Possible issue with color::from_hsl

[ErrorFlynn]

The method color::from_hsl seems to produce incorrect results. For example, color.from_hsl(210, .68, .80); produces {r_=169.32000000000005 g_=204.00000000000000 b_=238.67999999999998 ...}. The correct RGB values are 171, 205, 239 (#abcdef), as any online color picker will tell you (for example: https://colorpicker.me/#abcdef).

The reason I said "possible issue", is because I wrote my own conversion function, and it produces the same results as from_hsl! Are both my code and from_hsl using the wrong formula, or am I missing something? I'm guessing something else is happening, but can't imagine what. Here's my code:

color hsl2rgb(double h, double s, double l)
{
	double r, g, b;
	if(s == 0.0)
	{
		r = l * 255.0;
		g = r;
		b = r;
	}
	else
	{
		double t1;
		if(l < .5)
			t1 = l * (1.0 + s);
		else t1 = l + s - l * s;
		double t2 {2 * l - t1};
		h /= 360;

		auto h2rgb = [&](double val)
		{
			if(val < 0.0) val += 1.0;
			else if(val > 1.0) val -= 1.0;
			if(6.0 * val < 1.0)
				return t2 + (t1 - t2) * 6 * val;
			if(2 * val < 1.0)
				return t1;
			if(3 * val < 2.0)
				return t2 + (t1 - t2) * (.666 - val) * 6;
			return t2;
		};

		r = h2rgb(h + .333);
		g = h2rgb(h);
		b = h2rgb(h - .333);
	}
	return {static_cast<unsigned>(round(r*255)), static_cast<unsigned>(round(g*255)), static_cast<unsigned>(round(b*255))};
}

[ashbob999]

After doing some searching and implementing the same algorithm from different websites, i have gotten the exact same value each time for hsl(210, 0.68, 0.80) produces r=169, g=204, b=239 (#A9CCEF). From this website: https://convertacolor.com/.

There does not seem to be a problem with the algorithm but I think the problem lies in the colour picker websites (partially explained here)

Example
#ABCDEF -> hsl(210, 68%, 80.4%) they round 80.4% to 80%
So we get hsl(210, 0.68, 0.80) -> '#A9CCEF'
So if the websites round the saturation/lightness to an integer (if percentage) or 2 decimal places (if double), they will then be giving incorrect conversion values.

[ErrorFlynn]

Wow, I can't believe the websites are wrong, and I can't believe I got tripped up by this. Thanks a lot for the explanation!