blinky-esp/main/patterns/gradient.cpp

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

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


struct Gradient {
    Color at(Fixed x) const;

    static Gradient* make(int n) {
        Gradient *gradient = (Gradient*)malloc(
                sizeof(Gradient) + n * sizeof(*colors)
            );
        gradient->n_colors = n;
        return gradient;
    }

    unsigned int n_colors;
    Color colors[];
};

class GradientPattern : public Pattern {
public:
    GradientPattern(
                Gradient *_gradient,
                int _cycle_length=20, int _cycle_time_ms=-1,
                bool _reverse=false, bool _march=false
            ) : cycle_length(_cycle_length),
                cycle_time_ms(  _cycle_time_ms < 0 ?
                                _cycle_length * 500 : _cycle_time_ms
                    ),
                reverse(_reverse), march(_march), gradient(_gradient)
            {}

    ~GradientPattern() { free(gradient); }

    State* start(int) const { return new State(); }

    void step(Color[], int, State*) const;

private:
    struct State : Pattern::State {
        State() : last_us(0), offset(0) {}
        int64_t last_us;
        Fixed offset;
    };

    int cycle_length;
    int cycle_time_ms;
    bool reverse;
    bool march;
    Gradient *gradient;
};


static inline uint8_t mix(int l, int r, Fixed x) {
    return ((l << shift) + (x * (r - l))) >> shift;
}

Color Gradient::at(Fixed x) const {
    int i_left = (x * n_colors) >> shift;
    int i_right = i_left < n_colors - 1 ? i_left + 1 : 0;
    Fixed ratio = (x * n_colors) - (i_left << shift);
    //ESP_LOGI(TAG, "at(%d) = %d between %d and %d", x, ratio, i_left, i_right);
    Color cl = colors[i_left];
    Color cr = colors[i_right];
    Color color = {
            mix(cl.r, cr.r, ratio),
            mix(cl.g, cr.g, ratio),
            mix(cl.b, cr.b, ratio)
        };
    /*ESP_LOGI(TAG, "(%d, %d, %d) %f (%d, %d, %d) -> (%d, %d, %d)",
        cl.r, cl.g, cl.b,
        ratio / (float)factor,
        cr.r, cr.g, cr.b,
        color.r, color.g, color.b
    );*/
    return color;
}

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

    int64_t now_us = time_us();
    int64_t duration_us = state->last_us == 0 ? 0 : now_us - state->last_us;
    state->last_us = now_us;
    //ESP_LOGI(TAG, "duration %d", duration_us);

    /*
    int period_us = 1000000 / 60;
    int n_skipped = (duration_us - period_us / 2) / period_us;
    if (n_skipped) {
        ESP_LOGW(TAG, "Skipped %d frames", n_skipped);
    }
    */
    // Don't make a major animation jump if it's been terribly long
    if (duration_us > 100000) duration_us = 100000;


    int offset_delta = (duration_us << shift) / (cycle_time_ms * 1000);
    if (reverse) state->offset += offset_delta; else state->offset -= offset_delta;
    Fixed off = march ?
            (((int)state->offset * cycle_length) & ~((1 << shift) - 1)) / cycle_length :
            state->offset;
    //ESP_LOGI(TAG, "cycle time %d, delta %d, offset %d, off %d", cycle_time_ms, offset_delta, offset, off);
    for (int i = 0; i < len; ++i) {
        pixels[i] = gradient->at(off + ((i << shift) / cycle_length));
    }
}


Pattern* json_gradient_pattern(cJSON *pattern, const Presets::ColorMap &colors) {
    if (pattern->type != cJSON_Object) {
        ESP_LOGE(TAG, "Not an object: %s", pattern->string);
        return NULL;
    }
    cJSON *jcolors = cJSON_GetObjectItem(pattern, "colors");
    if (!jcolors) {
        ESP_LOGE(TAG, "No colors in %s", pattern->string);
        return NULL;
    }
    if (jcolors->type != cJSON_Array) {
        ESP_LOGE(TAG, "Not an array: %s", jcolors->string);
        return NULL;
    }

    Gradient *gradient = Gradient::make(cJSON_GetArraySize(jcolors));

    int i = 0;
    cJSON *jcolor;
    cJSON_ArrayForEach(jcolor, jcolors) {
        Color color = Presets::json_color(jcolor, colors);
        gradient->colors[i++] = color;
    }

    return new GradientPattern(gradient);
}