Hi, I am working on iPhone application that recognizes ISBN numbers (ISBN:
978-83-7380-900-0) I use tesseract for this, but it is not working very
well. I can see other applications, using same engine to work better.
to limit the characters i use this config line:
tess->SetVariable("tessedit_char_whitelist", "SN:0123456789X-"); so all "I"
are converted to "1", and "B" to 8. Using this it wont make mistake with
those letters, whick are not important to me. After that i use regular
expression to find the correct part of recognized text.
I also crop the image, so tesseract recognizes only part of the image, where
isbn is visible (i placed color rect on camera overlay, so user have to
place code in correct place) I also resize the image to 1000px width (also
tried other sizes)
It works quite well when the light is excellent, but it is really hard to
recognize correctly when the lighting isn't perfect.
The last digit of isbn number is a control sum.
What can I do to make it work better? Is there any way to say tesserect to
recognize text only in given regular expression? Maybe i should do something
with image first?
Sample images, that are not recognized correctly:
http://img412.imageshack.us/i/img0367si.jpg/
http://img264.imageshack.us/i/img0361d.jpg/
At the moment I am also making pictures at 2x zoom so camera is not so close
to the object. It gives better results, but it is easier to move the camera
and take fuzzy image.
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