echo >&2 Adds specified amount of border to PPM image.

#! /bin/sh

if [ -z "$1" ] || [ -n "$2" ]; then
echo >&2 Usage: ${0##*/} $percent border to add$
echo >&2 Adds specified amount of border to PPM image.
echo >&2 Adds additional border if necessary to get 3:2 or 2:3 aspect ratio.
exit 0
fi
BorderPercent=$1
cat > AddBorder-Temp.ppm
Dims=$(pnmfile AddBorder-Temp.ppm)
Dims=${Dims##*, }
Dims=${Dims%% max*}
InputWidth=${Dims% by*}
InputHeight=${Dims#*by }
if [ $(expr 2 \* $InputHeight) -gt $(expr 3 \* $InputWidth) ]; then
OutputWidth=$(expr $ \( $InputHeight \* \( 100 + $BorderPercent $ + 50 \) / 100 + 2 \) / 3 \* 2)
OutputHeight=$(expr $ \( $InputHeight \* \( 100 + $BorderPercent $ + 50 \) / 100 + 2 \) / 3 \* 3)
elif [ $InputHeight -gt $InputWidth ]; then
OutputWidth=$(expr $ \( $InputWidth \* \( 100 + $BorderPercent $ + 50 \) / 100 + 1 \) / 2 \* 2)
OutputHeight=$(expr $ \( $InputWidth \* \( 100 + $BorderPercent $ + 50 \) / 100 + 1 \) / 2 \* 3)
elif [ $(expr 2 \* $InputWidth) -gt $(expr 3 \* $InputHeight) ]; then
OutputWidth=$(expr $ \( $InputWidth \* \( 100 + $BorderPercent $ + 50 \) / 100 + 2 \) / 3 \* 3)
OutputHeight=$(expr $ \( $InputWidth \* \( 100 + $BorderPercent $ + 50 \) / 100 + 2 \) / 3 \* 2)
else
OutputWidth=$(expr $ \( $InputHeight \* \( 100 + $BorderPercent $ + 50 \) / 100 + 1 \) / 2 \* 3)
OutputHeight=$(expr $ \( $InputHeight \* \( 100 + $BorderPercent $ + 50 \) / 100 + 1 \) / 2 \* 2)
fi
echo >&2 ${0##*/}: Padding $InputWidth\*$InputHeight to $OutputWidth\*$OutputHeight
ppmmake rgb:C8/C8/C8 $OutputWidth $OutputHeight \
| pnmpaste AddBorder-Temp.ppm \
$(expr $ $OutputWidth - $InputWidth $ / 2) $(expr $ $OutputHeight - $InputHeight $ / 2)
rm AddBorder-Temp.ppm