ImageMagick

http://www.imagemagick.org/discourse-server/viewtopic.php?t=23723
remove all horizontal or vertical black lines that are at least 30 pixels long

convert example_box_ocr.png ^
  -define morphology:compose=lighten ^
  -morphology Thicken ^
1x30+0+0^<:0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 ^
  e.png

convert example_box_ocr.png ^
  -negate ^
  -define morphology:compose=darken ^
  -morphology Thinning Rectangle:1x30+0+0^< ^
  -negate ^
  e2.png


http://www.imagemagick.org/discourse-server/viewtopic.php?t=22338
convert billy.png -morphology close:2 "1x4: 0,1,1,0" result.png
 It is a morphological close (erode and dilate) attempt to remove two pixel tall horizontal black lines that have white above and below them.



-statistic median 7x7
-monochrome
-median
-morphology Smooth Octagon:1