Auto Tone

Fix flat or under/over-exposed images without manual curves work. Three modes:

• level (default) — -auto-level on the luminance channel. Stretches the histogram to [0,1] without touching colour balance. Safe, reversible-feeling.
• gamma — -auto-gamma. Drives the image's mean brightness toward 50% grey. Lifts dark scans, tames blown-out daylight.
• punch — -normalize (1% black + 1% white clip) followed by -auto-gamma. Stronger; the "press the button" preset for batch gallery prep.

When to use

• Underexposed indoor / night phone shots.
• Faded scans of old prints.
• Bulk normalisation of a gallery shot under varying light.
• Pre-step before sharpening or upscaling — auto-tone first so the next stage isn't operating on a flat histogram.

Do not use this skill when:

• Source is a RAW file — fix tone in darktable-cli where you have full bit depth.
• Image is intentionally low-key (silhouettes, night scenes with crushed shadows) or high-key (snow, fashion editorials). Auto-gamma flattens the look.
• The histogram is already well-distributed (a quick magick identify -format "%[fx:standard_deviation]" "$IN" ≥ 0.22 → likely already toned; auto-level becomes a no-op or worse).