01. October 2025
Hue shifting when you have to work in RGB
I work on the web and usually have access to CSS color, which lets you specify colors in the HSL (hue, saturation, lightness) space. That makes it easy to shift a color to make it redder by nudging the H value toward 0 or to send it closer to purple by moving it toward 360.
Recently, I needed to shift hue in GLSL, and which doesn’t have HSL. You only get the RGB (red, green, blue) color space. Fortunately, on a previous blog, I had written a post about hue shifting in RGB. I relearned how to do it from that.
So, I’m reproducing the original 2010 post here with added commentary. If you don’t want to read about how this works and just want to mess with a spectrum, here is my new tool for doing that.
Recently, I needed to shift hue in GLSL, and which doesn’t have HSL. You only get the RGB (red, green, blue) color space. Fortunately, on a previous blog, I had written a post about hue shifting in RGB. I relearned how to do it from that.
So, I’m reproducing the original 2010 post here with added commentary. If you don’t want to read about how this works and just want to mess with a spectrum, here is my new tool for doing that.