avidemux_shaders/gopro_8:7/compute_gopro_8:7.py

# RozK
# Computes fisheye removal parameters for GoPro 11+, 8:7 ratio, without hypersmooth,
# keeping the vertical FOV and widening the frame to preserve the diagonal FOV

# https://www.bobatkins.com/photography/technical/field_of_view.html
# https://community.gopro.com/s/article/HERO11-Black-Mini-Digital-Lenses-FOV-Information?language=fr

import math

frame_width = 8
frame_height = 7
input_ratio = frame_width / frame_height

input_vertical_fov = 108.0
input_diagonal_fov = 156.0

input_vertical_length = math.radians(input_vertical_fov * 0.5)
input_diagonal_length = math.radians(input_diagonal_fov * 0.5)

output_horizontal_length = math.sqrt((input_diagonal_length ** 2) / (input_vertical_length ** 2))
output_diagonal_length = math.hypot(output_horizontal_length, input_vertical_length)
output_diagonal_fov = math.degrees(math.atan(output_diagonal_length)) * 2.0

output_ratio = 1.0 / (output_horizontal_length / input_vertical_length)

print("Output FOV   = %f" % output_diagonal_fov)
print("Output Ratio = %f" % output_ratio)
print("= Resolutions =====================")

def width_rounded_8(height):
    width = int(round(height * input_ratio))
    return ((width + 4) // 8) * 8

print("HD             = %i x 720" % width_rounded_8(720))
print("Full HD        = %i x 1080" % width_rounded_8(1080))
print("4K             = %i x 2160" % width_rounded_8(2160))