#!/bin/bash

  ct=0
  until [ $ct -gt 719 ] # sets how often a cut will be made (+1) and how many snippets will be produced
  do
    ((ct+=1)) # a counter. starting at 1, increasing by 1
    ctt=`printf %03d $ct` # prints 3 digits numbers, important for naming the files
    sw=`awk -v x="$ct" 'BEGIN {wv=sin(2*3.1415926535*(4+(x/100))*(x/10))+0.9999 ; printf wv }'`
    # defines a sine function. shift 0.9999 above zero on y-axis. cycle duration will change over time
    mkdir -p cuts # creates a directory for the cut images
    echo " Cutting … $sw"
    magick filename.png +profile "icc" -gravity SouthWest -crop "%[fx:(w/20)+0]"x"%[fx:h]"+"%[fx:(w/2.1)*$sw]"+0 +repage cuts/$ctt.png
    # ImageMagick 7
    # cuts the image. the width of the snippets is set as a fraction of the width of the input image.
    # the position on the x-axis defines where the cut is made. it is calculated with the values of the variable ‘sw’
  done

  while :
  do
    echo ' Assembling ! '
    montage cuts/*.png -tile 60x -background white -geometry +0+0 -units PixelsPerInch -density 300 newfile.png
    # composes a new image. with -tile the number of snippets in a row is defined.
    # it should be a (integer) divisor of ct+1 to avoid gaps at the bottom of the new image
    break
  done