Moire Twist Ruler

Drop images here (PNG, JPEG, WebP)
or use Open images. Add a scales.csv (filename,nm_per_px) to set every scale at once.

1. Measured: domain length L

mean of the lines you draw

2. Calculated: twist angle θ

θ = 2 asin(a / 2L)

lines- selected-

Measure by

Pattern in this image

Colour map

Periods along the selected line

Don't use this one

Pixel size (nm per pixel)

Lattice constant a

Zoom

Each line you draw measures a moire domain length L; the twist angle is calculated from L. Drag from one domain node (AA site or wall crossing) to another a few domains away along a row. Set periods to the number of domains the line spans: a circle marks each period, so they should sit on the nodes. Drag again anywhere to add another line: every line is its own domain-length measurement (new lines start at 1 period, so one line across one domain is one length), and the image shows their mean, spread and count. Click a line to select it, drag its ends to adjust; Shift-drag always starts a new line, even on top of another. Arrow keys change image, + and - change periods, Delete removes the selected line.