line_iterator.py

#! /usr/bin/env python3
# Copyright 2021 Samsung Research America
# Copyright 2022 Afif Swaidan
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
 
"""
This is a Python3 API for a line iterator.
 
It provides the ability to iterate
through the points of a line.
"""
 
from cmath import sqrt
 
 
class LineIterator:
    """
    LineIterator.
 
    LineIterator Python3 API for iterating along the points of a given line
    """
 
    def __init__(self, x0: float, y0: float,
                 x1: float, y1: float,
                 step_size: float = 1.0):
        """
        Initialize the LineIterator.
 
        Args
        ----
            x0 (float): Abscissa of the initial point
            y0 (float): Ordinate of the initial point
            x1 (float): Abscissa of the final point
            y1 (float): Ordinate of the final point
            step_size (float): Optional, step along the longer axis, defaults to 1
 
        Raises
        ------
            TypeError: When one (or more) of the inputs is not a number
            ValueError: When step_size is not a positive number
 
        """
        if type(x0) not in [int, float]:
            raise TypeError('x0 must be a number (int or float)')
 
        if type(y0) not in [int, float]:
            raise TypeError('y0 must be a number (int or float)')
 
        if type(x1) not in [int, float]:
            raise TypeError('x1 must be a number (int or float)')
 
        if type(y1) not in [int, float]:
            raise TypeError('y1 must be a number (int or float)')
 
        if type(step_size) not in [int, float]:
            raise TypeError('step_size must be a number (int or float)')
 
        if step_size <= 0:
            raise ValueError('step_size must be a positive number')
 
        self.x0_x0_ = x0
        self.y0_y0_ = y0
        self.x1_x1_ = x1
        self.y1_y1_ = y1
        self.x_x_ = x0
        self.y_y_ = y0
        self.step_size_step_size_ = step_size
 
        if x1 == x0 and y1 == y0:
            self.valid_valid_ = False
            raise ValueError('Line has zero length (All 4 points have same coordinates)')
 
        self.valid_valid_ = True
        self.steep_steep_ = abs(y1 - y0) > abs(x1 - x0)
        if self.steep_steep_:
            self.m_m_ = (x1 - x0) / (y1 - y0)
            self.b_b_ = x1 - (self.m_m_ * y1)
        else:
            self.m_m_ = (y1 - y0) / (x1 - x0)
            self.b_b_ = y1 - (self.m_m_ * x1)
 
    def isValid(self):
        """Check if line is valid."""
        return self.valid_valid_
 
    def advance(self):
        """Advance along the longer axis and interpolate the other coordinate."""
        if self.steep_steep_:
            start, end, current = self.y0_y0_, self.y1_y1_, self.y_y_
        else:
            start, end, current = self.x0_x0_, self.x1_x1_, self.x_x_
 
        if end > start:
            if current >= end:
                self.valid_valid_ = False
                return
            next_coordinate = self.clampclamp(current + self.step_size_step_size_, start, end)
        else:
            if current <= end:
                self.valid_valid_ = False
                return
            next_coordinate = self.clampclamp(current - self.step_size_step_size_, end, start)
 
        if next_coordinate != end:
            rounded = round(next_coordinate, 5)
            # Keep rounding from erasing a small step or moving past the endpoint.
            if (end > start and rounded > current) or (end < start and rounded < current):
                next_coordinate = self.clampclamp(rounded, min(start, end), max(start, end))
 
        if next_coordinate == end:
            self.x_x_, self.y_y_ = self.x1_x1_, self.y1_y1_
            return
 
        if self.steep_steep_:
            self.y_y_ = next_coordinate
            if self.x0_x0_ != self.x1_x1_:
                self.x_x_ = round(self.m_m_ * self.y_y_ + self.b_b_, 5)
        else:
            self.x_x_ = next_coordinate
            if self.y0_y0_ != self.y1_y1_:
                self.y_y_ = round(self.m_m_ * self.x_x_ + self.b_b_, 5)
 
    def getX(self):
        """Get the abscissa of the current point."""
        return self.x_x_
 
    def getY(self):
        """Get the ordinate of the current point."""
        return self.y_y_
 
    def getX0(self):
        """Get the abscissa of the initial point."""
        return self.x0_x0_
 
    def getY0(self):
        """Get the ordinate of the initial point."""
        return self.y0_y0_
 
    def getX1(self):
        """Get the abscissa of the final point."""
        return self.x1_x1_
 
    def getY1(self):
        """Get the ordinate of the final point."""
        return self.y1_y1_
 
    def get_line_length(self):
        """Get the length of the line."""
        return sqrt(pow(self.x1_x1_ - self.x0_x0_, 2) + pow(self.y1_y1_ - self.y0_y0_, 2))
 
    def clamp(self, n: float, min_n: float, max_n: float):
        """
        Clamp n to be between min_n and max_n.
 
        Args
        ----
            n (float): input value
            min_n (float): minimum value
            max_n (float): maximum value
 
        Returns
        -------
            n (float): input value clamped between given min and max
 
        """
        if n < min_n:
            return min_n
        elif n > max_n:
            return max_n
        else:
            return n