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Mon, Jul 29, 12:14

hog.cpp
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/*
Copyright (C) 2014 Jerome Revaud
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>
*/
#include "hog.h"
#include "std.h"
/* compute horizontal gradient centered with [-1,0,1] mask
*/
void _diff_horiz(int tx, int ty, UBYTE* pixels, float* res) {
int x,y,pos=0;
float* r=res;
for(y=0; y<ty; y++,pos+=tx) {
*r++ = pixels[1+pos] - pixels[0+pos];
for(x=1; x<tx-1; x++)
*r++ = pixels[x+1+pos] - pixels[x-1+pos];
*r++ = pixels[x+pos] - pixels[x-1+pos];
}
}
/* compute vertical gradient centered with [-1,0,1] mask
*/
void _diff_vert(int tx, int ty, UBYTE* pixels, float* res) {
int x,y,pos=0;
for(x=0; x<tx; x++,pos++)
res[pos] = pixels[pos+tx] - pixels[pos];
for(y=1; y<ty-1; y++) {
pos = y*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = pixels[pos+tx] - pixels[pos-tx];
}
for(x=0; x<tx; x++,pos++)
res[pos] = pixels[pos] - pixels[pos-tx];
}
/* compute original, unsmoothed, gradient
*/
void _compute_pure_gradient( UBYTE_image* img, float_layers* grad ) {
ASSERT_SAME_SIZE(img,grad);
assert(grad->tz==2);
int tx = img->tx;
int ty = img->ty;
// compute horizontal gradient
_diff_vert(tx,ty,img->pixels,grad->pixels);
// compute vertical gradient
_diff_horiz(tx,ty,img->pixels,grad->pixels+tx*ty);
}
/* compute horizontal smoothing with 3-sized mask
*/
template<typename TData>
void _smooth_3_horiz(int tx, int ty, const int w_center, const int w_side, TData* pixels, TData* _res, int n_thread) {
int y;
const int sum_w = 2*w_side + w_center;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(y=0; y<ty; y++) {
int x,pos = y*tx;
TData* res = _res + pos;
*res++ = ( (w_center+w_side)*pixels[0+pos] + w_side*pixels[1+pos])/sum_w;
for(x=1; x<tx-1; x++)
*res++ = (w_side*pixels[x+1+pos] + w_center*pixels[x+pos] + w_side*pixels[x-1+pos])/sum_w;
*res++ = ( (w_center+w_side)*pixels[x+pos] + w_side*pixels[x-1+pos])/sum_w;
}
}
void _smooth_121_horiz(int tx, int ty, UBYTE* pixels, UBYTE* res, int n_thread) {
_smooth_3_horiz( tx, ty, 2, 1, pixels, res, n_thread );
}
template<typename TData>
void _smooth_5_horiz( int tx, int ty, const int w_center, const int w_side1, const int w_side2,
TData* pixels, TData* _res, int n_thread) {
int y;
const int sum_w = 2*(w_side1 + w_side2) + w_center;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(y=0; y<ty; y++) {
int x,pos = y*tx;
TData* res = _res + pos;
x=0;
*res++ = (
w_side2 * pixels[x +pos] +
w_side1 * pixels[x +pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] ) / sum_w;
x++;
*res++ = (
w_side2 * pixels[x-1+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] ) / sum_w;
for(x=2; x<tx-2; x++)
*res++ = (
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] ) / sum_w;
*res++ = (
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+1+pos] ) / sum_w;
x++;
*res++ = (
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x +pos] +
w_side2 * pixels[x +pos] ) / sum_w;
}
}
template<typename TData>
void _smooth_7_horiz(int tx, int ty, const int w_center, const int w_side1, const int w_side2, const int w_side3,
TData* pixels, TData* _res, int n_thread) {
int y;
const int sum_w = 2*(w_side1 + w_side2 + w_side3) + w_center;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(y=0; y<ty; y++) {
int x,pos = y*tx;
TData* res = _res + pos;
x=0;
*res++ = (
w_side3 * pixels[x +pos] +
w_side2 * pixels[x +pos] +
w_side1 * pixels[x +pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] +
w_side3 * pixels[x+3+pos] ) / sum_w;
x++;
*res++ = (
w_side3 * pixels[x-1+pos] +
w_side2 * pixels[x-1+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] +
w_side3 * pixels[x+3+pos] ) / sum_w;
x++;
*res++ = (
w_side3 * pixels[x-2+pos] +
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] +
w_side3 * pixels[x+3+pos] ) / sum_w;
for(x=3; x<tx-3; x++)
*res++ = (
w_side3 * pixels[x-3+pos] +
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] +
w_side3 * pixels[x+3+pos] ) / sum_w;
