feat: Farbrechnung mit CIE-Helligkeit und CW/WW-Mischung

src/light/nl_color.c

@@ -0,0 +1,73 @@
+#include "light/nl_color.h"
+
+uint16_t nl_cie_level(uint16_t bri)
+{
+    float lightness, y;
+    uint32_t v;
+
+    if (bri == 0)
+        return 0;
+    if (bri >= NL_BRI_SCALE)
+        return 65535;
+    lightness = (float)bri / 100.0f; /* 0..100 */
+    if (lightness <= 8.0f) {
+        y = lightness / 903.3f;
+    } else {
+        float t = (lightness + 16.0f) / 116.0f;
+        y = t * t * t;
+    }
+    v = (uint32_t)(y * 65535.0f + 0.5f);
+    return (uint16_t)(v == 0 ? 1 : (v > 65535 ? 65535 : v));
+}
+
+uint16_t nl_ct_cw_fraction(uint16_t ct, uint16_t ct_min, uint16_t ct_max)
+{
+    uint32_t m, mw, mc;
+
+    if (ct <= ct_min)
+        return 0;
+    if (ct >= ct_max)
+        return 65535;
+    m = 1000000u / ct;
+    mw = 1000000u / ct_min;
+    mc = 1000000u / ct_max;
+    return (uint16_t)(((mw - m) * 65535u) / (mw - mc));
+}
+
+static uint8_t to8(uint32_t lin)
+{
+    return (uint8_t)((lin * 255u + 32767u) / 65535u);
+}
+
+void nl_visual_to_channels(const nl_visual_t *v, uint16_t ct_min, uint16_t ct_max, uint8_t out[NL_CH_COUNT])
+{
+    uint32_t level = nl_cie_level(v->bri);
+
+    for (int i = 0; i < NL_CH_COUNT; i++)
+        out[i] = 0;
+    if (level == 0)
+        return;
+
+    if (v->mode == NL_MODE_COLOR) {
+        uint32_t lin[3];
+        int maxi = 0;
+        lin[0] = level * v->r / 255u;
+        lin[1] = level * v->g / 255u;
+        lin[2] = level * v->b / 255u;
+        for (int i = 0; i < 3; i++) {
+            out[NL_CH_R + i] = to8(lin[i]);
+            if (lin[i] > lin[maxi])
+                maxi = i;
+        }
+        /* keep the lowest brightness step visible */
+        if (!out[NL_CH_R] && !out[NL_CH_G] && !out[NL_CH_B] && lin[maxi] > 0)
+            out[NL_CH_R + maxi] = 1;
+    } else {
+        uint32_t cw = level * nl_ct_cw_fraction(v->ct, ct_min, ct_max) / 65535u;
+        uint32_t ww = level - cw;
+        out[NL_CH_CW] = to8(cw);
+        out[NL_CH_WW] = to8(ww);
+        if (!out[NL_CH_CW] && !out[NL_CH_WW])
+            out[cw >= ww ? NL_CH_CW : NL_CH_WW] = 1;
+    }
+}

src/light/nl_color.h

@@ -0,0 +1,19 @@
+#ifndef NL_COLOR_H
+#define NL_COLOR_H
+
+#include <stdint.h>
+
+#include "board/nl_board.h"
+#include "light/nl_light_types.h"
+
+/* Perceived brightness (0..NL_BRI_SCALE) to linear light (0..65535), CIE 1931 lightness.
+ * Every bri > 0 yields at least 1. */
+uint16_t nl_cie_level(uint16_t bri);
+
+/* Share of cold white (0..65535) for ct, linear in mired between ct_min and ct_max. */
+uint16_t nl_ct_cw_fraction(uint16_t ct, uint16_t ct_min, uint16_t ct_max);
+
+/* 8 bit channel values for the LED drivers. In white mode cw + ww equals the brightness. */
+void nl_visual_to_channels(const nl_visual_t *v, uint16_t ct_min, uint16_t ct_max, uint8_t out[NL_CH_COUNT]);
+
+#endif

src/light/nl_light_types.h

@@ -0,0 +1,29 @@
+#ifndef NL_LIGHT_TYPES_H
+#define NL_LIGHT_TYPES_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#define NL_BRI_SCALE 10000u /* visual brightness fixed point: 10000 = 100.00 % */
+
+typedef enum { NL_MODE_COLOR = 0, NL_MODE_WHITE = 1 } nl_light_mode_t;
+typedef enum { NL_POB_LAST = 0, NL_POB_ON = 1, NL_POB_OFF = 2 } nl_pob_t;
+
+/* Light state as seen by the API (brightness in percent). */
+typedef struct {
+    bool            on;
+    uint8_t         brightness; /* 1..100 */
+    nl_light_mode_t mode;
+    uint8_t         r, g, b;
+    uint16_t        ct;         /* Kelvin */
+} nl_light_state_t;
+
+/* What is currently visible; bri = 0 means dark. */
+typedef struct {
+    uint16_t        bri;        /* 0..NL_BRI_SCALE */
+    nl_light_mode_t mode;
+    uint8_t         r, g, b;
+    uint16_t        ct;
+} nl_visual_t;
+
+#endif