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Fix typos in readthedocs documentation. (#579) 

* Fix typos and possible mistakes.

* Revert two edits based on discussion in #579

Revert the two changes based on our discussion. 

I read the documentation and had a glimpse at the default code. And perhaps the confusion was caused by the figure that shows the Char Margin (M) and the Word Margin (W). Clearly, M is smaller than W in absolute terms, but as mentioned, they are both relative numbers.

Maybe it is useful to point that out in the figure but I am not sure how best to do it. 

Another option is to mention use something like `min_char_margin_threshold` or similar, in the hope that they are easier to understand. Just some thoughts!

* Triggering travis again

Co-authored-by: Pieter Marsman <pietermarsman@gmail.com>
pull/593/head^2
X 2021-08-27 03:58:50 +09:00 committed by GitHub
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18
docs/source/topic/converting_pdf_to_text.rst
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@ -4,11 +4,11 @@ Converting a PDF file to text
*****************************
Most PDF files look like they contain well structured text. But the reality is
that a PDF file does not contain anything that resembles a paragraphs,
that a PDF file does not contain anything that resembles paragraphs,
sentences or even words. When it comes to text, a PDF file is only aware of
the characters and their placement.
This makes extracting meaningful pieces of text from PDF's files difficult.
This makes extracting meaningful pieces of text from PDF files difficult.
The characters that compose a paragraph are no different from those that
compose the table, the page footer or the description of a figure. Unlike
other documents formats, like a `.txt` file or a word document, the PDF format
@ -20,7 +20,6 @@ interactive elements and higher-level application data. A PDF file contains
the objects making up a PDF document along with associated structural
information, all represented as a single self-contained sequence of bytes. [1]_
.. _topic_pdf_to_text_layout:
Layout analysis algorithm
@ -41,7 +40,6 @@ of layout objects on a PDF page.
The output of the layout analysis is a hierarchy of layout objects.
The output of the layout analysis heavily depends on a couple of parameters.
All these parameters are part of the :ref:`api_laparams` class.
@ -56,10 +54,9 @@ bottom-left corner and upper-right corner, i.e. its bounding box. Pdfminer
Characters that are both horizontally and vertically close are grouped onto
one line. How close they should be is determined by the `char_margin`
(M in figure) and the `line_overlap` (not in figure) parameter. The horizontal
*distance* between the bounding boxes of two characters should be smaller that
*distance* between the bounding boxes of two characters should be smaller than
the `char_margin` and the vertical *overlap* between the bounding boxes should
be smaller the the `line_overlap`.
be smaller than the `line_overlap`.
.. raw:: html
:file: ../_static/layout_analysis.html
@ -71,14 +68,14 @@ relative to the minimum height of either one of the bounding boxes.
Spaces need to be inserted between characters because the PDF format has no
notion of the space character. A space is inserted if the characters are
further apart that the `word_margin` (W in the figure). The `word_margin` is
further apart than the `word_margin` (W in the figure). The `word_margin` is
relative to the maximum width or height of the new character. Having a smaller
`word_margin` creates smaller words. Note that the `word_margin` should at
least be smaller than the `char_margin` otherwise none of the characters will
be separated by a space.
The result of this stage is a list of lines. Each line consists a list of
characters. These characters either original `LTChar` characters that
characters. These characters are either original `LTChar` characters that
originate from the PDF file, or inserted `LTAnno` characters that
represent spaces between words or newlines at the end of each line.
@ -107,7 +104,7 @@ of lines.
Grouping textboxes hierarchically
---------------------------------
the last step is to group the text boxes in a meaningful way. This step
The last step is to group the text boxes in a meaningful way. This step
repeatedly merges the two text boxes that are closest to each other.
The closeness of bounding boxes is computed as the area that is between the
@ -118,7 +115,6 @@ boxes of the individual lines.
.. raw:: html
:file: ../_static/layout_analysis_group_boxes.html
Working with rotated characters
===============================