Aegisub/FexTrackerSource/FexTracker.cpp

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// This file is part of FexTracker and (C) 2006 by Hajo Krabbenh<6E>ft (tentacle)
// All rights reserved but the aegisub project is allowed to use it.
// FexTracker.cpp : Defines the entry point for the DLL application.
//
#include "StdAfx.h"
#include "stdio.h"
FexTracker::FexTracker( int sx, int sy, int inFeatures )
{
printf( "[ using FexTracker (c)2006 Hajo Krabbenhoft ]\n" );
nFeatures = inFeatures;
minFeatures = 0;
mFeatures = 8;
lFeatures = (FexTrackingFeature*) new FexTrackingFeature[mFeatures];
SizX = sx;
SizY = sy;
CurImg = 0;
CurFrame = 0;
bDebug = 0;
float subsampling = float(Cfg.SearchRange) / min(Cfg.WindowX,Cfg.WindowY);
if (subsampling < 1.0) { /* 1.0 = 0+1 */
PyramidMaxLevels = 1;
} else if (subsampling <= 3.0) { /* 3.0 = 2+1 */
PyramidMaxLevels = 2;
PyramidSubsampling = 2;
} else if (subsampling <= 5.0) { /* 5.0 = 4+1 */
PyramidMaxLevels = 2;
PyramidSubsampling = 4;
} else if (subsampling <= 9.0) { /* 9.0 = 8+1 */
PyramidMaxLevels = 2;
PyramidSubsampling = 8;
} else {
/* The following lines are derived from the formula:
search_range =
window_halfwidth * \sum_{i=0}^{nPyramidLevels-1} 8^i,
which is the same as:
search_range =
window_halfwidth * (8^nPyramidLevels - 1)/(8 - 1).
Then, the value is rounded up to the nearest integer. */
float val = (float) (log(7.0*subsampling+1.0)/log(8.0));
PyramidMaxLevels = (int) (val + 0.99);
PyramidSubsampling = 8;
}
}
FexTracker::~FexTracker()
{
delete [] lFeatures;
if( CurImg ) delete CurImg;
}
void FexTracker::ProcessImage( float *Img, bool bFirst )
{
// Receive new image to track
// This assumes it chronologically directly follows the previously processed image
if( bFirst || !CurImg )
{
// First image in series
// Initialise a few things
CurFrame = 0;
CurImg = new FexImgPyramid( Img, SizX, SizY, Cfg.EdgeDetectSigma, Cfg.DetectSmoothSigma, PyramidSubsampling, PyramidMaxLevels );
nActiveFeatures = 0;
int tmp = nFeatures;
nFeatures = 0;
// Find initial features
FindFeatures( tmp );
}
else
{
// Check if we've lost too many features, and find some more if that's the case
CountActiveFeatures();
if( nActiveFeatures<minFeatures )
FindFeatures( minFeatures );
// Build image pyramid
NextImg = new FexImgPyramid( Img, SizX, SizY, Cfg.EdgeDetectSigma, Cfg.DetectSmoothSigma, PyramidSubsampling, PyramidMaxLevels );
// Now correlate the features to the new image
TrackFeatures();
delete CurImg;
CurImg = NextImg;
NextImg = 0;
}
CurFrame++;
}
void FexTracker::ProcessingDone()
{
if( CurImg ) delete CurImg;
CurImg = 0;
}
void FexTracker::CountActiveFeatures()
{
nActiveFeatures = 0;
for( int i=0;i<nFeatures;i++ )
{
// If the feature has a known position for the active frame, it's active
if( lFeatures[i].StartTime + lFeatures[i].Pos.size() >= CurFrame )
nActiveFeatures++;
}
}
FexTrackingFeature* FexTracker::operator [] ( int i )
{
if( i<0 || i>=nFeatures ) return 0;
return & lFeatures[i];
}
int FexTracker::GetEigenvalueForPoint( int px, int py )
{
// Determine window in the image to process
int sx = px - Cfg.WindowX;
int ex = px + Cfg.WindowX;
int sy = py - Cfg.WindowY;
int ey = py + Cfg.WindowY;
// Clip against the edges of the image
if( sx<0 )sx=0;
if( sy<0 )sy=0;
if( ex>SizX-1 )ex=SizX-1;
if( ey>SizY-1 )ey=SizY-1;
// Stride for the image
int imgSX = CurImg->lLevels[0]->sx;
// Pointers to X and Y gradient vectors
float* gradx = CurImg->lLevels[0]->GradX;
float* grady = CurImg->lLevels[0]->GradY;
// Accumulated entries into the correlation matrix [gxx gxy; gxy gyy]
register float gxx = 0, gyy = 0, gxy = 0;
// Loop over points inside the window
for( int y=sy;y<ey;y++ )
{
for( int x=sx;x<ex;x++ )
{
// Get X and Y gradient values of this point
float gx = gradx[ imgSX*y + x ];
float gy = grady[ imgSX*y + x ];
// Add to the matrix entries
gxx += gx*gx;
gyy += gy*gy;
gxy += gx*gy;
}
}
// Calculate the eigenvalue L for the correlation matrix
// 0 = det([gxx-L gxy; gxy gyy-L]) = (gxx-L)(gyy-L) - gxy*gxy = L*L + L*(-gxx-gyy) + gxx*gyy - gxy*gxy
// Only the smaller of the two eigenvalues has interest, and a factor 1/4 isn't relevant for comparison,
// so this is the smallest solution to the second-order polynomial.
