Simple multi-touch gesture Algorithm

Simple multi-touch gesture Algorithm

1. Zoom action


1) detected dual-finger


Down event. The distance between the two fingers is

olddistant;

2) calculate the distance between two fingers in real time when the two fingers move

sampledistant;

3) Calculate the scaling ratio:

zoom
= sampledistant / olddistant;

4) Repeat

2，

Step 3

An up event occurs.


2. Rotate action


1) detect dual-finger

Down event, record the dual-finger coordinate at this time

X coordinate and

The Y coordinate difference and the distance between the two fingers are recorded

olddisx,olddisy,olddistant;

2) When the double finger is moved, the distance between the two points is recorded.

distant,disx,disy.

3) If

Olddistant and

The distant value is close,

Disx, DISY, and

The value of olddisx and olddisy varies greatly.

Rotate action,

Rotate angle

DISY/disx, and

The ratio of olddisy to olddisx is determined.


4) duplicate

2）

3) Two steps

The up event ends the calculation.