*res++ = (
w_side3 * pixels[x-3+pos] +
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+2+pos] +
w_side3 * pixels[x+2+pos] ) / sum_w;
x++;
*res++ = (
w_side3 * pixels[x-3+pos] +
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x+1+pos] +
w_side2 * pixels[x+1+pos] +
w_side3 * pixels[x+1+pos] ) / sum_w;
x++;
*res++ = (
w_side3 * pixels[x-3+pos] +
w_side2 * pixels[x-2+pos] +
w_side1 * pixels[x-1+pos] +
w_center* pixels[x +pos] +
w_side1 * pixels[x +pos] +
w_side2 * pixels[x +pos] +
w_side3 * pixels[x +pos] ) / sum_w;
}
}
/* compute vertical smoothing with 3-sized mask
*/
template<typename TData>
void _smooth_3_vert(int tx, int ty, const int w_center, const int w_side, TData* pixels, TData* res, int n_thread) {
int x,y,pos=0;
const int sum_w = 2*w_side + w_center;
for(x=0; x<tx; x++,pos++)
res[pos] = ( (w_center+w_side)*pixels[pos] + w_side*pixels[pos+tx])/sum_w;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(y=1; y<ty-1; y++) {
int x,pos = y*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = ( w_side*pixels[pos+tx] + w_center*pixels[pos] + w_side*pixels[pos-tx])/sum_w;
}
pos = (ty-1)*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = ( (w_center+w_side)*pixels[pos] + w_side*pixels[pos-tx])/sum_w;
}
void _smooth_121_vert(int tx, int ty, UBYTE* pixels, UBYTE* res, int n_thread) {
_smooth_3_vert( tx, ty, 2, 1, pixels, res, n_thread );
}
template<typename TData>
void _smooth_5_vert(int tx, int ty, const int w_center, const int w_side1, const int w_side2,
TData* pixels, TData* res, int n_thread) {
int x,y,pos=0;
const int sum_w = 2*(w_side1 + w_side2) + w_center;
const int tx1=tx,tx2=2*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side2 * pixels[pos] +
w_side1 * pixels[pos] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2]
)/sum_w;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side2 * pixels[pos-tx1] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2]
)/sum_w;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(y=2; y<ty-2; y++) {
int x,pos = y*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2]
)/sum_w;
}
pos = (ty-2)*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx1]
)/sum_w;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos] +
w_side2 * pixels[pos]
)/sum_w;
}
template<typename TData>
void _smooth_7_vert(int tx, int ty, const int w_center, const int w_side1, const int w_side2, const int w_side3,
TData* pixels, TData* res, int n_thread) {
int x,y,pos=0;
const int sum_w = 2*(w_side1 + w_side2 + w_side3) + w_center;
const int tx1=tx,tx2=2*tx,tx3=3*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos] +
w_side2 * pixels[pos] +
w_side1 * pixels[pos] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2] +
w_side3 * pixels[pos+tx3]
)/sum_w;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos-tx1] +
w_side2 * pixels[pos-tx1] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2] +
w_side3 * pixels[pos+tx3]
)/sum_w;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos-tx2] +
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2] +
w_side3 * pixels[pos+tx3]
)/sum_w;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(y=3; y<ty-3; y++) {
int x,pos = y*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos-tx3] +
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2] +
w_side3 * pixels[pos+tx3]
)/sum_w;
}
pos = (ty-3)*tx;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos-tx3] +
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx2] +
w_side3 * pixels[pos+tx2]
)/sum_w;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos-tx3] +
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos+tx1] +
w_side2 * pixels[pos+tx1] +
w_side3 * pixels[pos+tx1]
)/sum_w;
for(x=0; x<tx; x++,pos++)
res[pos] = (
w_side3 * pixels[pos-tx3] +
w_side2 * pixels[pos-tx2] +
w_side1 * pixels[pos-tx1] +
w_center* pixels[pos] +
w_side1 * pixels[pos] +
w_side2 * pixels[pos] +
w_side3 * pixels[pos]
)/sum_w;
}
/* Smooth an image using a Gaussian filter.
