maskstuff.m

- (CGImageRef) newMaskFromImage: (UIImage *) image {
    // Prior to 10.2 SDK / Xcode 8 (dunno which it is), the mask creation worked
    // for all of the bucket overflow images.  It failed afterwards. Dunno if the
    // pngcrushing changed the color space unexpectedly, or what. But trying one and
    // then falling back to the other seems to work ok now.

    CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB ();
    
    CGImageRef maskRef = CGImageCreateCopyWithColorSpace (image.CGImage, cs);
    
    if (maskRef == NULL) {
        CGColorSpaceRef grayCs = CGColorSpaceCreateDeviceGray ();
        maskRef = CGImageCreateCopyWithColorSpace (image.CGImage, grayCs);
        if (maskRef == NULL) {
            NSLog(@"Could not create overflow mask with either rgb or gray color space");
        }
    }
    
    CGImageRef mask2 = CGImageMaskCreate (CGImageGetWidth (maskRef),
                                          CGImageGetHeight (maskRef),
                                          CGImageGetBitsPerComponent (maskRef),
                                          CGImageGetBitsPerPixel (maskRef),
                                          CGImageGetBytesPerRow (maskRef),
                                          CGImageGetDataProvider (maskRef),
                                          NULL, NO);
    CGColorSpaceRelease (cs);
    CGImageRelease (maskRef);

    return mask2;
    
} // newMaskFromImage



- (void) fillMask: (CGImageRef) mask  withColor: (UIColor *) color 
         atOffset: (CGPoint) offset {
    
    if (color == nil) color = [UIColor purpleColor];

    CGContextRef context = UIGraphicsGetCurrentContext ();

    CGContextSaveGState (context); {
        CGContextTranslateCTM (context, offset.x, offset.y);
        CGRect rect = { {0.0, 0.0}, { CGImageGetWidth(mask), CGImageGetHeight(mask) } };

        CGContextClipToMask (context, rect, mask);

        [color set];
        UIRectFill (rect);

    } CGContextRestoreGState (context);

} // fillMask