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/********************************
Author: Sravanthi Kota Venkata
********************************/
#include "tracking.h"
/** calcPyrLKTrack tries to find the displacement (translation in x and y) of features computed in the previous frame.
To compute the displacement, we interpolate the existing feature position around the pixel neighborhood.
For better results, we perform interpolatations across all pyramid levels.
Input: Previous frame blurred images, vertical and horizontal
Current frame edge images, vertical and horizontal
Current frame blurred images, for level 0 and 1
Number of features from previous frame
Window size
Accuracy
Number of iterations to compute motion vector
Features from the previous frame
currentFrameFeatures, Populate the current frame features' displacements
Output: Number of valid features
**/
I2D* calcPyrLKTrack(F2D* previousImageBlur_level1, F2D* previousImageBlur_level2, F2D* vertEdge_level1, F2D* vertEdge_level2, F2D* horzEdge_level1, F2D* horzEdge_level2, F2D* currentImageBlur_level1, F2D* currentImageBlur_level2, F2D* previousFrameFeatures, int nFeatures, int winSize, float accuracy, int max_iter, F2D* currentFrameFeatures)
{
int idx, level, pLevel, i, j, k, winSizeSq;
I2D *valid;
F2D *rate, *iPatch, *jPatch, *iDxPatch;
F2D *iDyPatch;
float tr, x, y, dX, dY, c_xx, c_yy, c_xy;
int imgSize_1, imgSize_2;
float mX, mY, dIt, eX, eY, c_det;
I2D *imgDims;
imgDims = iMallocHandle(2, 2);
subsref(imgDims,0,0) = previousImageBlur_level1->height;
subsref(imgDims,0,1) = previousImageBlur_level1->width;
subsref(imgDims,1,0) = previousImageBlur_level2->height;
subsref(imgDims,1,1) = previousImageBlur_level2->width;
pLevel = 2;
rate = fMallocHandle(1, 6);
asubsref(rate,0) = 1;
asubsref(rate,1) = 0.5;
asubsref(rate,2) = 0.25;
asubsref(rate,3) = 0.125;
asubsref(rate,4) = 0.0625;
asubsref(rate,5) = 0.03125;
winSizeSq = 4*winSize*winSize;
valid = iSetArray(1,nFeatures, 1);
/** For each feature passed from previous frame, compute the dx and dy, the displacements **/
for(i=0; i<nFeatures; i++)
{
dX = 0;
dY = 0;
/** Compute the x and y co-ordinate values at "pLevel" **/
x = subsref(previousFrameFeatures,0,i) * asubsref(rate,pLevel);
y = subsref(previousFrameFeatures,1,i) * asubsref(rate,pLevel);
c_det = 0;
/** For each pyramid level, try to find correspondence.
We look for the correspondence in a given window size
, (winSize x winSize) neighborhood **/
for(level = pLevel-1; level>=0; level--)
{
x = x+x;
y = y+y;
dX = dX + dX;
dY = dY + dY;
imgSize_1 = subsref(imgDims,level,0);
imgSize_2 = subsref(imgDims,level,1);
c_xx = 0;
c_xy = 0;
c_yy = 0;
if((x-winSize)<0 || (y-winSize)<0 || (y+winSize+1)>=imgSize_1 || (x+winSize+1)>=imgSize_2)
{
asubsref(valid,i) = 0;
break;
}
/** Perform interpolation. Use co-ord from previous
frame and use the images from current frame **/
if(level ==0)
{
iPatch = getInterpolatePatch(previousImageBlur_level1, imgSize_2, x, y, winSize);
iDxPatch = getInterpolatePatch(vertEdge_level1, imgSize_2, x, y, winSize);
iDyPatch = getInterpolatePatch(horzEdge_level1, imgSize_2, x, y, winSize);
}
if(level ==1)
{
iPatch = getInterpolatePatch(previousImageBlur_level2, imgSize_2, x, y, winSize);
iDxPatch = getInterpolatePatch(vertEdge_level2, imgSize_2, x, y, winSize);
iDyPatch = getInterpolatePatch(horzEdge_level2, imgSize_2, x, y, winSize);
}
/** Compute feature strength in similar way as calcGoodFeature **/
for(idx=0; idx<winSizeSq; idx++)
{
c_xx += asubsref(iDxPatch,idx) * asubsref(iDxPatch,idx);
c_xy += asubsref(iDxPatch,idx) * asubsref(iDyPatch,idx);
c_yy += asubsref(iDyPatch,idx) * asubsref(iDyPatch,idx);
}
c_det = (c_xx * c_yy -c_xy * c_xy);
tr = c_xx + c_yy;
if((c_det/(tr+0.00001)) < accuracy)
{
asubsref(valid,i) = 0;
fFreeHandle(iPatch);
fFreeHandle(iDxPatch);
fFreeHandle(iDyPatch);
break;
}
c_det = 1/c_det;
/** We compute dX and dY using previous frame and current
frame images. For this, the strength is computed at each
pixel in the new image. **/
for(k=0; k<max_iter; k++)
{
if( (x+dX-winSize)<0 || (y+dY-winSize)<0 || (y+dY+winSize+1)>=imgSize_1 || (x+dX+winSize+1)>=imgSize_2)
{
asubsref(valid,i) = 0;
break;
}
if(level == 0)
jPatch = getInterpolatePatch(currentImageBlur_level1, imgSize_2, x+dX, y+dY, winSize);
if(level == 1)
jPatch = getInterpolatePatch(currentImageBlur_level2, imgSize_2, x+dX, y+dY, winSize);
eX = 0;
eY = 0;
for(idx=0; idx<winSizeSq; idx++)
{
dIt = asubsref(iPatch,idx) - asubsref(jPatch,idx);
eX += dIt * asubsref(iDxPatch,idx);
eY += dIt * asubsref(iDyPatch,idx);
}
mX = c_det * (eX * c_yy - eY * c_xy);
mY = c_det * (-eX * c_xy + eY * c_xx);
dX = dX + mX;
dY = dY + mY;
if( (mX*mX+mY*mY) < accuracy)
{
fFreeHandle(jPatch);
break;
}
fFreeHandle(jPatch);
}
fFreeHandle(iPatch);
fFreeHandle(iDxPatch);
fFreeHandle(iDyPatch);
}
subsref(currentFrameFeatures,0,i) = subsref(previousFrameFeatures,0,i) + dX;
subsref(currentFrameFeatures,1,i) = subsref(previousFrameFeatures,1,i) + dY;
}
fFreeHandle(rate);
iFreeHandle(imgDims);
return valid;
}
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