Auto Deskew

Straighten a tilted image. Two backends, picked by content type:

• document (default) — magick -deskew 40%. Detects skew via the Radon-style projection profile that ImageMagick's deskew operator implements. Fast, robust on text/scans up to ±15°.
• photo — Python + OpenCV Hough-line transform. Detects the dominant horizontal/vertical line angle (horizons, building edges, table corners) and rotates by its negative. Use for photographs without a clean text baseline.

When to use

• Scanned documents that came in at an angle.
• Phone snapshots of pages, receipts, whiteboards.
• Slightly-tilted architectural / horizon photos (--mode photo).
• Pre-step before OCR — Tesseract accuracy degrades sharply past ±2° skew.

Do not use this skill when:

• The image is intentionally tilted (Dutch angle, artistic composition).
• Skew is severe (>15°) — usually means the document was captured upside down or sideways. Detect orientation first (exiftool -Orientation, or rotate by 90/180 multiples) before deskewing.
• The image has no straight reference lines (clouds, abstract textures) — Hough will return noise; rotation will be near-random.