AI Function 1:
Enhanced OCR Text Recognition

The text in PDF files can be placed as a native PDF text, as a text deconstructed in lines, as a text deconstructed in hatches, and as a text presented in raster pictures.

To recognize this kind of text the program uses artificial intelligence methods of OCR (Optical Character Recognition) and Symbol Recognition.

Enhanced Text recognition allows the program to recognize text in construction plans with different text directions. The direction of a text will be defined using a special editor.

Text Deconstructed in Lines

The right selection of Text representation is very important for correct text recognition.

The text for OCR text recognition can be placed in PDF as native Text, as text deconstructed in lines or path, as text deconstructed into hatches, or pixel pictures with a text.

The Analysis of a PDF file shall be done before the activation of a text representation. The Analysis of a PDF file shows in separate pictures what kind of text representation is used in the input PDF file.

If you find more than one text representation, choose all of it. Only choose Native Text Representation if the software is not able to convert native PDF text into native CAD text. In normal case do not activate the option "Include Native Texts".

The parameter for maximum and minimum text height are very important. The preseparation of a text works based on this parameter. Push the button “Preview”. If you see that not all text are separated then increase the maximum height. If you see a lot of free pixels are separated increase the minimum height.

If you choose the raster images as text representation, the threshold decides what pixel  belongs to the color black group and what pixels belongs to the white background. Push the button “Preview”. If you see that the text letters connect to each other then decrease the threshold.

The OCR Text recognition only works if the right text direction can be detected. Unfortunately, in one construction plan the text can exist in very different directions.

A manual preseparation of the text areas with a common direction is needed for well done OCR text recognition.  

Print2CAD offers a special editor for these text areas.

One “Text Area” will be defined with the help of 3 points. The first two points give the text direction and the third point gives the right upper corner of a text box.

In the text area editor you can choose different boxes for “Text Area” and for “Number Area”.

“Text Area” recognizes letters, numbers, and special characters like “+”, “-“ etc. If a number and a letter are in question (like the letter “l” and number “1”) the recognition will choose the letter “l”.

“Text Number” recognizes numbers, letters, and special characters like “+”, “-“ etc. If a number and letter are in question (like the letter “l” and number “1”) the recognition will choose the number “1”.

If the text area cuts one PDF element, this element will be not considered in the OCR text recognition.

Tips:
- Try to separate numbers and letters in different text areas.
- Try to separate in one text area only text with a common or similar text height.
- Try to separate clean text areas with no disruption from other drawing elements.

Tips for definition of Text Areas:

- Never define one common text area for the whole drawing
- A thorough selection of the text through text areas vastly improves the quality of the text recognition