Preprocessing can change measurements
Cropping limits the region of interest; resizing changes coordinate scale. Smoothing can reduce noise while altering the appearance of a fine defect. Associate originals with processing steps and version their settings. Preprocessing used with a model should remain consistent between training and application.
From pixels to physical measurement
A width in pixels is not automatically a width in millimetres. Assess image geometry, reference scale and lens effects. Parts at different heights may not share the same scale. For measurement tasks, calibrate and recheck against known references; report uncertainty and permitted deviation explicitly.
Validating an analysis result
Area, perimeter and position depend on the selected region and boundary definition. Repeat measurements on representative samples and compare against an independent method. Show the inspected region alongside the number in the user interface. This lets an operator recognise an incorrect selection or degraded image.