libvips/libsrc/histograms_lut/im_invertlut.c

269 lines
6.2 KiB
C

/* @(#) Given a mask of target values and real values, generate a LUT which
* @(#) will map reals to targets. Handy for linearising images from
* @(#) measurements of a colour chart. All values in [0,1]. Piecewise linear
* @(#) interpolation, extrapolate head and tail to 0 and 1.
* @(#)
* @(#) Eg. input line like:
* @(#)
* @(#) 0.1 0.2 0.3 0.1
* @(#)
* @(#) means a patch with 10% reflectance produces an image with 20% in
* @(#) channel 1, 30% in channel 2, and 10% in channel 3.
* @(#)
* @(#) Inputs don't need to be sorted (we do that). Generate any precision
* @(#) LUT ... typically ask for 256 elements.
*
* Written on: 5/6/01
* Modified on :
* 7/7/03 JC
* - generate image rather than doublemask (arrg)
*/
/*
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 <math.h>
#include <vips/vips.h>
#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif /*WITH_DMALLOC*/
/*
#define DEBUG
*/
/* Our state.
*/
typedef struct {
DOUBLEMASK *input; /* Input mask */
IMAGE *output; /* Output lut */
int lut_size; /* Number of output elements to generate */
double **data; /* Rows of unpacked matrix */
} State;
/* Use this to sort our input rows by the first column.
*/
static int
compare( const void *a, const void *b )
{
double **r1 = (double **) a;
double **r2 = (double **) b;
double diff = r1[0][0] - r2[0][0];
if( diff > 0 )
return( 1 );
else if( diff == 0 )
return( 0 );
else
return( -1 );
}
/* Free our state.
*/
static void
free_state( State *state )
{
if( state->data ) {
int i;
for( i = 0; i < state->input->ysize; i++ )
if( state->data[i] ) {
im_free( state->data[i] );
state->data[i] = NULL;
}
im_free( state->data );
state->data = NULL;
}
}
/* Fill our state.
*/
static int
build_state( State *state, DOUBLEMASK *input, IMAGE *output, int lut_size )
{
int x, y, i;
state->input = input;
state->output = output;
state->lut_size = lut_size;
state->data = NULL;
if( !(state->data = IM_ARRAY( NULL, input->ysize, double * )) )
return( -1 );
for( y = 0; y < input->ysize; y++ )
state->data[y] = NULL;
for( y = 0; y < input->ysize; y++ )
if( !(state->data[y] = IM_ARRAY( NULL, input->xsize, double )) )
return( -1 );
for( i = 0, y = 0; y < input->ysize; y++ )
for( x = 0; x < input->xsize; x++, i++ )
state->data[y][x] = input->coeff[i];
/* Sanity check for data range.
*/
for( y = 0; y < input->ysize; y++ )
for( x = 0; x < input->xsize; x++ )
if( state->data[y][x] > 1.0 ||
state->data[y][x] < 0.0 ) {
im_errormsg( "im_invertlut: element out of "
"range [0,1]" );
return( -1 );
}
/* Sort by 1st column in input.
*/
qsort( state->data, input->ysize, sizeof( double * ), compare );
#ifdef DEBUG
printf( "Input table, sorted by 1st column\n" );
for( y = 0; y < input->ysize; y++ ) {
printf( "%.4d ", y );
for( x = 0; x < input->xsize; x++ )
printf( "%.9f ", state->data[y][x] );
printf( "\n" );
}
#endif /*DEBUG*/
return( 0 );
}
static int
invertlut( State *state )
{
DOUBLEMASK *input = state->input;
int ysize = input->ysize;
int xsize = input->xsize;
IMAGE *output = state->output;
double *odata = (double *) output->data;
int bands = xsize - 1;
double **data = state->data;
int lut_size = state->lut_size;
int i;
/* Do each output channel separately.
*/
for( i = 0; i < bands; i++ ) {
/* The first and last lut positions we know real values for.
*/
int first = data[0][i + 1] * (lut_size - 1);
int last = data[ysize - 1][i + 1] * (lut_size - 1);
int k;
double fac;
/* Extrapolate bottom and top segments to (0,0) and (1,1).
*/
fac = data[0][0] / first;
for( k = 0; k < first; k++ )
odata[i + k * bands] = k * fac;
fac = (1 - data[ysize - 1][0]) / ((lut_size - 1) - last);
for( k = last + 1; k < lut_size; k++ )
odata[i + k * bands] =
data[ysize - 1][0] + (k - last) * fac;
/* Interpolate the data setions.
*/
for( k = first; k <= last; k++ ) {
/* Where we're at in the [0,1] range.
*/
double ki = (double) k / (lut_size - 1);
double irange, orange;
int j;
/* Search for the lowest real value < ki. There may
* not be one: if not, just use 0. Tiny error.
*/
for( j = ysize - 1; j >= 0; j-- )
if( data[j][i + 1] < ki )
break;
if( j == -1 )
j = 0;
/* Interpolate k as being between row data[j] and row
* data[j + 1].
*/
irange = data[j + 1][i + 1] - data[j][i + 1];
orange = data[j + 1][0] - data[j][0];
odata[i + k * bands] = data[j][0] +
orange * ((ki - data[j][i + 1]) / irange);
}
}
return( 0 );
}
int
im_invertlut( DOUBLEMASK *input, IMAGE *output, int lut_size )
{
State state;
if( !input || input->xsize < 2 || input->ysize < 1 ) {
im_errormsg( "im_invertlut: bad input matrix" );
return( -1 );
}
if( lut_size < 1 || lut_size > 65536 ) {
im_errormsg( "im_invertlut: bad lut_size" );
return( -1 );
}
im_initdesc( output,
lut_size, 1, input->xsize - 1,
IM_BBITS_DOUBLE, IM_BANDFMT_DOUBLE,
IM_CODING_NONE, IM_TYPE_HISTOGRAM, 1.0, 1.0, 0, 0 );
if( im_setupout( output ) )
return( -1 );
if( build_state( &state, input, output, lut_size ) ||
invertlut( &state ) ) {
free_state( &state );
return( -1 );
}
free_state( &state );
return( 0 );
}