Read What are image links and how to generate those?
b.blur {image_url} {blur radius}
blur radius is an integer meaning it belongs to $(1, 2, 3, ..., 68, 69, ..., 419, 420, ..., \infty)$
Returns a blurred image right back to the chat. The blur radius will determine how strong the blur filter should go. The mathematical formula used to blur images is the gaussian blur technique. Read more about gaussian blur techniques here.
Using smaller radius makes smooth images and reduces the sharpness and makes them pleasing to the eyes. Try for yourself.