Straighten & Perspective Correction
Level tilted horizons and correct converging verticals in buildings, with automatic crop to the largest valid rectangle.
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Rotation, flipping and perspective are composed into a single homogeneous matrix and applied in one resampling pass. Doing them as separate steps would mean resampling three times, and the interpolation softening compounds each time.
After straightening, the corners of the frame necessarily fall outside the original image. The result is automatically cropped to the largest rectangle that keeps the original aspect ratio and still fits entirely inside the rotated frame — the same behaviour Lightroom applies, and the reason you do not end up with white wedges in the corners.