88 lines
2.9 KiB
C++
88 lines
2.9 KiB
C++
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//
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// Copyright 2021 Prathamesh Tagore <prathameshtagore@gmail.com>
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//
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// Use, modification and distribution are subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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#include <boost/gil/point.hpp>
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#include <boost/gil/extension/rasterization/ellipse.hpp>
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#include <boost/core/lightweight_test.hpp>
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#include <cmath>
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#include <cstdint>
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#include <vector>
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namespace gil = boost::gil;
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// This function utilizes the fact that sum of distances of a point on an ellipse from its foci
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// is equal to the length of major axis of the ellipse.
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// Parameters b and a represent half of lengths of vertical and horizontal axis respectively.
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void test_rasterizer_follows_equation(
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std::vector<gil::point_t> const& trajectory_points, float a, float b)
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{
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float focus_x, focus_y;
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if (a > b) // For horizontal ellipse
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{
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focus_x = a * std::sqrt(1 - b * b / (a * a));
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focus_y = 0;
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}
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else // For vertical ellipse
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{
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focus_x = 0;
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focus_y = b * std::sqrt(1 - a * a / (b * b));
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}
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for (auto trajectory_point : trajectory_points)
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{
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// To suppress conversion warnings from compiler
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gil::point<float> point {
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static_cast<float>(trajectory_point[0]), static_cast<float>(trajectory_point[1])};
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double dist_sum = std::sqrt(std::pow(focus_x - point[0], 2) +
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std::pow(focus_y - point[1], 2)) + std::sqrt(std::pow( - focus_x - point[0], 2) +
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std::pow( - focus_y - point[1], 2));
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if (a > b)
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{
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BOOST_TEST(std::abs(dist_sum - 2 * a) < 1);
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}
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else
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{
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BOOST_TEST(std::abs(dist_sum - 2 * b) < 1);
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}
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}
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}
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// This function verifies that the difference between x co-ordinates and y co-ordinates for two
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// successive trajectory points is less than or equal to 1. This ensures that the curve is connected.
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void test_connectivity(std::vector<gil::point_t> const& points)
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{
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for (std::size_t i = 1; i < points.size(); ++i)
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{
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std::ptrdiff_t diff_x = points[i][0] - points[i - 1][0];
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std::ptrdiff_t diff_y = points[i][1] - points[i - 1][1];
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BOOST_TEST_LE(diff_x, 1);
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BOOST_TEST_LE(diff_y, 1);
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}
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}
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// We verify all test cases for the portion of ellipse in first quadrant, since all other portions
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// can be constructed with simple reflection, they tend to be correct if first quadrant is verified.
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int main()
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{
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for (float a = 1; a < 101; ++a)
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{
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for (float b = 1; b < 101; ++b)
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{
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auto rasterizer = gil::midpoint_ellipse_rasterizer{{},
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{static_cast<unsigned int>(a), static_cast<unsigned int>(b)}};
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std::vector<gil::point_t> points = rasterizer.obtain_trajectory();
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test_rasterizer_follows_equation(points, a, b);
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test_connectivity(points);
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}
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}
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return boost::report_errors();
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}
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