storm_imagery.cc File Reference

Code dealing with storm imagery (low level). More...

#include <gvars3/instances.h>
#include <cvd/image_io.h>
#include <cvd/convolution.h>
#include <TooN/wls.h>
#include <tr1/tuple>
#include "storm_imagery.h"
#include "debug.h"
#include "utility.h"

Go to the source code of this file.

Functions
vector< Image< float > >	load_and_preprocess_images2 (const vector< string > &names)
vector< Image< float > >	load_and_preprocess_images (const vector< string > &names)
pair< double, double >	auto_fixed_scaling (const vector< Image< float > > &ims, double frac)
vector< Image< float > >	load_and_normalize_images (const vector< string > &files)

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Detailed Description

Code dealing with storm imagery (low level).

Definition in file storm_imagery.cc.

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Function Documentation

pair<double, double> auto_fixed_scaling	(	const vector< Image< float > > &	ims,
		double	frac
	)

Compute the mean and variance of the (on average) darkest pixels, in order to find the correct scaling, by examining hte background.

Definition at line 197 of file storm_imagery.cc.

References assert_same_size(), and sq().

Referenced by load_and_normalize_images().

{
    assert_same_size(ims);
    
    //Compute the mean image (ish)
    Image<double> ave(ims[0].size());
    ave.fill(0);
    for(unsigned int i=0; i < ims.size(); i++)
        for(int y=0; y < ave.size().y; y++)
            for(int x=0; x < ave.size().x; x++)
                ave[y][x] += ims[i][y][x];
    
    //Find the smallest N% of the pixels...
    vector<pair<double, ImageRef> > pixels;
    for(int y=0; y < ave.size().y; y++)
        for(int x=0; x < ave.size().x; x++)
            pixels.push_back(make_pair(ave[y][x], ImageRef(x,y)));

    int npix = (int) floor(frac *pixels.size() + 0.5);
    npix = max(0, min(npix, (int) pixels.size()));

    nth_element(pixels.begin(), pixels.begin() + npix, pixels.end());

    pixels.resize(npix);
    
    //Now compute the mean and variance of those pixels.
    double sum=0, sum2=0;

    for(unsigned int i=0; i < ims.size(); i++)
    {   
        for(unsigned int j=0; j < pixels.size(); j++)
        {
            sum += ims[i][pixels[j].second];
            sum2 += sq(ims[i][pixels[j].second]);
        }
    }

    double num = 1.0 * pixels.size() * ims.size();
    double mean = sum / num;
    double std  = sqrt(((sum2/num) - mean*mean) * num / (num-1));

    cout << "Automatic determination of fixed scaling:" << endl
         << "mean       = " << mean << endl
         << "std        = " << std << endl
         << "sqrt(mean) = " << sqrt(mean*255)/255 << endl;
    
    return make_pair(mean, std);
}