void CombineTextures(Texture2D newTexture, Texture2D mainTexture, Texture2D overlay)
{

var offset = new Vector2(((newTexture.width - overlay.width)/2), ((newTexture.height - overlay.height)/2));

newTexture.SetPixels(mainTexture.GetPixels());

for(var y = 0; y < overlay.height; y++)
{
for(var x = 0; x < overlay.width; x++)
{
var pixelColorFore = overlay.GetPixel(x, y)*overlay.GetPixel(x, y).a;
var pixelColorBack = newTexture.GetPixel(x + Mathf.RoundToInt(offset.x), y + Mathf.RoundToInt(offset.y)) * (1 - pixelColorFore.a);
newTexture.SetPixel(x + Mathf.RoundToInt(offset.x), y + Mathf.RoundToInt(offset.y), pixelColorBack + pixelColorFore);
}
}

newTexture.Apply();
}