Given the row and column of a pixel in the output image, return the corresponding point on the complex plane. `bounds` is a pair giving the width and height of the image in pixels. `pixel` is a (column, row) pair indicating a particular pixel in that image. The `upper_left` and `lower_right` parameters are points on the complex plane designating the area our image covers.
(bounds: (usize, usize),
pixel: (usize, usize),
upper_left: Complex<f64>,
lower_right: Complex<f64>)