#!/usr/bin/env python
# -*- coding: utf-8 -*-
# lens_distortion.py
# Copyright (c) 2017-2021, Richard Gerum
#
# This file is part of the cameratransform package.
#
# cameratransform is free software: you can redistribute it and/or modify
# it under the terms of the MIT licence.
#
# cameratransform 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
# MIT License for more details.
#
# You should have received a copy of the license
# along with cameratransform. If not, see <https://opensource.org/licenses/MIT>
import numpy as np
from .parameter_set import ClassWithParameterSet, ParameterSet, Parameter, TYPE_DISTORTION
import json
def invert_function(x, func):
from scipy import interpolate
from scipy.interpolate import dfitpack
y = func(x)
dy = np.concatenate(([0], np.diff(y)))
y = y[dy>=0]
x = x[dy>=0]
try:
inter = interpolate.InterpolatedUnivariateSpline(y, x)
# dfitpack.error
except Exception: # pragma: no cover
inter = lambda x: x
return inter
class LensDistortion(ClassWithParameterSet): # pragma: no cover
offset = np.array([0, 0])
scale = 1
def __init__(self):
self.parameters = ParameterSet()
def imageFromDistorted(self, points):
# return the points as they are
return points
def distortedFromImage(self, points):
# return the points as they are
return points
def __str__(self):
string = ""
string += " lens (%s):\n" % type(self).__name__
for name in self.parameters.parameters:
string += " %s:\t\t%.3f\n" % (name, getattr(self, name))
return string
def setProjection(self, projection):
pass
def save(self, filename):
keys = self.parameters.parameters.keys()
export_dict = {key: getattr(self, key) for key in keys}
with open(filename, "w") as fp:
fp.write(json.dumps(export_dict))
def load(self, filename):
with open(filename, "r") as fp:
variables = json.loads(fp.read())
for key in variables:
setattr(self, key, variables[key])
[docs]class NoDistortion(LensDistortion):
"""
The default model for the lens distortion which does nothing.
"""
pass
[docs]class BrownLensDistortion(LensDistortion):
r"""
The most common distortion model is the Brown's distortion model. In CameraTransform, we only consider the radial part
of the model, as this covers all common cases and the merit of tangential components is disputed. This model relies on
transforming the radius with even polynomial powers in the coefficients :math:`k_1, k_2, k_3`. This distortion model is
e.g. also used by OpenCV or AgiSoft PhotoScan.
Adjust scale and offset of x and y to be relative to the center:
.. math::
x' &= \frac{x-c_x}{f_x}\\
y' &= \frac{y-c_y}{f_y}
Transform the radius from the center with the distortion:
.. math::
r &= \sqrt{x'^2 + y'^2}\\
r' &= r \cdot (1 + k_1 \cdot r^2 + k_2 \cdot r^4 + k_3 \cdot r^6)\\
x_\mathrm{distorted}' &= x' / r \cdot r'\\
y_\mathrm{distorted}' &= y' / r \cdot r'
Readjust scale and offset to obtain again pixel coordinates:
.. math::
x_\mathrm{distorted} &= x_\mathrm{distorted}' \cdot f_x + c_x\\
y_\mathrm{distorted} &= y_\mathrm{distorted}' \cdot f_y + c_y
"""
projection = None
def __init__(self, k1=None, k2=None, k3=None, projection=None):
self.parameters = ParameterSet(
# the intrinsic parameters
k1=Parameter(k1, default=0, range=(0, None), type=TYPE_DISTORTION),
k2=Parameter(k2, default=0, range=(0, None), type=TYPE_DISTORTION),
k3=Parameter(k3, default=0, range=(0, None), type=TYPE_DISTORTION),
)
for name in self.parameters.parameters:
self.parameters.parameters[name].callback = self._init_inverse
self._init_inverse()
def setProjection(self, projection):
self.projection = projection
self.parameters = ParameterSet(
k1=self.parameters.parameters["k1"],
k2=self.parameters.parameters["k2"],
k3=self.parameters.parameters["k3"],
image_width_px=self.projection.parameters.parameters["image_width_px"],
image_height_px=self.projection.parameters.parameters["image_height_px"],
focallength_x_px=self.projection.parameters.parameters["focallength_x_px"],
focallength_y_px=self.projection.parameters.parameters["focallength_y_px"],
center_x_px=self.projection.parameters.parameters["center_x_px"],
center_y_px=self.projection.parameters.parameters["center_y_px"],
)
for name in self.parameters.parameters:
self.parameters.parameters[name].callback = self._init_inverse
self._init_inverse()
def _init_inverse(self):
r = np.arange(0, 2, 0.1)
self._convert_radius_inverse = invert_function(r, self._convert_radius)
if self.projection is not None:
self.scale = np.array([self.projection.focallength_x_px, self.projection.focallength_y_px])
self.offset = np.array([self.projection.center_x_px, self.projection.center_y_px])
def _convert_radius(self, r):
return r*(1 + self.parameters.k1*r**2 + self.parameters.k2*r**4 + self.parameters.k3*r**6)
def imageFromDistorted(self, points):
# ensure that the points are provided as an array
# and rescale the points to that the center is at 0 and the border at 1
points = (np.array(points)-self.offset)/self.scale
# calculate the radius form the center
r = np.linalg.norm(points, axis=-1)[..., None]
# transform the points
points = points / r * self._convert_radius_inverse(r)
# rescale back to the image
return points * self.scale + self.offset
def distortedFromImage(self, points):
# ensure that the points are provided as an array
# and rescale the points to that the center is at 0 and the border at 1
points = (np.array(points)-self.offset)/self.scale
# calculate the radius form the center
r = np.linalg.norm(points, axis=-1)[..., None]
# transform the points
points = points / r * self._convert_radius(r)
# rescale back to the image
return points * self.scale + self.offset
[docs]class ABCDistortion(LensDistortion):
r"""
The ABC model is a less common distortion model, that just implements radial distortions. Here the radius is transformed
using a polynomial of 4th order. It is used e.g. in PTGui.
