libvips/libsrc/histograms_lut/im_lhisteq.c

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/* @(#) Performs local histogram equalisation on an image using a
* @(#) window of size xw by yw
* @(#) Works only on monochrome images
* @(#)
* @(#) int im_lhisteq(in, out, xwin, ywin)
* @(#) IMAGE *in, *out;
* @(#) int xwin, ywin;
* @(#)
* @(#) Returns 0 on sucess and -1 on error
*
* Copyright: 1991, N. Dessipris
*
* Author: N. Dessipris
* Written on: 24/10/1991
* Modified on :
* 25/1/96 JC
* - rewritten, adapting im_spcor()
* - correct result, 2x faster, partial, simpler, better arg checking
* 8/7/04
* - expand input rather than output with new im_embed() mode
* - _raw() output is one pixel larger
* - sets Xoffset/Yoffset
*/
/*
This file is part of VIPS.
VIPS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
These files are distributed with VIPS - http://www.vips.ecs.soton.ac.uk
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /*HAVE_CONFIG_H*/
#include <vips/intl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/* Hold global stuff here.
*/
typedef struct {
int xwin, ywin; /* Parameters */
int npels; /* Pels in window */
} LhistInfo;
/* lhist generate function.
*/
static int
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lhist_gen( REGION *or, void *seq, void *a, void *b )
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{
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REGION *ir = (REGION *) seq;
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LhistInfo *inf = (LhistInfo *) b;
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Rect irect;
Rect *r = &or->valid;
int le = r->left;
int to = r->top;
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int bo = IM_RECT_BOTTOM( r );
int ri = IM_RECT_RIGHT( r );
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int x, y, i, j;
int lsk;
int coff; /* Offset to move to centre of window */
/* What part of ir do we need?
*/
irect.left = or->valid.left;
irect.top = or->valid.top;
irect.width = or->valid.width + inf->xwin;
irect.height = or->valid.height + inf->ywin;
if( im_prepare( ir, &irect ) )
return( -1 );
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++ ) {
/* Get input and output pointers for this line.
*/
PEL *p = (PEL *) IM_REGION_ADDR( ir, le, y );
PEL *q = (PEL *) IM_REGION_ADDR( or, le, y );
PEL *p1, *p2;
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int hist[256];
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/* Find histogram for start of this line.
*/
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memset( hist, 0, 256 * sizeof( int ) );
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for( p1 = p, j = 0; j < inf->ywin; j++, p1 += lsk )
for( p2 = p1, i = 0; i < inf->xwin; i++, p2++ )
hist[*p2]++;
/* Loop for output pels.
*/
for( x = le; x < ri; x++, p++ ) {
/* Sum histogram up to current pel.
*/
int target = p[coff];
int sum = 0;
for( sum = 0, i = 0; i < target; i++ )
sum += hist[i];
/* Transform.
*/
*q++ = sum * 256 / inf->npels;
/* Adapt histogram - remove the pels from the left hand
* column, add in pels for a new right-hand column.
*/
for( p1 = p, j = 0; j < inf->ywin; j++, p1 += lsk ) {
hist[p1[0]]--;
hist[p1[inf->xwin]]++;
}
}
}
return( 0 );
}
int
im_lhisteq_raw( IMAGE *in, IMAGE *out, int xwin, int ywin )
{
LhistInfo *inf;
if( im_piocheck( in, out ) )
return( -1 );
if( in->Bbits != IM_BBITS_BYTE || in->BandFmt != IM_BANDFMT_UCHAR ||
in->Bands != 1 || in->Coding != IM_CODING_NONE ) {
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im_error( "im_lhisteq", _( "one band uchar uncoded only" ) );
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return( -1 );
}
if( xwin > in->Xsize || ywin > in->Ysize ) {
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im_error( "im_lhisteq", _( "window too large" ) );
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return( -1 );
}
if( im_cp_desc( out, in ) )
return( -1 );
out->Xsize -= xwin - 1;
out->Ysize -= ywin - 1;
/* Save parameters.
*/
if( !(inf = IM_NEW( out, LhistInfo )) )
return( -1 );
inf->xwin = xwin;
inf->ywin = ywin;
inf->npels = xwin * ywin;
/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause
* too many recalculations on overlaps.
*/
if( im_demand_hint( out, IM_FATSTRIP, in, NULL ) )
return( -1 );
/* Write the hist.
*/
if( im_generate( out,
im_start_one, lhist_gen, im_stop_one, in, inf ) )
return( -1 );
out->Xoffset = -xwin / 2;
out->Yoffset = -xwin / 2;
return( 0 );
}
/* The above, with a border to make out the same size as in.
*/
int
im_lhisteq( IMAGE *in, IMAGE *out, int xwin, int ywin )
{
IMAGE *t1 = im_open_local( out, "im_lhisteq:1", "p" );
if( !t1 ||
im_embed( in, t1, 1,
xwin / 2, ywin / 2,
in->Xsize + xwin - 1, in->Ysize + ywin - 1 ) ||
im_lhisteq_raw( t1, out, xwin, ywin ) )
return( -1 );
out->Xoffset = 0;
out->Yoffset = 0;
return( 0 );
}