ColorByScroll.cs --- Coloring NGUI Sprite by ScrollView percent, using gradient. ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// ExtentionsUIScrollView.cs --- NGUI - UIScrollView extention. It helps getting horizontal, vertical percent from UIScrollView. Ju…

ColorByScroll.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ColorByScroll : MonoBehaviour
{
    public UIScrollView scrollView;
    public Gradient gradient;

    private UI2DSprite ui2DSprite;
    private UISprite uiSprite;

	public Axis axis = Axis.HORIZONTAL;
	public enum Axis { HORIZONTAL, VERTICAL }

    void Start()
    {
        ui2DSprite = GetComponent<UI2DSprite>();
        uiSprite = GetComponent<UISprite>();

        scrollView.panel.onClipMove += UpdateColor;
    }

    private void UpdateColor(UIPanel panel)
    {
        float percent = axis == Axis.HORIZONTAL ? 
			scrollView.PercentHorizontal() : 
			scrollView.PercentVertical();

        var color = gradient.Evaluate(percent);
		
        if (ui2DSprite != null) ui2DSprite.color = color;
        if (uiSprite != null) uiSprite.color = color;
    }
}

ExtentionsUIScrollView.cs

using UnityEngine;

public static class ExtentionsUIScrollView
{
    public static float PercentHorizontal(this UIScrollView scrollView)
    {
        Bounds b = scrollView.bounds;
        Vector2 bmin = b.min;
        Vector2 bmax = b.max;

        Vector4 clip = scrollView.panel.finalClipRegion;
        int intViewSize = Mathf.RoundToInt(clip.z);
        if ((intViewSize & 1) != 0) intViewSize -= 1;
        float halfViewSize = intViewSize * 0.5f;
        halfViewSize = Mathf.Round(halfViewSize);

        if (scrollView.panel.clipping == UIDrawCall.Clipping.SoftClip)
            halfViewSize -= scrollView.panel.clipSoftness.x;

        float contentSize = bmax.x - bmin.x;
        float viewSize = halfViewSize * 2f;
        float contentMin = bmin.x;
        float viewMin = clip.x - halfViewSize;

        contentMin = viewMin - contentMin;

        float max = contentSize - viewSize;
        return Mathf.Max(0, Mathf.Min(1f, contentMin / max));
    }

    public static float PercentVertical(this UIScrollView scrollView)
    {
        Bounds b = scrollView.bounds;
        Vector2 bmin = b.min;
        Vector2 bmax = b.max;

        Vector4 clip = scrollView.panel.finalClipRegion;
        int intViewSize = Mathf.RoundToInt(clip.w);
        if ((intViewSize & 1) != 0) intViewSize -= 1;
        float halfViewSize = intViewSize * 0.5f;
        halfViewSize = Mathf.Round(halfViewSize);

        if (scrollView.panel.clipping == UIDrawCall.Clipping.SoftClip)
            halfViewSize -= scrollView.panel.clipSoftness.y;

        float contentSize = bmax.y - bmin.y;
        float viewSize = halfViewSize * 2f;
        float contentMin = bmin.y;
        float viewMin = clip.y - halfViewSize;

        contentMin = viewMin - contentMin;

        float max = contentSize - viewSize;
        return Mathf.Max(0, Mathf.Min(1f, contentMin / max));
    }
}