*/
template<typename TData>
void _smooth_gaussian_alltype( const int tx, const int ty, TData* img, float _sigma, TData* res, int n_thread ) {
const float MAX_SIGMA = 1.86f;
TData* img2 = img;
if(_sigma>MAX_SIGMA) { // reallocate if more than one smoothing pass is required
img2 = NEWA(TData,tx*ty);
memcpy(img2,img,tx*ty*sizeof(TData));
}
TData* tmp = NEWA(TData,tx*ty);
TData* old_res = res;
float remaining = _sigma*_sigma;
while( 1 ) {
float sigma = MIN(MAX_SIGMA,sqrt(remaining));
remaining -= sigma*sigma;
// compute gaussian filter coefficients
const int wcenter = 1000;
const int wside1 = int(0.5 + wcenter*exp( -pow2(1./sigma)/2 ));
const int wside2 = int(0.5 + wcenter*exp( -pow2(2./sigma)/2 ));
const int wside3 = int(0.5 + wcenter*exp( -pow2(3./sigma)/2 ));
const int wside4 = int(0.5 + wcenter*exp( -pow2(4./sigma)/2 ));
assert( wside4 < wcenter/10 || !"error: smoothing is too large" );
if ( wside2 < wcenter/10 ) {
_smooth_3_horiz( tx, ty, wcenter, wside1, img2, tmp, n_thread );
_smooth_3_vert( tx, ty, wcenter, wside1, tmp, res, n_thread );
} else if( wside3 < wcenter/10 ) {
_smooth_5_horiz( tx, ty, wcenter, wside1, wside2, img2, tmp, n_thread );
_smooth_5_vert( tx, ty, wcenter, wside1, wside2, tmp, res, n_thread );
} else {
_smooth_7_horiz( tx, ty, wcenter, wside1, wside2, wside3, img2, tmp, n_thread );
_smooth_7_vert( tx, ty, wcenter, wside1, wside2, wside3, tmp, res, n_thread );
}
if(remaining < 0.001)
break;
else {
TData* tmp3;
tmp3 = img2;
img2 = res;
res = tmp3;
}
}
if(res!=old_res) { // copy to true res
memcpy(old_res,res,tx*ty*sizeof(TData));
img2 = res;
}
if(_sigma>MAX_SIGMA)
free(img2);
free(tmp);
}
void _smooth_gaussian( UBYTE_image* img, float _sigma, UBYTE_image* res, int n_thread ) {
ASSERT_SAME_SIZE(img,res);
_smooth_gaussian_alltype(img->tx,img->ty,img->pixels,_sigma,res->pixels,n_thread);
}
/* compute gradient smoothed with Sobel mask
*/
void _compute_sobel_gradient( UBYTE_image* img, float_layers* grad, int n_thread ) {
ASSERT_SAME_SIZE(img,grad);
assert(grad->tz==2);
int tx = img->tx;
int ty = img->ty;
UBYTE* tmp = NEWA(UBYTE,tx*ty);
// compute horizontal gradient
_smooth_121_horiz(tx,ty,img->pixels,tmp, n_thread);
_diff_vert(tx,ty,tmp,grad->pixels);
// compute vertical gradient
_smooth_121_vert(tx,ty,img->pixels,tmp, n_thread);
_diff_horiz(tx,ty,tmp,grad->pixels+tx*ty);
// free everything
free(tmp);
}
/* Compute the dx,dy gradient on the image based on a [-1,0,1] mask.
=0 : no prior smoothing
=1 : sobel smoothing
*/
void _compute_grad_101( UBYTE_image* img, int method, float_layers* grad, int n_thread ) {
ASSERT_SAME_SIZE(img,grad);
assert(grad->tz==2);
// compute gradient
if( method == 0 )
_compute_pure_gradient(img, grad);
else if( method == 1 )
_compute_sobel_gradient(img, grad, n_thread);
else
assert(!"error: unknown method for compute_grad_101");
}
/* Compute the Histogram of oriented gradient for each pixel.
