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/********************************
Author: Sravanthi Kota Venkata
********************************/
#include "tracking.h"
/** Compute the sum of pixels over pixel neighborhood.
Neighborhood = winSize*winSize
This will be useful when we compute the displacement
of the neighborhood across frames instead of tracking each pixel.
Input: src Image
# rows, cols, size of window
Output: windowed-sum image, ret.
Example:
winSize = 4, cols = 8, rows = 16
nave_half = 2, nave = 4
Say, the first row of the image is:
3 8 6 2 4 8 9 5
a1 = 0 0 3 8 6 2 4 8 9 5 0 0 (append nave_half zeros to left and right border)
asum = (sum the first nave # pixels - 0 0 3 8 ) = 11
ret(0,0) = 11
For ret(0,1), we need to move the window to the right by one pixel and subtract
from a1sum the leftmost pixel. So, we add value 6 and subtract value at a1(0,0), = 0 here.
ret(0,1) = 17 = a1sum
For ret(0,2), a1sum - a1(0,1) + a1(2+nave) = 17 - 0 + 2 = 19 = a1sum
For ret(0,3), a1sum - a1(0,2) + a1(3+nave) = 19 - 3 + 4 = 20 = a1sum
We proceed this way for all the rows and then perform summantion across all cols.
**/
F2D* calcAreaSum(F2D* src, int cols, int rows, int winSize)
{
int nave, nave_half, i, j, k;
F2D *ret, *a1;
float a1sum;
nave = winSize;
nave_half = floor((nave+1)/2);
ret = fMallocHandle(rows, cols);
a1 = fSetArray(1, cols+nave,0);
for(i=0; i<rows; i++)
{
for(j=0; j<cols; j++) {
asubsref(a1,j+nave_half) = subsref(src,i,j);
}
a1sum = 0;
for(k=0; k<nave; k++) {
a1sum += asubsref(a1,k);
}
for(j=0; j<cols; j++)
{
subsref(ret,i,j) = a1sum;
a1sum += asubsref(a1,j+nave) - asubsref(a1,j);
}
}
fFreeHandle(a1);
a1 = fSetArray(1, rows+nave,0);
for(i=0; i<cols; i++)
{
for(j=0; j<rows; j++) {
asubsref(a1,j+nave_half) = subsref(ret,j,i);
}
a1sum = 0;
for(k=0; k<nave; k++) {
a1sum += asubsref(a1,k);
}
for(j=0; j<rows; j++)
{
subsref(ret,j,i) = a1sum;
a1sum += asubsref(a1,j+nave) - asubsref(a1,j);
}
}
fFreeHandle(a1);
return ret;
}
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