To capture touches on an image
We use a clinically validated pain scale which is a ten centimetre line on a piece of paper.
We ask patients to touch the place that most represents the level of pain
The distance from the origin to the place touched is the pain score for that individual.
The line must be exactly 10cm long so system needs to be able to
(a) show an image with pre-specified real world geometry (i.e. show this image at 12x12 cm)
(b) capture the pixels/cm/coordinates from bottom left corner for either one or multiple touches of the image
We show a child a picture of a human body and ask them to touch all the places it hurts
We record the coordinates of each touch
10x10 image - 100 pixels * 100 pixels
Child touches point 1 cm across and 1cm up
data looks like this