CG: DDA e Bresenham

#include <iostream>

using namespace std;

/******************************************
 *        COLORAÇÂO DE CARACTERES       */
const std::string RED("\033[0;31m");
const std::string GREEN("\033[1;32m");
const std::string YELLOW("\033[1;33m");
const std::string CYAN("\033[0;36m");
const std::string MAGENTA("\033[0;35m");
const std::string RESET("\033[0m");
/******************************************/

inline int abs(int n) { return n > 0 ? n : -n; }
inline int round(float n) { return (int) (n + 0.5); }

int size;
bool** buffer;

void drawLineDDA(int xa, int ya, int xb, int yb)
{
    int dx = xb - xa,
        dy = yb - ya;

    int steps = abs(dx) > abs(dy) ? abs(dx) : abs(dy);

    float   xIncrement = dx / (float) steps,
            yIncrement = dy / (float) steps,
            x = xa,
            y = ya;

    buffer[round(y)][round(x)] = true;;

    for (int k = 0; k < steps; k++)
    {
        x += xIncrement;
        y += yIncrement;

        buffer[round(y)][round(x)] = true;
    }
}

void drawLineBres_(int xa, int ya, int xb, int yb, bool inverted)
{
    int dx = xb - xa,
        dy = yb - ya,
        slope;

    if (xa > xb)
        return drawLineBres_(xb, yb, xa, ya, inverted);
    if (abs(dy) > abs(dx))
        return drawLineBres_(ya, xa, yb, xb, ! inverted);

    if (dy < 0)
    {
        slope = -1;
        dy = -dy;
    }
    else slope = 1;

    int incE = 2 * dy,
        incNE = 2 * (dy - dx),
        p = 2 * dy - dx;

    for (; xa <= xb; xa++)
    {
        if (inverted)
            buffer[xa][ya] = true;
        else
            buffer[ya][xa] = true;

        if (p < 0)
            p += incE;
        else {
            p += incNE;
            ya += slope;
        }
    }
}

void drawLineBres(int xa, int ya, int xb, int yb) {
    drawLineBres_(xa, ya, xb, yb, false);
}

void clear()
{
    for (int i = 0; i < size; i++)
        for (int j = 0; j < size; j++)
            buffer[i][j] = false;
}

void display()
{
    for (int i = size - 1; i >= 0; i--) {
        cout << RED << (i < 10 ? " " : "") << i << RESET;

        for (int j = 0; j < size; j++)
            if (buffer[i][j])
                cout << " o";
            else
                cout << MAGENTA << " ." << RESET;
        cout << endl;
    }

    cout << "  " << RED;
    for (int i = 0; i < size; i++)
        cout << (i < 10 ? " " : "") << i;
    cout << RESET << endl << endl;
}

/* Exemplo de uso:
 * Tamanho: 30          # Cria um buffer de tamanho 30x30
 * Pontos: 4 19 9 13    # Mostra gráfico da reta que vai do ponto (4, 19) ao (9, 13)
 *                      # Pontos no formato (x, y) */
int main()
{
    cout << "Tamanho (largura/altura): ";
    cin >> size;

    buffer = new bool*[size];
    for (int i = 0; i < size; i++)
        buffer[i] = new bool[size];

    int xa, ya, xb, yb;
    cout << "Pontos (xa xb ya yb): ";
    cin >> xa >> ya >> xb >> yb;
    cout << endl;

    cout << "DDA:" << endl;
    clear();
    drawLineDDA(xa, ya, xb, yb);
    display();

    cout << "Bresenham:" << endl;
    clear();
    drawLineBres(xa, ya, xb, yb);
    display();

    return 0;
}