Adjust scale and offset of x and y to be relative to the center:
.. math::
s &= 0.5 \cdot \mathrm{min}(\mathrm{im}_\mathrm{width}, \mathrm{im}_\mathrm{height})\\
x' &= \frac{x-c_x}{s}\\
y' &= \frac{y-c_y}{s}
Transform the radius from the center with the distortion:
.. math::
r &= \sqrt{x^2 + y^2}\\
r' &= d \cdot r + c \cdot r^2 + b \cdot r^3 + a \cdot r^4\\
d &= 1 - a - b - c
Readjust scale and offset to obtain again pixel coordinates:
.. math::
x_\mathrm{distorted} &= x_\mathrm{distorted}' \cdot s + c_x\\
y_\mathrm{distorted} &= y_\mathrm{distorted}' \cdot s + c_y
"""
projection = None
def __init__(self, a=None, b=None, c=None):
self.parameters = ParameterSet(
# the intrinsic parameters
a=Parameter(a, default=0, type=TYPE_DISTORTION),
b=Parameter(b, default=0, type=TYPE_DISTORTION),
c=Parameter(c, default=0, type=TYPE_DISTORTION)
)
for name in self.parameters.parameters:
self.parameters.parameters[name].callback = self._init_inverse
self._init_inverse()
def setProjection(self, projection):
self.projection = projection
self.parameters = ParameterSet(
a=self.parameters.parameters["a"],
b=self.parameters.parameters["b"],
c=self.parameters.parameters["c"],
image_width_px=self.projection.parameters.parameters["image_width_px"],
image_height_px=self.projection.parameters.parameters["image_height_px"],
focallength_x_px=self.projection.parameters.parameters["focallength_x_px"],
focallength_y_px=self.projection.parameters.parameters["focallength_y_px"],
center_x_px=self.projection.parameters.parameters["center_x_px"],
center_y_px=self.projection.parameters.parameters["center_y_px"],
)
for name in self.parameters.parameters:
self.parameters.parameters[name].callback = self._init_inverse
self._init_inverse()
def _init_inverse(self):
self.d = 1 - self.a - self.b - self.c
r = np.arange(0, 2, 0.1)
self._convert_radius_inverse = invert_function(r, self._convert_radius)
if self.projection is not None:
self.scale = np.min([self.projection.image_width_px, self.projection.image_height_px]) / 2
self.offset = np.array([self.projection.center_x_px, self.projection.center_y_px])
def _convert_radius(self, r):
return self.d * r + self.c * r**2 + self.b * r**3 + self.a * r**4
def imageFromDistorted(self, points):
# ensure that the points are provided as an array
# and rescale the points to that the center is at 0 and the border at 1
points = (np.array(points)-self.offset)/self.scale
# calculate the radius form the center
r = np.linalg.norm(points, axis=-1)[..., None]
# transform the points
points = points / r * self._convert_radius_inverse(r)
# rescale back to the image
return points * self.scale + self.offset
def distortedFromImage(self, points):
# ensure that the points are provided as an array
# and rescale the points to that the center is at 0 and the border at 1
points = (np.array(points)-self.offset)/self.scale
# calculate the radius form the center
r = np.linalg.norm(points, axis=-1)[..., None]
# transform the points
points = points / r * self._convert_radius(r)
# rescale back to the image
return points * self.scale + self.offset