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