Thumbnail generation for website gallery

mkthumbs.sh

#!/bin/bash
# mkthumbs.sh – generates thumbnails and large versions only when needed
# Usage: ./mkthumbs.sh [subdirectory]

set -euo pipefail

SUBDIR="${1:-}"  # optional first argument
SRC_DIR="content/gallery/${SUBDIR}"
DST_THUMB="static/gallery/thumbs/${SUBDIR}"
DST_FULL="static/gallery/full/${SUBDIR}"

mkdir -p "$DST_THUMB" "$DST_FULL"

find "$SRC_DIR" -type f \( -iname "*.jpg" -o -iname "*.jpeg" -o -iname "*.png" \) | while read -r img; do
  name=$(basename "$img")
  name_noext="${name%.*}"
  out_thumb="$DST_THUMB/${name_noext}.jpg"
  out_full="$DST_FULL/${name_noext}.jpg"

  regenerate_thumb=false
  regenerate_full=false

  # Check if thumbnail needs to be (re)generated
  if [[ ! -f "$out_thumb" || "$img" -nt "$out_thumb" ]]; then
    regenerate_thumb=true
  fi

  # Check if large version needs to be (re)generated
  if [[ ! -f "$out_full" || "$img" -nt "$out_full" ]]; then
    regenerate_full=true
  fi

  # Generate thumbnail if needed
  if $regenerate_thumb; then
    echo "→ Thumb: $SUBDIR/$name"
    magick "$img" -auto-orient -thumbnail 300x300^ -gravity center -extent 300x300 -quality 80 "$out_thumb"
  fi

  # Generate large version if needed
  if $regenerate_full; then
    echo "→ Full:  $SUBDIR/$name"
    magick "$img" -auto-orient -resize 1600x1600\> -quality 50 "$out_full"
  fi

done