OpenGL-BoundaryFill-Circle.cpp

#include <math.h>
#include <gl/glut.h>

struct Point {
	GLint x;
	GLint y;
};

struct Color {
	GLfloat r;
	GLfloat g;
	GLfloat b;
};

void init() {
	glClearColor(1.0, 1.0, 1.0, 0.0);
	glColor3f(0.0, 0.0, 0.0);
	glPointSize(1.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0, 640, 0, 480);
}

Color getPixelColor(GLint x, GLint y) {
	Color color;
	glReadPixels(x, y, 1, 1, GL_RGB, GL_FLOAT, &color);
	return color;
}

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

}

void BoundaryFill(int x, int y, Color fillColor, Color boundaryColor) {
	Color currentColor = getPixelColor(x, y);
	if(currentColor.r != boundaryColor.r && currentColor.g != boundaryColor.g && currentColor.b != boundaryColor.b) {
		setPixelColor(x, y, fillColor);
		BoundaryFill(x+1, y, fillColor, boundaryColor);
		BoundaryFill(x-1, y, fillColor, boundaryColor);
		BoundaryFill(x, y+1, fillColor, boundaryColor);
		BoundaryFill(x, y-1, fillColor, boundaryColor);
	}
}

void onMouseClick(int button, int state, int x, int y)
{
	Color fillColor = {1.0f, 0.0f, 0.0f};		// red color will be filled
	Color boundaryColor = {0.0f, 0.0f, 0.0f}; // black- boundary

	Point p = {321, 241}; // a point inside the circle

	BoundaryFill(p.x, p.y, fillColor, boundaryColor);
}

void draw_circle(Point pC, GLfloat radius) {
	GLfloat step = 1/radius;
	GLfloat x, y;

	for(GLfloat theta = 0; theta <= 360; theta += step) {
		x = pC.x + (radius * cos(theta));
		y = pC.y + (radius * sin(theta));
		glVertex2i(x, y);
	}
}

void display(void) {
	Point pt = {320, 240};
	GLfloat radius = 20;

	glClear(GL_COLOR_BUFFER_BIT);
	glBegin(GL_POINTS);
		draw_circle(pt, 50);
	glEnd();
	glFlush();
}

int main(int argc, char** argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
	glutInitWindowSize(640, 480);
	glutInitWindowPosition(200, 200);
	glutCreateWindow("Open GL");
	init();
	glutDisplayFunc(display);
	glutMouseFunc(onMouseClick);
	glutMainLoop();
	return 0;
}