tomwalters@0: /*
tomwalters@0:     Copyright (c) Applied Psychology Unit, Medical Research Council. 1988, 1989
tomwalters@0:     ===========================================================================
tomwalters@0: 
tomwalters@0:     Permission to use, copy, modify, and distribute this software without fee 
tomwalters@0:     is hereby granted for research purposes, provided that this copyright 
tomwalters@0:     notice appears in all copies and in all supporting documentation, and that 
tomwalters@0:     the software is not redistributed for any fee (except for a nominal shipping 
tomwalters@0:     charge). Anyone wanting to incorporate all or part of this software in a
tomwalters@0:     commercial product must obtain a license from the Medical Research Council.
tomwalters@0: 
tomwalters@0:     The MRC makes no representations about the suitability of this 
tomwalters@0:     software for any purpose.  It is provided "as is" without express or implied 
tomwalters@0:     warranty.
tomwalters@0:  
tomwalters@0:     THE MRC DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 
tomwalters@0:     ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL THE
tomwalters@0:     A.P.U. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY 
tomwalters@0:     DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN 
tomwalters@0:     AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 
tomwalters@0:     OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
tomwalters@0: */
tomwalters@0: 
tomwalters@0: /*
tomwalters@0:     grey.c
tomwalters@0:     ======
tomwalters@0: 
tomwalters@0:     Greyscale routines for mapping arrays of shorts into
tomwalters@0:     columns of pixel values (dithered if necessary).
tomwalters@0: 
tomwalters@0: 
tomwalters@0:     Copyright (c), 1989  The Medical Research Council, Applied Psychology Unit.
tomwalters@0: 
tomwalters@0: 
tomwalters@0:     Author  : John Holdsworth
tomwalters@0:     Written : 11th May, 1989.
tomwalters@0: 
tomwalters@0:     Edited  :
tomwalters@0: 
tomwalters@0: */
tomwalters@0: #if defined( NeXT )
tomwalters@0: #include <stdlib.h>
tomwalters@0: #else
tomwalters@0: #include <malloc.h>
tomwalters@0: #endif
tomwalters@0: #include "grey.h"
tomwalters@0: 
tomwalters@0: 
tomwalters@0: #ifndef lint
tomwalters@0: static char *sccs_id = "@(#)grey.c	1.9     J. Holdsworth (MRC-APU)  11/8/90" ;
tomwalters@0: #endif
tomwalters@0: 
tomwalters@0: /* standard recursive dither patterns for grey scales */
tomwalters@0: 
tomwalters@0: static int dither(n,x,y)
tomwalters@0: int n,x,y;
tomwalters@0: {
tomwalters@0:     static int seed[2][2] = {{ 0, 2 } , { 3, 1 }};
tomwalters@0: 
tomwalters@0:     if( n==2 )
tomwalters@0: 	return ( seed[y][x] ) ;
tomwalters@0:     else
tomwalters@0: 	return ( dither(n/2,x%(n/2),y%(n/2))*4 + seed[y%n/(n/2)][x%n/(n/2)] );
tomwalters@0: 
tomwalters@0: }
tomwalters@0: 
tomwalters@0: int *DitherLine( size, line, length, min, max )
tomwalters@0: int size, line, length, min, max ;
tomwalters@0: {
tomwalters@0:     int i, *dither_line = (int *) malloc( (unsigned) length * sizeof ( *dither_line ) ) ;
tomwalters@0: 
tomwalters@0:     if( dither_line != (int *) 0 ) {
tomwalters@0: 	for( i=0; i < size && i < length ; i++ )
tomwalters@0: 	    dither_line[ i ] = min + (double) dither( size, i, line ) * ( max - min ) / ( size * size ) + 0.5  ;
tomwalters@0: 
tomwalters@0: 	/* repeat for rest of line */
tomwalters@0: 
tomwalters@0: 	for( ; i < length ; i++ )
tomwalters@0: 	    dither_line[ i ] = dither_line[ i%size ] ;
tomwalters@0:     }
tomwalters@0: 
tomwalters@0:     return ( dither_line ) ;
tomwalters@0: }
tomwalters@0: 
tomwalters@0: int **Dithers( size, length, min, max )
tomwalters@0: int size, length, min, max ;
tomwalters@0: {
tomwalters@0:     int i, **diths = (int **) malloc( (unsigned) size * sizeof ( *diths ) ) ;
tomwalters@0: 
tomwalters@0:     if( diths != (int **) 0 )
tomwalters@0: 	for( i=0 ; i<size ; i++ )
tomwalters@0: 	    diths[i] = DitherLine( size, i, length, min, max ) ;
tomwalters@0: 
tomwalters@0:     return ( diths ) ;
tomwalters@0: }
tomwalters@0: 
tomwalters@0: void FreeDithers( diths, size )
tomwalters@0: int **diths, size ;
tomwalters@0: {
tomwalters@0:     int i ;
tomwalters@0: 
tomwalters@0:     for( i=0 ; i<size ; i++ )
tomwalters@0: 	free( (char *) diths[i] ) ;
tomwalters@0: 
tomwalters@0:     free( (char *) diths ) ;
tomwalters@0: 
tomwalters@0:     return ;
tomwalters@0: }
tomwalters@0: 
tomwalters@0: /*
tomwalters@0: 
tomwalters@0:     makeLookup prepares 64k byte lookup table for mapping shorts to pixel values.
