一.
1
void myDisplay(void)
{
   // 请在此添加你的代码

   glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glPointSize(3);
    glBegin(GL_POINTS);
    glColor3f(1.0f, 0.0f, 0.0f);   
    glVertex2f(-0.4f, -0.4f);
    glColor3f(0.0f, 1.0f, 0.0f);   
    glVertex2f(0.0f, 0.0f);
    glColor3f(0.0f, 0.0f, 1.0f);   
    glVertex2f(0.4f, 0.4f);
    glEnd();


    glFlush();
}

2.
void myDisplay(void)
{
   // 请在此添加你的代码
   glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f (1.0f, 1.0f, 1.0f); 
    glRectf(-0.5f, -0.5f, 0.5f, 0.5f);

    glBegin (GL_TRIANGLES);
    glColor3f (1.0f, 0.0f, 0.0f);   
    glVertex2f (0.0f, 1.0f);
    glColor3f (0.0f, 1.0f, 0.0f);   
    glVertex2f (0.8f, -0.5f);
    glColor3f (0.0f, 0.0f, 1.0f);   
    glVertex2f (-0.8f, -0.5f);
    glEnd ();

    glPointSize(3);
    glBegin (GL_POINTS);
    glColor3f (1.0f, 0.0f, 0.0f);   
    glVertex2f (-0.4f, -0.4f);
    glColor3f (0.0f, 1.0f, 0.0f);   
    glVertex2f (0.0f, 0.0f);
    glColor3f (0.0f, 0.0f, 1.0f);   
    glVertex2f (0.4f, 0.4f);
    glEnd ();

    glFlush();
}
3. void myDisplay(void)
{
   // 请在此添加你的代码
   /********** Begin ********/

    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f (1.0f, 0.0f, 0.0f); 
    glRectf(25.0, 25.0, 75.0, 75.0);

    glPointSize(10);
    glBegin (GL_POINTS);
    glColor3f (0.0f, 1.0f, 0.0f);   
    glVertex2f (0.0f, 0.0f);
    glEnd ();

    //LineDDA(0, 0, 200, 300);

    glBegin (GL_LINES);
    glColor3f (0.0f, 1.0f, 0.0f);   
    glVertex2f (100.0f, 0.0f);
    glColor3f (0.0f, 1.0f, 0.0f);   
    glVertex2f (180.0f, 240.0f);    
    glEnd ();


   /********** End **********/
    glFlush();
}
void Init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
}
4.
void LineDDA(int x0,int y0,int x1,int y1/*,int color*/)
{
    int  x, dy, dx, y;
    float m;
    dx=x1-x0;
    dy=y1-y0;
    m=dy/dx;
    y=y0;

    glColor3f (1.0f, 1.0f, 0.0f);   
    glPointSize(1);
    for(x=x0;x<=x1; x++)
    {
        glBegin (GL_POINTS);
        glVertex2i (x, (int)(y+0.5));
        glEnd ();
        y+=m;
    }
}

void myDisplay(void)
{
   // 请在此添加你的代码
   /********** Begin ********/

   LineDDA( 0, 0, 200,300 );


   /********** End **********/
    glFlush();
}
void Init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
}

5.
void MidPLine(int x1, int y1, int xn, int yn)
{
 // 请在此添加你的代码
    int dx, dy,dt,db,d,x,y;
    dx = xn - x1;
    dy = yn - y1;
    d = dx - 2*dy;
    dt = 2*dx - 2*dy;
    db = -2*dy;
    x = x1, y = y1;


    glColor3f(0.0f,3.0f,0.0f);
    glPointSize(1);
    glBegin(GL_POINTS);
    glVertex2i(x, y);
    glEnd;

    while(x < xn){
        if(d < 0){
            x ++;
            y ++;
            d += dt;
        }
        else{
            x ++;
            d += db;
        }
        glBegin (GL_POINTS);
        glVertex2i ((int)(x), (int)(y));
        glEnd ();

    }

    glFlush();
}

void myDisplay(void)
{
   // 请在此添加你的代码
   /********** Begin ********/
   glClearColor(0.0,0.0,0.0,0.0);
   glClear(GL_COLOR_BUFFER_BIT);
   MidPLine( 10, 50, 300, 260);


   /********** End **********/
    glFlush();
}
void Init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_SMOOTH);
}