Given a background photo, you can draw lines on top of it whose relative lengths are shown. Double-clicking on a line allows you to set a 'reference size', all the other numbers are adjusted accordingly.
Use this for instance by taking a picture of something with a ruler in the same focus; use the ruler to set a reference size and now you have correct measurements for the other parts in the picture.
In this example, we mark a known distance (40mm) so that we can get the value
for the distance to be measured (12.70mm).
Basic UI:
- Open augenmass.html in your browser.
- Choose background image file. (Nothing is uploaded anywhere, this is just used locally by your browser).
- Draw lines. First click first point, second click second point. ESC key if you want to cancel the current line.
- Double-click on a number to enter some value. The other lines are automatically re-calculated according to that factor.
(Note, I don't really know JavaScript; if you see things to improve, just send me a pull request).