This project was hacked together in a day to extract data tables from images, because of the quick and rather naive implementation it only handles fixed-width non-antialiased "Courier New" at 12pt, but manages to do a reasonable job of it.
- Written in PHP / Very Portable
- Extremely slow / Easy to Debug
- Nearly no testing / Open-source
- Does nothing fancy / Easy to understand
- Cannot differentiate between '0' (zero) and 'O' in Courier New 12pt.
The software uses an automatically generated 'possibility intersection table' (made-up term) to logically deduce which character exists within the search area.
The table is built by counting which letters have white or black pixels at each position within the fixed sized font area. The 'possible letters' are eliminated by performing an intersection of all letters which have a black or white pixel against the previous list of possible letters.
Example:
Letter E | Letter L
|
###### | ###
# # | #
# # | #
### | #
# | #
Would build a table with:
0x0: E,L
1x0: E,L
2x0: E,L
3x0: E
The starts of lines are identified by performing a brute force search for the first letter, afterwards the whole lines are scanned from left to right to produce the text in the correct output order.
The code should be considered public domain, fonts and included images/text may not be used with modified versions of the software as they are for demonstration purposes only.
Because I went through 6 commercially available pieces of OCR software which were unable to extract the demo data with reasonable accuracy (even with extensive training and manual tweaking).
Big respect to the developers PrimeOCR: the only comercially available software which was able to achieve this deceptively simple task.