Typical OCR software can handle only binary images with black pixels representing text and white pixels representing background. It isn't unusual in modern documents to have inverted text zones and normal text zones within the same document.


The document structure analysis and character recognition are usually done in several phases:
scanning
thresholding
skew detection and correction
despeckle or speckle removal
line removal
border removal
detection of preprinted elements (like boxes)
page orientation detection and correction
layout analysis
classification
character recognition (normal and inverse)

Each step must be completed well enough for the performance of the sequence and result to be successful. ZoneHelper detects and automatically converts inverted text zones and change white-on-black text to normal black-on-white text.
ZoneHelper expects as input a monochrome image.