Damned Screenshots

            
/*
 * Code to take screenshots in
 * glut by Alexandre Jasmin. Based on...
 */

/*
 * A skeleton/template GLUT program
 *
 * Written by Brian Paul and in the public domain.
 */

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include <GL/glut.h>


static GLfloat Xrot = 0, Yrot = 0, Zrot = 0;
static GLboolean Anim = GL_FALSE;

static GLint ViewportWidth, ViewportHeight;


static void ScreenShot( void )
{
   int i;
   FILE *f;
   unsigned short int si;
   size_t ImageSize;
   unsigned char *Image;
   
   /* Height X Width X 3 bytes per pixel */
   ImageSize = ViewportHeight * ViewportWidth * 3;

   /*  Alocate a memory buffer to store the image */
   if (!(Image = malloc(ImageSize)))
   {
      perror("malloc()");
      return; 
   }

   /* Copy the front buffer to our image buffer */
   glPixelStorei(GL_PACK_ALIGNMENT, 1);
   glReadBuffer(GL_FRONT);
   glReadPixels(0, 0, ViewportWidth, ViewportHeight, GL_RGB, GL_UNSIGNED_BYTE, Image);
   
   /* Create or overwrite scr_shot.tga */
   if (!(f = fopen("scr_shot.tga", "wb")))
   {
      perror("fopen()");
      free(Image);
      return;
   }
   /* write tga file header */
   fputc('\x00', f); /* ID Length: 0 */
   fputc('\x00', f); /* Color Map Type: no color-map */
   fputc('\x02', f); /* Image Type: Uncompressed, True-color */
   for (i=0; i<5; i++) /* Color Map Specification: no color-map */
	   fputc('\x00', f);

   si = 0; /* X-origin of Image: 0 */
   fwrite(&si, sizeof(short int), 1, f);
   si = 0; /* Y-origin of Image: 0 */
   fwrite(&si, sizeof(short int), 1, f);

   si = ViewportWidth; /* Image Width */
   fwrite(&si, sizeof(short int), 1, f);
   si = ViewportHeight; /* Image Height */
   fwrite(&si, sizeof(short int), 1, f);


   fputc('\x18', f); /* Pixel Depth: 24 */

   fputc('\x00', f); /* Image Descriptor */

   /* write the image itself */
   fwrite(Image, ImageSize, 1, f);

   /* close the file */
   if (fclose(f)==EOF)
   {
      perror("fclose()");
   }

   /* free memory */
   free(Image);
}


static void Idle( void )
{
   Xrot += 3.0;
   Yrot += 4.0;
   Zrot += 2.0;
   glutPostRedisplay();
}


static void Display( void )
{
   glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

   glPushMatrix();
   glRotatef(Xrot, 1, 0, 0);
   glRotatef(Yrot, 0, 1, 0);
   glRotatef(Zrot, 0, 0, 1);

   glutSolidCube(2.0);

   glPopMatrix();

   glutSwapBuffers();
}


static void Reshape( int width, int height )
{
   ViewportWidth = width;
   ViewportHeight = height;
   
   glViewport( 0, 0, width, height );
   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();
   glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -15.0 );
}


static void Key( unsigned char key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
	  case 's':
		  ScreenShot();
	      break;
      case 'a':
         Anim = !Anim;
         if (Anim)
            glutIdleFunc(Idle);
         else
            glutIdleFunc(NULL);
         break;
      case 'z':
         Zrot -= step;
         break;
      case 'Z':
         Zrot += step;
         break;
      case 27:
         exit(0);
         break;
   }
   glutPostRedisplay();
}


static void SpecialKey( int key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case GLUT_KEY_UP:
         Xrot -= step;
         break;
      case GLUT_KEY_DOWN:
         Xrot += step;
         break;
      case GLUT_KEY_LEFT:
         Yrot -= step;
         break;
      case GLUT_KEY_RIGHT:
         Yrot += step;
         break;
   }
   glutPostRedisplay();
}


static void Init( void )
{
   /* setup lighting, etc */
   glEnable(GL_DEPTH_TEST);
   glEnable(GL_LIGHTING);
   glEnable(GL_LIGHT0);
}


int main( int argc, char *argv[] )
{
   glutInit( &argc, argv );
   glutInitWindowPosition( 0, 0 );
   glutInitWindowSize( 400, 400 );
   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
   glutCreateWindow(argv[0]);
   glutReshapeFunc( Reshape );
   glutKeyboardFunc( Key );
   glutSpecialFunc( SpecialKey );
   glutDisplayFunc( Display );
   Init();
   glutMainLoop();
   return 0;
}