avidemux_shaders/gopro_8:7/unfish_gopro_8:7.py

# Fisheye removal for GoPro 11+, 8:7 ratio, without hypersmooth
# Copyright (C) 2025 Jean-Baptiste Berlioz
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import math

print("\n--- physical sensor ---\n")

# https://www.sony-semicon.com/files/62/pdf/p-13_IMX677-AAPH5-J_Flyer.pdf

sensor_pixel_size = 1.12 * 0.001 # mm

# https://community.gopro.com/s/article/HERO11-Black-Video-Settings-And-Resolutions

gopro_array_horizontal = 5312 # p
gopro_array_vertical   = 4648 # p

gopro_texture_horizontal = 3840 # p
gopro_texture_vertical   = 3360 # p

gopro_size_horizontal = gopro_array_horizontal * sensor_pixel_size
gopro_size_vertical   = gopro_array_vertical   * sensor_pixel_size
gopro_size_diagonal   = math.hypot(gopro_size_horizontal, gopro_size_vertical)

print("gopro  size : horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (mm)" % (
    gopro_size_horizontal,
    gopro_size_vertical,
    gopro_size_diagonal))

# https://thinglabs.io/gopro-focal-length-guide

gopro_focal_length = 2.97 # mm

gopro_radius_horizontal = gopro_size_horizontal * 0.5
gopro_radius_vertical   = gopro_size_vertical   * 0.5
gopro_radius_diagonal   = gopro_size_diagonal   * 0.5

# https://en.wikipedia.org/wiki/Fisheye_lens

equidistant_angle  = lambda radius: math.degrees(radius / gopro_focal_length)

gopro_fov_horizontal = 2.0 * equidistant_angle(gopro_radius_horizontal)
gopro_fov_vertical   = 2.0 * equidistant_angle(gopro_radius_vertical)
gopro_fov_diagonal   = 2.0 * equidistant_angle(gopro_radius_diagonal)

print("gopro  fov  : horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (deg)" % (
    gopro_fov_horizontal,
    gopro_fov_vertical,
    gopro_fov_diagonal))

print("\n--- rectilinear re-projection ---\n")

rectilinear_focal_length = lambda radius: radius * math.tan(math.radians(90.0 - equidistant_angle(radius)))

rectilinear_focal_length_horizontal = rectilinear_focal_length(gopro_radius_horizontal)
rectilinear_focal_length_vertical   = rectilinear_focal_length(gopro_radius_vertical)
rectilinear_focal_length_diagonal   = rectilinear_focal_length(gopro_radius_diagonal)

print("linear focal: horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (mm)" % (
    rectilinear_focal_length_horizontal,
    rectilinear_focal_length_vertical,
    rectilinear_focal_length_diagonal))

rectilinear_radius = lambda angle:  rectilinear_focal_length_vertical * math.tan(math.radians(angle))
rectilinear_angle  = lambda radius: math.degrees(math.atan(radius / rectilinear_focal_length_vertical))

rectilinear_fov_horizontal = 2.0 * rectilinear_angle(gopro_radius_horizontal)
rectilinear_fov_vertical   = 2.0 * rectilinear_angle(gopro_radius_vertical)
rectilinear_fov_diagonal   = 2.0 * rectilinear_angle(gopro_radius_diagonal)

print("linear fov  : horizontal = %7.3f, vertical = %7.3f, diagonal = %7.3f (deg)" % (
    rectilinear_fov_horizontal,
    rectilinear_fov_vertical,
    rectilinear_fov_diagonal))

print("\n--- shader parameters ---\n")

output_size_horizontal = 2.0 * rectilinear_radius(gopro_fov_horizontal * 0.5)
output_size_vertical   = gopro_size_vertical

output_scale_horizontal = output_size_horizontal / gopro_size_horizontal

print("""// parameters
const vec2 sensor_size = vec2(%.6f, %.6f);
const float equidistant_focal_length = %.6f;
const float rectilinear_focal_length = %.6f;
const vec2 rectilinear_scale = vec2(%.6F, 1.0);""" % (
    gopro_size_horizontal, gopro_size_vertical,
    gopro_focal_length,
    rectilinear_focal_length_vertical,
    output_scale_horizontal)
)

print("\n--- filters parameters ---\n")

output_ratio_horizontal = 4.0
output_ratio_vertical   = 3.0

output_crop_ratio      = output_ratio_vertical / (output_ratio_horizontal / output_scale_horizontal)

output_crop_horizontal = gopro_texture_horizontal
output_crop_vertical   = output_crop_horizontal * output_crop_ratio

print("crop  : width = %d, height = %d" % (
    output_crop_horizontal,
    round(output_crop_vertical)))

def print_output_array(array_vertical):
    array_horizontal = (array_vertical / output_ratio_vertical) * output_ratio_horizontal
    print("resize: width = %d, height = %d" % (
        round(array_horizontal / 4.0) * 4,
        array_vertical))

print_output_array(2160)
print_output_array(1080)