/* ppmtopgm.c - convert a portable pixmap to a portable graymap
**
** Copyright (C) 1989 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation.  This software is provided "as is" without express or
** implied warranty.
*/

#include "ppm.h"
#include "pgm.h"
#include "lum.h"

int
main( int argc, char* argv[] )
    {
    FILE* ifp;
    pixel* pixelrow;
    register pixel* pP;
    gray* grayrow;
    register gray* gP;
    int rows, cols, format, row;
    register int col;
    pixval maxval;

    ppm_init( &argc, argv );

    if ( argc > 2 )
	pm_usage( "[ppmfile]" );

    if ( argc == 2 )
	ifp = pm_openr( argv[1] );
    else
	ifp = stdin;

    ppm_readppminit( ifp, &cols, &rows, &maxval, &format );
    pgm_writepgminit( stdout, cols, rows, maxval, 0 );
    pixelrow = ppm_allocrow( cols );
    grayrow = pgm_allocrow( cols );

    for ( row = 0; row < rows; ++row )
	{
	ppm_readppmrow( ifp, pixelrow, cols, maxval, format );
	if ( maxval <= 255 )
	    /* Use fast approximation to 0.299 r + 0.587 g + 0.114 b. */
	    for ( col = 0, pP = pixelrow, gP = grayrow;
		  col < cols;
		  ++col, ++pP, ++gP )
		*gP = (gray)
		    ( ( times77[PPM_GETR( *pP )] + times150[PPM_GETG( *pP )] +
		        times29[PPM_GETB( *pP )] ) >> 8 );
	else
	    /* Can't use fast approximation, so fall back on floats. */
	    for ( col = 0, pP = pixelrow, gP = grayrow;
		  col < cols;
		  ++col, ++pP, ++gP )
		*gP = (gray) ( PPM_LUMIN( *pP ) + 0.5 );
	pgm_writepgmrow( stdout, grayrow, cols, maxval, 0 );
	}

    pm_closer( ifp );
    pm_closew( stdout );

    exit( 0 );
    }