You may save your points in an array and draw a polygon instead, or triangle fans.
glBegin(GL_POLYGON);
or:
void BresenhamKrug(int xCenter, int yCenter,int r){ //napravite parametarski poziv
int x=0,y=r;
int d=3-(2*r);
glColor3f(0.5,0.3,1.);
glBegin(GL_POLYGON);
while(x<=y)
{
glVertex2i(xCenter+x,yCenter+y); glVertex2i(xCenter+y,yCenter+x);
glVertex2i(xCenter-x,yCenter+y); glVertex2i(xCenter+y,yCenter-x);
glVertex2i(xCenter-x,yCenter-y); glVertex2i(xCenter-y,yCenter-x);
glVertex2i(xCenter+x,yCenter-y); glVertex2i(xCenter-y,yCenter+x);
if (d<0)
d += (4*x)+6;
else{
d += (4*(x-y))+10;
y--;
}
x++;
}
glEnd();
glFlush();
}
but not sure a simple circle equation would not have been sufficient..drawing circle, rasterization being handled by openGL.