///////////////////////////////////////////////////////////////////// // File: ocrpara.h // Description: OCR Paragraph Output Type // Author: David Eger // Created: 2010-11-15 // // (C) Copyright 2010, 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_CCSTRUCT_OCRPARA_H_ #define TESSERACT_CCSTRUCT_OCRPARA_H_ #include "publictypes.h" #include "elst.h" #include "strngs.h" class ParagraphModel; struct PARA : public ELIST_LINK { public: PARA() : model(NULL), is_list_item(false), is_very_first_or_continuation(false), has_drop_cap(false) {} // We do not own the model, we just reference it. // model may be NULL if there is not a good model for this paragraph. const ParagraphModel *model; bool is_list_item; // The first paragraph on a page often lacks a first line indent, but should // still be modeled by the same model as other body text paragraphs on the // page. bool is_very_first_or_continuation; // Does this paragraph begin with a drop cap? bool has_drop_cap; }; ELISTIZEH(PARA) // A geometric model of paragraph indentation and alignment. // // Measurements are in pixels. The meaning of the integer arguments changes // depending upon the value of justification. Distances less than or equal // to tolerance apart we take as "equivalent" for the purpose of model // matching, and in the examples below, we assume tolerance is zero. // // justification = LEFT: // margin the "ignored" margin to the left block edge. // first_indent indent from the left margin to a typical first text line. // body_indent indent from the left margin of a typical body text line. // // justification = RIGHT: // margin the "ignored" margin to the right block edge. // first_indent indent from the right margin to a typical first text line. // body_indent indent from the right margin of a typical body text line. // // justification = CENTER: // margin ignored // first_indent ignored // body_indent ignored // // ====== Extended example, assuming each letter is ten pixels wide: ======= // // +--------------------------------+ // | Awesome | ParagraphModel(CENTER, 0, 0, 0) // | Centered Title | // | Paragraph Detection | // | OCR TEAM | // | 10 November 2010 | // | | // | Look here, I have a paragraph.| ParagraphModel(LEFT, 0, 20, 0) // |This paragraph starts at the top| // |of the page and takes 3 lines. | // | Here I have a second paragraph| ParagraphModel(LEFT, 0, 20, 0) // |which indicates that the first | // |paragraph is not a continuation | // |from a previous page, as it is | // |indented just like this second | // |paragraph. | // | Here is a block quote. It | ParagraphModel(LEFT, 30, 0, 0) // | looks like the prior text | // | but it is indented more | // | and is fully justified. | // | So how does one deal with | ParagraphModel(LEFT, 0, 20, 0) // |centered text, block quotes, | // |normal paragraphs, and lists | // |like what follows? | // |1. Make a plan. | ParagraphModel(LEFT, 0, 0, 30) // |2. Use a heuristic, for example,| ParagraphModel(LEFT, 0, 0, 30) // | looking for lines where the | // | first word of the next line | // | would fit on the previous | // | line. | // |8. Try to implement the plan in | ParagraphModel(LEFT, 0, 0, 30) // | Python and try it out. | // |4. Determine how to fix the | ParagraphModel(LEFT, 0, 0, 30) // | mistakes. | // |5. Repeat. | ParagraphModel(LEFT, 0, 0, 30) // | For extra painful penalty work| ParagraphModel(LEFT, 0, 20, 0) // |you can try to identify source | // |code. Ouch! | // +--------------------------------+ class ParagraphModel { public: ParagraphModel(tesseract::ParagraphJustification justification, int margin, int first_indent, int body_indent, int tolerance) : justification_(justification), margin_(margin), first_indent_(first_indent), body_indent_(body_indent), tolerance_(tolerance) { // Make one of {first_indent, body_indent} is 0. int added_margin = first_indent; if (body_indent < added_margin) added_margin = body_indent; margin_ += added_margin; first_indent_ -= added_margin; body_indent_ -= added_margin; } ParagraphModel() : justification_(tesseract::JUSTIFICATION_UNKNOWN), margin_(0), first_indent_(0), body_indent_(0), tolerance_(0) { } // ValidFirstLine() and ValidBodyLine() take arguments describing a text line // in a block of text which we are trying to model: // lmargin, lindent: these add up to the distance from the leftmost ink // in the text line to the surrounding text block's left // edge. // rmargin, rindent: these add up to the distance from the rightmost ink // in the text line to the surrounding text block's right // edge. // The caller determines the division between "margin" and "indent", which // only actually affect whether we think the line may be centered. // // If the amount of whitespace matches the amount of whitespace expected on // the relevant side of the line (within tolerance_) we say it matches. // Return whether a given text line could be a first paragraph line according // to this paragraph model. bool ValidFirstLine(int lmargin, int lindent, int rindent, int rmargin) const; // Return whether a given text line could be a first paragraph line according // to this paragraph model. bool ValidBodyLine(int lmargin, int lindent, int rindent, int rmargin) const; tesseract::ParagraphJustification justification() const { return justification_; } int margin() const { return margin_; } int first_indent() const { return first_indent_; } int body_indent() const { return body_indent_; } int tolerance() const { return tolerance_; } bool is_flush() const { return (justification_ == tesseract::JUSTIFICATION_LEFT || justification_ == tesseract::JUSTIFICATION_RIGHT) && abs(first_indent_ - body_indent_) <= tolerance_; } // Return whether this model is likely to agree with the other model on most // paragraphs they are marked. bool Comparable(const ParagraphModel &other) const; STRING ToString() const; private: tesseract::ParagraphJustification justification_; int margin_; int first_indent_; int body_indent_; int tolerance_; }; #endif // TESSERACT_CCSTRUCT_OCRPARA_H_