Improvements in Tesseract and pre-processing steps

[Rangarajan kgr]

I am working on Tesseract library and below is the input for the Tesseract,

At the initial step of implementation I have used only the "MRZ" zone of the ID card. 

But the actual intention is to scan the entire document and get all the texts in the ID card.

 

I have gone through this document and to improve quality of Tesseract th first step is the image should be 300 dpi.

1) How to convert the captured camera image in ios to 300 dpi?

2) What should be the best contrast and brigtness level for Tesseract to give best outputs?

3) Is there anyother pre-processing step that I can apply to an image to get good accuracy?

4) For better accuracy what is the recommended image resolution?

[Rick Leir]

For pre-processing, I am using ImageMagick to correct for uneven lighting across the image. The method is discussed in these two threads:

http://www.imagemagick.org/discourse-server/viewtopic.php?f=22&t=26190
http://www.imagemagick.org/discourse-server/viewtopic.php?f=7&t=26192

Actually, I am using GraphicsMagick now because its documentation is better.