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More commenting work on FexTracker. 

Originally committed to SVN as r587.
This commit is contained in:
Niels Martin Hansen 2006-12-21 23:20:04 +00:00
parent d972e6e69c
commit 4573ec72fa
1 changed files with 47 additions and 14 deletions
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61
FexTrackerSource/FexTracker.cpp
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@ -313,53 +313,73 @@ void FexTracker::TrackFeatures()
{
for( int i=0;i<nFeatures;i++ )
{
if( lFeatures[i].StartTime + lFeatures[i].Pos.size() < CurFrame ) continue; //feature was lost
// Check if this feature was already lost in an earlier frame
if( lFeatures[i].StartTime + lFeatures[i].Pos.size() < CurFrame ) continue;
int FeatureFrame = CurFrame - lFeatures[i].StartTime;
float orig_px = lFeatures[i].Pos[FeatureFrame-1].x;
float orig_py = lFeatures[i].Pos[FeatureFrame-1].y;
vec2 op;
vec2 op; // Original point
// Calculate position of original point on top level of the pyramid
op.x = orig_px * CurImg->lLevels[ CurImg->nLevels-1 ]->CoordMul / CurImg->Subsampling;
op.y = orig_py * CurImg->lLevels[ CurImg->nLevels-1 ]->CoordMul / CurImg->Subsampling;
vec2 np;
np = op;
vec2 np; // New point
np = op; // Assume no motion initially
int l;
for( l=CurImg->nLevels-1;l>=0;l-- )
{
// Move coordinates one level down in the pyramid
op.x *= CurImg->Subsampling;
op.y *= CurImg->Subsampling;
np.x *= CurImg->Subsampling;
np.y *= CurImg->Subsampling;
// And try to track the feature
if( !TrackOneFeature( l, op, np ) ) break;
}
if( l!=-1 ) continue; //we aborted
// Did the loop finish? If not, tracking failed and the feature was lost
if( l!=-1 ) continue;
// Tracked outside the frame? Feature lost.
if( np.x<0 || np.y<0 || np.x>SizX || np.y>SizY ) continue;
// Otherwise add the new position to the feature's point list
lFeatures[i].Pos.Add( np );
}
}
bool FexTracker::TrackOneFeature( int lvl, vec2 op, vec2& np )
{
// Motion estimate one feature on one level in the image pyramid
// @op (in) is the coordinate for the point on the previous frame
// @np (out) is the coordinate for the new location of the point, based on the information in this level of the pyramid
// Border epsilon, defines what is "too close" to the edge of the image
static float bordereps = 1.1f;
// Check that the point isn't already "almost outside" the image, and let tracking fail if it is
if( op.x - Cfg.WindowX < bordereps || op.x + Cfg.WindowX > CurImg->lLevels[lvl]->sx - bordereps ) return 0;
if( op.y - Cfg.WindowY < bordereps || op.y + Cfg.WindowY > CurImg->lLevels[lvl]->sy - bordereps ) return 0;
if( np.x - Cfg.WindowX < bordereps || np.x + Cfg.WindowX > CurImg->lLevels[lvl]->sx - bordereps ) return 0;
if( np.y - Cfg.WindowY < bordereps || np.y + Cfg.WindowY > CurImg->lLevels[lvl]->sy - bordereps ) return 0;
// Temporary images for holding data in the window around the feature
// Desired width of the window
int isx = (Cfg.WindowX*2+1);
// Desired number of pixels in the window
int imsiz = isx*(Cfg.WindowY*2+1);
// Simple difference between image data in window around current frame/position and next frame/position
float *diff = new float[imsiz];
// Something with gradients around old/new position
float *gradx = new float[imsiz];
float *grady = new float[imsiz];
bool bOk = 1;
// Iteratively obtain better precision motion estimation (FIXME)
for( int iteration=0;iteration<Cfg.MaxIterations;iteration++ )
{
// Calculate diffs and gradients ((FIXME)
GetDiffForPointset( lvl, op, np, diff );
GetGradForPointset( lvl, op, np, gradx, grady );
/*
@ -367,6 +387,8 @@ bool FexTracker::TrackOneFeature( int lvl, vec2 op, vec2& np )
imdebug("lum b=32f w=%d h=%d %p /255", isx, imsiz/isx, gradx);
imdebug("lum b=32f w=%d h=%d %p /255", isx, imsiz/isx, grady);
*/
// Calculate gradient correlation matrix and some other matrix related to gradients and differences
register float gx, gy, di;
float gxx = 0, gyy = 0, gxy = 0, ex = 0, ey = 0;
@ -383,6 +405,7 @@ bool FexTracker::TrackOneFeature( int lvl, vec2 op, vec2& np )
ey += di*gy;
}
// Too small determinant in the gradient corr. matrix? (what does that mean?)
