109 lines
2.4 KiB
C++
109 lines
2.4 KiB
C++
#pragma once
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#include <cmath>
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// https://stackoverflow.com/a/6930407
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template <typename S, typename T> S rgb_to_hsv(const T& in)
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{
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S out;
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float min, max, delta;
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min = in[0] < in[1] ? in[0] : in[1];
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min = min < in[2] ? min : in[2];
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max = in[0] > in[1] ? in[0] : in[1];
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max = max > in[2] ? max : in[2];
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out[2] = max; // v
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delta = max - min;
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if(delta < 0.000001f)
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{
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out[1] = 0;
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out[0] = 0; // undefined, maybe nan?
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return out;
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}
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if(max > 0.0f) { // NOTE: if Max is == 0, this divide would cause a crash
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out[1] = (delta / max); // s
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} else {
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// if max is 0, then r = g = b = 0
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// s = 0, h is undefined
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out[1] = 0.0f;
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out[0] = NAN; // its now undefined
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return out;
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}
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if(in[0] >= max) // > is bogus, just keeps compiler happy
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out[0] = (in[1] - in[2]) / delta; // between yellow & magenta
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else {
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if(in[1] >= max)
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out[0] = 2.0 + ( in[2] - in[0] ) / delta; // between cyan & yellow
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else
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out[0] = 4.0 + ( in[0] - in[1] ) / delta; // between magenta & cyan
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}
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out[0] *= 60.0f; // degrees
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if(out[0] < 0.0f)
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out[0] += 360.0f;
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return out;
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}
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template <typename S, typename T> S hsv_to_rgb(const T& in)
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{
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float hh, p, q, t, ff;
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long i;
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S out;
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if(in[1] <= 0.0f) { // < is bogus, just shuts up warning
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out[0] = in[2];
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out[1] = in[2];
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out[2] = in[2];
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return out;
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}
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hh = in[0];
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if(hh >= 360.0f)
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hh = 0.0f;
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hh /= 60.0f;
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i = (long)hh;
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ff = hh - i;
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p = in[2] * (1.0f - in[1]);
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q = in[2] * (1.0f - (in[1] * ff));
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t = in[2] * (1.0f - (in[1] * (1.0f - ff)));
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switch(i) {
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case 0:
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out[0] = in[2];
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out[1] = t;
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out[2] = p;
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break;
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case 1:
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out[0] = q;
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out[1] = in[2];
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out[2] = p;
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break;
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case 2:
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out[0] = p;
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out[1] = in[2];
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out[2] = t;
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break;
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case 3:
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out[0] = p;
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out[1] = q;
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out[2] = in[2];
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break;
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case 4:
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out[0] = t;
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out[1] = p;
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out[2] = in[2];
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break;
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case 5:
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default:
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out[0] = in[2];
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out[1] = p;
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out[2] = q;
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break;
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}
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return out;
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}
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