tesseract/src/textord/tabvector.h

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///////////////////////////////////////////////////////////////////////
// File: tabvector.h
// Description: Class to hold a near-vertical vector representing a tab-stop.
// Author: Ray Smith
// Created: Thu Apr 10 16:25:01 PST 2008
//
// (C) Copyright 2008, Google Inc.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
///////////////////////////////////////////////////////////////////////
#ifndef TESSERACT_TEXTORD_TABVECTOR_H_
#define TESSERACT_TEXTORD_TABVECTOR_H_
#include "blobgrid.h"
#include "clst.h"
#include "elst.h"
#include "elst2.h"
#include "rect.h"
#include "bbgrid.h"
#include <algorithm>
class BLOBNBOX;
class ScrollView;
namespace tesseract {
extern double_VAR_H(textord_tabvector_vertical_gap_fraction, 0.5,
"Max fraction of mean blob width allowed for vertical gaps in vertical text");
extern double_VAR_H(textord_tabvector_vertical_box_ratio, 0.5,
"Fraction of box matches required to declare a line vertical");
// The alignment type that a tab vector represents.
// Keep this enum synced with kAlignmentNames in tabvector.cpp.
enum TabAlignment {
TA_LEFT_ALIGNED,
TA_LEFT_RAGGED,
TA_CENTER_JUSTIFIED,
TA_RIGHT_ALIGNED,
TA_RIGHT_RAGGED,
TA_SEPARATOR,
TA_COUNT
};
// Forward declarations. The classes use their own list types, so we
// need to make the list types first.
class TabFind;
class TabVector;
class TabConstraint;
ELIST2IZEH(TabVector)
CLISTIZEH(TabVector)
ELISTIZEH(TabConstraint)
// TabConstraint is a totally self-contained class to maintain
// a list of [min,max] constraints, each referring to a TabVector.
// The constraints are manipulated through static methods that act
// on a list of constraints. The list itself is cooperatively owned
// by the TabVectors of the constraints on the list and managed
// by implicit reference counting via the elements of the list.
class TabConstraint : public ELIST_LINK {
public:
// This empty constructor is here only so that the class can be ELISTIZED.
// TODO(rays) change deep_copy in elst.h line 955 to take a callback copier
// and eliminate CLASSNAME##_copier.
TabConstraint() = default;
// Create a constraint for the top or bottom of this TabVector.
static void CreateConstraint(TabVector* vector, bool is_top);
// Test to see if the constraints are compatible enough to merge.
static bool CompatibleConstraints(TabConstraint_LIST* list1,
TabConstraint_LIST* list2);
// Merge the lists of constraints and update the TabVector pointers.
// The second list is deleted.
static void MergeConstraints(TabConstraint_LIST* list1,
TabConstraint_LIST* list2);
// Set all the tops and bottoms as appropriate to a mean of the
// constrained range. Delete all the constraints and list.
static void ApplyConstraints(TabConstraint_LIST* constraints);
private:
TabConstraint(TabVector* vector, bool is_top);
// Get the max of the mins and the min of the maxes.
static void GetConstraints(TabConstraint_LIST* constraints,
int* y_min, int* y_max);
// The TabVector this constraint applies to.
TabVector* vector_;
// If true then we refer to the top of the vector_.
bool is_top_;
// The allowed range of this vector_.
int y_min_;
int y_max_;
};
// Class to hold information about a single vector
// that represents a tab stop or a rule line.
class TabVector : public ELIST2_LINK {
public:
// TODO(rays) fix this in elst.h line 1076, where it should use the
// copy constructor instead of operator=.
TabVector() = default;
~TabVector() = default;
// Public factory to build a TabVector from a list of boxes.
// The TabVector will be of the given alignment type.
// The input vertical vector is used in fitting, and the output
// vertical_x, vertical_y have the resulting line vector added to them
// if the alignment is not ragged.
// The extended_start_y and extended_end_y are the maximum possible
// extension to the line segment that can be used to align with others.
// The input CLIST of BLOBNBOX good_points is consumed and taken over.
static TabVector* FitVector(TabAlignment alignment, ICOORD vertical,
int extended_start_y, int extended_end_y,
BLOBNBOX_CLIST* good_points,
int* vertical_x, int* vertical_y);
// Build a ragged TabVector by copying another's direction, shifting it
// to match the given blob, and making its initial extent the height
// of the blob, but its extended bounds from the bounds of the original.
TabVector(const TabVector& src, TabAlignment alignment,
const ICOORD& vertical_skew, BLOBNBOX* blob);
// Copies basic attributes of a tab vector for simple operations.
// Copies things such startpt, endpt, range, width.
// Does not copy things such as partners, boxes, or constraints.
// This is useful if you only need vector information for processing, such
// as in the table detection code.
