Render/pen.cpp at master · dorinbotan/Render · GitHub

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#include "pen.h"

void drawLine(int x0, int y0, int x1, int y1, TGAImage &image, TGAColor color) {
    bool steep = false;
    if (abs(x0 - x1) < abs(y0 - y1)) {
        swap(x0, y0);
        swap(x1, y1);
        steep = true;
    }
    if (x0 > x1) {
        swap(x0, x1);
        swap(y0, y1);
    }

    int dx = x1 - x0;
    int dy = y1 - y0;
    int derror2 = abs(dy) * 2;
    int error2 = 0;
    int y = y0;
    int ydir = (y1 > y0) ? 1 : -1;

    for (int x = x0; x <= x1; x++) {
        if (steep) {
            image.set(y, x, color);
        } else {
            image.set(x, y, color);
        }
        error2 += derror2;
        if (error2 > dx) {
            y += ydir;
            error2 -= dx * 2;
        }
    }
}

void drawRect(int x, int y, int width, int height, TGAImage &image, TGAColor color)
{
    drawLine(x, y, width - x, y, image, color);
    drawLine(x, y, x, height - y, image, color);
    drawLine(width, y, width - x, height - y, image, color);
    drawLine(x, height, width - x, height - y, image, color);
}

void drawSquare(int x, int y, int width, TGAImage &image, TGAColor color)
{
    drawRect(x, y, width, width, image, color);
}

void drawTriangle(int x0, int y0, int x1, int y1, int x2, int y2, TGAImage &image, TGAColor color)
{
    drawLine(x0, y0, x1, y1, image, color);
    drawLine(x1, y1, x2, y2, image, color);
    drawLine(x2, y2, x0, y0, image, color);
}

void drawCircle(int x1, int y1, int r, TGAImage &image, TGAColor color) {
    int x = 0;
    int y = r;
    int delta = 1 - 2 * r;
    int error = 0;

    while(y >= 0) {
        image.set(x1 + x, y1 + y, color);
        image.set(x1 + x, y1 - y, color);
        image.set(x1 - x, y1 + y, color);
        image.set(x1 - x, y1 - y, color);

        error = 2 * (delta + y) - 1;

        if(delta < 0 && error <= 0) {
            delta += 2 * ++x + 1;
            continue;
        }

        error = 2 * (delta - x) - 1;

        if(delta > 0 && error > 0) {
            delta += 1 - 2 * --y;
            continue;
        }
        else
            x++;

        delta += 2 * (x - y);
        y--;
    }
}