blinky-esp/main/patterns/sparkle.cpp

static const char *TAG = "random";
#include <esp_log.h>

#include <list>
#include <cstring>

#include <esp_random.h>

#include "presets.hpp"
#include "utils.hpp"

/*
static const int8_t ndist[64] = {-127, -104, -92, -84, -77, -72, -67, -62, -58, -55, -51, -48, -45, -42, -39, -37, -34, -32, -29, -27, -25, -22, -20, -18, -16, -14, -11, -9, -7, -5, -3, -1, 1, 3, 5, 7, 9, 11, 14, 16, 18, 20, 22, 25, 27, 29, 32, 34, 37, 39, 42, 45, 48, 51, 55, 58, 62, 67, 72, 77, 84, 92, 104, 127};

int norm(int mean) {
    return (mean * 128) / ndist[esp_random() % 64];
}
*/

static inline Color fade(Color c, unsigned int i) {
    return {
            (uint8_t)((c.r * i) / 255),
            (uint8_t)((c.g * i) / 255),
            (uint8_t)((c.b * i) / 255)
        };
}

struct Sparkle {
    Sparkle() : start_us(0), end_us(0), pos(0) {}
    Sparkle(Color _color, int64_t time_us, int mean_dur_us, int len):
                start_us(time_us), end_us(time_us + (mean_dur_us)),
                pos(esp_random() % len), color(_color) {}

    bool expired(int64_t time_us) { return time_us >= end_us; }

    uint8_t intensity_at(int64_t time_us) {
        if (time_us < start_us || time_us >= end_us) return 0;
        int64_t midpoint_us = (start_us + end_us) / 2;
        if (time_us >= midpoint_us) time_us = start_us + (end_us - time_us);
        return (((time_us - start_us) * 255) * 2) / (end_us - start_us);
    }

    Color color_at(int64_t time_us) {
        return fade(color, intensity_at(time_us));
    }

    int64_t start_us;
    int64_t end_us;
    int pos;
    Color color;
};


class SparklePattern : public Pattern {
private:
    struct State : Pattern::State {
        State(int n) : n_sparkles(n), sparkles(new Sparkle[n]) {}
        ~State() { delete[] sparkles; }

        int n_sparkles;
        Sparkle *sparkles;
    };

public:
    SparklePattern(const Color *_colors, int _n_colors, int _duration_ms, int _delay_ms, int _density) :
                n_colors(_n_colors), colors(_colors),
                duration_us(_duration_ms * 1000),
                delay_us(_delay_ms * 1000), density(_density)
            {}
    ~SparklePattern() { if (colors) delete[] colors; }

    State* start(int len) const { return new State((len / density) + 1); }

    void step(Color pixels[], int len, Pattern::State *_state) const {
        State *state = (State*)_state;

        int64_t now_us = time_us();

        memset(pixels, 0, sizeof(*pixels) * len);

        int64_t start_us = now_us;
        for (int i = 0; i < state->n_sparkles; ++i, start_us += delay_us / state->n_sparkles) {
            Sparkle &sparkle = state->sparkles[i];

            if (sparkle.expired(now_us)) {
                sparkle = Sparkle(
                        colors[esp_random() % n_colors],
                        start_us, duration_us, len
                    );
            } else {
                pixels[sparkle.pos] = sparkle.color_at(now_us);
            }
        }
    }

private:
    int n_colors;
    const Color* colors;
    int duration_us;
    int delay_us;
    int density;
};


Pattern* json_sparkle_pattern(cJSON *pattern, const Presets::ColorMap &colormap) {
    int duration_ms = 250;
    int delay_ms = 3000;
    int density = 10;
    int n_colors = 0;
    Color *colors = NULL;

    if (pattern->type != cJSON_Object) {
        ESP_LOGE(TAG, "Not an object: %s", pattern->string);
        return NULL;
    }

    cJSON *jcolors = cJSON_GetObjectItem(pattern, "colors");
    if (!jcolors || jcolors->type != cJSON_Array) {
        ESP_LOGW(TAG, "No colors in %s", pattern->string);
    } else {
        n_colors = cJSON_GetArraySize(jcolors);
        colors = new Color[n_colors];
        int i = 0;
        cJSON *jcolor;
        cJSON_ArrayForEach(jcolor, jcolors) {
            colors[i++] = Presets::json_color(jcolor, colormap);
        }
    }

    cJSON *jnum = cJSON_GetObjectItem(pattern, "delay");
    if (jnum) {
        if (jnum->type != cJSON_Number) {
            ESP_LOGE(TAG, "Not a number: %s", jnum->string);
        } else {
            delay_ms = jnum->valuedouble * 1000.;
        }
    }

    jnum = cJSON_GetObjectItem(pattern, "duration");
    if (jnum) {
        if (jnum->type != cJSON_Number) {
            ESP_LOGE(TAG, "Not a number: %s", jnum->string);
        } else {
            duration_ms = jnum->valuedouble * 1000.;
        }
    }

    jnum = cJSON_GetObjectItem(pattern, "density");
    if (jnum) {
        if (jnum->type != cJSON_Number) {
            ESP_LOGE(TAG, "Not a number: %s", jnum->string);
        } else {
            density = jnum->valuedouble;
        }
    }

    if (n_colors == 0) {
        n_colors = 1;
        colors = new Color{255,255,255};
    }

    return new SparklePattern(colors, n_colors, duration_ms, delay_ms, density);
}