float det = gxx*gyy - gxy*gxy;
if( det < Cfg.MinDeterminant )
{
@ -390,11 +413,13 @@ bool FexTracker::TrackOneFeature( int lvl, vec2 op, vec2& np )
break;
}
// So apparently those two matrices together tell something about the movement
float dx = (gyy*ex - gxy*ey)/det;
float dy = (gxx*ey - gxy*ex)/det;
np.x += dx;
np.y += dy;
// Check if the feature moved too close to a border, in which case it's lost
if( ( np.x - Cfg.WindowX < bordereps || np.x + Cfg.WindowX > CurImg->lLevels[lvl]->sx - bordereps )
|| ( np.y - Cfg.WindowY < bordereps || np.y + Cfg.WindowY > CurImg->lLevels[lvl]->sy - bordereps ) )
{
@ -402,11 +427,14 @@ bool FexTracker::TrackOneFeature( int lvl, vec2 op, vec2& np )
break;
}
// If the feature didn't move enough in this iteration, assume its motion is properly estimated
if( fabs(dx) < Cfg.MinDisplacement && fabs(dy) < Cfg.MinDisplacement )break;
}
delete [] gradx;
delete [] grady;
// I think this checks if there's too large a difference between the image at the current and the next frame
// around the motion estimated feature
if( bOk )
{
GetDiffForPointset( lvl, op, np, diff );
@ -424,20 +452,24 @@ bool FexTracker::TrackOneFeature( int lvl, vec2 op, vec2& np )
inline float Interpolate( float *img, int ImgSX, float x, float y )
{
int xt = (int) x; /* coordinates of top-left corner */
int yt = (int) y;
float ax = x - xt;
float ay = y - yt;
float *ptr = img + (ImgSX*yt) + xt;
// Bilinear interpolation between (x,y) and ((int)x,(int)y)
int xt = (int) x; /* coordinates of top-left corner */
int yt = (int) y;
float ax = x - xt;
float ay = y - yt;
float *ptr = img + (ImgSX*yt) + xt;
return ( (1-ax) * (1-ay) * *ptr +
ax * (1-ay) * *(ptr+1) +
(1-ax) * ay * *(ptr+(ImgSX)) +
ax * ay * *(ptr+(ImgSX)+1) );
return ( (1-ax) * (1-ay) * *ptr +
ax * (1-ay) * *(ptr+1) +
(1-ax) * ay * *(ptr+(ImgSX)) +
ax * ay * *(ptr+(ImgSX)+1) );
}
void FexTracker::GetDiffForPointset( int lvl, vec2 op, vec2 np, float* diff )
{
// Calculate the difference between the current frame and the next frame
// locally around the feature point
// (using the currently motion estimated coordinates for the new position)
float* img1 = CurImg->lLevels[lvl]->Img;
int isx1 = CurImg->lLevels[lvl]->sx;
float* img2 = NextImg->lLevels[lvl]->Img;
@ -452,6 +484,7 @@ void FexTracker::GetDiffForPointset( int lvl, vec2 op, vec2 np, float* diff )
}
void FexTracker::GetGradForPointset( int lvl, vec2 op, vec2 np, float* gradx, float* grady )
{
// Dark magic
int isx = CurImg->lLevels[lvl]->sx;
float* gx1 = CurImg->lLevels[lvl]->GradX;