//
//	Adapted from: OpenGL, A Primer, E. Angel, Addison Wesley
// 

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

#include <GL/glut.h>

int n;
int m;


GLubyte *image;


void display(void)
{


	glClear(GL_COLOR_BUFFER_BIT);

	glBegin(GL_QUADS);
		glTexCoord2f(0.0,0.0);
		glVertex2i(10,10);
		glTexCoord2f(0.0,1.0);
		glVertex2i(10,m-11);
		glTexCoord2f(1.0,1.0);
		glVertex2i(n-11,m-11);
		glTexCoord2f(1.0,0.0);
		glVertex2i(n-11,10);
	glEnd();

	glFlush();
}


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];
	
	printf("enter file name\n");
	scanf("%s", b);
	fd = fopen(b, "rb");				// flag b may be not necessary on Unix
	fscanf(fd,"%[^\n] ", b);
	if(b[0]!='P'|| b[1] != '6')			// P6 is binary encoded, P3 is ASCII
	{
		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(GLubyte) * nm);

	{
		GLubyte * tmp=malloc(3 * sizeof(GLubyte) * nm);
		fread(tmp, sizeof(GLubyte), 3 * nm, fd);
	
		//
		// The image in tmp is not in the correct order...
		//
		for(i=0;i<nm;i++) 
		{
			image[3*nm-3*i-3]=tmp[0];
			image[3*nm-3*i-2]=tmp[1];
			image[3*nm-3*i-1]=tmp[2];
			tmp+=3;
		}
		tmp-=3*nm;
		free(tmp);
	}

	
	printf("read image\n");
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB );
    glutInitWindowSize(n, m);
	glutInitWindowPosition(0,0);
    glutCreateWindow("image");
	glutReshapeFunc(myreshape);
    glutDisplayFunc(display);

	glEnable(GL_TEXTURE_2D);
	glTexImage2D(GL_TEXTURE_2D,0, GL_RGB, n, m, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
	glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP);
	glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T,GL_CLAMP);
	glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
	glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
	glClearColor(0.0, 0.0, 0.0, 1.0);
	glColor3f(1.0,1.0,1.0);
    glutMainLoop();

}