Unityでフィルター処理してみた ref: http://qiita.com/Es_Program/items/3198f0a66eb2434c4e43

file0.txt

X = \sum_{i=1}^{9} S_iM_i

MaskPattern.cs

using UnityEngine;
using System.Collections;
using System;

public class MaskPattern : MonoBehaviour {
    [Tooltip("マスクパターンを実装するシェーダを持つマテリアル")]
    public Material mat;
    [Tooltip("マスク。3x3の部分しか使用しない。")]
    public Matrix4x4 matrix;
    [Tooltip("基本的にはマスク数の9、適用しないマスク値0の分の明度が必要な場合等で変更。")]
    public float div = 9;

    private void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        mat.SetFloat("_TexWidth", source.width);
        mat.SetFloat("_TexHeight", source.height);
        mat.SetMatrix("_Matrix", matrix);
        mat.SetFloat("_Div", div);
        Graphics.Blit(source, destination, mat);
    }
}

MaskPattern.shader

Shader "Hidden/MaskPattern"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }

    SubShader
    {
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);
                o.uv = v.uv;
                return o;
            }

            sampler2D _MainTex;
            uniform float _TexWidth;
            uniform float _TexHeight;
            uniform matrix _Matrix;
            uniform float _Div;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 ret_col;
                int u, v;
                for (u = -1; u < 2; ++u)
                    for (v = -1; v < 2; ++v)
                    {
                        float x = i.uv.x + u / _TexWidth;
                        float y = i.uv.y + v / _TexHeight;
                        ret_col += tex2D(_MainTex, float2(x, y))*_Matrix[u + 1][v + 1];
                    }
                return ret_col / _Div;
            }
            ENDCG
        }
    }
}