Unity3D NGUI刮刮卡效果

using UnityEngine;

[RequireComponent(typeof(UITexture))]
public class ChangeTexturePixel : MonoBehaviour {
private UITexture mUITex;
private Texture2D MyTex;
public int Radius = 10;
public Color Col = new Color(0,0,0,0);
void Awake()
{
mUITex = GetComponent<UITexture>();
var tex = mUITex.mainTexture as Texture2D;
MyTex = new Texture2D(tex.width, tex.height, tex.format, false);
MyTex.SetPixels(tex.GetPixels());
MyTex.Apply();
mUITex.mainTexture = MyTex;
}

void ChangePixelColorByCircle(int x, int y, int radius, Color col)
{
for (int i = -Radius; i < Radius; i++)
{
var py = y + i;
if (py < 0 || py >= MyTex.height)
{
continue;
}

for (int j = -Radius; j < Radius; j++)
{
var px = x + j;
if (px < 0 || px >= MyTex.width)
{
continue;
}
if (new Vector2(px - x, py - y).magnitude > Radius)
{
continue;
}
MyTex.SetPixel(px, py, Col);
}
}
MyTex.Apply();
}

int[] WorldPos2Pix(Vector3 worldPos)
{
var temp = transform.InverseTransformPoint(worldPos);
var pos = new Vector2(temp.x+mUITex.width/2,temp.y+mUITex.height/2);
float rateX = mUITex.width / (float)MyTex.width;
float rateY = mUITex.height / (float)MyTex.height;

return new []
{
(int)(pos.x / rateX), (int)(pos.y/rateY)
};

}

void Update ()
{
if (Input.GetMouseButton(0))
{
Vector3 worldPos = UICamera.currentCamera.ScreenToWorldPoint(Input.mousePosition);
var posA = WorldPos2Pix(worldPos);
ChangePixelColorByCircle(posA[0], posA[1], Radius, Col);
}
}
}