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/********************************
Author: Sravanthi Kota Venkata
********************************/
#include "sift.h"
#include <math.h>
#include <assert.h>
const double win_factor = 1.5 ;
const int nbins = 36 ;
const float threshold = 0.01;
/**
This function is similar to imageBlur in common/c folder.
Here, we can specify the sigma value for the gaussian filter
function.
**/
void imsmooth(F2D* array, float dsigma, F2D* out)
{
int M,N ;
int i,j,k;
float s ;
/* ------------------------------------------------------------------
** Check the arguments
** --------------------------------------------------------------- */
M = array->height;
N = array->width;
s = dsigma;
/* ------------------------------------------------------------------
** Do the job
** --------------------------------------------------------------- */
if(s > threshold)
{
int W = (int) ceil(4*s) ;
float temp[2*W+1];
F2D* buffer;
float acc = 0.0;
buffer = fSetArray(M,N,0);
for(j = 0 ; j < (2*W+1) ; ++j)
{
temp[j] = (float)(expf(-0.5 * (j - W)*(j - W)/(s*s))) ;
acc += temp[j];
}
for(j = 0 ; j < (2*W+1) ; ++j)
{
temp[j] /= acc ;
}
/*
** Convolve along the columns
**/
for(j = 0 ; j < M ; ++j)
{
for(i = 0 ; i < N ; ++i)
{
int startCol = MAX(i-W,0);
int endCol = MIN(i+W, N-1);
int filterStart = MAX(0, W-i);
assert(j < array->height);
assert(j < buffer->height);
assert(i < buffer->width);
for(k=startCol; k<=endCol; k++) {
assert(k < array->width);
assert(filterStart < 2*W+1);
subsref(buffer,j,i) += subsref(array, j, k) * temp[filterStart++];
}
}
}
/*
** Convolve along the rows
**/
for(j = 0 ; j < M ; ++j)
{
for(i = 0 ; i < N ; ++i)
{
int startRow = MAX(j-W,0);
int endRow = MIN(j+W, M-1);
int filterStart = MAX(0, W-j);
for(k=startRow; k<=endRow; k++)
subsref(out,j,i) += subsref(buffer,k,i) * temp[filterStart++];
}
}
fFreeHandle(buffer);
}
else
{
for(i=0;i<M*N;i++)
asubsref(out, i) = asubsref(array, i);
}
return;
}
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