中点算法和Bresenham算法画线

使用EasyX c++库

中点算法直线绘制

//中点算法划线:横向直线绘制
void DDAline(int x1, int y1, int x2, int y2, int color) {
    int x;
    float dx, dy, y, k;
    dx = x2 - x1, dy = y2 - y1;
    if (dx == 0) {
        for (y = min(y1, y2); y < max(y1, y2); y++) {
            putpixel(x1, y, color);
        }
        return;
    }
    k = dy / dx;
    if (x1 < x2)y = y1;
    else y = y2;
    for (x = min(x1, x2); x <= max(x1, x2); x++) {
        putpixel(x, int(y + 0.5), color);
        y = y + k;
    }
}

Bresenham算法直线绘制

//Bresenham算法画线:棋盘纵向网格绘制
void Bresenhamline(int x1, int y1, int x2, int y2, int color) {
    int x;
    float dx, dy, y, e;
    dx = x2 - x1, dy = y2 - y1;
    if (dx == 0) {
        for (y = min(y1, y2); y < max(y1, y2); y++) {
            putpixel(x1, y, color);
        }
        return;
    }
    if (dy == 0) {
        for (x = min(x1, x2); x < max(x1, x2); x++) {
            putpixel(x, y1, color);
        }
        return;
    }
    x = x1, y = y1;
    if (x1 < x2) {
        if (y1 < y2) {
            if (dy <= dx) {
                e = -dx;
                for (int i = 0; i <= dx; i++)
                {
                    putpixel(x, y, color);
                    x++, e = e + 2 * dy;
                    if (e >= 0) {
                        y++; e = e - 2 * dx;
                    }
                }
            }
            else {
                e = -dy;
                for (int i = 0; i <= dy; i++)
                {
                    putpixel(x, y, color);
                    y++, e = e + 2 * dx;
                    if (e >= 0) {
                        x++; e = e - 2 * dy;
                    }
                }
            }
        }
        else {
            if (-dy <= dx) {
                e = -dx;
                for (int i = 0; i <= dx; i++)
                {
                    putpixel(x, y, color);
                    x++, e = e + 2 * dy;
                    if (e <= 0) {
                        y--; e = e + 2 * dx;
                    }
                }
            }
            else {
                e = -dy;
                for (int i = 0; i <= -dy; i++)
                {
                    putpixel(x, y, color);
                    y--, e = e + 2 * dx;
                    if (e >= 0) {
                        x++; e = e + 2 * dy;
                    }
                }
            }
        }
    }
    else { //x = x2, y = y2; 
        if (y1 < y2) {
            if (dy <= -dx) {
                e = -dx;
                for (int i = 0; i <= -dx; i++)
                {
                    putpixel(x, y, color);
                    x--, e = e + 2 * dy;
                    if (e >= 0) {
                        y++; e = e + 2 * dx;
                    }
                }
            }
            else {
                e = -dy;
                for (int i = 0; i <= dy; i++)
                {
                    putpixel(x, y, color);
                    y++, e = e - 2 * dx;
                    if (e >= 0) {
                        x--; e = e - 2 * dy;
                    }
                }
            }
        }
        else {
            if (-dy <= -dx) {
                e = -dx;
                for (int i = 0; i <= -dx; i++)
                {
                    putpixel(x, y, color);
                    x--, e = e + 2 * dy;
                    if (e <= 0) {
                        y--; e = e - 2 * dx;
                    }
                }
            }
            else {
                e = -dy;
                for (int i = 0; i <= -dy; i++)
                {
                    putpixel(x, y, color);
                    y--, e = e + 2 * dx;
                    if (e <= 0) {
                        x--; e = e - 2 * dy;
                    }
                }
            }
        }
    }
}

主函数执行程序

    //绘制网格线

        //直线整体纵向平移需要更改坐标(y1,y2)相同单位
    DDAline(x1, y1 - 50, x2, y2 - 50, BLACK);
    DDAline(x1, y1, x2, y2, BLACK);
        //直线整体横向平移需要更改坐标(x1,x2)相同单位
    Bresenhamline(300, 40, 300, 440, BLACK);
    Bresenhamline(300 - 50, 40, 300 - 50, 440, BLACK);