Using Ruler on the Face ? How ?

[augustya]

If I have a Photo of a subject and i want a draw a line circular on the forehead but which is like 6 cms from the middle point between the eyebrows going up towards the hairline, how can I measure the distance (From the middle Point of the eyebrow and going upwards towards hairline) Can I place a ruler on the face ? Also how can I draw a line starting from the left temple point connecting to the right temple point on the face?

[thomaso]

You could use the ruler and drag its origin to the wanted position between the eyebrows, then the ruler shows the 6 cm distance to the left/right + top/bottom of this centre.

Adding guides (dragged from the ruler) may also indicate the desired distance.

Alternatively a 'helper object' may work, for example in this screenshot the selected Ellipse shape with diameter 12 cm = radius 6 cm:

If you want to use the Pixel Selection Tool / create a pixel selection with the wanted radius you can create a circular selection from a certain center by pressing the command and the shift key when drawing the selection.

Additionally, Affinity V2 has a Measuring Tool:

https://affinity.help/photo2/English.lproj/pages/DesignAids/measuring.html