I have a function in C++ which draws an ellipse. Now I want to add a fill option to that ellipse. How do I do that? I tried using the flood fill algorithm, but it does not work correctly when the surface already contains paintings.
Here is my current algorithm:
const double TwoPI = ( PI * 2 );
const double Step = ( PI / 180.0f );
for( double i = 0; i < TwoPI; i += Step )
float x_offset = ( radiusX * cos( (float) i ) );
float y_offset = ( radiusY * sin( (float) i ) );
int x = int( a_X + x_offset );
int y = int( a_Y + y_offset );
if( prevX == -1 && prevY == -1 )
Plot( x, y, color );
Line( prevX, prevY, x, y, color );
Well, one idea could be to just traverse half the circle, and instead compute points that are symmetrically placed around i.e. the y axis. Then draw a horizontal line between them, filling in all the pixels.