Alpha value of one means that colour is entirely opaque. While first three define what colour you are actually going to get (see Wikipedia if you need more information on this), alpha channel defines how non-transparent (opaque) your colour is going to be. If you don't know how transparency works at all, here's a short explanation:Įvery pixel of your images used in GameMaker is composed from 4 components - red, green, blue, and alpha. But, since the introduction of 32-bit images (and thus actual transparency) in GameMaker 8.0, you can no longer call transparency a colour. Since earlier versions of GameMaker used 24-bit bitmaps, one of image colours could have been sacrificed to indicate transparency, and it might have looked like a separate colour as such. If you have been using GameMaker since version 7 or lower, you may remember those times when you had different colors in image, such as red, green, blue, and transparency: The source of this unasked pixel issue is not actually even GameMaker' fault - it's in the pixels. This article goes a bit in-depth about why these occur and how to fix them. These normally look like the left part of above image, being either random black/white dots or a whole semi-transparent outline around the image. If you've ever tried to scale imagery (sprites / backgrounds) up while having texture (/pixel) interpolation turned on, you might have encountered some drawing artifacts. With the glitch (left) and without (right)