55 lines
1.1 KiB
Lua
55 lines
1.1 KiB
Lua
--- Convert RGB colour to HSL (hue/saturation/luminance)
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-- The output image will have H instead of R,
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-- S instead of G and L instead of B.
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function render_frame(f, t)
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local w, h = f.width, f.height
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for y = 0, h-1 do
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for x = 0, w-1 do
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local r, g, b = f(x, y)
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local h, s, l = RGB2HSL(r, g, b)
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f[y*w+x] = {h, s, l}
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end
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end
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end
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function clip_colorval(v)
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if v < 0 then
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return 0
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elseif v > 255 then
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return 255
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else
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return math.floor(v)
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end
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end
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function RGB2HSL(R, G, B)
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local r, g, b = R/255, G/255, B/255
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local h, s, l
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local minrgb, maxrgb = math.min(r, math.min(g, b)), math.max(r, math.max(g, b))
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l = (minrgb + maxrgb) / 2
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if minrgb == maxrgb then
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h, s = 0, 0
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else
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if l < 0.5 then
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s = (maxrgb - minrgb) / (maxrgb + minrgb)
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else
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s = (maxrgb - minrgb) / (2 - maxrgb - minrgb)
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end
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if r == maxrgb then
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h = (g - b) / (maxrgb - minrgb) + 0
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elseif g == maxrgb then
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h = (b - r) / (maxrgb - minrgb) + 2
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else
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h = (r - g) / (maxrgb - minrgb) + 4
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end
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end
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if h < 0 then h = h + 6 end
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if h >= 6 then h = h - 6 end
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return clip_colorval(h*255/6), clip_colorval(s*255), clip_colorval(l*255)
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end
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