Heavily inspired by PDF::Reader::Turtletext, HocrTurtletext provides convenient methods to extract content from a hOCR file. hOCR output is commonly produced by OCR software such as tesseract-ocr.
Add this line to your application's Gemfile:
gem 'hocr_turtletext'
And then execute:
$ bundle
Or install it yourself as:
$ gem install hocr_turtletext
Typical usage:
hocr_path = '/tmp/page1.hocr'
options = { :y_precision => 7 }
reader = HocrTurtletext::Reader.new(hocr_path, options)
Options:
x_whitespace_threshold
: Words with a x distance of less than this threshold will be concatenated with a space. Try increasing this value if words/letters that are supposed to belong together are separated.
y_precision
: Different rows of text with y positions that are less than y_precision of difference will be put together into one row. Try increasing this value if words that are supposed to be on the same row are detected as separate rows.
This method works nearly identically to its counterpart from PDF::Reader::Turtletext. The main difference is that we are not dealing with multiple pages in our hOCR input, so there is no need to support page selection.
Given that we know the text we want to find is relatively positioned (for example)
below a certain bit of text, to the left of another, and above some other text, use
the bounding_box
method to describe the region and extract the matching text.
textangle = reader.bounding_box do
below /electricity/i
above 10
right_of 240.0
left_of "Total ($)"
end
textangle.text
=> [['string','string'],['string']] # array of rows, each row is an array of text elements in the row
The range of methods that can be used within the bounding_box
block are all optional, and include:
inclusive
- whether region selection should be inclusive or exclusive of the specified positions (default is false).below
- a string, regex or number that describes the upper limit of the text box (default is top border of the page)`.above
- a string, regex or number that describes the lower limit of the text box (default is bottom border of the page).left_of
- a string, regex or number that describes the right limit of the text box (default is right border of the page).right_of
- a string, regex or number that describes the left limit of the text box (default is left border of the page).
Note that left_of
and right_of
constraints do not need to be within the vertical
range of the box being described.
For example, you could use an element in the page header to describe the left_of
limit
for a table at the bottom of the page, if it has the correct alignment needed to describe your text region.
Similarly, above
and below
constraints do not need to be within the horizontal
range of the box being described.
An explicit block parameter may be used with the bounding_box
method:
textangle = reader.bounding_box do |r|
r.below /electricity/i
r.left_of "Total ($)"
end
textangle.text
=> [['string','string'],['string']] # array of rows, each row is an array of text elements in the row
By default, the bounding_box
method makes exclusive selection (i.e. not including the
region limits).
To specify an inclusive region, use the inclusive!
command:
textangle = reader.bounding_box do
inclusive!
below /electricity/i
left_of "Total ($)"
end
Alternatively, set inclusive
to true:
textangle = reader.bounding_box do
inclusive true
below /electricity/i
left_of "Total ($)"
end
Or with a block parameter, you may also assign inclusive
to true:
textangle = reader.bounding_box do |r|
r.inclusive = true
r.below /electricity/i
r.left_of "Total ($)"
end
If you know (or can calculate) the x,y positions of the required text region, you can extract the region's text using the text_in_region
method.
text = reader.text_in_region(
10, # minimum x (left-most)
900, # maximum x (right-most)
200, # minimum y (top-most)
400, # maximum y (bottom-most)
false # inclusive of x/y position if true (default false)
)
=> [['string','string'],['string']] # array of rows, each row is an array of text elements in the row
Note that the x,y origin is at the top-left. This differs from how it works in PDF::Reader::Turtletext, where the origin was bottom-left of the page.
If you are doing low-level text extraction with text_in_region
for example,
it is usually necessary to locate specific text to provide a positional reference.
Use the text_position
method to locate text by exact or partial match.
It returns a Hash of x/y co-ordinates that is the bottom-left corner of the text.
text_by_exact_match = reader.text_position("Transaction Table")
=> { :x => 10.0, :y => 600.0 }
text_by_regex_match = reader.text_position(/transaction summary/i)
=> { :x => 10.0, :y => 300.0 }
Note: in the case of multiple matches, only the first match is returned.
After checking out the repo, run bin/setup
to install dependencies. Then, run rake spec
to run the tests. You can also run bin/console
for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run bundle exec rake install
. To release a new version, update the version number in version.rb
, and then run bundle exec rake release
, which will create a git tag for the version, push git commits and tags, and push the .gem
file to rubygems.org.
- Check issue tracker if someone is working on what you plan to work on
- Fork project
- Create new branch
- Make changes in new branch
- Submit pull request
The gem is available as open source under the terms of the MIT License.
- Paul Gallagher, creator of the PDF::Reader::Turtletext gem, from which large sections of this gem was copied/modified from.