Unity: Reduce size of Render Texture before executing Texture2D.ReadPixels - unity3d

Question

I'm working on a code where I basically have to take a low quality screenshot about every 30 milliseconds. The script is attached to a camara.
What I want to do is reduce the render texture size. The way the code is right now changing either W or H basically gets me a SECTION of of all that is being seen by the camara instead of a reduced size version. So my question is how can I resized or downsample what is read into the screenshot (Texture2D) but that it still is a representation of the entire screen.
public class CameraRenderToImage : MonoBehaviour
{
private RemoteRenderServer rrs;
void Start(){
TimeStamp.SetStart();
Camera.onPostRender += OnPostRenderCallback;
}
void OnPostRenderCallback(Camera cam){
if (TimeStamp.HasMoreThanThisEllapsed(30)){
TimeStamp.SetStart();
int W = Screen.width;
int H = Screen.height;
Texture2D screenshot = new Texture2D(W,H, TextureFormat.RGB24, false);
screenshot.ReadPixels( new Rect(0, 0, W,H), 0, 0);
byte[] bytes = screenshot.EncodeToPNG();
System.IO.File.WriteAllBytes("check_me_out.png", bytes);
TimeStamp.Tok("Encode to PNG and Save");
}
}
// Remove the onPostRender callback
void OnDestroy()
{
Camera.onPostRender -= OnPostRenderCallback;
}
}

Answer 1

If you need to resize your render texture from script you can refer to the next code snippet
void Resize(RenderTexture renderTexture, int width, int height) {
if (renderTexture) {
renderTexture.Release();
renderTexture.width = width;
renderTexture.height = height;
}
}
To make it possible to resize the render texture you first need to make sure it is released.
To get Texture2d:
private Texture2D ToCompressedTexture(ref RenderTexture renderTexture)
{
var texture = new Texture2D(renderTexture.width, renderTexture.height, TextureFormat.ARGB32, false);
var previousTarget = RenderTexture.active;
RenderTexture.active = renderTexture;
texture.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
RenderTexture.active = previousTarget;
texture.Compress(false);
texture.Apply(false, true);
renderTexture.Release();
renderTexture = null;
return texture;
}