🦟 Bug fix

Summary

• The implementation of Hue of Color::HSV() does not seem right, where HSV stands for hue, saturation, value.
• OS Version: Ubuntu 20.04
• Source build from b399035, branch ign-math6
• Also update the expected behavior in the color tutorial accordingly.
• Change test cases for Color

Why also change the test cases:

• Here is a document of Ignition Math that said the range of Hue should be [0, 360].
• The current Hue implementation does not seem to fit in any HSV standard as far as I know.
• Repeatedly converting back and forth between RGB and HSV will change the value of the color drastically.

Description

• Color::HSV() in Color.cc has an incorrect output hue (index 0 of return Vector3f object)

Example 1: Converting the RGB (0.5, 0.6, 0.7) to HSV.

• Expected output: (210, 0.286, 0.7), can verify with RGB to HSV
• Actual output: (3.5, 0.286, 0.7)

Example 2: Converting the RGB (0.0, 0.0, 0.0) to HSV.

• Expected output: (0, 0, 0)
• Actual output: (-1, 0, 0)

Examples can be verified by putting the following file in /examples

#include <iostream>
#include <ignition/math/Color.hh>

int main() 
{
  ignition::math::Color b = ignition::math::Color(0.0, 0.0, 0.0);
  std::cout << "The RGBA value of b: " << b << std::endl;
  std::cout << "The HSV value of b: " << b.HSV() << std::endl;

  ignition::math::Color a = ignition::math::Color(0.5, 0.6, 0.7);
  std::cout << "The RGBA value of a: " << a << std::endl;
  std::cout << "The HSV value of a: " << a.HSV() << std::endl;
}

Incorrect Output on terminal

Correct Output on terminal

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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