tomwalters@0:     setmap is a routine to be called to locate the window system's color map
tomwalters@0:     and set it up returning  the number of pixels availiable and allocating an
tomwalters@0:     array containing these values in order of increasing blackness.
tomwalters@0: 
tomwalters@0: */
tomwalters@0: 
tomwalters@0: #define GREY_DITHER_SIZE 8
tomwalters@0: 
tomwalters@0: #define PIXEL_TABLE_SIZE ((1l<<16)-1)
tomwalters@0: 
tomwalters@0: struct _lookup *makeLookup( getgreyscale, black, white, height )
tomwalters@0: char *(*getgreyscale)() ;
tomwalters@0: int black, white ;
tomwalters@0: int height ;
tomwalters@0: {
tomwalters@0:     register char *tableptr, *end, pixval ;
tomwalters@0:     char *greyscale  ;
tomwalters@0:     struct _lookup *lookup ;
tomwalters@0:     int npixels, pix, min, diff ;
tomwalters@0: 
tomwalters@0:     if( ( lookup = (struct _lookup *) malloc( (unsigned) sizeof (*lookup) ) ) != 0 &&
tomwalters@0: 	( lookup->pixeltable =        malloc( (unsigned) PIXEL_TABLE_SIZE ) ) != 0 &&
tomwalters@0: 	( lookup->output     =        malloc( (unsigned) height + 1       ) ) != 0 ) {
tomwalters@0: 
tomwalters@0: 	/* output null terminated for potential printing out */
tomwalters@0: 
tomwalters@0: 	lookup->output[height] = '\000' ;
tomwalters@0: 
tomwalters@0: 	/* get black to white greyscale */
tomwalters@0: 
tomwalters@0: 	greyscale = getgreyscale( &npixels ) ;
tomwalters@0: 
tomwalters@0: 
tomwalters@0: 	if( black < white ) {
tomwalters@0: 	    min  =         black ;
tomwalters@0: 	    diff = white - black ;
tomwalters@0: 	}
tomwalters@0: 	else {
tomwalters@0: 	    min  =         white ;
tomwalters@0: 	    diff = black - white ;
tomwalters@0: 	}
tomwalters@0: 
tomwalters@0: 	lookup->dithers = Dithers( GREY_DITHER_SIZE, height, min, min + diff / ( npixels - 1 ) ) ;
tomwalters@0: 
tomwalters@0: 	tableptr = lookup->pixeltable ;
tomwalters@0: 
tomwalters@0: 	for( pix=0 ; pix<npixels ; pix++ ) {
tomwalters@0: 
tomwalters@0: 	    if( black < white )
tomwalters@0: 		pixval = greyscale[          pix] ;
tomwalters@0: 	    else
tomwalters@0: 		pixval = greyscale[npixels-1-pix] ;
tomwalters@0: 
tomwalters@0: 	    if( pix < npixels-1 )
tomwalters@0: 		end = lookup->pixeltable + diff * pix / ( npixels - 1 ) + 1 ;
tomwalters@0: 	    else
tomwalters@0: 		end = lookup->pixeltable + PIXEL_TABLE_SIZE ;
tomwalters@0: 
tomwalters@0: 	    while( tableptr < end )
tomwalters@0: 		*tableptr++ = pixval ;
tomwalters@0: 	}
tomwalters@0: 
tomwalters@0: 	return ( lookup ) ;
tomwalters@0:     }
tomwalters@0: 
tomwalters@0:     return ( 0 ) ;
tomwalters@0: }
tomwalters@0: 
tomwalters@0: /*
tomwalters@0:     doLookup just performs the lookup of pixel values to convert an
tomwalters@0:     array of short values into the corresponding pixels for output.
