Separate image of text into component character images

Question

I\'d like to separate an image of text into it\'s component characters, also as images. For example, using the sample below I\'d end up with 14 images.

I\'m only go

Answer 1

I know I am few years late :-) but you can do this sort of thing with ImageMagick pretty easily now, straight at the command-line without compiling anything, as it has Connected Component Analysis built-in:

Here is one way to do it like that:

#!/bin/bash
image="$1"
draw=$(convert $image                              \
   -threshold 50%                                  \
   -define connected-components:verbose=true       \
   -define connected-components:area-threshold=10  \
   -connected-components 8                         \
   -auto-level objects.png | \
   awk 'BEGIN{command=""}
        /\+0\+0/||/id:/{next}
        {
          geom=$2
          gsub(/x/," ",geom)
          gsub(/+/," ",geom)
          split(geom,a," ")
          d=sprintf("-draw \x27rectangle %d,%d %d,%d\x27 ",a[3],a[4],a[3]+a[1],a[4]+a[2])
          command = command d
          #printf "%d,%d %d,%d\n",a[3],a[4],a[3]+a[1],a[4]+a[2]
        }
        END{print command}')

eval convert "$image" -fill none -strokewidth 2 -stroke red $draw result.png

The result looks like this:

First, I threshold your image at 50% so that there are only pure blacks and whites in it, no tonal gradations. Then I tell ImageMagick to output details of the bounding boxes it finds, and that I am not interested in objects smaller than 10 pixels of total area. I then allow pixels to be 8-connected, i.e. to their diagonal neighbours (NE,SE,NW,SW) as well as their left-right and above-below neighbours. Finally I parse the bounding box output with awk to draw in red lines around the bounding boxes.

The output of the initial command that I parse with awk looks like this:

Objects (id: bounding-box centroid area mean-color):
  0: 539x53+0+0 263.7,24.3 20030 srgba(255,255,255,1)
  11: 51x38+308+14 333.1,30.2 869 srgba(0,0,0,1)
  13: 35x39+445+14 461.7,32.8 670 srgba(0,0,0,1)
  12: 35x39+365+14 381.7,32.8 670 srgba(0,0,0,1)
  2: 30x52+48+0 60.4,27.0 634 srgba(0,0,0,1)
  1: 41x52+1+0 20.9,16.6 600 srgba(0,0,0,1)
  8: 30x39+174+14 188.3,33.1 595 srgba(0,0,0,1)
  7: 30x39+102+14 116.3,33.1 595 srgba(0,0,0,1)
  9: 30x39+230+14 244.3,33.1 595 srgba(0,0,0,1)
  10: 35x39+265+14 282.2,33.0 594 srgba(0,0,0,1)
  16: 33x37+484+15 500.2,33.0 520 srgba(0,0,0,1)
  17: 22x28+272+19 282.3,32.8 503 srgba(255,255,255,1)
  5: 18x51+424+2 432.5,27.9 389 srgba(0,0,0,1)
  6: 18x51+520+2 528.5,27.9 389 srgba(0,0,0,1)
  15: 6x37+160+15 162.5,33.0 222 srgba(0,0,0,1)
  14: 6x37+88+15 90.5,33.0 222 srgba(0,0,0,1)
  18: 22x11+372+19 382.6,24.9 187 srgba(255,255,255,1)
  19: 22x11+452+19 462.6,24.9 187 srgba(255,255,255,1)
  3: 6x8+88+0 90.5,3.5 48 srgba(0,0,0,1)
  4: 6x8+160+0 162.5,3.5 48 srgba(0,0,0,1)

and the awk turns that into this

convert http://imgur.com/AVW7A.png -fill none -strokewidth 2 -stroke red \
-draw 'rectangle 308,14 359,52'        \
-draw 'rectangle 445,14 480,53'        \
-draw 'rectangle 365,14 400,53'        \
-draw 'rectangle 48,0 78,52'           \
-draw 'rectangle 1,0 42,52'            \
-draw 'rectangle 174,14 204,53'        \
-draw 'rectangle 102,14 132,53'        \
-draw 'rectangle 230,14 260,53'        \
-draw 'rectangle 265,14 300,53'        \
-draw 'rectangle 484,15 517,52'        \
-draw 'rectangle 272,19 294,47'        \
-draw 'rectangle 424,2 442,53'         \
-draw 'rectangle 520,2 538,53'         \
-draw 'rectangle 160,15 166,52'        \
-draw 'rectangle 88,15 94,52'          \
-draw 'rectangle 372,19 394,30'        \
-draw 'rectangle 452,19 474,30'        \
-draw 'rectangle 88,0 94,8'            \
-draw 'rectangle 160,0 166,8' result.png