Second Assignment DDA algorithm for line drawing using Mouse

Draw the polygons by using the mouse. Choose colors by clicking on the designed color pane. Use window port to draw. (Use DDA algorithm for line drawing)

#include<string.h>
#include<GL/glut.h>
#define ROUND(x)((int)(x+0.5))
struct Point
{
GLint x;
GLint y;
};

struct Color
{
GLfloat r;
GLfloat g;
GLfloat b;
};
Color getPixelColor(GLint x, GLint y)  //Fun for getting color of pixel
{
 Color color;
glReadPixels(x,y,1,1,GL_RGB, GL_FLOAT, &color);
return color;
}

void setPixelColor(GLint x, GLint y, Color color)   //set color of pixel
{
   glColor3f(color.r, color.g, color.b);
glBegin(GL_POINTS);
glVertex2i(x,y);
glEnd();
glFlush();
}

void floodFill(GLint x, GLint y, Color oldColor, Color newColor)//seed fill algorithm
{
Color color;
color= getPixelColor(x,y);
if(color.r == oldColor.r && color.g == oldColor.g && color.b == oldColor.b)
{
setPixelColor(x,y, newColor);
floodFill(x+1,y, oldColor, newColor);
floodFill(x,y+1, oldColor, newColor);
floodFill(x-1,y, oldColor, newColor);
floodFill(x,y-1, oldColor, newColor);
}
}

int Height =650, Width=650;
int startX,startY;
static Point vertex [1];
static int pt=0;
Color fillcolor;
void myMouse(int button, int state, int x, int y);
void drawline(double X1,double Y1, double X2, double Y2) //line drawing using dda
{
float x,y,dx,dy,length;
int i;

dx=abs(X2-X1);
dy=abs(Y2-Y1);
if(dx>=dy)
  length=dx;
else
length=dy;
dx=(X2-X1)/length;
dy=(Y2-Y1)/length;
x=X1;
y=Y1;
i=1;
while(i<=length)
{
  glColor3f(1.0,1.0,0.0);
glBegin(GL_POINTS);

glVertex2i(ROUND(x),ROUND(y));
glEnd();
glFlush();
x=x+dx;
y=y+dy;
i=i+1;

}
glFlush();

}

void display(void)
{
 char string[]="Step 1: Draw Polygon and press Enter key to draw final edge";

 glClear(GL_COLOR_BUFFER_BIT);
glColor3f(1.0,1.0,1.0);
glRasterPos2f(10,600);
int len,i;
len=(int)strlen(string);
for(i=0;i<len;i++)
{
glutBitmapCharacter(GLUT_BITMAP_9_BY_15,string[i]);
}
glColor3f(1.0,0.0,0.0);
glRecti(10,30,60,10);
glColor3f(0.0,1.0,0.0);
glRecti(90,30,140,10);
glColor3f(0.0,0.0,1.0);
glRecti(170,30,220,10);
glFlush();//send all output to display
}

void myinit()
{
  glClearColor(0.0,0.0,0.0,1.0); //set background as black
  glColor3f(1.0,1.0,0.0);   // Draw in yellow
  glMatrixMode(GL_PROJECTION);//Establish coordinate system
  glLoadIdentity();
  gluOrtho2D(0.0,650.0,0.0,650.0);

}

void myKeyboard(unsigned char key, int mouseX, int mouseY)
{
 char string[]="Step 2:pick clicking on desired color rectangle";
switch(key)
{
case 13:  // If Enter key is pressed
glColor3f(1.0,1.0,1.0);
glRasterPos2f(10,580);
int len,i;
len=(int)strlen(string);
for(i=0;i<len;i++)
{
  glutBitmapCharacter(GLUT_BITMAP_9_BY_15,string[i]);
}
drawline(vertex[0].x, vertex[0].y,startX,startY);//draw final edge of poly
pt=2;
break;

case 27:  //If Esc key pressed
exit(0);
}

}

void myMouse(int button,int state,int x,int y)
{
if(button==GLUT_LEFT_BUTTON && state == GLUT_DOWN)
{

if(pt==0)  // to accept first point
{
vertex[pt].x=x;
vertex[pt].y=Height-y;
startX=x;
startY=Height-y;
pt++;
}
else if(pt==1)//to draw edges of poly
{
drawline(vertex[0].x,vertex[0].y,x,Height-y);
vertex[0].x=x;
vertex[0].y=Height-y;
}

else if(pt==2)  //accept desired color
{
 fillcolor=getPixelColor(x,Height-y);
char string[]="Step 3:Click inside the polygon to fill color";
glColor3f(1.0,1.0,1.0);
glRasterPos2f(10,560);
int len,i;
len=(int)strlen(string);
for(i=0;i<len;i++)
{
   glutBitmapCharacter(GLUT_BITMAP_9_BY_15,string[i]);
}
pt=3;
}
else if(pt==3) //fill polygon
{
 Color newColor={fillcolor.r,fillcolor.g,fillcolor.b};
Color oldColor= { 0.0f,0.0f,0.0f};
floodFill(x,Height-y,oldColor,newColor);
pt=4;
}
}
glFlush();
}

int main(int argc, char **argv)
{
  glutInit(&argc,argv);  //Initialize toolkit
glutInitDisplayMode(GLUT_SINGLE  | GLUT_RGB);  //set display mode
glutInitWindowSize(650,650); //Set window size
glutInitWindowPosition(0,0); //set window position on screen

//Open screen window

glutCreateWindow("Draw Polygon using Interaction using OpenGL");
glutDisplayFunc(display);  //Register redraw func
glutKeyboardFunc(myKeyboard);  //Register mouse fun
glutMouseFunc(myMouse);
myinit();
glutMainLoop();
return 0;
}




Compile Bove program as   g++ 2.cpp -lGL -lGLU -lglut
and execute as ./a.out




you will get following out