[Example] [Dcdr] How to write PPM format

PpmRasterizer.cpp

// WARNING: this is a deprecated code from dcdr project; 
// This can be broken, but still can be used as example how to write ppm file.
// Enjoy.

#include <vector>
#include <ifstream>

namespace Dcdr
{
    // ------------- dcdr/Types.h ---------------
    namepsace Types
    {
        typedef size_t Offset;
        typedef float Real;

        stuct Vec3
        {
            Real r, g, b;
        };
    }

    // ------------- dcdr/renderer/ISurfaceRasterizer.h ---------------
    class ISurfaceRasterizer
    {
    public:
        virutal void set_image_size(Types::Size width, Types::Size height) = 0;
        virutal void draw_pixel(Types::Vec3 color, Types::Offset x, Types::Offset y) = 0;

        virtual ~ISurfaceRasterizer() = default;
    };

    // ------------- dcdr/renderer/PpmRasterizer.h ---------------
    class PpmRasterizer : public ISurfaceRasterizer
    {
    public:
        PpmRasterizer(Types::Offset width, Types::Offset height) :
                width_(width),
                height_(height),
                pixels_()
        {}

        void set_image_size(Types::Size width, Types::Size height) override
        {
            pixels_.resize(width * height);
        }

        void draw_pixel(Types::Vec3 color, Types::Offset x, Types::Offset y) override
        {
            pixels_[y * width_ + x][0] = (unsigned char)(color.r * 255);
            pixels_[y * width_ + x][1] = (unsigned char)(color.g * 255);
            pixels_[y * width_ + x][2] = (unsigned char)(color.b * 255);
        }

        void save_file(const std::string& filename)
        {
            std::ofstream file(filename, std::ofstream::binary);

            file << "P3" << std::endl;
            file << width_ << " " << height_ << std::endl;
            file << "255" << std::endl;

            for (auto& pixel : pixels_)
                file << Types::Offset(pixel[0]) << " " 
                     << Types::Offset(pixel[1]) << " " 
                     << Types::Offset(pixel[2])
                     << std::endl;
        }

    private:
        Types::Offset width_;
        Types::Offset height_;

        std::vector<unsigned char[3]> pixels_;
    };
}