#!/bin/bash
#./concave.sh $input.jpg ##output to $outfile (a2.jpg)
#fpath=$(basename "${1}");outfile="${fpath%.*}"-c.png; bc=none 
outfile="a2.jpg" #a2.png
bc=white #none
distort=0.25 #.2
trimpad="-fuzz 0.1 -trim +repage"
distort=`convert xc: -format "%[fx:-$distort]" info:`

a=`convert xc: -format "%[fx:1+$distort]" info:`
b=`convert xc: -format "%[fx:-$distort]" info:`
input="$1"
tmpA0="./texteffect_00_$$.mpc"

convert -quality 95 $input $tmpA0
width=`identify -format %w $tmpA0`
height=`identify -format %h $tmpA0`
w2=`convert xc: -format "%[fx:$width/2]" info:`
h2=`convert xc: -format "%[fx:$height/2]" info:`

xc=$w2
yc=$h2

vp="-virtual-pixel background"
convert $tmpA0 $vp -fuzz 0.3% -trim +repage $tmpA0
ww=`convert $tmpA0 -format "%w" info:`
hh=`convert $tmpA0 -format "%h" info:`
halfw=`convert xc: -format "%[fx:$ww/2]" info:`

b=`convert xc: -format "%[fx:$b*(2*min($ww,$hh)/(1.3*($ww+$hh)))^2]" info:`
fac=1.5 #1.25

newhh=`convert xc: -format "%[fx:$hh*$fac]" info:`
convert $tmpA0 $vp -resize x${newhh}! -background $bc -filter lanczos \
-gravity north -extent ${ww}x${newhh} \
-distort barrelinverse "0 0 0 1   0 $b 0 $a   $halfw 0" \
$trimpad $tmpA0

convert $tmpA0 "$outfile"
rm $tmpA0 *.cache

exit