/*
 *  readImage.c
 *  This program reads a raw image and displays it.
 *  Author: Judy Challinger
 *
 *  To create a raw image from another image type, use
 *  the "convert" utility that is part of ImageMagick
 *  on the Unix system. Try "man convert." For example:
 *
 *  convert -flip CindiPup.jpg CindiPup.rgb
 * .
 */
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>

GLubyte  *imageData;
GLsizei   width, height;

/*
 * Reads a raw image file into an array.
 * 
 * filename - name of the raw image file
 * width - width of the image
 * height - height of the image
 * 
 * returns - pointer to an array of bytes containing the image data
 */
GLubyte*  readImage(const char* filename, GLsizei width, GLsizei height)
{
    FILE * file;

    // open file
    file = fopen(filename, "rb");
    if (file == NULL) return 0;

    // allocate back buffer
    imageData = (GLubyte*) malloc(width * height * 3);

    // read data
    fread(imageData, width * height * 3, 1, file);
    fclose(file);

    return imageData;
}

/**
 * Initializes OpenGL
 */
void init(void)
{
   glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
   glClearColor (0.0, 0.0, 0.0, 0.0);
}

/*
 * Display callback
 */
void display(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   glRasterPos2i(0, 0);
   glDrawPixels(width, height, GL_RGB, GL_UNSIGNED_BYTE, imageData);
   glFlush();
}

/*
 * Reshape callback
 * 
 * w - new window width
 * h - new window height
 */
void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho (0, w, 0, h, -1.0, 1.0);
   glMatrixMode(GL_MODELVIEW);
}

/*
 * Keyboard callback
 *
 * key - the key that was pressed
 * x - cursor x coordinate
 * y - cursor y coordinate
 */
void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      // escape key
      case 27:
         exit(0);
   }
}

/*  
 * Main
 */
int main(int argc, char** argv)
{
   width = 256;
   height = 256;
   imageData = readImage("CindiPup.rgb", width, height);    

   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize(width, height);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutReshapeFunc(reshape);
   glutKeyboardFunc(keyboard);
   glutDisplayFunc(display);
   glutMainLoop();
   return 0;
}