###Tips:

set up your camera
1. Create a camera in your scene
2. Render Mode of Canvas - Screen Space Camera, choose the camera you just created
the input of saveImage() is the Gameobject that you want to make screenshot of (e.g. a panel)


	public Camera camera;
	RenderTexture renderTexture;

	public void saveImage (GameObject go) {
		float width = Screen.width + go.GetComponent().offsetMax.x - go.GetComponent().offsetMin.x;
		float height = Screen.height - go.GetComponent ().offsetMin.y + go.GetComponent ().offsetMax.y;
	
		renderTexture = new RenderTexture (Screen.width, Screen.height, 0);
		camera.targetTexture = renderTexture;
		camera.Render ();

		RenderTexture.active = renderTexture;
		Texture2D virtualPhoto =
			new Texture2D((int)width, (int)height, TextureFormat.RGB24, false);
		// false, meaning no need for mipmaps
		virtualPhoto.ReadPixels( new Rect(go.GetComponent().offsetMin.x, 
			go.GetComponent().offsetMin.y, 
			width, height), 0, 0);

		RenderTexture.active = null; //can help avoid errors 
		camera.targetTexture = null;
		// consider ... Destroy(tempRT);

		byte[] bytes;
		bytes = virtualPhoto.EncodeToPNG();
		//saveToCloud or
		//File.WriteAllBytes(Application.dataPath + "/img/SavedScreen.png", bytes);