DropMe

using System.Reflection;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;

public class DropMe : MonoBehaviour, IDropHandler, IPointerEnterHandler, IPointerExitHandler
{
public Image containerImage;
public Image receivingImage;
private Color normalColor;
public Color highlightColor = Color.yellow;

public void OnEnable ()
{
if (containerImage != null)
normalColor = containerImage.color;
}

public void OnDrop(PointerEventData data)
{
containerImage.color = normalColor;

if (receivingImage == null)
return;

Sprite dropSprite = GetDropSprite (data);
if (dropSprite != null)
receivingImage.overrideSprite = dropSprite;
}

public void OnPointerEnter(PointerEventData data)
{
if (containerImage == null)
return;

Sprite dropSprite = GetDropSprite (data);
if (dropSprite != null)
containerImage.color = highlightColor;
}

public void OnPointerExit(PointerEventData data)
{
if (containerImage == null)
return;

containerImage.color = normalColor;
}

private Sprite GetDropSprite(PointerEventData data)
{
var originalObj = data.pointerDrag;
if (originalObj == null)
return null;

var dragMe = originalObj.GetComponent<DragMe>();
if (dragMe == null)
return null;

var srcImage = originalObj.GetComponent<Image>();
if (srcImage == null)
return null;

return srcImage.sprite;
}
}