Question Trouble converting float2 to index in Compute Shader

Hello, I'm having trouble converting float2 to a one dimensional index value.

I want to use an input color array instead of a source texture, so I fetched source texture pixels and have stored them in the color array. I then sent an input buffer containing those colors to a Compute Shader, which I then want to use for sampling.

However, for some reason when I try to sample a color from an array I get a really strange result:



Although, if I use a source image instead, I get a desired result:



Below is the Compute Shader code I use.

Code (CSharp):

1. Texture2D<float4> source; //A source texture.
2.  
3. StructuredBuffer<float4>   input; //An array of colors that contain source image pixels.
4. RWStructuredBuffer<float4> output; //An output color array.
5.  
6. int width; //Result image width.
7. int height; //Result image height.
8.  
9. Buffer<float> sc; //Pre-computed sin and cos values.
10.  
11. [numthreads(1, 1, 1)]
12. void Rotate(uint3 id : SV_DispatchThreadID)
13. {
14.     int w = width;
15.     int h = height;
16.  
17.     float2x2 r2 = float2x2(sc[1], -sc[0], sc[0], sc[1]);
18.  
19.     float2 center = float2(w, h) / 2;
20.     float2 pos = mul(r2, id - center) + center;
21.  
22.     if (min(pos.x, pos.y) < 0 || max(pos.x - w, pos.y - h) >= 0 || id.x >= width || id.y >= height)
23.     {
24.         output[id.x + id.y * w] = float4(0, 0, 0, 0);
25.     }
26.     else
27.     {
28.         output[id.x + id.y * w] = source[pos.xy]; //Works
29.         output[id.x + id.y * w] = input[pos.x + pos.y * w]; //Doesn't work
30.     }
31. }

Can someone please help me? I'm not sure what am I doing wrong here... :/