/* mgrtopbm.c - read a MGR bitmap and produce a portable bitmap
**
** 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 <stdio.h>
#include "pbm.h"
#include "mgr.h"

main( argc, argv )
int argc;
char *argv[];
    {
    FILE *ifd;
    register bit *bitrow, *bP;
    bit getbit();
    int rows, cols, depth, padright, row, col;

    pm_progname = argv[0];

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

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

    getinit( ifd, &cols, &rows, &depth, &padright );
    if ( depth != 1 )
	pm_error( "MGR file has depth of %d, must be 1", depth, 0,0,0,0 );

    pbm_writepbminit( stdout, cols, rows );
    bitrow = pbm_allocrow( cols );

    for ( row = 0; row < rows; row++ )
	{
	/* Get data, bit-reversed within each byte. */
        for ( col = 0, bP = bitrow; col < cols; col++, bP++ )
	    *bP = getbit( ifd );
	/* Discard line padding */
        for ( col = 0; col < padright; col ++ )
	    (void) getbit( ifd );
	pbm_writepbmrow( stdout, bitrow, cols );
	}

    pm_close( ifd );

    exit( 0 );
    }


unsigned char item;
int bitsperitem, bitshift;

getinit( file, colsP, rowsP, depthP, padrightP )
FILE *file;
int *colsP, *rowsP, *depthP, *padrightP;
    {
    struct b_header head;
    int pad;

    if ( fread( &head, sizeof(struct old_b_header), 1, file ) != 1 )
	{
	perror( "reading header" );
	exit( 1 );
	}
    if ( head.magic[0] == 'y' && head.magic[1] == 'z' )
	{ /* new style bitmap */
	if ( fread( &head.depth, sizeof(head) - sizeof(struct old_b_header), 1, file ) != 1 )
	    {
	    perror( "reading rest of header" );
	    exit( 1 );
	    }
	*depthP = (int) head.depth - ' ';
	pad = 8;
	}
    else if ( head.magic[0] == 'x' && head.magic[1] == 'z' )
	{ /* old style bitmap with 32-bit padding */
	*depthP = 1;
	pad = 32;
	}
    else if ( head.magic[0] == 'z' && head.magic[1] == 'z' )
	{ /* old style bitmap with 16-bit padding */
	*depthP = 1;
	pad = 16;
	}
    else if ( head.magic[0] == 'z' && head.magic[1] == 'y' )
	{ /* old style 8-bit pixmap with 16-bit padding */
	*depthP = 8;
	pad = 16;
	}
    else
	pm_error(
	    "bad magic chars in MGR file: '%c%c'",
	    head.magic[0], head.magic[1], 0,0,0 );
    *colsP = ( ( (int) head.h_wide - ' ' ) << 6 ) + ( (int) head.l_wide - ' ' );
    *rowsP = ( ( (int) head.h_high - ' ' ) << 6 ) + ( (int) head.l_high - ' ' );
    *padrightP = ( ( *colsP + pad - 1 ) / pad ) * pad - *colsP;

    bitsperitem = 8;
    }

bit
getbit( file )
FILE *file;
    {
    bit b;

    if ( bitsperitem == 8 )
	{
	item = getc( file );
	bitsperitem = 0;
	bitshift = 7;
	}
    bitsperitem++;
    b = ( ( item >> bitshift) & 1 ) ? PBM_BLACK : PBM_WHITE;
    bitshift--;
    return b;
    }