OCR, ROI's and Whitelists
Posted: Wed May 06, 2009 2:24 pm
Hi
We have used GDPicturePro control for sometime and I downloaded the new version with OCR yesterday. I have been doing some basic evaluation on the OCR methods using the sample program supplied and come up with a couple of questions . . . . .
1) Different results when OCR’ing the entire document and when using ROI
I am testing using a document with our name and address on it. When I OCR the entire document our company name “MARDAK” gets read as “IVIARDAK” and a confidence level of 33.33 for each character. However if a create a ROI of the top half of the page, it now reads it correctly as “MARDAK” and a confidence level of 30.58 for each character.
How does defining an ROI change the ability to OCR characters and is it more accurate to chop the page up into ROI’s rather than reading the entire page?
2) Use of Whitelists and the affect on OCR
Using the same document as above, towards the bottom of the document are 3 numbers. If you set a ROI round these numbers (20.00, 3.50 and 23.50), they get read correctly except the last number is “zs.s0” and a confidence of 49.41. However, if I set a whitelist of “0123456789.” and repeat the OCR, all the number are read correctly with a confidence of 25.30.
Does the Whitelist also act to direct the OCR process to the type of characters that are expected, and therefore, should one be specified if numbers are expected in a particular ROI?
These tests were carried out using the GDPicturePro OCX and the VB6 OCR example program supplied. This program was tweaked to show the character/OCR confidence level when looping through placing the red boxes round each character.
I have attached a copy of the document I was using to test this to the log.
Many thanks
Nigel
We have used GDPicturePro control for sometime and I downloaded the new version with OCR yesterday. I have been doing some basic evaluation on the OCR methods using the sample program supplied and come up with a couple of questions . . . . .
1) Different results when OCR’ing the entire document and when using ROI
I am testing using a document with our name and address on it. When I OCR the entire document our company name “MARDAK” gets read as “IVIARDAK” and a confidence level of 33.33 for each character. However if a create a ROI of the top half of the page, it now reads it correctly as “MARDAK” and a confidence level of 30.58 for each character.
How does defining an ROI change the ability to OCR characters and is it more accurate to chop the page up into ROI’s rather than reading the entire page?
2) Use of Whitelists and the affect on OCR
Using the same document as above, towards the bottom of the document are 3 numbers. If you set a ROI round these numbers (20.00, 3.50 and 23.50), they get read correctly except the last number is “zs.s0” and a confidence of 49.41. However, if I set a whitelist of “0123456789.” and repeat the OCR, all the number are read correctly with a confidence of 25.30.
Does the Whitelist also act to direct the OCR process to the type of characters that are expected, and therefore, should one be specified if numbers are expected in a particular ROI?
These tests were carried out using the GDPicturePro OCX and the VB6 OCR example program supplied. This program was tweaked to show the character/OCR confidence level when looping through placing the red boxes round each character.
I have attached a copy of the document I was using to test this to the log.
Many thanks
Nigel