/* October 2003
 * Brian J.Ross
 * Brock University, Dept of Computer Science
 * COSC 3P98 Midterm solution A
 *
 * A simple gradient renderer.
 */
#if !defined(Linux)
  #include <windows.h>           //Not Linux must be windows
#endif

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdio.h>

#define MINDIM 0
#define MAXDIM 500


struct glob {
   float xmin;
   float xmax;
};
struct glob global = {0.0, 500.0};


void drawGradient(bot_x, bot_y, top_x, top_y, r1, g1, b1, r2, g2, b2) 
	float bot_x, bot_y, top_x, top_y;
	int  r1, g1, b1, r2, g2, b2; {
	float delta, r_inc, g_inc, b_inc;
	float red, green, blue;
	int x, y;

	delta = (top_x - bot_x);
	r_inc = (r2-r1)/delta;
	g_inc = (g2-g1)/delta;
	b_inc = (b2-b1)/delta;

	red = (float)r1;
	green = (float)g1;
	blue = (float)b1;

	glBegin(GL_POINTS);
	for (x = (int)bot_x; x < top_x; x++) {
		glColor3ub((short)red, (short)green, (short)blue);
		for (y = bot_y; y < top_y; y++) {
		    glVertex2f((float)x, (float)y);
		};
		red = red +  r_inc;
		green = green + g_inc;
		blue = blue + b_inc;
	};
	glEnd();
}

void mydisplay(void) {

	glClear(GL_COLOR_BUFFER_BIT);
	drawGradient(30.0, 30.0, 250.0, 200.0, 50, 0, 20, 200, 200, 25);
	glFlush();
}

int main(argc, argv)
	int argc;
	char **argv; {

	glutInit(&argc, argv);
	glutInitWindowSize(MAXDIM, MAXDIM);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutCreateWindow("Midterm solution A");

	glutDisplayFunc(mydisplay);

	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(global.xmin, global.xmax, global.xmin, global.xmax);
	glClearColor (1.0, 1.0, 1.0, 1.0);

	glutMainLoop();
	return 0;
}