Programming

// imgdata is the image data to be written into a pgm image file

int writePgm( char* Filename, unsigned char* imgdata, int width, int height )
{
   void *buf;
   int ret=0;

   unsigned long long int bytes_written=0;
   int ps=getpagesize();
   posix_memalign(&buf, ps, height*width*2);  //each pixel is equvivalent to 2 bytes
   memcpy(buf ,imgdata, height*width*2);

   FILE* stream;
   int fd = open(Filename, O_CREAT | O_WRONLY |O_DIRECT, 00666);
   stream = fdopen(fd, "wb");

   if( stream == NULL)
   {
     perror( "Can't open image file" );
     return 1;
   }
   
   fprintf( stream, "P5\n%u %u 255\n", width, height );
   
   fwrite( buf, ps, width*height/ps, stream );
   
   fclose( stream );
   close(fd);
   return 0;
}