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Calculate lighter/darker RGB colors in Python

4 points by coderdude 15y ago

coderdude 15y ago
I'm using this to calculate colors for a button pack I'm working on. This guy's blog is really cool and it doesn't look like a lot of people know about it yet. Every entry is a neat snippet. Mostly related to web development.
gcr 15y ago
Is that the right way of doing it though? Often it's more useful to make colors a certain factor brighter or darker, not a certain offset brighter, like this: def adjust_color_darken(r,g,b, factor): return [ r*factor, g*factor, b*factor ] def adjust_color_lighten(r,g,b, factor): return [ 255 - (255-r)*(1-factor), 255 - (255-g)*(1-factor), 255 - (255-b)*(1-factor) ] The original snippet also doesn't work for colors whose values are less than 16. def hex_to_rgb(hex): return [(hex_color[x:x+2],16) for x in [1, 3, 5]] def rgb_to_hex(r,g,b): return "#%02x%02x%02x" % (r,g,b) A more "correct" solution might be to convert the RGB colors to HSV or some other color space, adjust the brightness, and convert back to RGB.
- coderdude 15y ago
  Wow, thanks for that. Good to know that there's a better way to go about this. I did have to fix the bug with values < 16, but my solution was just to slap a zfill on it.
- eurleif 15y ago
  I think HSL would probably be a better choice than HSV. Python has HSL support built in, so you can do that pretty easily: from colorsys import rgb_to_hls, hls_to_rgb def adjust_color_lightness(r, g, b, factor): h, l, s = rgb_to_hls(r / 255.0, g / 255.0, b / 255.0) l = max(min(l * factor, 1.0), 0.0) r, g, b = hls_to_rgb(h, l, s) return int(r * 255), int(g * 255), int(b * 255) def lighten_color(r, g, b, factor=0.1): return adjust_color_lightness(r, g, b, 1 + factor) def darken_color(r, g, b, factor=0.1): return adjust_color_lightness(r, g, b, 1 - factor) Though, I'm not sure if doing it by multiplying is correct. I don't like that lighten_color(*darken_color(r, g, b)) != (r, g, b)
- deleted 15y ago
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4 points by coderdude 15y ago

I'm using this to calculate colors for a button pack I'm working on. This guy's blog is really cool and it doesn't look like a lot of people know about it yet. Every entry is a neat snippet. Mostly related to web development.

gcr 15y ago

Is that the right way of doing it though? Often it's more useful to make colors a certain factor brighter or darker, not a certain offset brighter, like this: def adjust_color_darken(r,g,b, factor): return [ r*factor, g*factor, b*factor ] def adjust_color_lighten(r,g,b, factor): return [ 255 - (255-r)*(1-factor), 255 - (255-g)*(1-factor), 255 - (255-b)*(1-factor) ] The original snippet also doesn't work for colors whose values are less than 16. def hex_to_rgb(hex): return [(hex_color[x:x+2],16) for x in [1, 3, 5]] def rgb_to_hex(r,g,b): return "#%02x%02x%02x" % (r,g,b) A more "correct" solution might be to convert the RGB colors to HSV or some other color space, adjust the brightness, and convert back to RGB.

coderdude 15y ago
Wow, thanks for that. Good to know that there's a better way to go about this. I did have to fix the bug with values < 16, but my solution was just to slap a zfill on it.
eurleif 15y ago
I think HSL would probably be a better choice than HSV. Python has HSL support built in, so you can do that pretty easily: from colorsys import rgb_to_hls, hls_to_rgb def adjust_color_lightness(r, g, b, factor): h, l, s = rgb_to_hls(r / 255.0, g / 255.0, b / 255.0) l = max(min(l * factor, 1.0), 0.0) r, g, b = hls_to_rgb(h, l, s) return int(r * 255), int(g * 255), int(b * 255) def lighten_color(r, g, b, factor=0.1): return adjust_color_lightness(r, g, b, 1 + factor) def darken_color(r, g, b, factor=0.1): return adjust_color_lightness(r, g, b, 1 - factor) Though, I'm not sure if doing it by multiplying is correct. I don't like that lighten_color(*darken_color(r, g, b)) != (r, g, b)
deleted 15y ago
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