float val = gxx + gyy - sqrtf((gxx - gyy)*(gxx - gyy) + 4*gxy*gxy);
// Limit the value
if( val>(1<<30) ) val=(1<<30);
return (int) val;
}
// An int triple (?!) denoting a coordinate pair and an eigenvalue for that position
typedef struct{
int val, x, y;
}littleFeature;
// Swap two triples of ints (in reality two littleFeature)
#define SWAP3(list, i, j) \
{register int *pi, *pj, tmp; \
pi=list+3*(i); pj=list+3*(j); \
\
tmp=*pi; \
*pi++=*pj; \
*pj++=tmp; \
\
tmp=*pi; \
*pi++=*pj; \
*pj++=tmp; \
\
tmp=*pi; \
*pi=*pj; \
*pj=tmp; \
}
// Sort a list of int-triples (littleFeature structs)
void _quicksort(int *pointlist, int n)
{
unsigned int i, j, ln, rn;
while (n > 1)
{
SWAP3(pointlist, 0, n/2);
for (i = 0, j = n; ; )
{
do
--j;
while (pointlist[3*j] < pointlist[0]);
do
++i;
while (i < j && pointlist[3*i] > pointlist[0]);
if (i >= j)
break;
SWAP3(pointlist, i, j);
}
SWAP3(pointlist, j, 0);
ln = j;
rn = n - ++j;
if (ln < rn)
{
_quicksort(pointlist, ln);
pointlist += 3*j;
n = rn;
}
else
{
_quicksort(pointlist + 3*j, rn);
n = ln;
}
}
}
#undef SWAP3
void FexTracker::FindFeatures( int minFeatures )
{
// Detect new features, so there's at least minFeatures available
// First calculate eigenvalues for each pixel in the image...
int nli=0; // Number of LIttle features
littleFeature *list = new littleFeature[SizX*SizY];
for( int y=0;y<SizY;y++ )
{
for( int x=0;x<SizX;x++ )
{
int v = GetEigenvalueForPoint( x, y );
// ... if the eigenvalue for a pixel is larger than zero, include it in the list...
if( v>0 )
{
list[nli].val = v;
list[nli].x = x;
list[nli].y = y;
nli++;
}
}
}
// ... and sort the list
_quicksort( (int*)list, nli );
// I'll call these "interest points", since they're just candidates for features...
