ocr_line vs. ocrx_line

[kba]

@zdenop asked 2012 on the hocr ML without an answer:

I need clarification of ocr_line vs. ocrx_line

hOCR spec define ocrx_line as:

• any kind of "line" returned by an OCR system that differs from the
  standard ocr_line above
• might be some kind of "logical" line

hocr-tools provide this example of ocr_line[1]:

 <span class='ocr_line' title='bbox 461 648 2077 707'>Alice was beginning to get very tired of sitting by her sister on the bank,</span>

And tesseract-ocr (r729) produce this hocr output:

  <span class='ocr_line' id='line_2' title="bbox 464 651 2074 704">
      <span class='ocrx_word' id='word_5' title="bbox 464 651 569 688">Alice</span>
      <span class='ocrx_word' id='word_6' title="bbox 591 665 667 688">was</span>
       ...
      <span class='ocrx_word' id='word_19' title="bbox 1962 660 2074 704">bank,</span>
  </span>

Does tesseract-ocr ocr_line meets criteria of "standard ocr_line" or
should it use ocrx_line?

[zuphilip]

Could the handling of catchwords (=Kustode) be an example where one could try to use a ocrx_line instead/besides the usual ocr_lines?

[amitdo]

Maybe one of them is something like this:

<p>line one in a paragraph.<br>
line two in a paragraph</p>

??

[amitdo]

http://word.tips.net/T000170_Understanding_Hard_and_Soft_Returns.html

[amitdo]

Oh, I now see that there is a property hardbreak for ocr_line.

[wanghaisheng]

suppose u got a table ,if you can output content you can start a new one just like this

Command	Description
git status	List all new or modified files
	blahblah.....

you can consider these two line as a logical one instead two separate ones

[amitdo]

You mean a row in a table?

[wanghaisheng]

yes

[kba]

Thanks for the examples, rowspan makes sense, as does line continuation.

Catch word (those words printers put in the bottom margin as a helper/"checksum" which page should come next) are also an interesting example that probably warrants a new issue.

I've created an example for ocrx_line, hopefully a sensible one.

[amitdo]

I just found this message:
https://groups.google.com/forum/#!topic/ocropus/-s33xn9fBGY

[amitdo]

@tmbdev wrote in #39:

ocrx_line is engine-specific line markup. It exists for those cases where your OCR engine outputs text lines that don't correspond to "normal" text lines.

The most common case is if you apply an engine that's not capable of column segmentation to a multi-column document and you want to prevent subsequent processing stages from assuming that the text lines it gets contain text in reading order.

Basically, if you use ocrx_line instead of ocr_line, you're (intentionally) breaking most subsequent processing, since most OCR output processing will look for ocr_line tags (and assume they are in reading order).