Interpretation of greyscale PNGs inconsistent with browser's rendering

Interestingly, SmartSprites (and e.g. Photoshop) render greyscale PNGs differently than browsers, which can cause the images to look faded inside the sprite. While I'm not sure which interpretation is "right", it would be food for SmartSprites to use rendering consistent with the browsers' interpretation, if possible.

For the time being, the workaround is to use full RGB PNGs as input for SmartSprites.