261 lines
6.1 KiB
C
261 lines
6.1 KiB
C
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/* @(#) Functions which calculates statistical differenciating according to
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* @(#) the formula given in page 45 of the book "An intro to digital image
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* @(#) processing" by Wayne Niblack
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* @(#)
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* @(#) At point (i,j) the output is given by the eqn:
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* @(#)
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* @(#) vout(i,j) = a*m0 +(1-a)*meanv +
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* @(#) (vin(i,j) - meanv) * beta*sigma0/(sigma0+beta*stdv)
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* @(#)
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* @(#) Values a, m0, beta and sigma0 are entered
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* @(#) meanv and stdv are the values calculated over a moving window
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* @(#) xwin and ywin are the sizes of the used window
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* @(#) The resultant coefficients are written as floats
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* @(#) in out which has a size of in
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* @(#)
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* @(#) int im_stdif(in, im, alpha, mean0, beta, sigma0, xwin, ywin)
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* @(#) IMAGE *in, *out;
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* @(#) int xwin, ywin;
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* @(#) double alpha, mean0, beta, sigma0;
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* @(#)
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* @(#) Returns 0 on sucess and -1 on error.
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*
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* Copyright: 1990, N. Dessipris.
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*
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* Author: Nicos Dessipris
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* Written on: 02/05/1990
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* Modified on :
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* 6/8/93 JC
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* - now works for odd window sizes
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* - ANSIfication
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* 25/5/95 JC
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* - new IM_ARRAY() macro
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* 25/1/96 JC
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* - im_lhisteq() adapted to make new im_stdif()
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* - now partial, plus rolling window
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* - 5x faster, amazingly
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* - works
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* 7/4/04
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* - now uses im_embed() with edge stretching on the input, not
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* the output
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*/
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/*
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This file is part of VIPS.
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VIPS is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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/*
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These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif /*HAVE_CONFIG_H*/
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#include <vips/intl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <vips/vips.h>
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#ifdef WITH_DMALLOC
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#include <dmalloc.h>
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#endif /*WITH_DMALLOC*/
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/* Hold global stuff here.
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*/
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typedef struct {
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int xwin, ywin; /* Parameters */
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double a, m0, b, s0;
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} StdifInfo;
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/* stdif generate function.
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*/
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static int
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stdif_gen( REGION *or, REGION *ir, IMAGE *in, StdifInfo *inf )
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{
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Rect irect;
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Rect *r = &or->valid;
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int le = r->left;
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int to = r->top;
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int bo = IM_RECT_BOTTOM(r);
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int ri = IM_RECT_RIGHT(r);
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int x, y, i, j;
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int lsk;
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int coff; /* Offset to move to centre of window */
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int npel = inf->xwin * inf->ywin;
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/* What part of ir do we need?
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*/
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irect.left = or->valid.left;
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irect.top = or->valid.top;
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irect.width = or->valid.width + inf->xwin;
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irect.height = or->valid.height + inf->ywin;
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if( im_prepare( ir, &irect ) )
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return( -1 );
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lsk = IM_REGION_LSKIP( ir );
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coff = lsk * (inf->ywin/2) + inf->xwin/2;
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for( y = to; y < bo; y++ ) {
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/* Get input and output pointers for this line.
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*/
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PEL *p = (PEL *) IM_REGION_ADDR( ir, le, y );
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PEL *q = (PEL *) IM_REGION_ADDR( or, le, y );
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PEL *p1, *p2;
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int sum = 0;
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int sum2 = 0;
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/* Precompute some factors.
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*/
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double f1 = inf->a * inf->m0;
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double f2 = 1.0 - inf->a;
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double f3 = inf->b * inf->s0;
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/* Find sum, sum of squares for the start of this line.
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*/
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for( p1 = p, j = 0; j < inf->ywin; j++, p1 += lsk )
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for( p2 = p1, i = 0; i < inf->xwin; i++, p2++ ) {
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int t = *p2;
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sum += t;
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sum2 += t * t;
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}
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/* Loop for output pels.
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*/
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for( x = le; x < ri; x++, p++ ) {
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/* Find stats.
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*/
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double mean = (double)sum / npel;
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double var = (double)sum2 / npel - (mean * mean);
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double sig = sqrt( var );
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/* Transform.
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*/
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double res = f1 + f2*mean + ((double) p[coff] - mean) *
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(f3 / (inf->s0 + inf->b*sig));
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/* And write.
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*/
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if( res < 0.0 )
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*q++ = 0;
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else if( res >= 256.0 )
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*q++ = 255;
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else
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*q++ = res + 0.5;
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/* Adapt sums - remove the pels from the left hand
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* column, add in pels for a new right-hand column.
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*/
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for( p1 = p, j = 0; j < inf->ywin; j++, p1 += lsk ) {
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int t1 = p1[0];
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int t2 = p1[inf->xwin];
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sum -= t1;
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sum2 -= t1 * t1;
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sum += t2;
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sum2 += t2 * t2;
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}
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}
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}
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return( 0 );
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}
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int
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im_stdif_raw( IMAGE *in, IMAGE *out,
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double a, double m0, double b, double s0,
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int xwin, int ywin )
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{
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StdifInfo *inf;
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if( m0 < 0 || m0 > 255 || a < 0 || a > 1.0 || b < 0 || b > 2 ||
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s0 < 0 || s0 > 255 ) {
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im_errormsg( "im_stdif: parameters out of range" );
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return( -1 );
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}
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if( im_piocheck( in, out ) )
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return( -1 );
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if( in->Bbits != IM_BBITS_BYTE || in->BandFmt != IM_BANDFMT_UCHAR ||
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in->Bands != 1 || in->Coding != IM_CODING_NONE ) {
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im_errormsg( "im_stdif: one band uchar uncoded only" );
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return( -1 );
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}
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if( xwin > in->Xsize || ywin > in->Ysize ) {
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im_errormsg( "im_stdif: window too large" );
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return( -1 );
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}
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if( im_cp_desc( out, in ) )
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return( -1 );
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out->Xsize -= xwin;
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out->Ysize -= ywin;
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/* Save parameters.
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*/
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if( !(inf = IM_NEW( out, StdifInfo )) )
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return( -1 );
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inf->xwin = xwin;
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inf->ywin = ywin;
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inf->a = a;
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inf->m0 = m0;
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inf->b = b;
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inf->s0 = s0;
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/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause
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* too many recalculations on overlaps.
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*/
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if( im_demand_hint( out, IM_FATSTRIP, in, NULL ) )
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return( -1 );
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/* Write the hist.
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*/
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if( im_generate( out,
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im_start_one, stdif_gen, im_stop_one, in, inf ) )
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return( -1 );
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return( 0 );
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}
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/* The above, with a border to make out the same size as in.
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*/
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int
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im_stdif( IMAGE *in, IMAGE *out,
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double a, double m0, double b, double s0,
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int xwin, int ywin )
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{
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IMAGE *t1 = im_open_local( out, "im_stdif:1", "p" );
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if( !t1 ||
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im_embed( in, t1, 1, xwin / 2, ywin / 2,
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in->Xsize + xwin - 1,
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in->Ysize + ywin - 1 ) ||
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im_stdif_raw( t1, out, a, m0, b, s0, xwin, ywin ) )
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return( -1 );
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return( 0 );
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}
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