color.hpp

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// SPDX-License-Identifier: Apache-2.0
// Copyright 2026 Chris Leishman
 
#pragma once
 
#include <bit>
#include <cstdint>
#include <esp_lcd_panel_io.h>
 
namespace idfxx::lcd {
 
enum class rgb_element_order : int {
    rgb = LCD_RGB_ELEMENT_ORDER_RGB, 
    bgr = LCD_RGB_ELEMENT_ORDER_BGR, 
};
 
enum class rgb_data_endian : int {
    big = LCD_RGB_DATA_ENDIAN_BIG,       
    little = LCD_RGB_DATA_ENDIAN_LITTLE, 
};
 
class rgb565 {
public:
    constexpr rgb565() noexcept = default;
 
    constexpr rgb565(uint8_t r, uint8_t g, uint8_t b) noexcept
        : _repr(_to_panel_order(static_cast<uint16_t>(((r & 0xF8u) << 8) | ((g & 0xFCu) << 3) | (b >> 3)))) {}
 
    [[nodiscard]] static constexpr rgb565 from_value(uint16_t value) noexcept {
        rgb565 c;
        c._repr = _to_panel_order(value);
        return c;
    }
 
    [[nodiscard]] constexpr uint16_t value() const noexcept { return _to_panel_order(_repr); }
 
    friend constexpr bool operator==(rgb565, rgb565) noexcept = default;
 
private:
    // Byte-swaps a packed value into big-endian panel order (an involution,
    // so it converts back as well).
    static constexpr uint16_t _to_panel_order(uint16_t value) noexcept {
        if constexpr (std::endian::native == std::endian::little) {
            return std::byteswap(value);
        } else {
            return value;
        }
    }
 
    uint16_t _repr = 0;
};
 
static_assert(sizeof(rgb565) == 2);
 
} // namespace idfxx::lcd