Convert SVGs into PNGs using Inkscape

export_svgs.sh

#!/usr/bin/env bash
#
# Convert SVGs into PNGs using Inkscape.
#
# PNGs are saved to the same location as their corresponding SVG files.
# If sizes are specified, they are appended to the names of the PNGs.
#
# The env var INKSCAPE_BIN can be set to configure the path to Inkscape.
#
# Usage: ./export_svgs.sh <input_path> [size [size]...]
#
# input_path can be a file or a directory.
#
# If a size isn't specified, Inkscape will just do its default behaviour:
# ./export_svgs.sh image.svg
#
# A size can be specified as a single integer, which will be used for width
# and height:
# ./export_svgs.sh image.svg 900
#
# A size can also be specified as two integers joined by an 'x' character.
# The left integer is the width and the right is the height:
# ./export_svgs.sh image.svg 300x500
#
# Multiple sizes can be specified:
# ./export_svgs.sh image.svg 300x500 900 600x400 875

set -euo pipefail
shopt -s inherit_errexit

export_svg() {
    local input_file="${1:?"export_svg: argument 1 'input_file' is unset"}"
    local size="${2}"
    local svg_name="${input_file%.*}"
    local args=()
    local size_suffix=""
    local size_message="default size"

    # Parse the size.
    if [[ "${size}" ]]; then
        # Split the size by an "x" character
        readarray -tdx dimensions < <(printf '%s' "${size}")

        # Check if there was a split.
        if [[ "${#dimensions[@]}" = 1 ]]; then
            # There's no split; use same value for width and height.
            size_message="${size}x${size}"
            size_suffix="_${size}"
            args=(-w "${size}" -h "${size}")
        else
            # There is a split; left value is width and right is height.
            size_message="${size}"
            size_suffix="_${dimensions[0]}_${dimensions[1]}"
            args=(-w "${dimensions[0]}" -h "${dimensions[1]}")
        fi
    fi

    args+=(-o "${svg_name}${size_suffix}.png" "${input_file}")

    printf '%s\n' "Exporting ${svg_name} at ${size_message}..."

    if ! "${INKSCAPE_BIN:-"inkscape"}" "${args[@]}"; then
        printf '%s\n' "Failed to export ${svg_name} at ${size_message}" >&2
        return 1
    fi
}

export_svgs() {
    local input_files
    local sizes=("${@:2}")
    local argstr=""
    local arg_n=2

    # Check if argument 1 is a file or directory.
    if [[ -d "$1" ]]; then
        # Its a directory; get all SVG files in it.
        input_files=("$1"/*.svg)
    elif [[ -f "$1" ]]; then
        input_files=("$1")
    else
        echo "Argument 1 is not an existing file or directory." >&2
        return 1
    fi

    # Create a single string of arguments for all calls.
    # xargs will split this string into arguments for each call.
    for i in "${!input_files[@]}"; do
        # Check if any sizes were specified.
        if (( "${#sizes[@]}" )); then
            # Add args for each size.
            for size_i in "${!sizes[@]}"; do
                argstr="${argstr} ${input_files[$i]} ${sizes[$size_i]}"
            done
        else
            # No sizes were specified.
            argstr="${argstr} ${input_files[$i]}"
            arg_n=1
        fi
    done

    # Export all SVGs in all sizes in parallel, up to 8 simultaneous calls.
    export -f export_svg
    export INKSCAPE_BIN
    printf "%s" "${argstr}" | xargs -n "${arg_n}" -P 8 bash -c 'export_svg "${@}"' _
}

export_svgs "$@"