Receptive Field Arithmetic

Formula

$$ \begin{aligned} j_{n} &= s^{n} \\ r_{n+1} &= r_{n} + (k - 1) \cdot j_n \end{aligned} $$

• $ j $ is the distance between two consecutive features on the feature map in terms of pixels of the original image.

• $ r ​$ is the size of the receptive field for a feature on the feature map in terms of pixels of the original image.

  |·[*]···[*]···[*]·|: $ r_{n+1} = \frac{r_{n}}{2} + \left\lfloor\frac{k}{2} \right\rfloor \cdot j_n + 0 + \left\lfloor \frac{k}{2} \right\rfloor \cdot j_n + \frac{r_{n}}{2} $

Illustration¹

(The left one is more intuitive and natural.)

by Jon