How To Write Your Own Photoshop Filters
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Getting random
If you want to get funky, you can do some more complicated math and throw in random numbers as well. Let's take the above R example. If you change it from src(x+ctl(0),y+ctl(1),0) to src(x+(ctl(0)-rnd(1,35)),y+ctl(1),0), it will subtract a random number between 1 and 35 from the slider value of Control 0. The number will be random for each individual pixel, giving you the effect of generating noise in the red channel. Try it out by just pasting my formula into your R entry field in Filter Factory and playing around with the first slider.

Note than when you throw in additional calculations, you need to enclose them in another set of parentheses. So instead of x+ctl(0), you have x+(ctl(0)-rnd(1,35)). Not too tricky, eh, Avery?

Finishing up
So now you're ready to make your own filters for generating noise and for shuffling around channels. All you have to do now is click the "Make" button and enter in your information. Make sure you put a check mark next to each of the controls you want to use and give them names that a user will understand.

I highly recommend you download my sample filters and look at what I've done to achieve the various effects included in the pack. To load my settings, simply click the "Load" button in Filter Factory and load up the settings file for the filter you want to examine. Remember, once you create a filter, you won't be able to extract its settings for later modification, so you'll need to manually save them using the "Save" button in the Filter Factory interface. The added advantage of saving your settings is that you can load them onto a different platform and create your filter for that platform.

There's a lot more to Filter Factory than we've explored here. A whole lot more. But when you're dealing with gnomes, it's best to take it slow. In future installments, we'll look at more functions, as well as some crazy stuff called "logical operators." But you've got the basics of it now, so go to it. Next week I'll tell you how to customize your interface on the Mac just like I've customized mine. No formulas involved. That ought to make Avery happy.

Dave Nagel is the producer of Creative Mac and Digital Media Designer; host of the Creative Mac, Adobe InDesign, Adobe LiveMotion and Synthetik Studio Artist WWUGs; and executive producer of Creative Mac, Digital Media Designer, Digital Pro Sound, Digital Webcast, Plug-in Central, Presentation Master, ProAudio.net and Video Systems sites. All are part of the Digital Media Net family of online industry hubs.

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