tomwalters@0:     when few pixel values are availiable dithering is used to make the
tomwalters@0:     most of them.
tomwalters@0: 
tomwalters@0: */
tomwalters@0: 
tomwalters@0: char *lookup( col, lookup, input, match, height )
tomwalters@0: int col ;
tomwalters@0: struct _lookup *lookup ;
tomwalters@0: short *input ;
tomwalters@0: int *match, height ;
tomwalters@0: {
tomwalters@0:     register int diff ;
tomwalters@0:     register int *mptr = match ;
tomwalters@0:     register int *mend = match + height ;
tomwalters@0:     register char *dptr = lookup->output ;
tomwalters@0:     register char *lookuptable = lookup->pixeltable ;
tomwalters@0:     register int *ditherptr = lookup->dithers[ col%GREY_DITHER_SIZE ] ;
tomwalters@0: 
tomwalters@0:     while( mptr < mend ) {
tomwalters@0: 
tomwalters@0: 	diff = input[ *mptr++ ] - *ditherptr++ ;
tomwalters@0: 
tomwalters@0: 	if( diff > 0 )
tomwalters@0: 	    *dptr++ = lookuptable[ diff ] ;
tomwalters@0: 	else
tomwalters@0: 	    *dptr++ = lookuptable[   0  ] ;
tomwalters@0:     }
tomwalters@0: 
tomwalters@0:     return ( lookup->output ) ;
tomwalters@0: }
tomwalters@0: 
tomwalters@0: void freeLookup( lookup )
tomwalters@0: struct _lookup *lookup ;
tomwalters@0: {
tomwalters@0:     if( lookup != 0 ) {
tomwalters@0: 
tomwalters@0: 	free( lookup->pixeltable ) ;
tomwalters@0: 
tomwalters@0: 	free( lookup->output ) ;
tomwalters@0: 
tomwalters@0: 	FreeDithers( lookup->dithers, GREY_DITHER_SIZE ) ;
tomwalters@0: 
tomwalters@0: 	free( (char *) lookup ) ;
tomwalters@0:     }
tomwalters@0: }
tomwalters@0: 
tomwalters@0: /* for compattability */
tomwalters@0: 
tomwalters@0: void doLookup( col, lookup, input, match, height, data )
tomwalters@0: int col ;
tomwalters@0: struct _lookup *lookup ;
tomwalters@0: short *input ;
tomwalters@0: int *match, height ;
tomwalters@0: char *data ;
tomwalters@0: {
tomwalters@0:     register int diff ;
tomwalters@0:     register int *mptr = match ;
tomwalters@0:     register int *mend = match + height ;
tomwalters@0:     register char *dptr = data ;
tomwalters@0:     register char *lookuptable = lookup->pixeltable ;
tomwalters@0:     register int *ditherptr = lookup->dithers[ col%GREY_DITHER_SIZE ] ;
tomwalters@0: 
tomwalters@0:     while( mptr < mend ) {
tomwalters@0: 
tomwalters@0: 	diff = input[ *mptr++ ] - *ditherptr++ ;
tomwalters@0: 
tomwalters@0: 	if( diff > 0 )
tomwalters@0: 	    *dptr++ = lookuptable[ diff ] ;
tomwalters@0: 	else
tomwalters@0: 	    *dptr++ = lookuptable[   0  ] ;
tomwalters@0:     }
tomwalters@0: 
tomwalters@0:     return ;
tomwalters@0: }
tomwalters@0: