103 lines
2.4 KiB
C++
103 lines
2.4 KiB
C++
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#include "color.h"
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// taken from
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// https://stackoverflow.com/questions/3018313/algorithm-to-convert-rgb-to-hsv-and-hsv-to-rgb-in-range-0-255-for-both
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hsv_t rgb2hsv(color_t in) {
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hsv_t out;
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double min, max, delta;
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min = in.red < in.green ? in.red : in.green;
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min = min < in.blue ? min : in.blue;
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max = in.red > in.green ? in.red : in.green;
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max = max > in.blue ? max : in.blue;
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out.val = max; // v
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delta = max - min;
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if (delta < 0.00001) {
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out.sat = 0;
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out.hue = 0; // undefined, maybe nan?
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return out;
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}
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if (max > 0.0) { // NOTE: if Max is == 0, this divide would cause a crash
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out.sat = (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.sat = 0.0;
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out.hue = NAN; // its now undefined
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return out;
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}
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if (in.red >= max) // > is bogus, just keeps compilor happy
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out.hue = (in.green - in.blue) / delta; // between yellow & magenta
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else if (in.green >= max)
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out.hue = 2.0 + (in.blue - in.red) / delta; // between cyan & yellow
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else
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out.hue = 4.0 + (in.red - in.green) / delta; // between magenta & cyan
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out.hue *= 60.0; // degrees
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if (out.hue < 0.0)
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out.hue += 360.0;
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return out;
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}
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color_t hsv2rgb(hsv_t in) {
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double hh, p, q, t, ff;
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long i;
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color_t out;
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if (in.sat <= 0.0) { // < is bogus, just shuts up warnings
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out.red = in.val;
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out.green = in.val;
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out.blue = in.val;
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return out;
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}
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hh = in.hue;
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if (hh >= 360.0)
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hh = 0.0;
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hh /= 60.0;
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i = (long) hh;
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ff = hh - i;
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p = in.val * (1.0 - in.sat);
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q = in.val * (1.0 - (in.sat * ff));
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t = in.val * (1.0 - (in.sat * (1.0 - ff)));
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switch (i) {
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case 0:
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out.red = in.val;
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out.green = t;
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out.blue = p;
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break;
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case 1:
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out.red = q;
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out.green = in.val;
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out.blue = p;
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break;
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case 2:
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out.red = p;
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out.green = in.val;
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out.blue = t;
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break;
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case 3:
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out.red = p;
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out.green = q;
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out.blue = in.val;
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break;
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case 4:
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out.red = t;
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out.green = p;
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out.blue = in.val;
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break;
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case 5:
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default:
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out.red = in.val;
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out.green = p;
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out.blue = q;
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break;
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}
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return out;
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}
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