Scale Bar

Two independent calibrated scale bars rendered over the image. Bar length is auto-rounded to a nice number (1, 2, 5, 10, …) for the current image width, and units auto-promote (1000 nm → 1 µm, 1000 µm → 1 mm, …).

Usage

Enable the scale-bar checkbox. Click Settings to set per-bar pixel size, unit (nm, µm, mm, m, Å, px), corner position, color, width (fraction of image), and vertical offset (for stacking). Bar 2 defaults to yellow, 40 px above bar 1.

Adding a new unit or rounding rule

Unit promotion and the 1/2/5 rounding ladder live in _get_nice_scale() and _format_label() in src/pystream/plugins/scalebar.py. To add a new base unit (e.g. pm), add it to the unit combobox and extend the conversion ladder in _format_label().