KLT_FeatureHistory

typedef struct {
int nFrames;
KLT_Feature *feature;
} *KLT_FeatureHistory;

A KLT_FeatureHistory is an array of features. The nFrames field indicates the number of features allocated, or rather the number of frames in which the feature's data is given. It must not be changed manually.

NOTE: Although a feature list and a feature history look similar, the former is intended to refer to an array of features from a single image, while the latter refers to the same feature tracked through several images.

The following code illustrates how to access the data in a feature history: 

KLT_FeatureHistory fh;
int frame;

for (frame = 0 ; frame < fh->nFrames ; frame++)  {
     printf("(%5.1f,%5.1f) = %d\n", 
          fh->feature[frame]->x,
          fh->feature[frame]->y,
          fh->feature[frame]->val);
}