Tone Curve Editor
Draw a tone curve with monotone cubic interpolation — no overshoot, no banding.
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Interpolation uses PCHIP (monotone cubic) rather than a natural cubic spline. An ordinary spline overshoots between control points, and on a tone curve that overshoot appears as tonal reversals and visible banding in smooth gradients. PCHIP guarantees monotonicity within each segment, which is precisely the property a tone curve needs.
Click empty space to add a point, drag to move, double-click to remove. The two endpoints can only move vertically so the curve always spans the full domain.