Check out example codes for "gaussian blur unity sprite 2D". It will help you in understanding the concepts better.

Code Example 1

Shader "Custom/GaussianBlur"
{ 
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        radius ("Radius", Range(0,30)) = 15
        resolution ("Resolution", float) = 800  
        hstep("HorizontalStep", Range(0,1)) = 0.5
        vstep("VerticalStep", Range(0,1)) = 0.5  
    }

    SubShader
    {
        Tags {"Queue"="Transparent" "IgnoreProjector"="true" "RenderType"="Transparent"}
        ZWrite Off Blend SrcAlpha OneMinusSrcAlpha Cull Off
        Pass
        {    
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma fragmentoption ARB_precision_hint_fastest
            #include "UnityCG.cginc"

            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };    
            struct v2f
            {
                half2 texcoord  : TEXCOORD0;
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
            };

            sampler2D _MainTex;
            float radius;
            float resolution;

            //the direction of our blur
            //hstep (1.0, 0.0) -> x-axis blur
            //vstep(0.0, 1.0) -> y-axis blur
            //for example horizontaly blur equal:
            //float hstep = 1;
            //float vstep = 0;
            float hstep;
            float vstep;

            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = UnityObjectToClipPos(IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color;
                return OUT;
            }

            float4 frag(v2f i) : COLOR
            {    
                float2 uv = i.texcoord.xy;
                float4 sum = float4(0.0, 0.0, 0.0, 0.0);
                float2 tc = uv;

                //blur radius in pixels
                float blur = radius/resolution/4;     

                sum += tex2D(_MainTex, float2(tc.x - 4.0*blur*hstep, tc.y - 4.0*blur*vstep)) * 0.0162162162;
                sum += tex2D(_MainTex, float2(tc.x - 3.0*blur*hstep, tc.y - 3.0*blur*vstep)) * 0.0540540541;
                sum += tex2D(_MainTex, float2(tc.x - 2.0*blur*hstep, tc.y - 2.0*blur*vstep)) * 0.1216216216;
                sum += tex2D(_MainTex, float2(tc.x - 1.0*blur*hstep, tc.y - 1.0*blur*vstep)) * 0.1945945946;

                sum += tex2D(_MainTex, float2(tc.x, tc.y)) * 0.2270270270;

                sum += tex2D(_MainTex, float2(tc.x + 1.0*blur*hstep, tc.y + 1.0*blur*vstep)) * 0.1945945946;
                sum += tex2D(_MainTex, float2(tc.x + 2.0*blur*hstep, tc.y + 2.0*blur*vstep)) * 0.1216216216;
                sum += tex2D(_MainTex, float2(tc.x + 3.0*blur*hstep, tc.y + 3.0*blur*vstep)) * 0.0540540541;
                sum += tex2D(_MainTex, float2(tc.x + 4.0*blur*hstep, tc.y + 4.0*blur*vstep)) * 0.0162162162;
                return sum;
            }    
            ENDCG
        }
    }
    Fallback "Sprites/Default"    
}

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