TabVector* ShallowCopy() const;
// Simple accessors.
const ICOORD& startpt() const {
return startpt_;
}
const ICOORD& endpt() const {
return endpt_;
}
int extended_ymax() const {
return extended_ymax_;
}
int extended_ymin() const {
return extended_ymin_;
}
int sort_key() const {
return sort_key_;
}
int mean_width() const {
return mean_width_;
}
void set_top_constraints(TabConstraint_LIST* constraints) {
top_constraints_ = constraints;
}
void set_bottom_constraints(TabConstraint_LIST* constraints) {
bottom_constraints_ = constraints;
}
TabVector_CLIST* partners() {
return &partners_;
}
void set_startpt(const ICOORD& start) {
startpt_ = start;
}
void set_endpt(const ICOORD& end) {
endpt_ = end;
}
bool intersects_other_lines() const {
return intersects_other_lines_;
}
void set_intersects_other_lines(bool value) {
intersects_other_lines_ = value;
}
// Inline quasi-accessors that require some computation.
// Compute the x coordinate at the given y coordinate.
int XAtY(int y) const {
int height = endpt_.y() - startpt_.y();
if (height != 0)
return (y - startpt_.y()) * (endpt_.x() - startpt_.x()) / height +
startpt_.x();
else
return startpt_.x();
}
// Compute the vertical overlap with the other TabVector.
int VOverlap(const TabVector& other) const {
return std::min(other.endpt_.y(), endpt_.y()) -
std::max(other.startpt_.y(), startpt_.y());
}
// Compute the vertical overlap with the given y bounds.
int VOverlap(int top_y, int bottom_y) const {
return std::min(top_y, static_cast<int>(endpt_.y())) - std::max(bottom_y, static_cast<int>(startpt_.y()));
}
// Compute the extended vertical overlap with the given y bounds.
int ExtendedOverlap(int top_y, int bottom_y) const {
return std::min(top_y, extended_ymax_) - std::max(bottom_y, extended_ymin_);
}
// Return true if this is a left tab stop, either aligned, or ragged.
bool IsLeftTab() const {
return alignment_ == TA_LEFT_ALIGNED || alignment_ == TA_LEFT_RAGGED;
}
// Return true if this is a right tab stop, either aligned, or ragged.
bool IsRightTab() const {
return alignment_ == TA_RIGHT_ALIGNED || alignment_ == TA_RIGHT_RAGGED;
}
// Return true if this is a separator.
bool IsSeparator() const {
return alignment_ == TA_SEPARATOR;
}
// Return true if this is a center aligned tab stop.
bool IsCenterTab() const {
return alignment_ == TA_CENTER_JUSTIFIED;
}
// Return true if this is a ragged tab top, either left or right.
bool IsRagged() const {
return alignment_ == TA_LEFT_RAGGED || alignment_ == TA_RIGHT_RAGGED;
}
// Return true if this vector is to the left of the other in terms
// of sort_key_.
bool IsLeftOf(const TabVector& other) const {
return sort_key_ < other.sort_key_;
}
// Return true if the vector has no partners.
bool Partnerless() {
return partners_.empty();
}
// Return the number of tab boxes in this vector.
int BoxCount() {
return boxes_.length();
}
// Lock the vector from refits by clearing the boxes_ list.
void Freeze() {
boxes_.shallow_clear();
}
// Flip x and y on the ends so a vector can be created from flipped input.
void XYFlip() {
int x = startpt_.y();
startpt_.set_y(startpt_.x());
startpt_.set_x(x);
x = endpt_.y();
endpt_.set_y(endpt_.x());
endpt_.set_x(x);
}
// Reflect the tab vector in the y-axis.
void ReflectInYAxis() {
startpt_.set_x(-startpt_.x());
endpt_.set_x(-endpt_.x());
sort_key_ = -sort_key_;
if (alignment_ == TA_LEFT_ALIGNED)
alignment_ = TA_RIGHT_ALIGNED;
else if (alignment_ == TA_RIGHT_ALIGNED)
alignment_ = TA_LEFT_ALIGNED;
if (alignment_ == TA_LEFT_RAGGED)
alignment_ = TA_RIGHT_RAGGED;
else if (alignment_ == TA_RIGHT_RAGGED)
alignment_ = TA_LEFT_RAGGED;
}
// Separate function to compute the sort key for a given coordinate pair.
static int SortKey(const ICOORD& vertical, int x, int y) {
ICOORD pt(x, y);
return pt * vertical;
}
// Return the x at the given y for the given sort key.
static int XAtY(const ICOORD& vertical, int sort_key, int y) {
if (vertical.y() != 0)
return (vertical.x() * y + sort_key) / vertical.y();
else
return sort_key;
}
// Sort function for E2LIST::sort to sort by sort_key_.
static int SortVectorsByKey(const void* v1, const void* v2) {
const TabVector* tv1 = *static_cast<const TabVector* const*>(v1);
const TabVector* tv2 = *static_cast<const TabVector* const*>(v2);
return tv1->sort_key_ - tv2->sort_key_;
}
// More complex members.
