#take_screenshot by Josef Meile <jmeile@hotmail.com> @ June, 2019
#
#Takes a screenshot of the raspberry pi chromium kiosk and saves it to the
#specified SCREENSHOT_DIR
#
#If you want to use this on a crontab, then it must be on the one of the user
#running the kiosk. If you do it on the root crontab, then it won't work; even
#if you put 'export DISPLAY=:0 && ' in front of the command
#
#Remarks:
#- Scrot has big problems when using shell variables on its first argument: they
#  won't be replaced. I though it would be nice to have an IMAGE_FORMAT file to
#  specify the image format, ie: jpg or png, then use it as follows:
#  scrot '%H.%M.%S_$wx$h.$IMAGE_FORMAT'; however it won't work. I tried several
#  ways, ie: $(scrot '%H.%M.%S_$wx$h.$IMAGE_FORMAT'), but it seems that scrot
#  blocks shell variables. If you find a way, let me know. So, if you want to
#  use other format, then edit directly the scrot command (last line) and put
#  the image extension manually, ie: scrot '%H.%M.%S_$wx$h.jpg'

#-------------------------> Customization begins here

#Image quality (1-100) high value means high size, low compression. Default: 75.
#(Effect differs depending on file format chosen).
IMAGE_QUALITY=50

#Log file to now when x was restarted
LOG_FILE=/media/your_mount_point/your_folder/takescreenshot.txt

#DISPLAY :0 is the x11 display where the kiosk is running
#export DISPLAY=:0
#Update: DISPLAY :0 is not always the display where the kiosk is running.
#When killing x11 several times, the new display will be always the old one
#plus one. This command will get the current active display
export DISPLAY=`w -oush | grep -Eo ' :[0-9]+' | uniq | cut -d \  -f 2`

#Where to store the screenshots
SCREENSHOT_DIR="/media/your_mount_point/your_folder"

#-------------------------> Customization ends here

DAY=`date +'%d'`
MONTH=`date +'%m'`
YEAR=`date +'%Y'`
HOUR=`date +'%H'`
MIN=`date +'%M'`
SEC=`date +'%S'`

export SAVE_TO_DIR="$SCREENSHOT_DIR/$YEAR.$MONTH.$DAY"
mkdir -p "$SAVE_TO_DIR"

#Will generate jpg files
FILE_NAME=$(scrot '%H.%M.%S_$wx$h.jpg' -e 'echo $f ; mv $f \$SAVE_TO_DIR' -q $IMAGE_QUALITY -z)

#This will generate png files

#FILE_NAME=$(scrot '%H.%M.%S_$wx$h.png' -e 'echo $f ; mv $f \$SAVE_TO_DIR' -q $IMAGE_QUALITY -z)

#Now see if the file is a "Aw, Snap! Something went wrong while displaying this
#webpage." error. They are usually 36694 bytes long
FILE_SIZE=$(wc -c "$SAVE_TO_DIR/$FILE_NAME" | awk '{print $1}')
CHROMIUM_ERROR_SIZE=36694
if [ "$FILE_SIZE" -eq "$CHROMIUM_ERROR_SIZE" ] ; then
  echo "Restarting x on $DAY.$MONTH.$YEAR at $HOUR:$MIN:$SEC" | tee -a $LOG_FILE
  /home/pi/startx
else
  echo "X wasn't restarted"
fi