The magazine of the Melbourne PC User Group Interesting Effects with Colour Geoffrey Heard

In graphics, I'm a "type and vector" kind of guy with pretty straight up and down requirements when it comes to raster images, Mainly I want to get photographs "right" for print or for the Web so that they best represent to viewers the reality I saw. From time to time, though, I want to distort, to manipulate. I have fiddled tentatively with posterising, colour inversion, blurring and one or two other tools, plug-ins or filters for special effects, but never with a lot of confidence. I've had some useful results though.

Then the other day, I was chatting with some friends on a graphics forum about transforming photographs into something that resembled the old comic book pictures, when they first began printing thern with a limited number of colours. Obviously, one step was to reduce the number of colours and shades in the photograph. Posterizing, which does exactly that, took us some way towards what we wanted, a lot more work eventually produced a very realistic "comic book" appearance.

But one step suggested really bowled me over switching the colour space before posterising. Being a vector guy, I would never have thought of that where my head comes from, that would make no difference.

Next thing, I was hauling out a generally undistinguished picture of an distinguished breakfast to see how different colour spaces and posterising could breathe lift into it.

The examples tell the story. Different colour space = different outcomes.

I also tried different levels of brightness in the beginning original. Ha! Some interesting variations in results again.

After I had gone through ,switching colour space from RGB to CMYK and finally LAB colour, I got really daring —what about Indexed colour, in which you specify haw many colours your work to use, then posterising so there is a two step reduction in colours?

That involved switching the colour space to Indexed, setting the number colours (I tried several figures and settled on 32 for a good effect), and switching back to RGB or Lab colour to enable posterising.

Again, the illustrations tell the story.

Surprisingly, this two, step reduction in colours resulted in a more continuous tone effect - at extreme posterisation levels because the lighter middle tones were transformed into variable dot patterns instead of being dumped to white or a solid of one of the limited range of colours/shades available.

Just like the comics!

Now what about we add some zoom blur to that dotty one? Oh! I just tried a contour trace! Very interesting!
If you haven't tried it, do it now. You'll love it! I played with my images in Canvas, but posterising, switching colour space and indexed colour all work very much the same in Photoshop and Corel Photo-Paint. In Corel, indexed colour is referred to as Palleted colour.

About the Author
Geoffrey Heard is a Melbourne writer, photographer, DTPer and publisher. http://www.worsleypress.com

Reprinted from the June 2006 issue of PC Update, the magazine of Melbourne PC User Group, Australia

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