Have you ever used someone else's render and got a thin border of "scunge" around the outside? This neat little trick easily removes that fine line of scunge from any cut-out image.
1. You will need to start with an already cut-out image (also know as a "render"). Its easy enough to make an image transparent if it has a background composed of only one colour, just grab the Magic Wand Tool (W), click anywhere on the background, then press Backspace. Here is the image I am starting with, a cut-out render from Call of Duty: United Offensive:

2. Now, this looks pretty nice huh? But look at this, when I paste it onto a black background there is some "scunge" around lower parts of the render (highlighted in red):

3. This is the magic part, go to Layer>Matting>Defringe and set it to 1 pixel as shown below and click OK:

That is all there is to it, now look at the render over a black background, no more scunge:






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