com.unity.uiextensions/Scripts/Effects/UIFlippable.cs

/// Credit ChoMPHi
/// Sourced from - http://forum.unity3d.com/threads/script-flippable-for-ui-graphics.291711/

using System.Collections.Generic;

namespace UnityEngine.UI.Extensions
{
    [RequireComponent(typeof(RectTransform), typeof(Graphic)), DisallowMultipleComponent]
    [AddComponentMenu("UI/Effects/Extensions/Flippable")]
    public class UIFlippable : MonoBehaviour, IVertexModifier
    {     
        [SerializeField] private bool m_Horizontal = false;
        [SerializeField] private bool m_Veritical = false;
     
        /// <summary>
        /// Gets or sets a value indicating whether this <see cref="UnityEngine.UI.UIFlippable"/> should be flipped horizontally.
        /// </summary>
        /// <value><c>true</c> if horizontal; otherwise, <c>false</c>.</value>
        public bool horizontal
        {
            get { return this.m_Horizontal; }
            set { this.m_Horizontal = value; }
        }
     
        /// <summary>
        /// Gets or sets a value indicating whether this <see cref="UnityEngine.UI.UIFlippable"/> should be flipped vertically.
        /// </summary>
        /// <value><c>true</c> if vertical; otherwise, <c>false</c>.</value>
        public bool vertical
        {
            get { return this.m_Veritical; }
            set { this.m_Veritical = value; }
        }
     
        protected void OnValidate()
        {
            this.GetComponent<Graphic>().SetVerticesDirty();
        }
     
        public void ModifyVertices(List<UIVertex> verts)
        {
            RectTransform rt = this.transform as RectTransform;
         
            for (int i = 0; i < verts.Count; ++i)
            {
                UIVertex v = verts[i];
             
                // Modify positions
                v.position = new Vector3(
                    (this.m_Horizontal ? (v.position.x + (rt.rect.center.x - v.position.x) * 2) : v.position.x),
                    (this.m_Veritical ?  (v.position.y + (rt.rect.center.y - v.position.y) * 2) : v.position.y),
                    v.position.z
                );
             
                // Apply
                verts[i] = v;
            }
        }
    }
}