[Compute Shader] Porting an Image Effect Shader - Kuwahara Filter

Hi All I am trying to port an image Effect Shader to Compute Shader because I want to learn compute shaders. I chose to port Kuwahara Filter because I am generally interested in image filtering. Below is my port which give a black screen. Any help will be appreciated as I am very new to this and there isn't much info on the subject around. The original image effect shader is in the link above.

 // 
 #pragma kernel CSMain
 #include "UnityCG.cginc"
 
 
 // Create a RenderTexture with enableRandomWrite flag and set it
 // with cs.SetTexture
 
 Texture2D<float4> Source;
 RWTexture2D<float4> Destination;
 int Radius = 5;
 SamplerState samplerSource;
 
 [numthreads(8,8,1)]
 void CSMain(uint3 id : SV_DispatchThreadID)
 {
 
 
     float3 mean[4] = {
     { 0, 0, 0 },
     { 0, 0, 0 },
     { 0, 0, 0 },
     { 0, 0, 0 }
     };
 
     float3 sigma[4] = {
         { 0, 0, 0 },
     { 0, 0, 0 },
     { 0, 0, 0 },
     { 0, 0, 0 }
     };
 
     float2 start[4] = { { -Radius, -Radius },{ -Radius, 0 },{ 0, -Radius },{ 0, 0 } };
 
 
     float2 pos;
     float3 col;
     uint width;
     uint height;
     uint levels;
     Source.GetDimensions(0, width, height, levels);
 
     float widthf = (float)width;
     float heightf = (float)height;
 
 
     for (int k = 0; k < 4; k++) {
         for (int i = 0; i <= Radius; i++) {
             for (int j = 0; j <= Radius; j++) {
                 pos = float2(i, j) + start[k];
                 col = Source.SampleLevel(samplerSource, float2(pos.x * 1.0/width, pos.y * 1.0/height), 0);
                 mean[k] += col;
                 sigma[k] += col * col;
             }
         }
     }
 
     float sigma2;
 
     float n = pow(Radius + 1, 2);
     float4 color = Source[id.xy];
     float min = 1;
 
     for (int l = 0; l < 4; l++) {
         mean[l] /= n;
         sigma[l] = abs(sigma[l] / n - mean[l] * mean[l]);
         sigma2 = sigma[l].r + sigma[l].g + sigma[l].b;
 
         if (sigma2 < min) {
             min = sigma2;
             color.rgb = mean[l].rgb;
         }
     }
 
     Destination[id.xy] = color;
 
 }