Programmatically divide scanned images into separate images

Question

In order to improve OCR quality, I need to preprocess my scanned images. Sometimes I need to OCR the image with few pictures (components on the page and they are at different angles - for example, a few paper documents scanned at one time), for example:

Is it possible to automatically programmatically divide such images into separate images that will contain every logical document? For example with a tool like ImageMagick or something else? Is there any solutions/technics exists for such problem?

Answer 1

In ImageMagick 6, you can blur the image enough that the text overlaps and threshold so that the text boxes are each one large black region on a white background. Then you can use connected-components to find each separate black gray(0) region and its bounding box. Then crop the original image for each such region using the bounding box values.

Input:

Unix Syntax (adjust the blur to be just large enough to keep the text regions solid black):

infile="image.png"
inname=`convert -ping $infile -format "%t" info:`
OLDIFS=$IFS
IFS=$'\n'
arr=(`convert $infile -blur 0x5 -auto-level -threshold 99% -type bilevel +write tmp.png \
-define connected-components:verbose=true \
-connected-components 8 \
null: | tail -n +2 | sed 's/^[ ]*//'`)
num=${#arr[*]}
IFS=$OLDIFS
for ((i=0; i<num; i++)); do
#echo "${arr[$i]}"
color=`echo ${arr[$i]} | cut -d\  -f5`
bbox=`echo ${arr[$i]} | cut -d\  -f2`
echo "color=$color; bbox=$bbox"
if [ "$color" = "gray(0)" ]; then
convert $infile -crop $bbox +repage -fuzz 10% -trim +repage ${inname}_$i.png
fi
done

Textual Listing:

color=gray(255); bbox=892x1008+0+0
color=gray(0); bbox=337x430+36+13
color=gray(0); bbox=430x337+266+630
color=gray(0); bbox=202x147+506+252

tmp.png showing the blurred and thresholded regions:

Cropped Images: