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192 lines
7.3 KiB
C++
192 lines
7.3 KiB
C++
/////////////////////////////////////////////////////////////////////
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// File: ocrpara.h
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// Description: OCR Paragraph Output Type
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// Author: David Eger
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// Created: 2010-11-15
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//
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// (C) Copyright 2010, Google Inc.
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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///////////////////////////////////////////////////////////////////////
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#ifndef TESSERACT_CCSTRUCT_OCRPARA_H_
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#define TESSERACT_CCSTRUCT_OCRPARA_H_
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#include "publictypes.h"
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#include "elst.h"
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#include "strngs.h"
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class ParagraphModel;
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struct PARA : public ELIST_LINK {
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public:
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PARA() : model(nullptr), is_list_item(false),
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is_very_first_or_continuation(false), has_drop_cap(false) {}
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// We do not own the model, we just reference it.
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// model may be nullptr if there is not a good model for this paragraph.
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const ParagraphModel *model;
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bool is_list_item;
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// The first paragraph on a page often lacks a first line indent, but should
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// still be modeled by the same model as other body text paragraphs on the
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// page.
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bool is_very_first_or_continuation;
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// Does this paragraph begin with a drop cap?
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bool has_drop_cap;
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};
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ELISTIZEH(PARA)
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// A geometric model of paragraph indentation and alignment.
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//
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// Measurements are in pixels. The meaning of the integer arguments changes
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// depending upon the value of justification. Distances less than or equal
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// to tolerance apart we take as "equivalent" for the purpose of model
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// matching, and in the examples below, we assume tolerance is zero.
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//
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// justification = LEFT:
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// margin the "ignored" margin to the left block edge.
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// first_indent indent from the left margin to a typical first text line.
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// body_indent indent from the left margin of a typical body text line.
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//
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// justification = RIGHT:
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// margin the "ignored" margin to the right block edge.
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// first_indent indent from the right margin to a typical first text line.
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// body_indent indent from the right margin of a typical body text line.
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//
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// justification = CENTER:
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// margin ignored
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// first_indent ignored
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// body_indent ignored
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//
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// ====== Extended example, assuming each letter is ten pixels wide: =======
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//
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// +--------------------------------+
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// | Awesome | ParagraphModel(CENTER, 0, 0, 0)
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// | Centered Title |
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// | Paragraph Detection |
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// | OCR TEAM |
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// | 10 November 2010 |
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// | |
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// | Look here, I have a paragraph.| ParagraphModel(LEFT, 0, 20, 0)
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// |This paragraph starts at the top|
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// |of the page and takes 3 lines. |
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// | Here I have a second paragraph| ParagraphModel(LEFT, 0, 20, 0)
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// |which indicates that the first |
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// |paragraph is not a continuation |
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// |from a previous page, as it is |
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// |indented just like this second |
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// |paragraph. |
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// | Here is a block quote. It | ParagraphModel(LEFT, 30, 0, 0)
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// | looks like the prior text |
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// | but it is indented more |
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// | and is fully justified. |
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// | So how does one deal with | ParagraphModel(LEFT, 0, 20, 0)
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// |centered text, block quotes, |
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// |normal paragraphs, and lists |
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// |like what follows? |
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// |1. Make a plan. | ParagraphModel(LEFT, 0, 0, 30)
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// |2. Use a heuristic, for example,| ParagraphModel(LEFT, 0, 0, 30)
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// | looking for lines where the |
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// | first word of the next line |
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// | would fit on the previous |
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// | line. |
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// |8. Try to implement the plan in | ParagraphModel(LEFT, 0, 0, 30)
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// | Python and try it out. |
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// |4. Determine how to fix the | ParagraphModel(LEFT, 0, 0, 30)
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// | mistakes. |
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// |5. Repeat. | ParagraphModel(LEFT, 0, 0, 30)
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// | For extra painful penalty work| ParagraphModel(LEFT, 0, 20, 0)
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// |you can try to identify source |
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// |code. Ouch! |
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// +--------------------------------+
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class ParagraphModel {
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public:
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ParagraphModel(tesseract::ParagraphJustification justification,
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int margin,
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int first_indent,
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int body_indent,
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int tolerance)
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: justification_(justification),
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margin_(margin),
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first_indent_(first_indent),
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body_indent_(body_indent),
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tolerance_(tolerance) {
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// Make one of {first_indent, body_indent} is 0.
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int added_margin = first_indent;
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if (body_indent < added_margin)
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added_margin = body_indent;
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margin_ += added_margin;
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first_indent_ -= added_margin;
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body_indent_ -= added_margin;
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}
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ParagraphModel()
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: justification_(tesseract::JUSTIFICATION_UNKNOWN),
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margin_(0),
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first_indent_(0),
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body_indent_(0),
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tolerance_(0) { }
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// ValidFirstLine() and ValidBodyLine() take arguments describing a text line
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// in a block of text which we are trying to model:
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// lmargin, lindent: these add up to the distance from the leftmost ink
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// in the text line to the surrounding text block's left
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// edge.
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// rmargin, rindent: these add up to the distance from the rightmost ink
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// in the text line to the surrounding text block's right
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// edge.
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// The caller determines the division between "margin" and "indent", which
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// only actually affect whether we think the line may be centered.
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//
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// If the amount of whitespace matches the amount of whitespace expected on
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// the relevant side of the line (within tolerance_) we say it matches.
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// Return whether a given text line could be a first paragraph line according
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// to this paragraph model.
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bool ValidFirstLine(int lmargin, int lindent, int rindent, int rmargin) const;
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// Return whether a given text line could be a first paragraph line according
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// to this paragraph model.
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bool ValidBodyLine(int lmargin, int lindent, int rindent, int rmargin) const;
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tesseract::ParagraphJustification justification() const {
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return justification_;
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}
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int margin() const { return margin_; }
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int first_indent() const { return first_indent_; }
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int body_indent() const { return body_indent_; }
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int tolerance() const { return tolerance_; }
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bool is_flush() const {
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return (justification_ == tesseract::JUSTIFICATION_LEFT ||
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justification_ == tesseract::JUSTIFICATION_RIGHT) &&
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abs(first_indent_ - body_indent_) <= tolerance_;
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}
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// Return whether this model is likely to agree with the other model on most
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// paragraphs they are marked.
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bool Comparable(const ParagraphModel &other) const;
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STRING ToString() const;
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private:
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tesseract::ParagraphJustification justification_;
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int margin_;
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int first_indent_;
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int body_indent_;
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int tolerance_;
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};
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#endif // TESSERACT_CCSTRUCT_OCRPARA_H_
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