#!/bin/bash

# start Y position of masked line
YVALUE=-40
# start X position of masked line
XVALUE=-40
# end Y position
YVALUE2=520
# end X position
XVALUE2=760
# Total number of times to call script
ETOTAL=200

until [ $(echo  $XVALUE | awk '{printf "%.0f",$1}') -gt 800 ]; do

#add to x
XVALUE=$(echo "scale=2; $XVALUE + ( 800 / $ETOTAL )" | bc)
echo "x1 = $XVALUE"
#add to y
YVALUE=$(echo "scale=2; $YVALUE + ( 560 / $ETOTAL )" | bc)
echo "y1 = $YVALUE"
#subtract form second x
XVALUE2=$(echo "scale=2; $XVALUE2 - ( 800 / $ETOTAL )" | bc)
echo "x2 = $XVALUE2"
#subtract to second y
YVALUE2=$(echo "scale=2; $YVALUE2 - ( 560 / $ETOTAL )" | bc)
echo "y2 = $YVALUE2"
done