Determine the perceived bightness of RGBA colors

Asked Nov 22 '20 at 14:53

Active Nov 22 '20 at 14:53

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I was looking for an algorithm to calculate the perceived brightness of colors (I was using the naïve simple mean). I found interesting answers here, but I ran into a problem: I'm dealing with RGBA colors. When A = 255, it's equivalent to RGB and that thread works perfectly. However, if we consider RGBA(255, 255, 255, 0), those formulas give me maximum brightness, but not even there's a color.

I would be thankful if anyone can point me any theory that I could rely to do this.

asked Nov 22 '20 at 14:53

Héliton Martins

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You should convert RGBA into RGB. Because we do not know the background image, we cannot answer you. But when yo merge background and your image, you get RGB, and so you already know the answer. – Giacomo Catenazzi Nov 22 '20 at 16:27
It makes sense. So to merge the background and the image, I can just get the weighted mean of each channel (alpha channel being the weight)? – Héliton Martins Nov 22 '20 at 17:50
https://stackoverflow.com/questions/11447830/simulate-color-transparency – Giacomo Catenazzi Nov 22 '20 at 19:49
Great. Thank you! – Héliton Martins Nov 22 '20 at 19:51

Determine the perceived bightness of RGBA colors

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