Momentum-Apps/firmware/dither_image.ino

#include "dither_image.h"

void dither_image(camera_fb_t* frame_buffer) {
    for (uint8_t y = 0; y < frame_buffer->height; ++y) {
        for (uint8_t x = 0; x < frame_buffer->width; ++x) {
            size_t current = (y * frame_buffer->width) + x;
            uint8_t oldpixel = frame_buffer->buf[current];
            uint8_t newpixel = oldpixel >= 128 ? 255 : 0;
            frame_buffer->buf[current] = newpixel;
            int8_t quant_error = oldpixel - newpixel;

            // Apply error diffusion based on the selected algorithm
            switch (camera_model.ditherAlgorithm) {
            case JARVIS_JUDICE_NINKE:
                frame_buffer->buf[(y * frame_buffer->width) + x + 1] +=
                    quant_error * 7 / 48;
                frame_buffer->buf[(y * frame_buffer->width) + x + 2] +=
                    quant_error * 5 / 48;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x - 2] +=
                    quant_error * 3 / 48;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x - 1] +=
                    quant_error * 5 / 48;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x] +=
                    quant_error * 7 / 48;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x + 1] +=
                    quant_error * 5 / 48;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x + 2] +=
                    quant_error * 3 / 48;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x - 2] +=
                    quant_error * 1 / 48;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x - 1] +=
                    quant_error * 3 / 48;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x] +=
                    quant_error * 5 / 48;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x + 1] +=
                    quant_error * 3 / 48;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x + 2] +=
                    quant_error * 1 / 48;
                break;
            case STUCKI:
                frame_buffer->buf[(y * frame_buffer->width) + x + 1] +=
                    quant_error * 8 / 42;
                frame_buffer->buf[(y * frame_buffer->width) + x + 2] +=
                    quant_error * 4 / 42;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x - 2] +=
                    quant_error * 2 / 42;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x - 1] +=
                    quant_error * 4 / 42;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x] +=
                    quant_error * 8 / 42;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x + 1] +=
                    quant_error * 4 / 42;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x + 2] +=
                    quant_error * 2 / 42;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x - 2] +=
                    quant_error * 1 / 42;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x - 1] +=
                    quant_error * 2 / 42;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x] +=
                    quant_error * 4 / 42;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x + 1] +=
                    quant_error * 2 / 42;
                frame_buffer->buf[(y + 2) * frame_buffer->width + x + 2] +=
                    quant_error * 1 / 42;
                break;
            case FLOYD_STEINBERG:
            default:
                // Default to Floyd-Steinberg dithering if an invalid
                // algorithm is selected
                frame_buffer->buf[(y * frame_buffer->width) + x + 1] +=
                    quant_error * 7 / 16;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x - 1] +=
                    quant_error * 3 / 16;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x] +=
                    quant_error * 5 / 16;
                frame_buffer->buf[(y + 1) * frame_buffer->width + x + 1] +=
                    quant_error * 1 / 16;
                break;
            }
        }
    }
}