Noise Filter

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////////////////////CPU SIDE////////////////////
////////////////////////////////////////////////
using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
public class Noise : MonoBehaviour
{

    public float intensity;
    private Material material;

    void Awake()
    {
        material = new Material(Shader.Find("My Shaders/Noise")); //Use the shader.
    }

    void OnRenderImage(RenderTexture source, RenderTexture destination) //Before the buffer is sent to the camera, modify it with above shader.
    {
        if (intensity == 0)
        {
            Graphics.Blit(source, destination); //Intensity is 0. Blit the image straight to the screen.
            return;
        }

        material.SetFloat("_Scale", intensity); //Uniform the value to the shader.
        Graphics.Blit(source, destination, material); //Blit the modified image to the screen.
    }
}

////////////////////////////////////////////////
////////////////////GPU SIDE////////////////////
////////////////////////////////////////////////
Shader "My Shaders/Noise"
{
    Properties
    {
        _MainTex ("Buffer", 2D) = "white" {}
        _Scale ("Intensity", Range (0, 1)) = 0
    }
    SubShader
    {
        Pass
        {
            CGPROGRAM
            #pragma vertex vert_img
            #pragma fragment frag

            #include "UnityCG.cginc"

            uniform sampler2D _MainTex;
            uniform float _Scale;

            float rand(float2 co) //The infamous "One-Liner"
            {
                const float2 random = float2(12.9898,78.233);
                const float multiplier = 43758.5453;

                return frac(sin(dot(co.xy, random)) * multiplier);
            }

            float4 frag(v2f_img input) : COLOR
            {
                float4 textureMap = tex2D(_MainTex, input.uv);

                float value = rand((input.uv * (unity_DeltaTime.x + input.uv))); //Use the current texCoord as the random input. Using deltaTime ensures a different result every frame.
                float3 randNoise = float3(value, value, value); //A float3 of the above result. All channels same colour to get a greyscale result (White noise)

                float4 result = textureMap;
                result.rgb = lerp(textureMap.rgb, randNoise, _Scale); //Mix the two results based on the weight provided by _Scale.
                return result;
            }
            ENDCG
        }
    }
}