Utility function to convert between pixel to angle and vice versa in Eye Tracking. Ported from matlab code. Original article here: https://courses.washington.edu/matlab1/matlab/

pix-angle-utils.py

import math

class Display:
    def __init__(self, dist, width, resolution):
        self.distance = dist
        self.width = width
        self.resolution = resolution


# Credit to gmb zre 11/1/07, ported to python by Viet Ta
def pix2angle(display, pix):
    pix_size = display.size / display.resolution[0]  # cm/pix
    sz = pix * pix_size
    return 2 * math.degrees(math.atan(sz / (2 * display.distance)))


# Credit to gmb zre 11/1/07, ported to python by Viet Ta
def angle2pix(display, ang):
    pix_size = display.size / display.resolution[0]  # cm/pix
    sz = 2 * display.distance * math.tan(math.radians(ang / 2))  # cm
    return round(sz / pix_size)

display = Display(60, 44.5, [1680, 1050])
pix = 100
ang = 2.529
print(pix2angle(display, pix))
print(angle2pix(display, ang))