// Computes the center of mass and second moments for the old baseline and
// 2nd moment normalizations. Returns the outline length.
// The input denorm should be the normalizations that have been applied from
// the image to the current state of this TBLOB.
int TBLOB::ComputeMoments(FCOORD* center, FCOORD* second_moments) const {
// Compute 1st and 2nd moments of the original outline.
LLSQ accumulator;
TBOX box = bounding_box();
// Iterate the outlines, accumulating edges relative the box.botleft().
CollectEdges(box, NULL, &accumulator, NULL, NULL);
*center = accumulator.mean_point() + box.botleft();
// The 2nd moments are just the standard deviation of the point positions.
double x2nd = sqrt(accumulator.x_variance());
double y2nd = sqrt(accumulator.y_variance());
if (x2nd < 1.0) x2nd = 1.0;
if (y2nd < 1.0) y2nd = 1.0;
second_moments->set_x(x2nd);
second_moments->set_y(y2nd);
return accumulator.count();
}
// Helper returns the mean direction vector from the given stats. Use the
// mean direction from dirs if there is information available, otherwise, use
// the fit_vector from point_diffs.
static FCOORD MeanDirectionVector(const LLSQ& point_diffs, const LLSQ& dirs,
const FCOORD& start_pt,
const FCOORD& end_pt) {
FCOORD fit_vector;
if (dirs.count() > 0) {
// There were directions, so use them. To avoid wrap-around problems, we
// have 2 accumulators in dirs: x for normal directions and y for
// directions offset by 128. We will use the one with the least variance.
FCOORD mean_pt = dirs.mean_point();
double mean_dir = 0.0;
if (dirs.x_variance() <= dirs.y_variance()) {
mean_dir = mean_pt.x();
} else {
mean_dir = mean_pt.y() + 128;
}
fit_vector.from_direction(Modulo(IntCastRounded(mean_dir), 256));
} else {
// There were no directions, so we rely on the vector_fit to the points.
// Since the vector_fit is 180 degrees ambiguous, we align with the
// supplied feature_dir by making the scalar product non-negative.
FCOORD feature_dir(end_pt - start_pt);
fit_vector = point_diffs.vector_fit();
if (fit_vector.x() == 0.0f && fit_vector.y() == 0.0f) {
// There was only a single point. Use feature_dir directly.
fit_vector = feature_dir;
} else {
// Sometimes the least mean squares fit is wrong, due to the small sample
// of points and scaling. Use a 90 degree rotated vector if that matches
// feature_dir better.
FCOORD fit_vector2 = !fit_vector;
// The fit_vector is 180 degrees ambiguous, so resolve the ambiguity by
// insisting that the scalar product with the feature_dir should be +ve.
if (fit_vector % feature_dir < 0.0)
fit_vector = -fit_vector;
if (fit_vector2 % feature_dir < 0.0)
fit_vector2 = -fit_vector2;
// Even though fit_vector2 has a higher mean squared error, it might be
// a better fit, so use it if the dot product with feature_dir is bigger.
if (fit_vector2 % feature_dir > fit_vector % feature_dir)
fit_vector = fit_vector2;
}
}
return fit_vector;
}
// Fits a straight baseline to the points. Returns true if it had enough
// points to be reasonably sure of the fitted baseline.
// If use_box_bottoms is false, baselines positions are formed by
// considering the outlines of the blobs.
bool BaselineRow::FitBaseline(bool use_box_bottoms) {
// Deterministic fitting is used wherever possible.
fitter_.Clear();
// Linear least squares is a backup if the DetLineFit produces a bad line.
LLSQ llsq;
BLOBNBOX_IT blob_it(blobs_);
for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
BLOBNBOX* blob = blob_it.data();
if (!use_box_bottoms) blob->EstimateBaselinePosition();
const TBOX& box = blob->bounding_box();
int x_middle = (box.left() + box.right()) / 2;
#ifdef kDebugYCoord
if (box.bottom() < kDebugYCoord && box.top() > kDebugYCoord) {
tprintf("Box bottom = %d, baseline pos=%d for box at:",
box.bottom(), blob->baseline_position());
box.print();
}
#endif
fitter_.Add(ICOORD(x_middle, blob->baseline_position()), box.width() / 2);
llsq.add(x_middle, blob->baseline_position());
}
// Fit the line.
ICOORD pt1, pt2;
baseline_error_ = fitter_.Fit(&pt1, &pt2);
baseline_pt1_ = pt1;
baseline_pt2_ = pt2;
if (baseline_error_ > max_baseline_error_ &&
fitter_.SufficientPointsForIndependentFit()) {
// The fit was bad but there were plenty of points, so try skipping
// the first and last few, and use the new line if it dramatically improves
// the error of fit.
double error = fitter_.Fit(kNumSkipPoints, kNumSkipPoints, &pt1, &pt2);
if (error < baseline_error_ / 2.0) {
baseline_error_ = error;
baseline_pt1_ = pt1;
baseline_pt2_ = pt2;
}
}
int debug = 0;
#ifdef kDebugYCoord
Print();
debug = bounding_box_.bottom() < kDebugYCoord &&
bounding_box_.top() > kDebugYCoord
? 3 : 2;
#endif
// Now we obtained a direction from that fit, see if we can improve the
// fit using the same direction and some other start point.
FCOORD direction(pt2 - pt1);
double target_offset = direction * pt1;
good_baseline_ = false;
FitConstrainedIfBetter(debug, direction, 0.0, target_offset);
// Wild lines can be produced because DetLineFit allows vertical lines, but
// vertical text has been rotated so angles over pi/4 should be disallowed.
// Near vertical lines can still be produced by vertically aligned components
// on very short lines.
double angle = BaselineAngle();
if (fabs(angle) > M_PI * 0.25) {
// Use the llsq fit as a backup.
baseline_pt1_ = llsq.mean_point();
baseline_pt2_ = baseline_pt1_ + FCOORD(1.0f, llsq.m());
// TODO(rays) get rid of this when m and c are no longer used.
double m = llsq.m();
double c = llsq.c(m);
baseline_error_ = llsq.rms(m, c);
good_baseline_ = false;
}
return good_baseline_;
}
