gistfile1.txt

- (UIImage *)optimizedWaveformMask;
{
    if (optimizedWaveformMask) return optimizedWaveformMask;
    
    UIImage *originalWaveformImage = track.waveformImage;
    if (!originalWaveformImage) return nil;
    
    CGRect maskRect = CGRectZero, imageRect = CGRectZero;
    maskRect.size = CGSizeMake(CGRectGetWidth(self.bounds) * [self contentScaleFactor],
                               CGRectGetHeight(self.bounds) * [self contentScaleFactor]);
    imageRect = maskRect;
    
    if (halfWaveform) {
        if (self.isFliped == NO) {
            imageRect.origin.y -= imageRect.size.height;
        }
        imageRect.size.height *= 2;
    }
    UIGraphicsBeginImageContext(maskRect.size);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    [originalWaveformImage drawInRect:imageRect];
    
    CGContextSetBlendMode(ctx, kCGBlendModeXOR);
    CGContextSetFillColorWithColor(ctx,[UIColor blackColor].CGColor);
    CGContextFillRect(ctx, maskRect);
    
    optimizedWaveformMask = [UIGraphicsGetImageFromCurrentImageContext() retain];
    UIGraphicsEndImageContext();
    return optimizedWaveformMask;
}