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Assets/Standard Assets/Utility/AlphaButtonClickMask.cs

@@ -0,0 +1,58 @@
+using UnityEngine;
+using UnityEngine.UI;
+using System.Collections;
+
+public class AlphaButtonClickMask : MonoBehaviour, ICanvasRaycastFilter 
+{
+    protected Image _image;
+
+    public void Start()
+    {
+        _image = GetComponent<Image>();
+
+        Texture2D tex = _image.sprite.texture as Texture2D;
+
+        bool isInvalid = false;
+        if (tex != null)
+        {
+            try
+            {
+                tex.GetPixels32();
+            }
+            catch (UnityException e)
+            {
+                Debug.LogError(e.Message);
+                isInvalid = true;
+            }
+        }
+        else
+        {
+            isInvalid = true;
+        }
+
+        if (isInvalid)
+        {
+            Debug.LogError("This script need an Image with a readbale Texture2D to work.");
+        }
+    }
+
+    public bool IsRaycastLocationValid(Vector2 sp, Camera eventCamera)
+    {
+        Vector2 localPoint;
+        RectTransformUtility.ScreenPointToLocalPointInRectangle(_image.rectTransform, sp, eventCamera, out localPoint);
+
+		Vector2 pivot = _image.rectTransform.pivot;
+		Vector2 normalizedLocal = new Vector2(pivot.x + localPoint.x / _image.rectTransform.rect.width, pivot.y + localPoint.y / _image.rectTransform.rect.height);
+        Vector2 uv = new Vector2(
+            _image.sprite.rect.x + normalizedLocal.x * _image.sprite.rect.width, 
+            _image.sprite.rect.y + normalizedLocal.y * _image.sprite.rect.height );
+
+        uv.x /= _image.sprite.texture.width;
+        uv.y /= _image.sprite.texture.height;
+
+        //uv are inversed, as 0,0 or the rect transform seem to be upper right, then going negativ toward lower left...
+        Color c = _image.sprite.texture.GetPixelBilinear(uv.x, uv.y);
+
+        return c.a> 0.1f;
+    }
+}