int oldN = nFeatures;
// Look through all newly found interest-points and add the most interesting to our
// list of features, until we have at least minFeatures
for( int i=0;i<nli && nActiveFeatures<minFeatures;i++ )
{
// Check if this interest point is too close to an existing feature, to avoid excessive clustering
int j;
for( j=0;j<nFeatures;j++ )
{
// Check that we didn't lose this feature
if( lFeatures[j].StartTime + lFeatures[j].Pos.size() < CurFrame ) continue;
// Calculate distance between the interest point of the outer loop and this feature
float dx = list[i].x - lFeatures[j].Pos[ CurFrame - lFeatures[j].StartTime ].x;
float dy = list[i].y - lFeatures[j].Pos[ CurFrame - lFeatures[j].StartTime ].y;
float sqr = dx*dx+dy*dy;
// And see if it's close enough
if( sqr < Cfg.MinDistanceSquare ) break;
}
if( j!=nFeatures ) continue; // Found an existing feature too close, so skip this interest point
// Check if we need to allocate more space for features
if( nFeatures >= mFeatures )
{
// Allocate new, larger feature list and copy old features into new list
mFeatures = nFeatures+9;
mFeatures -= mFeatures%8;
FexTrackingFeature * nlFeatures = (FexTrackingFeature*) new FexTrackingFeature[mFeatures];
for( int cpy=0;cpy<nFeatures;cpy++ )
{
nlFeatures[ cpy ].Eigenvalue = lFeatures[ cpy ].Eigenvalue;
nlFeatures[ cpy ].StartTime = lFeatures[ cpy ].StartTime;
nlFeatures[ cpy ].Influence = lFeatures[ cpy ].Influence;
for( int cpy2=0;cpy2<lFeatures[ cpy ].Pos.size();cpy2++ )
nlFeatures[ cpy ].Pos.Add( lFeatures[ cpy ].Pos[cpy2] );
}
// ... finally replacing the old list
delete [] lFeatures;
lFeatures = nlFeatures;
}
// Add this interest point to the end of the feature list
lFeatures[nFeatures].Eigenvalue = list[i].val;
vec2 pt;
pt.x = (float)list[i].x;
pt.y = (float)list[i].y;
lFeatures[nFeatures].Pos.Add( pt );
lFeatures[nFeatures].StartTime = CurFrame;
lFeatures[nFeatures].Influence = 0;
nFeatures++;
nActiveFeatures++;
}
// Subtract 1 from the start time of all newly found features
for( int j=oldN;j<nFeatures;j++ )
lFeatures[j].StartTime = max(0,lFeatures[j].StartTime-1);
delete []list;
}
void FexTracker::TrackFeatures()
{
for( int i=0;i<nFeatures;i++ )
{
// 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; // 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; // 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;
}
// 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 );
/*
imdebug("lum b=32f w=%d h=%d %p /255", isx, imsiz/isx, diff);
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;
for( int i=0;i<imsiz;i++ )
{
di = diff[i];
gx = gradx[i];
gy = grady[i];
gxx += gx*gx;
gyy += gy*gy;
gxy += gx*gy;
ex += di*gx;
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 )
{
bOk = 0;
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 ) )
{
bOk = 0;
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 );
float sum = 0;
for( int i=0;i<imsiz;i++ )
sum += fabsf( diff[i] );
if( sum / float(imsiz) > Cfg.MaxResidue ) bOk = 0;
}
delete [] diff;
return bOk;
}
inline float Interpolate( float *img, int ImgSX, float x, float y )
{
// 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) );
}
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;
int isx2 = NextImg->lLevels[lvl]->sx;
for( int y = -Cfg.WindowY; y <= Cfg.WindowY; y++ )
{
for( int x = -Cfg.WindowX; x <= Cfg.WindowX; x++ )
{
*diff++ = Interpolate(img1,isx1,op.x+x,op.y+y) - Interpolate(img2,isx2,np.x+x,np.y+y);
}
}
}
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;
float* gx2 = NextImg->lLevels[lvl]->GradX;
float* gy1 = CurImg->lLevels[lvl]->GradY;
float* gy2 = NextImg->lLevels[lvl]->GradY;
for( int y = -Cfg.WindowY; y <= Cfg.WindowY; y++ )
{
for( int x = -Cfg.WindowX; x <= Cfg.WindowX; x++ )
{
*gradx++ = Interpolate(gx1,isx,op.x+x,op.y+y) + Interpolate(gx2,isx,np.x+x,np.y+y);
*grady++ = Interpolate(gy1,isx,op.x+x,op.y+y) + Interpolate(gy2,isx,np.x+x,np.y+y);
}
}
}
/*
static float _minEigenvalue(float gxx, float gxy, float gyy)
{
return (float) ((gxx + gyy - sqrt((gxx - gyy)*(gxx - gyy) + 4*gxy*gxy))/2.0f);
}
//gen eigenvalue matrix:
gxx = 0; gxy = 0; gyy = 0;
for (yy = y-window_hh ; yy <= y+window_hh ; yy++)
{
for (xx = x-window_hw ; xx <= x+window_hw ; xx++)
{
gx = *(gradx->data + ncols*yy+xx);
gy = *(grady->data + ncols*yy+xx);
gxx += gx * gx;
gxy += gx * gy;
gyy += gy * gy;
}
}
//get eigenvalue number
val = _minEigenvalue(gxx, gxy, gyy);
for every frame:
for every feature:
through all pyramid levels from lowres to highres:
calculate diff, gradx, grady
gen eigenvalue matrix
error vector = [gradx, grady]*imdiff
float det = gxx*gyy - gxy*gxy;
if (det < small) return KLT_SMALL_DET;
*dx = (gyy*ex - gxy*ey)/det;
*dy = (gxx*ey - gxy*ex)/det;
add [dx,dy] to search position
*/