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feature_detect_features.c
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feature_detect_features.c
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#include "header.h"
#include "proto.h"
void feature_detect_features(
int octave_nbr,
int interval_nbr,
double ***gauss_pyr_image,
int *gauss_pyr_width,
int *gauss_pyr_height,
double ***dog_pyr_image,
feat_struct **pfeat_arr,
int *pfeat_nbr
)
{
int img_border;
double contrast_thresh;
int feat_nbr;
feat_struct *feat_arr;
int octave;
int interval;
int i;
int j;
int status;
int err_flag;
int extremum_interval;
int extremum_i;
int extremum_j;
double extremum_xinterval;
double extremum_xi;
double extremum_xj;
double extremum_xdog;
double dog;
double prelim_contrast_thresh;
int width;
int height;
int pixel;
/*
Set the image border in which the feaures are ignored
*/
img_border= 5;
/*
Set the contrast threshold
*/
contrast_thresh= 0.04;
prelim_contrast_thresh= 0.5 * contrast_thresh / (double)interval_nbr;
/*
Initialize the feature storage array
*/
feat_nbr= 0;
feat_arr= 0;
for ( octave= 0 ; octave< octave_nbr ; octave++ ) {
width= gauss_pyr_width[octave];
height= gauss_pyr_height[octave];
for ( interval= 1 ; interval<= interval_nbr ; interval++ ) {
for ( i= 0+img_border ;
i< gauss_pyr_height[octave]-img_border ;
i++ ) {
for ( j= 0+img_border ;
j< gauss_pyr_width[octave]-img_border ;
j++ ) {
pixel= i*width+j;
/*
Get the Difference of Gaussian at that pixel
*/
dog= dog_pyr_image[octave][interval][pixel];
/*
Check if it has enough contrast
*/
if ( !( fabs(dog) > prelim_contrast_thresh ) ) {
/*
Not enough contrast!
*/
continue;
}
/*
Looks like pixel has enough contrast
*/
/*
See if it's an extremum
status = 1 means yes
status = 0 means no
*/
status= feature_is_extremum(
gauss_pyr_image,
gauss_pyr_width,
gauss_pyr_height,
dog_pyr_image,
octave,
interval,
i,
j
);
if ( status == 0 ) {
/*
Not an extremum!
*/
continue;
}
/*
Looks like we have an extremum
*/
/*
Fine-tune the location of the extremum
(extremum_xinterval,extremum_xi,extremum_xj) is
the offset vector to add to (interval,i,j)
to get the actual location of the extremum
extremum_xdog is the dog at that actual location
*/
err_flag= feature_interpolate_extremum_location_main(
octave_nbr,
interval_nbr,
gauss_pyr_image,
gauss_pyr_width,
gauss_pyr_height,
dog_pyr_image,
img_border,
octave,
interval,
i,
j,
&extremum_interval,
&extremum_i,
&extremum_j,
&extremum_xinterval,
&extremum_xi,
&extremum_xj,
&extremum_xdog
);
if ( err_flag == 1 ) {
/*
Looks like
we could not compute the exact location of the extremum
*/
continue;
}
/*
If here,
looks like we have a bona fide extremum
*/
/*
Check the pixel contrast
*/
if ( fabs(extremum_xdog) < contrast_thresh/(double)interval_nbr ) {
/*
Not enough contrast for that feature to be kept
*/
continue;
}
/*
Check if feature is too edge-like
*/
err_flag= feature_check_extremum_edge_like(
octave_nbr,
interval_nbr,
gauss_pyr_image,
gauss_pyr_width,
gauss_pyr_height,
dog_pyr_image,
img_border,
octave,
extremum_interval,
extremum_i,
extremum_j
);
if ( err_flag == 1 ) {
/*
Looks like we come up emty-handed
*/
continue;
}
/*
Store the feature
*/
feature_add_feature(
octave,
extremum_interval,
extremum_i,
extremum_j,
extremum_xinterval,
extremum_xi,
extremum_xj,
(double)0,
(double)0,
(double)0,
(double *)0,
(int)0,
&feat_arr,
&feat_nbr
);
}
}
}
}
(*pfeat_arr)= feat_arr;
(*pfeat_nbr)= feat_nbr;
}