Number of orientations is determined by hog->tz;
method determines orientation bining:
=0 : atan + linear interpolation
=1 : fast cos projection
*/
void _compute_hog( float_layers* grad, int method, float_layers* hog, int n_thread ) {
ASSERT_SAME_SIZE(grad,hog);
const int n_ori = hog->tz;
const int npix = hog->tx*hog->ty;
const float* dx = grad->pixels;
const float* dy = grad->pixels + npix;
if( method == 0 ) {
// use atan
memset(hog->pixels,0,n_ori*npix*sizeof(float));
int i;
for(i=0; i<npix; i++) {
float norm = sqrt(dy[i]*dy[i] + dx[i]*dx[i]);
float angle = atan2(dy[i],dx[i]); // angle in [-pi,pi]
float b_angle = (angle + M_PI)/n_ori;
int q_angle = int(0.5 + b_angle); // first bin
float coef = b_angle-q_angle;
q_angle = (q_angle + 3*n_ori/2) % n_ori;
hog->pixels[ ((q_angle ) )*npix + i ] += (1-coef)*norm;
hog->pixels[ ((q_angle+1)%n_ori)*npix + i ] += ( coef)*norm;
}
} else if (method == 1 ) {
int l;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(l=0; l<n_ori; l++) {
float angle = -2*(l-2)*M_PI/n_ori;
float kos = cos( angle );
float zin = sin( angle );
float* layer_l = hog->pixels + l*npix;
int i;
for(i=0; i<npix; i++) {
float value = kos*dx[i] + zin*dy[i];
layer_l[i] = (value > 0 ) ? value : 0;
}
}
} else
assert(!"error: unknown method for compute_hog");
}
/* compute 8 directions of gradient per pixels
using 4 oriented filters extremely simple like [-1,1]
*/
void _compute_hog_8_direct( UBYTE_image* image, float_layers* hog_out, int n_thread ) {
ASSERT_SAME_SIZE(image,hog_out);
assert(hog_out->tz==8);
int j,tx=image->tx, ty=image->ty;
int npix=tx*image->ty;
// init output
memset(hog_out->pixels,0,8*npix*sizeof(float));
// compute horizontal filter
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(j=0; j<ty; j++) {
UBYTE* img = image->pixels + j*tx;
UBYTE* lastimg = img + tx-1;
float* hog0f = hog_out->pixels + 0*npix + j*tx; // first
float* hog0l = hog0f+1; // last
float* hog1f = hog_out->pixels + 4*npix + j*tx; // first
float* hog1l = hog1f+1; // last
for(; img<lastimg; img++) {
float diff = img[1] - img[0];
float pos,neg;
if( diff < 0 ) {
pos = 0;
neg = -diff/2.f;
} else {
neg = 0;
pos = diff/2.f;
}
*hog0f++ += neg;
*hog1f++ += pos;
*hog0l++ += neg;
*hog1l++ += pos;
}
}
// compute veritical filter
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(j=0; j<ty-1; j++) {
UBYTE* img = image->pixels + j*tx;
UBYTE* lastimg = img + tx;
const int offset = tx;
UBYTE* img2 = img + offset;
float* hog0f = hog_out->pixels + 2*npix + j*tx; // first
float* hog0l = hog0f + offset; // last
float* hog1f = hog_out->pixels + 6*npix + j*tx; // first
float* hog1l = hog1f + offset; // last
while(img<lastimg) {
float diff = (*img2++) - (*img++);
float pos,neg;
if( diff < 0 ) {
pos = 0;
neg = -diff/2.f;
} else {
neg = 0;
pos = diff/2.f;
}
*hog0f++ += neg;
*hog1f++ += pos;
*hog0l++ += neg;
*hog1l++ += pos;
}
}
const float div_diag = 2*1.2666f; // learned
// compute diagonal filter 1
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(j=0; j<ty-1; j++) {
UBYTE* img = image->pixels + j*tx;
UBYTE* lastimg = img + tx-1;
const int offset = 1+tx;
UBYTE* img2 = img + offset;
float* hog0f = hog_out->pixels + 1*npix + j*tx; // first
float* hog0l = hog0f + offset; // last
float* hog1f = hog_out->pixels + 5*npix + j*tx; // first
float* hog1l = hog1f + offset; // last
while(img<lastimg) {
float diff = (*img2++) - (*img++);
float pos,neg;
if( diff < 0 ) {
pos = 0;
neg = -diff/div_diag;
} else {
neg = 0;
pos = diff/div_diag;
}
*hog0f++ += neg;
*hog1f++ += pos;
*hog0l++ += neg;
*hog1l++ += pos;
}
}
// compute diagonal filter 2
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(j=1; j<ty; j++) {
UBYTE* img = image->pixels + j*tx;
UBYTE* lastimg = img + tx-1;
const int offset = 1-tx;
UBYTE* img2 = img + offset;
float* hog0f = hog_out->pixels + 7*npix + j*tx; // first
float* hog0l = hog0f + offset; // last
float* hog1f = hog_out->pixels + 3*npix + j*tx; // first
float* hog1l = hog1f + offset; // last
while(img<lastimg) {
float diff = (*img2++) - (*img++);
float pos,neg;
if( diff < 0 ) {
pos = 0;
neg = -diff/div_diag;
} else {
neg = 0;
pos = diff/div_diag;
}
*hog0f++ += neg;
*hog1f++ += pos;
*hog0l++ += neg;
*hog1l++ += pos;
}
}
}
/* Post-processing of the HOG: cross-orientation inhibition.
