scrnsht.c

/*
    ssystem 1.6
    Copyright (C) 1997-1999  Raul Alonso <amil@las.es>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include <stdio.h>
#include <stdlib.h>
#include "jpeglib.h"
#include "ssystem.h"

/* based on screenshot function from PyroTechnics v1.3
	http://www.ling.ed.ac.uk/~oliphant/pyro

   and on IJG sample code	
*/
void ScreenShot(char *filename)
{
  int i;
  unsigned char *pixels;
  struct jpeg_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
  FILE * outfile;               /* target file */
  JSAMPROW row_pointer[1];      /* pointer to JSAMPLE row[s] */
  int row_stride;               /* physical row width in image buffer */
            
  cinfo.err = jpeg_std_error(&jerr);
  /* Now we can initialize the JPEG compression object. */
  jpeg_create_compress(&cinfo);
  if ((outfile = fopen(filename, "wb")) == NULL) {
  	error("can't write screenshot\n");
  	exit(-1);
  }
  jpeg_stdio_dest(&cinfo, outfile);
  cinfo.image_width = width;      /* image width and height, in pixels */
  cinfo.image_height = height;
  cinfo.input_components = 3;           /* # of color components per pixel */
  cinfo.in_color_space = JCS_RGB;       /* colorspace of input image */
  jpeg_set_defaults(&cinfo);                            
  jpeg_set_quality(&cinfo, jpeg_quality, TRUE /* limit to baseline-JPEG values */);
  jpeg_start_compress(&cinfo, TRUE);

  pixels=(unsigned char *)malloc(height*width*3);
  glReadPixels(0,0,width,height,GL_RGB,GL_UNSIGNED_BYTE,
			   pixels);

  row_stride = width * 3;
  i=cinfo.image_height-1;
  while (i >= 0) {
      /* jpeg_write_scanlines expects an array of pointers to scanlines.
       * Here the array is only one element long, but you could pass
       * more than one scanline at a time if that's more convenient.
       */
       row_pointer[0] = & pixels[i * row_stride];
       (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
       i--;
  }
  jpeg_finish_compress(&cinfo);
  fclose(outfile);
  jpeg_destroy_compress(&cinfo);                                 

  free(pixels);
}