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85 lines
2.7 KiB
85 lines
2.7 KiB
9 years ago
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/** @file */
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/* The MIT License
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*
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* Copyright (c) 2008, Naotoshi Seo <sonots(at)sonots.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef CV_LOGSUM_INCLUDED
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#define CV_LOGSUM_INCLUDED
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#include "cv.h"
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#include "cvaux.h"
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#include "cxcore.h"
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#include <float.h>
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#include <math.h>
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/**
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* Compute log(sum) of log values
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*
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* Get log(a + b + c) from log(a), log(b), log(c)
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* Useful to take sum of probabilities from log probabilities
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* Useful to avoid loss of precision caused by taking exp
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*
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* @param arr array having log values. 32F or 64F
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* @return CvScalar log sum for each channel
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*/
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CVAPI(CvScalar) cvLogSum( const CvArr *arr )
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{
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IplImage* img = (IplImage*)arr, imgstub;
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IplImage *tmp, *tmp2;
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int ch;
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CvScalar sumval;
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CvScalar minval, maxval;
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CV_FUNCNAME( "cvLogSum" );
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__CV_BEGIN__;
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if( !CV_IS_IMAGE(img) )
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{
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CV_CALL( img = cvGetImage( img, &imgstub ) );
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}
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tmp = cvCreateImage( cvGetSize(img), img->depth, img->nChannels );
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tmp2 = cvCreateImage( cvGetSize(img), img->depth, img->nChannels );
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// to avoid loss of precision caused by taking exp as much as possible
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// if this trick is not required, cvExp -> cvSum are enough
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for( ch = 0; ch < img->nChannels; ch++ )
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{
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cvSetImageCOI( img, ch + 1 );
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cvMinMaxLoc( img, &minval.val[ch], &maxval.val[ch] );
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}
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cvSetImageCOI( img, 0 );
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cvSubS( img, maxval, tmp );
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cvExp( tmp, tmp2 );
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sumval = cvSum( tmp2 );
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for( ch = 0; ch < img->nChannels; ch++ )
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{
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sumval.val[ch] = log( sumval.val[ch] ) + maxval.val[ch];
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}
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cvReleaseImage( &tmp );
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cvReleaseImage( &tmp2 );
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__CV_END__;
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return sumval;
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}
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#endif
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