for one pixel i and orientation o: hog[i,o] = max(0, hog[i,o] - coef*hog[i,:].mean())
*/
void subtract_mean_ori( float_layers* hog, float coef, int n_thread ) {
const int npix = hog->tx*hog->ty;
int l;
float* sum = NEWAC(float, npix);
float* max = NEWAC(float, npix);
// compute mean per pixel
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(l=0; l<hog->tz; l++) {
float* p = sum;
float* m = max;
float* hog_pix = hog->pixels + l*npix;
int i;
for(i=0; i<npix; i++,m++) {
float v = *hog_pix++;
*p++ += v;
float max = *m;
if(v>max) *m=v;
}
}
// subtract coef*mean
coef /= hog->tz;
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(l=0; l<hog->tz; l++) {
float* p = sum;
float* m = max;
float* hog_pix = hog->pixels + l*npix;
int i;
for(i=0; i<npix; i++) {
float Max = *m++; // max
float mean = coef * (*p++); // == mean * coef
if( mean >= Max )
*hog_pix = 0;
else {
*hog_pix = Max*(1 - (Max - (*hog_pix))/(Max - mean + 1e-8f));
if(*hog_pix<0) *hog_pix = 0;
}
hog_pix++;
}
}
free(sum);
free(max);
}
/* Pass the gradient image through a sigmoid
*/
void sigmoid_array( float_array* img, float coef, float offset, int n_thread ) {
assert(coef>0);
const int npix=img->tx;
// float* p = img->pixels;
// for(i=0; i<npix; i++) {
// float v = *p;
// *p++ = 2.f/(1.f + exp(-coef*v + offset)) - 1.f;
// }
int l;
// optimization: precompute some values of sigmoid
// 2/(1 + exp(-arange(0,8,0.5)+offset)) -1
const int npc = 64;
float precom[npc+1];
for(l=0; l<=npc; l++) precom[l]= 1.f/(1.f + exp(-l/8.f + offset));
for(l=1; l<=npc; l++) precom[l] = (precom[l]-precom[0]) / (1 - precom[0]); // renorm between 0 and 1
precom[0] = 0;
const float maxindex = npc - 0.001;
#define NSUB 32
#if defined(USE_OPENMP)
#pragma omp parallel for num_threads(n_thread)
#endif
for(l=0; l<NSUB; l++) {
int start = (l*npix)/NSUB;
int end = (l+1)*npix/NSUB;
int npixsub = end-start;
float* p = img->pixels + start;
int i;
for(i=0; i<npixsub; i++) {
float v = 8*(coef*(*p));
if(v>maxindex) v=maxindex;
int n = int(v);
float w = v-n;
*p++ = (1-w)*precom[n] + w*precom[n+1];
}
}
}
/* Compute a spatially smoothed version of the HOG.
*/
void smooth_hog_gaussian( float_layers* hog, float smoothing, int n_thread ) {
int l;
const int npix = hog->tx*hog->ty;
for(l=0; l<hog->tz; l++)
_smooth_gaussian_alltype(hog->tx,hog->ty,hog->pixels+l*npix,smoothing,hog->pixels+l*npix, n_thread);
}

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