On Fri, Aug 16, 2019 at 10:40:59AM -0700, pe...@easthope.ca wrote: > From: Dan Ritter > Date: Wed, 14 Aug 2019 08:26:18 -0400 > > Set the background to transparent. >
[...] > Really I don't understand the representation used in GIMP. From what > I've read, there are three channels, R, G, B. OK. Plus an optional > 4th, alpha. What is it? There are four: RGBA -- [1] should address your other questions. The alpha channel is useful when you overlay images (like in your arrow case): you want the arrow be "on top" of your image, but you don't want the arrow's background obscuring the rest of your image. You could achieve that with a "mask" (an array of bits of your image's size with an 1 for each "relevant" pixel and a 0 for each "irrelevant" one). This is an alpha channel with one bit depth. A deeper alpha channel allows semi-transparency, where the foreground image could, for example, merge "softly" into the background. A neat effect would be to make your arrow semi-transparent: you would still see through, as if the arrow was smoked glass. Best you play with that under Gimp, then you'll "get" it quickly. Cheers [1] https://en.wikipedia.org/wiki/RGBA -- t
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