color-util: split out HSV color conversion into color-util.[ch]

src/shared/color-util.c

@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <math.h>
+
+#include "color-util.h"
+#include "macro.h"
+
+void hsv_to_rgb(double h, double s, double v,
+                uint8_t* ret_r, uint8_t *ret_g, uint8_t *ret_b) {
+
+        double c, x, m, r, g, b;
+
+        assert(s >= 0 && s <= 100);
+        assert(v >= 0 && v <= 100);
+        assert(ret_r);
+        assert(ret_g);
+        assert(ret_b);
+
+        h = fmod(h, 360);
+        c = (s / 100.0) * (v / 100.0);
+        x = c * (1 - fabs(fmod(h / 60.0, 2) - 1));
+        m = (v / 100) - c;
+
+        if (h >= 0 && h < 60)
+                r = c, g = x, b = 0.0;
+        else if (h >= 60 && h < 120)
+                r = x, g = c, b = 0.0;
+        else if (h >= 120 && h < 180)
+                r = 0.0, g = c, b = x;
+        else if (h >= 180 && h < 240)
+                r = 0.0, g = x, b = c;
+        else if (h >= 240 && h < 300)
+                r = x, g = 0.0, b = c;
+        else
+                r = c, g = 0.0, b = x;
+
+        *ret_r = (uint8_t) ((r + m) * 255);
+        *ret_g = (uint8_t) ((g + m) * 255);
+        *ret_b = (uint8_t) ((b + m) * 255);
+}

src/shared/color-util.h

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <inttypes.h>
+
+void hsv_to_rgb(
+                double h, double s, double v,
+                uint8_t* ret_r, uint8_t *ret_g, uint8_t *ret_b);

src/shared/meson.build

@@ -39,6 +39,7 @@ shared_sources = files(
         'chown-recursive.c',
         'clean-ipc.c',
         'clock-util.c',
+        'color-util.c',
         'common-signal.c',
         'compare-operator.c',
         'condition.c',