100 lines
2.3 KiB
C
100 lines
2.3 KiB
C
/* im_scale
|
|
*
|
|
* Author: John Cupitt
|
|
* Written on: 22/4/93
|
|
* Modified on:
|
|
* 30/6/93 JC
|
|
* - adapted for partial v2
|
|
* - ANSI
|
|
* 31/8/93 JC
|
|
* - calculation of offset now includes scale
|
|
* 8/5/06
|
|
* - set Type on output too
|
|
* 16/10/06
|
|
* - what? no, don't set Type, useful to be able to scale histograms, for
|
|
* example
|
|
* 1/2/10
|
|
* - gtkdoc
|
|
*/
|
|
|
|
/*
|
|
|
|
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 <vips/vips.h>
|
|
|
|
/**
|
|
* im_scale:
|
|
* @in: input image
|
|
* @out: output image
|
|
*
|
|
* Search the image for the maximum and minimum value, then return the image
|
|
* as unsigned 8-bit, scaled so that the maximum value is 255 and the
|
|
* minimum is zero.
|
|
*
|
|
* See also: im_clip2fmt(), im_scaleps().
|
|
*
|
|
* Returns: 0 on success, -1 on error
|
|
*/
|
|
int
|
|
im_scale( IMAGE *in, IMAGE *out )
|
|
{
|
|
DOUBLEMASK *stats;
|
|
IMAGE *t = im_open_local( out, "im_scale:1", "p" );
|
|
double mx, mn;
|
|
double scale, offset;
|
|
|
|
/* Measure min and max, calculate transform.
|
|
*/
|
|
if( !t || !(stats = im_stats( in )) )
|
|
return( -1 );
|
|
mn = stats->coeff[0];
|
|
mx = stats->coeff[1];
|
|
im_free_dmask( stats );
|
|
|
|
if( mn == mx )
|
|
/* Range of zero: just return black.
|
|
*/
|
|
return( im_black( out, in->Xsize, in->Ysize, in->Bands ) );
|
|
scale = 255.0 / (mx - mn);
|
|
offset = -(mn * scale);
|
|
|
|
/* Transform!
|
|
*/
|
|
if( im_lintra( scale, in, offset, t ) ||
|
|
im_clip2fmt( t, out, IM_BANDFMT_UCHAR ) )
|
|
return( -1 );
|
|
|
|
return( 0 );
|
|
}
|