dmj's Graphics Tips: Edge Emboss

dmj's graphics tips: edge emboss

Okay, here's an easy one that has some interesting uses (read: I use it often). Load up a nice image in Picture Publisher, and select Image > Effects. Scroll down to User Defined in the Distortion category. This lets you input any 3x3 convolution filter and use it. There are lots of uses for this, but PP comes up with a default filter of the following:

1.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 -1.00
This in itself isn't too bad - it's a diagonal edge detection filter which can do some interesting things on textures with gradients (apply Tone Balance when you're done - but that's another tip). But if you replace this with a slightly different kernel:

-1.00 0.00 0.00 0.00 1.00 0.00 0.00 0.00 1.00
Now you've got yourself what I call "Edge Emboss". It lights up transitions in brightness, while leaving the original image mostly intact. PP's Emboss effect greys out the image, and its Engrave effect always shadows in black (not too useful). I've also got milder and stronger versions of the Edge Emboss kernel:

-0.50 0.00 0.00 -1.00 -0.50 0.00 0.00 1.00 0.00 -0.50 1.00 0.50 0.00 0.50 1.00 0.00 0.50 1.00
If you enter these yourself, remember to save them before applying the effect - Picture Publisher will reset the kernel to its Diagonal Edge Detect every time you open the Effects Browser. If you don't want to enter these numbers yourself, you can download them in PP's .UDF format.
Here's a sample of what this filter, by itself, can do:

Before

After

This is with the medium strength filter. You can change the lighting direction by shifting the outside values in the kernel around. I use this filter for all sorts of things... see the next tip for an example.

This filter is similar, but not identical, to the "Relief" option in KPT Convolver.

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