// Extend this vector to include the supplied blob if it doesn't
// already have it.
void ExtendToBox(BLOBNBOX* blob);
// Set the ycoord of the start and move the xcoord to match.
void SetYStart(int start_y);
// Set the ycoord of the end and move the xcoord to match.
void SetYEnd(int end_y);
// Rotate the ends by the given vector.
void Rotate(const FCOORD& rotation);
// Setup the initial constraints, being the limits of
// the vector and the extended ends.
void SetupConstraints();
// Setup the constraints between the partners of this TabVector.
void SetupPartnerConstraints();
// Setup the constraints between this and its partner.
void SetupPartnerConstraints(TabVector* partner);
// Use the constraints to modify the top and bottom.
void ApplyConstraints();
// Merge close tab vectors of the same side that overlap.
static void MergeSimilarTabVectors(const ICOORD& vertical,
TabVector_LIST* vectors, BlobGrid* grid);
// Return true if this vector is the same side, overlaps, and close
// enough to the other to be merged.
bool SimilarTo(const ICOORD& vertical,
const TabVector& other, BlobGrid* grid) const;
// Eat the other TabVector into this and delete it.
void MergeWith(const ICOORD& vertical, TabVector* other);
// Add a new element to the list of partner TabVectors.
// Partners must be added in order of increasing y coordinate of the text line
// that makes them partners.
// Groups of identical partners are merged into one.
void AddPartner(TabVector* partner);
// Return true if other is a partner of this.
bool IsAPartner(const TabVector* other);
// Print basic information about this tab vector.
void Print(const char* prefix);
// Print basic information about this tab vector and every box in it.
void Debug(const char* prefix);
// Draw this tabvector in place in the given window.
void Display(ScrollView* tab_win);
// Refit the line and/or re-evaluate the vector if the dirty flags are set.
void FitAndEvaluateIfNeeded(const ICOORD& vertical, TabFind* finder);
// Evaluate the vector in terms of coverage of its length by good-looking
// box edges. A good looking box is one where its nearest neighbour on the
// inside is nearer than half the distance its nearest neighbour on the
// outside of the putative column. Bad boxes are removed from the line.
// A second pass then further filters boxes by requiring that the gutter
// width be a minimum fraction of the mean gutter along the line.
void Evaluate(const ICOORD& vertical, TabFind* finder);
// (Re)Fit a line to the stored points. Returns false if the line
// is degenerate. Althougth the TabVector code mostly doesn't care about the
// direction of lines, XAtY would give silly results for a horizontal line.
// The class is mostly aimed at use for vertical lines representing
// horizontal tab stops.
bool Fit(ICOORD vertical, bool force_parallel);
// Return the partner of this TabVector if the vector qualifies as
// being a vertical text line, otherwise nullptr.
TabVector* VerticalTextlinePartner();
// Return the matching tabvector if there is exactly one partner, or
// nullptr otherwise. This can be used after matching is done, eg. by
// VerticalTextlinePartner(), without checking if the line is vertical.
TabVector* GetSinglePartner();
private:
// Constructor is private as the static factory is the external way
// to build a TabVector.
TabVector(int extended_ymin, int extended_ymax,
TabAlignment alignment, BLOBNBOX_CLIST* boxes);
// Delete this, but first, repoint all the partners to point to
// replacement. If replacement is nullptr, then partner relationships
// are removed.
void Delete(TabVector* replacement);
private:
// The bottom of the tab line.
ICOORD startpt_;
// The top of the tab line.
ICOORD endpt_;
// The lowest y that the vector might extend to.
int extended_ymin_;
// The highest y that the vector might extend to.
int extended_ymax_;
// Perpendicular distance of vector from a given vertical for sorting.
int sort_key_;
// Result of Evaluate 0-100. Coverage of line with good boxes.
int percent_score_;
// The mean width of the blobs. Meaningful only for separator lines.
int mean_width_;
// True if the boxes_ list has been modified, so a refit is needed.
bool needs_refit_;
// True if a fit has been done, so re-evaluation is needed.
bool needs_evaluation_;
// True if a separator line intersects at least 2 other lines.
bool intersects_other_lines_;
// The type of this TabVector.
TabAlignment alignment_;
// The list of boxes whose edges are aligned at this TabVector.
BLOBNBOX_CLIST boxes_;
// List of TabVectors that have a connection with this via a text line.
TabVector_CLIST partners_;
// Constraints used to resolve the exact location of the top and bottom
// of the tab line.
TabConstraint_LIST* top_constraints_;
TabConstraint_LIST* bottom_constraints_;
};
} // namespace tesseract.
#endif // TESSERACT_TEXTORD_TABVECTOR_H_