circuitpython/shared-module/displayio/ColorConverter.c

/*
 * This file is part of the Micro Python project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2018 Scott Shawcroft for Adafruit Industries
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "shared-bindings/displayio/ColorConverter.h"

void common_hal_displayio_colorconverter_construct(displayio_colorconverter_t* self) {
}

uint16_t displayio_colorconverter_compute_rgb565(uint32_t color_rgb888) {
    uint32_t r5 = (color_rgb888 >> 19);
    uint32_t g6 = (color_rgb888 >> 10) & 0x3f;
    uint32_t b5 = (color_rgb888 >> 3) & 0x1f;
    uint32_t packed = r5 << 11 | g6 << 5 | b5;
    // swap bytes
    return __builtin_bswap16(packed);
}

uint8_t displayio_colorconverter_compute_luma(uint32_t color_rgb888) {
    uint32_t r8 = (color_rgb888 >> 16);
    uint32_t g8 = (color_rgb888 >> 8) & 0xff;
    uint32_t b8 = color_rgb888 & 0xff;
    return (r8 * 19) / 255 + (g8 * 182) / 255 + (b8 + 54) / 255;
}

void compute_bounds(uint8_t r8, uint8_t g8, uint8_t b8, uint8_t* min, uint8_t* max) {
    if (r8 > g8) {
        if (b8 > r8) {
            *max = b8;
        } else {
            *max = r8;
        }
        if (b8 < g8) {
            *min = b8;
        } else {
            *min = g8;
        }
    } else {
        if (b8 > g8) {
            *max = b8;
        } else {
            *max = g8;
        }
        if (b8 < r8) {
            *min = b8;
        } else {
            *min = r8;
        }
    }
}

uint8_t displayio_colorconverter_compute_chroma(uint32_t color_rgb888) {
    uint32_t r8 = (color_rgb888 >> 16);
    uint32_t g8 = (color_rgb888 >> 8) & 0xff;
    uint32_t b8 = color_rgb888 & 0xff;
    uint8_t max;
    uint8_t min;
    compute_bounds(r8, g8, b8, &min, &max);
    return max - min;
}

uint8_t displayio_colorconverter_compute_hue(uint32_t color_rgb888) {
    uint32_t r8 = (color_rgb888 >> 16);
    uint32_t g8 = (color_rgb888 >> 8) & 0xff;
    uint32_t b8 = color_rgb888 & 0xff;
    uint8_t max;
    uint8_t min;
    compute_bounds(r8, g8, b8, &min, &max);
    uint8_t c = max - min;
    if (c == 0) {
        return 0;
    }

    int32_t hue = 0;
    if (max == r8) {
        hue = (((int32_t) (g8 - b8) * 40) / c) % 240;
    } else if (max == g8) {
        hue = (((int32_t) (b8 - r8) + (2 * c)) * 40) / c;
    } else if (max == b8) {
        hue = (((int32_t) (r8 - g8) + (4 * c)) * 40) / c;
    }
    if (hue < 0) {
        hue += 240;
    }

    return hue;
}

void displayio_colorconverter_compute_tricolor(const _displayio_colorspace_t* colorspace, uint8_t pixel_hue, uint8_t pixel_luma, uint32_t*  color) {

    int16_t hue_diff = colorspace->tricolor_hue - pixel_hue;
    if ((-10 <= hue_diff && hue_diff <= 10) || hue_diff <= -220 || hue_diff >= 220) {
        if (colorspace->grayscale) {
            *color = 0;
        } else {
            *color = 1;
        }
    } else if (!colorspace->grayscale) {
        *color = 0;
    }
}

bool displayio_colorconverter_convert(displayio_colorconverter_t *self, const _displayio_colorspace_t* colorspace, uint32_t input_color, uint32_t* output_color) {
    if (colorspace->depth == 16) {
        *output_color = displayio_colorconverter_compute_rgb565(input_color);
        return true;
    } else if (colorspace->tricolor) {
        uint8_t luma = displayio_colorconverter_compute_luma(input_color);
        *output_color = luma >> (8 - colorspace->depth);
        if (displayio_colorconverter_compute_chroma(input_color) <= 16) {
            if (!colorspace->grayscale) {
                *output_color = 0;
            }
            return true;
        }
        uint8_t pixel_hue = displayio_colorconverter_compute_hue(input_color);
        displayio_colorconverter_compute_tricolor(colorspace, pixel_hue, luma, output_color);
        return true;
    } else if (colorspace->grayscale && colorspace->depth <= 8) {
        uint8_t luma = displayio_colorconverter_compute_luma(input_color);
        *output_color = luma >> (8 - colorspace->depth);
        return true;
    }
    return false;
}

void common_hal_displayio_colorconverter_convert(displayio_colorconverter_t *self, const _displayio_colorspace_t* colorspace, uint32_t input_color, uint32_t* output_color) {
    displayio_colorconverter_convert(self, colorspace, input_color, output_color);
}

// Currently no refresh logic is needed for a ColorConverter.
bool displayio_colorconverter_needs_refresh(displayio_colorconverter_t *self) {
    return false;
}

void displayio_colorconverter_finish_refresh(displayio_colorconverter_t *self) {
}