file-compression（文件压缩）

File Compression

Compress files with Python-first workflows and Node.js fallback workflows.

Supported File Types

• PDF: .pdf
• Image: .jpg, .jpeg, .png, .webp

What This Skill Can Do

• Compress PDF with preset quality levels.
• Compress image with quality/resize/format controls.
• Switch backend automatically when dependencies are missing.
• Detect bad compression results and retry with better strategy.

Installation Spec (Before Running)

Required binaries:

• python3 (recommended >= 3.8)
• node
• gs (Ghostscript, required for PDF Ghostscript paths)

Python install spec:

python3 -m pip install -r {baseDir}/requirements.txt

Node install spec:

cd {baseDir}
npm install

Ghostscript install examples:

• macOS: brew install ghostscript
• Ubuntu/Debian: sudo apt-get update && sudo apt-get install -y ghostscript

Safety note:

• Explain to the user before each install command that third-party packages are being installed.
• If installation fails, report the failing command and switch to available fallback backend.

CLI Options Cheat Sheet

PDF (scripts/compress_pdf.py):

• --preset screen|ebook|printer|prepress
• --strategy auto|ghostscript|pikepdf
• --remove-metadata
• --no-linearize
• --overwrite

PDF Node (scripts/compress_pdf_node.mjs):

• --preset screen|ebook|printer|prepress

Image (scripts/compress_image.py):

• --quality <1-100>
• --format keep|jpeg|png|webp
• --max-width <n>
• --max-height <n>
• --strategy auto|pillow|node
• --overwrite

Image Node (scripts/compress_image_node.mjs):

• --quality <1-100>
• --format keep|jpeg|png|webp
• --max-width <n>
• --max-height <n>

Example Set (Python + Node)

PDF default:

python {baseDir}/scripts/compress_pdf.py in.pdf out.pdf

PDF aggressive:

python {baseDir}/scripts/compress_pdf.py in.pdf out.pdf --preset screen --strategy ghostscript

PDF with pikepdf:

python {baseDir}/scripts/compress_pdf.py in.pdf out.pdf --strategy pikepdf --remove-metadata

PDF via Node:

node {baseDir}/scripts/compress_pdf_node.mjs in.pdf out.pdf --preset ebook

Image default:

python {baseDir}/scripts/compress_image.py in.jpg out.jpg --quality 75

Image convert + resize:

python {baseDir}/scripts/compress_image.py in.png out.webp --format webp --quality 72 --max-width 1920

Image force Node backend:

python {baseDir}/scripts/compress_image.py in.jpg out.jpg --strategy node --quality 70

Image direct Node:

node {baseDir}/scripts/compress_image_node.mjs in.jpg out.jpg --quality 70 --max-width 1600

Environment and Fallback

Check and install in this order:

1. Python: python3 --version (fallback: python --version)
2. Node: node --version
3. Ghostscript: gs --version (required for PDF Ghostscript paths)
4. Python deps when needed:

- pip install pikepdf - pip install pillow

1. Node deps when needed:

- npm install

Fallback policy:

• PDF: ghostscript -> pikepdf -> node-ghostscript
• Image: pillow -> node-sharp

If python3.8+ is unavailable, try python3.11/3.10/3.9/3.8; if still blocked, use Node flow when possible.

Execution Transparency

Always communicate each step:

1. Tell user what you are checking or running.
2. Show the exact command before execution.
3. For slow steps (pip install, npm install, large Ghostscript jobs), say you are waiting.
4. After each step, report result and next action.

Bad Result Recovery

When output_size >= input_size, do not stop:

1. Report exact from/to numbers and compression ratio.
2. Explain likely cause:

- PDF: already optimized, scanned-image content, metadata overhead, unsuitable preset. - Image: unsuitable format conversion, quality too high, small-file overhead.

1. Retry with alternate strategy:

- PDF: ebook -> screen, then switch backend. - Image: lower quality, switch backend, convert to webp, optionally resize.

1. Return the best attempt and state which command produced it.

Agent Response Contract

After every compression task, always return:

1. Output absolute path.
2. from <before_size> to <after_size>.
3. saved <delta_size> (<ratio>%).
4. Backend used.