pixel.hpp

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#pragma once

#include "color.hpp"
#include "exception.hpp"
#include <SDL_pixels.h>

namespace sdl
{
class Pixel
{
public:
    Pixel(void* target, SDL_PixelFormat const& fmt) : target_{target}, fmt_{fmt} {}

    Pixel& operator=(Color const& c)
    {
        set_color(c);
        return *this;
    }
    void set_color(Color const& c) { set_raw(c.as_uint(fmt_)); }

    Color color() const { return Color{get_raw(), fmt_}; }

    Uint8 r() const { return color().r; }
    Uint8 g() const { return color().g; }
    Uint8 b() const { return color().b; }
    Uint8 a() const { return color().a; }

    void set_r(Uint8 r)
    {
        auto c = color();
        c.r    = r;
        set_color(c);
    }
    void set_g(Uint8 g)
    {
        auto c = color();
        c.g    = g;
        set_color(c);
    }
    void set_b(Uint8 b)
    {
        auto c = color();
        c.b    = b;
        set_color(c);
    }
    void set_a(Uint8 a)
    {
        auto c = color();
        c.a    = a;
        set_color(c);
    }

private:
    void set_raw(Uint32 raw)
    {
        switch (fmt_.BytesPerPixel)
        {
        case 1: *static_cast<Uint8*>(target_) = static_cast<Uint8>(raw); break;
        case 2: *static_cast<Uint16*>(target_) = static_cast<Uint16>(raw); break;
        case 3:
            if constexpr (SDL_BYTEORDER == SDL_BIG_ENDIAN)
            {
                static_cast<Uint8*>(target_)[0] = static_cast<Uint8>((raw >> 16) & 0xFF);
                static_cast<Uint8*>(target_)[1] = static_cast<Uint8>((raw >> 8) & 0xFF);
                static_cast<Uint8*>(target_)[2] = static_cast<Uint8>(raw & 0xFF);
            }
            else
            {
                static_cast<Uint8*>(target_)[0] = static_cast<Uint8>(raw & 0xFF);
                static_cast<Uint8*>(target_)[1] = static_cast<Uint8>((raw >> 8) & 0xFF);
                static_cast<Uint8*>(target_)[2] = static_cast<Uint8>((raw >> 16) & 0xFF);
            }
            break;
        case 4: *static_cast<Uint32*>(target_) = raw; break;
        }
    }
    Uint32 get_raw() const
    {
        switch (fmt_.BytesPerPixel)
        {
        case 1: return *static_cast<Uint8*>(target_);
        case 2: return *static_cast<Uint16*>(target_);
        case 3:
            if constexpr (SDL_BYTEORDER == SDL_BIG_ENDIAN)
            {
                return static_cast<Uint8*>(target_)[0] << 16 | static_cast<Uint8*>(target_)[1] << 8
                       | static_cast<Uint8*>(target_)[2];
            }
            else
            {
                return static_cast<Uint8*>(target_)[0] | static_cast<Uint8*>(target_)[1] << 8
                       | static_cast<Uint8*>(target_)[2] << 16;
            }
        case 4: return *static_cast<Uint32*>(target_);
        }

        // TODO decide if landing here is an important error and throw, or just return a black pixel
        return 0;
    }

    void* target_;
    const SDL_PixelFormat& fmt_;
};

} // namespace sdl