Remove background color in image processing for OCR

Question

I am trying to remove background color so as to improve the accuracy of OCR against images. A sample would look like below:

Answer 1

In Imagemagick, you can use the -lat function to do that.

convert image.jpg -colorspace gray -negate -lat 50x50+5% -negate result.jpg

convert image.jpg -colorspace HSB -channel 2 -separate +channel \
-white-threshold 35% \
-negate -lat 50x50+5% -negate \
-morphology erode octagon:1 result2.jpg