How do I change sprite size with multitouch ?

My game for a multitouch board has different elements on the screen acting like documents on a desk. I'm looking for a way to scale the object by pinching them with two fingers.

I've the intuition I have 1) to record two touch points when object is touched, 2) record their distance when both touches occur and 3)monitor their distance change when they are in touch and send this relative change to the object.

OK but how do I program this ?

I have this old demo:

howtoconstructdemos.com/zoom-a-sprite-or-entire-screen-with-pinch-touch-gesture

I believe I've also seen an official example for zooming with pinch.

I have this old demo:

https://howtoconstructdemos.com/zoom-a-sprite-or-entire-screen-with-pinch-touch-gesture/

I believe I've also seen an official example for zooming with pinch.

Thank you ! that's interesting indeed !! I see your example relies a lot on UID but I need to be able to apply this to the elements of a family and families don't have UID. Is there a workaround ?

OK, I managed to have it work with elements and adapt it to my project. Thats wonderful ! Thank you very much.

Here is the file if it can be useful to anyone.

dropbox.com/s/tsu1unckxdinog2/Zoom%20an%20element.c3p

I added a drag function to the Family but there seem to have conflict between drag touch and touch used for rescale. Any idea on how to fix this ?

You can check touch count, and if more than one finger is touching the screen, then disable drag&drop.

Quite right.

This works :)

Now, when scaling one family element, disable touch to other elements