Bash Script to convert irregulary sized SVGs (different aspect ratio and sizes each) into 1:1 aspect ratio while also centering its contents

conv-svg.sh

#!/bin/bash

INPUT="$1"
SIZE=$2
OUTPUT="$3"

INKSCAPE="${INKSCAPE:-/Applications/Inkscape.app/Contents/MacOS/inkscape}"

if [ -z "$INPUT" ] || [ -z "$SIZE" ] || [ -z "$OUTPUT" ]; then
    echo "Usage: $0 [input] [size] [output]"
    exit 1
fi

# Get dimensions of the entire svg document, ignore children as we'll resize everything at once later
bounding_boxes=`$INKSCAPE $1 -S | head -n1`
# element_name,x,y,width,height
original_width=$(echo $bounding_boxes | cut -d ',' -f4)
original_height=$(echo $bounding_boxes | cut -d ',' -f5)

WIDTH_MULTIPLICATOR=$(echo "scale=3; $original_width / $SIZE" | bc)
HEIGHT_MULTIPLICATOR=$(echo "scale=3; $original_height / $SIZE" | bc)

OFFSET_X=0
OFFSET_Y=0
if (( $(echo "scale=3; $original_height > $original_width" |bc -l) )); then
    OFFSET_X=$(echo "scale=3; ($SIZE - ($original_width / $HEIGHT_MULTIPLICATOR)) / 2" | bc)
else
    OFFSET_Y=$(echo "scale=3; ($SIZE - ($original_height / $WIDTH_MULTIPLICATOR)) / 2" | bc)
fi

# Handle edge cases where a negative offset may occur, rsvg-convert can't handle negative values and will print
# "Found argument '-.' which wasn't expected, or isn't valid in this context"
if [[ "$OFFSET_X" == -* ]]; then
    OFFSET_X=0
fi

if [[ "$OFFSET_Y" == -* ]]; then
    OFFSET_Y=0
fi

rsvg-convert -a -f svg --page-height "$SIZE" --page-width "$SIZE" -w "$SIZE" -h "$SIZE" --left "$OFFSET_X" --top "$OFFSET_Y" "$INPUT" > "$OUTPUT"

To batch-process files in the current directory, and output them to ../fixed (must exist!)

for file in *.svg; do; ../conv-svg.sh "$file" 40 "../fixed/$file"; done