TouchButtonBehaviour

using UnityEngine;
using UnityEngine.UI;
using System.Collections;

[RequireComponent (typeof (Image))]

public class TouchButtonBehaviour : MonoBehaviour {

    [HideInInspector]
    public bool output;                             //Boolean output

    public bool normalize = false;                  //ButtonUp () if input position is outside graphics

    private RectTransform button;                   //Button transform
    private int latchedFinger = -1;                 //Latched finger to avoid other fingers to steal button

    private float distanceX = 0;
    private float distanceY = 0;

    private float canvasScale;

    void Start () {
        // Cache this component at startup instead of looking up every frame
        button = GetComponent <RectTransform> ();

        //Get canvas scale
        canvasScale = GetComponentInParent <Canvas> ().scaleFactor;
    }

    void ButtonDown () {
        output = true;
    }

    void ButtonUp () {
        output = false;
        latchedFinger = -1;
    }

    void Update () {
        //Graphics size /2 to calculate distance between input position and graphics position
        float sizeX = button.sizeDelta.x/2 * canvasScale;
        float sizeY = button.sizeDelta.y/2 * canvasScale;

        #if UNITY_EDITOR

        //Distance between button graphics and mouse position
        distanceX = button.position.x - Input.mousePosition.x;
        distanceY = button.position.y - Input.mousePosition.y;

        //Calculate if mouse position is inside button graphics
        bool containsMousePosition = distanceX >= -sizeX &&
                                     distanceX <=  sizeX &&
                                     distanceY >= -sizeY &&
                                     distanceY <=  sizeY ;

        //Allow click if it's inside button graphics
        if (Input.GetMouseButtonDown (0) && containsMousePosition)
            ButtonDown ();

        if (!containsMousePosition && output == true && normalize)
            ButtonUp ();

        // Reset button if click ended
        if (Input.GetMouseButtonUp (0))
            ButtonUp ();

        #else

        foreach (Touch touch in Input.touches){
            //Distance between button graphics snd touch position
            distanceX = button.position.x - touch.position.x;
            distanceY = button.position.y - touch.position.y;

            //Calculate if touch position is inside button graphics
            bool containsTouchPosition = distanceX >= -sizeX &&
                                         distanceX <=  sizeX &&
                                         distanceY >= -sizeY &&
                                         distanceY <=  sizeY ;

            //Allow click if it's inside button graphics & get latched finger id
            if (containsTouchPosition && touch.phase == TouchPhase.Began){
                latchedFinger = touch.fingerId;
                ButtonDown ();
            }
            if (!containsTouchPosition && output == true && normalize && touch.fingerId == latchedFinger)
                ButtonUp ();

            // Reset button if touch ended
            if (touch.fingerId == latchedFinger && (touch.phase == TouchPhase.Ended || touch.phase == TouchPhase.Canceled))
                ButtonUp ();
        }

        #endif
    }
}