//
//	From: OpenGL, A Primer, E. Angel, Addison Wesley
// 

#include <stdio.h>
#include <stdlib.h>

#include <GL/glut.h>

int n;
int m;


GLuint *image;


void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);
	glRasterPos2i(0,0);
    glDrawPixels(n,m,GL_RGB, GL_UNSIGNED_INT, image);

	glFlush();
	printf("finished display \n");
}


void myreshape(int h, int w)
{
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0, (GLfloat) n, 0.0, (GLfloat) m);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glViewport(0,0,h,w);
}


int main(int argc, char **argv)
{
	FILE *fd;
	int  k, nm;
	char c;
	int i;
	char b[100];
	float s;
	int red, green, blue;

	printf("enter file name\n");
	scanf("%s", b);
	fd = fopen(b, "r");
	fscanf(fd,"%[^\n] ",b);
	if(b[0]!='P'|| b[1] != '3')
	{
		printf("%s is not a PPM file!\n", b); 
		exit(0);
	}
	printf("%s is a PPM file\n",b);
	fscanf(fd, "%c",&c);
	while(c == '#') 
	{
		fscanf(fd, "%[^\n] ", b);
		printf("%s\n",b);
		fscanf(fd, "%c",&c);
	}
	ungetc(c,fd); 
	fscanf(fd, "%d %d %d", &n, &m, &k);

	printf("%d rows  %d columns  max value= %d\n",n,m,k);

	nm = n*m;

	image=malloc(3*sizeof(GLuint)*nm);


	s=255./k;

	for(i=0;i<nm;i++) 
	{
		fscanf(fd,"%d %d %d",&red, &green, &blue );
		image[3*nm-3*i-3]=red;
		image[3*nm-3*i-2]=green;
		image[3*nm-3*i-1]=blue;
	}


	printf("read image\n");
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );
    glutInitWindowSize(n, m);
	glutInitWindowPosition(0,0);
    glutCreateWindow("image");
	glutReshapeFunc(myreshape);
    glutDisplayFunc(display);
	glPixelTransferf(GL_RED_SCALE, s);
	glPixelTransferf(GL_GREEN_SCALE, s);
	glPixelTransferf(GL_BLUE_SCALE, s);
	glPixelStorei(GL_UNPACK_SWAP_BYTES,GL_TRUE);
	glClearColor(1.0, 1.0, 1.0, 1.0);
    glutMainLoop();


}