to-jxl

Convert Images to JPEG XL

Encode images to JPEG XL (.jxl) format using cjxl. Supports lossless, visually lossless, and web quality presets, with optional effort (compression) tuning.

When to use

• Converting photos to JXL for archival, where file size matters and quality must be preserved.
• Lossless-transcoding existing JPEG files to save ~20% file size without re-compression artifacts.
• Creating web-optimized JXL variants with controlled visual loss.

Inputs to gather

• Input file or directory — single image, folder, or recursive tree. If omitted, ask for the path.
• Quality preset — ask which tier: lossless (full fidelity, -d 0), visually-lossless (imperceptible loss, -d 1.0, default), or web (visible compression acceptable, -d 3.0). Default: visually-lossless.
• Effort level — optional, range 1–9 (1 = fastest, 9 = slowest/best compression). Default: 7. Only ask if the user is concerned about speed vs file size.

Procedure

1. Check tooling

command -v cjxl || echo "cjxl not installed — install with: sudo apt install libjxl-tools"

Abort if missing.

2. Map quality presets to distance

• lossless → -d 0
• visually-lossless → -d 1.0
• web → -d 3.0

Set effort=7 unless the user overrides.

3. Determine scope

• Single file: run one conversion.
• Directory (non-recursive): ask before processing, then loop over image files in the folder.
• Recursive: use find to locate all images in the tree.

Ask for confirmation before batch operations.

4. Convert

Single file:

cjxl -d <distance> -e <effort> input.jpg output.jxl

Batch (folder or recursive):

find <target> -maxdepth <1|999> -type f \
  \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' \
     -o -iname '*.gif' -o -iname '*.webp' -o -iname '*.tif' \) \
  -exec cjxl -d <distance> -e <effort> {} {.}.jxl \;

Show progress (file count, time remaining estimate if batch is large).

5. Report