Converting Texture To Texture2d And Getpixels

I need to get the average color of a Texture generated at runtime (actually the video background of Vuforia camera). To do that, I converted this Texture to a Texture2D using a script found on this forum:

Code (CSharp):

1.    Texture mainTexture = renderer.material.mainTexture;
2.               Texture2D texture2D = new Texture2D(mainTexture.width, mainTexture.height, TextureFormat.RGBA32, false);
3.  
4.               RenderTexture currentRT = RenderTexture.active;
5.  
6.               RenderTexture renderTexture = new RenderTexture(mainTexture.width, mainTexture.height, 32);
7.               Graphics.Blit(mainTexture, renderTexture);
8.  
9.               RenderTexture.active = renderTexture;
10.               texture2D.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
11.               texture2D.Apply();
12.  
13.               Color[] pixels = texture2D.GetPixels();
14.  
15.               RenderTexture.active = currentRT;

This works fine on editor but when testing it on an android device, GetPixels() only returns a red color value, blue and green ones remain 0. Yet, the texture is clear, the only thing is that it is shown on a redscale.
I thought it could come from an unsupported texture format but I have not been able to find any information about that.
Does anyone know the reason for which it happens?

 

After some more research, I suspect this problem to come from the Blit() function because my renderTexture has already turned red. However, I still can't find on which point as the texture formats are the same on both editor and mobile, and I haven't found any other thread about it. Isn't there an alternative to this function to convert a Texture to a RenderTexture?