Whats a mask / alpha channel / transparency channel?
These terms all refer to some additional icon data that represents how opaque each pixel in the icon should be. For each pixel in the icon, if the corresponding pixel in the alpha channel is black then the pixel will be completely transparent (so won’t be shown at all), white means it will be shown exactly as-is (completely opaque) and levels of gray in between represent varying levels of transparency (so a mid gray will give half of the icon value and half of whatever was underneath the icon). Several image formats can store alpha information (see How do I make icons for use in GDesk above); alternatively you can save the icon alpha channel as a seperate image and load it using Set Mask. For example, to round the corners of a square icon create a white alpha channel or image and then set the corners black in the pattern required. In addition if you set some of the edge pixels to be mid-gray then you’ll get a slight blurring (known as anti-aliasing) which can substantially improve the
