How can I pad an NSImage with white pixels in Objective-C?

If what you need to do is add a white border around and image, here's some code

-(NSImage *)addBorderToImage: (NSImage *)oldImage
                        width: (CGFloat)w;
{
    NSSize      size;
    NSRect      iRect;
    NSImage     *newImage;

    size = oldImage.size;
    iRect.origin.x = w;
    iRect.origin.y = w;
    iRect.size = size;

    size.width += 2 * w;
    size.height += 2 * w;

    newImage = [[NSImage alloc] initWithSize: size];

    [newImage lockFocus];
    [[NSColor whiteColor] drawSwatchInRect: NSMakeRect( 0 , 0 , size.width, size.height)];
    [oldImage drawInRect: iRect];
    [newImage unlockFocus];

    return newImage;
}
code-block