Okay i took all the data from this topic, some info i found on the internet, some personal thoughts and tried to create a proper script. It's not that complicated as of now.
Kinda simplified but these are the steps:
1. Detect
any background and remove it, replacing it with transparency. This is accomplished by this awesome prebuilt script from hackerb9
https://github.com/hackerb9/mktrans
2.1 Add a 1 px white border around cards
2.2 Create a mask using the 1px border to understand where cards are
3. Use the mask to extract the single cards
Now i'd like to apply some minimal antialiasing
before extracting the single cards but only
after creating the mask, this is very important because i need a clear contrasting line between white and black when extracting the cards using the mask otherwise it won't work properly.
This is some relevant code from the script:
Code: Select all
#Variables declaration
FILENAME=$1
FILENAME_NO_EXTENSION=$(echo $FILENAME | cut -d '.' -f 1)
DECKNAME=$2
echo ''
echo '*******************************'
echo ' Input file: '$FILENAME
echo ' Deck name: '$DECKNAME
echo '*******************************'
echo ''
#Replace bg color with transparent alpha channel
echo '1. Removing background...'
bash ./mktrans -A $FILENAME
#Add 1 pixel transparent border and make sure all color under the transparency is white:
convert $FILENAME_NO_EXTENSION-transparent.png -bordercolor none -border 1 -background white -alpha background -bordercolor white tmp_border.png
#Threshold to black and white - creating a mask used to cut single cards in the next step
echo '2. Creating mask...'
convert tmp_border.png -alpha off -negate -threshold 0 -type bilevel tmp_mask.png
#Run connected components labeling to extract the bounds of the white thresholded cards using the mask
#and crop the white background image to extract the cards
echo '3. Extracting cards...'
OLD_IFS=$IFS
IFS=$'\n'
arr=(`convert tmp_mask.png \
-define connected-components:verbose=true \
-define connected-components:area-threshold=10 \
-define connected-components:mean-color=true \
-connected-components 8 \
null: | tail -n +2 | sed 's/^[ ]*//'`)
IFS=$OLD_IFS
num=${#arr[*]}
for ((i=0; i<num; i++))
do
bbox=`echo "${arr[$i]}" | cut -d\ -f2`
color=`echo "${arr[$i]}" | cut -d\ -f5`
if [ "$color" = "gray(255)" ]; then
convert tmp_border.png -crop $bbox +repage -background none -deskew 40% ${DECKNAME}${i}.png
echo -n '.'
fi
done
