForInteriorFrame:frame];
        NSImage *image = [[NSImage alloc] initWithContentsOfURL:url];
        [image setScalesWhenResized:YES];
        [image setSize:NSMakeSize(IMAGE_HEIGHT, IMAGE_WIDTH)];

        [NSGraphicsContext saveGraphicsState];
        imageFrame = NSInsetRect(imageFrame, 1, 1);
        NSBezierPath *clipPath = [NSBezierPath bezierPathWithRoundedRect:imageFrame cornerRadius:5.0];
        [clipPath setWindingRule:NSEvenOddWindingRule];
        [clipPath addClip];
        [NSGraphicsContext restoreGraphicsState];   
        [image drawInRect:imageFrame fromRect:NSMakeRect(0, 0, 0, 0) operation:NSCompositeSourceIn fraction:1.0];
        [image release];
    }
}
...

Any ideas on how to this?

Answer 1

You need to keep the clip set when drawing your image, and restore the context after instead. Also I don't think you want to be using "in" compositing but rather "over" if you just want to draw your image normally without taking the destination opacity in consideration. Try something like:

[NSGraphicsContext saveGraphicsState];

NSBezierPath *path = [NSBezierPath bezierPathWithRoundedRect:imageFrame
                                                     xRadius:5
                                                     yRadius:5];
[path addClip];

[image drawInRect:imageFrame
         fromRect:NSZeroRect
        operation:NSCompositeSourceOver
         fraction:1.0];

[NSGraphicsContext restoreGraphicsState];

Answer 2

+ (NSImage*)roundCorners:(NSImage *)image
{

NSImage *existingImage = image;
NSSize existingSize = [existingImage size];
NSSize newSize = NSMakeSize(existingSize.width, existingSize.height);
NSImage *composedImage = [[[NSImage alloc] initWithSize:newSize] autorelease];

[composedImage lockFocus];
[[NSGraphicsContext currentContext] setImageInterpolation:NSImageInterpolationHigh];

NSRect imageFrame = NSRectFromCGRect(CGRectMake(0, 0, 1024, 1024));
NSBezierPath *clipPath = [NSBezierPath bezierPathWithRoundedRect:imageFrame xRadius:200 yRadius:200];
[clipPath setWindingRule:NSEvenOddWindingRule];
[clipPath addClip];

[image drawAtPoint:NSZeroPoint fromRect:NSMakeRect(0, 0, newSize.width, newSize.height) operation:NSCompositeSourceOver fraction:1];

[composedImage unlockFocus];

return composedImage;
}