PNG Graphics Tip

I’m starting to get into using 24-bit PNG files more and more, though I’m reluctant to use large-dimension images in this format as their file sizes tend to balloon. However, it’s hard to resist the charm of a logo that can be seamlessly matted over just about any kind of background.

One trick — which works best with mostly flat-coloured logos — that I’ve discovered is to posterise the logo with Photoshop before rendering out to a transparent PNG. Posterise discards colour information from the file — most people set the intensity level quite high, which results in a visible banding through the image. I’d take that down to about 7-9, which preserves the integrity of the image but makes the colour range more managable. I’ve seen file sizes halve without any serious image degradation.

Here’s a close-up crop of a before-and-after posterise treatment. Can you can spot a substantial difference?