Add a toggle for colorblind friendly progress bar colors (#25318)

* Add a toggle for progress bar colors

* yeah this thing

* PJB review

* optimization

Content.Client/UserInterface/Systems/ProgressColorSystem.cs

@@ -0,0 +1,77 @@
+using Content.Shared.CCVar;
+using Robust.Shared.Configuration;
+
+namespace Content.Client.UserInterface.Systems;
+
+/// <summary>
+/// This system handles getting an interpolated color based on the value of a cvar.
+/// </summary>
+public sealed class ProgressColorSystem : EntitySystem
+{
+    [Dependency] private readonly IConfigurationManager _configuration = default!;
+
+    private bool _colorBlindFriendly;
+
+    private static readonly Color[] Plasma =
+    {
+        new(240, 249, 33),
+        new(248, 149, 64),
+        new(204, 71, 120),
+        new(126, 3, 168),
+        new(13, 8, 135)
+    };
+
+    /// <inheritdoc/>
+    public override void Initialize()
+    {
+        Subs.CVar(_configuration, CCVars.AccessibilityColorblindFriendly, OnColorBlindFriendlyChanged, true);
+    }
+
+    private void OnColorBlindFriendlyChanged(bool value, in CVarChangeInfo info)
+    {
+        _colorBlindFriendly = value;
+    }
+
+    public Color GetProgressColor(float progress)
+    {
+        if (!_colorBlindFriendly)
+        {
+            if (progress >= 1.0f)
+            {
+                return new Color(0f, 1f, 0f);
+            }
+
+            // lerp
+            var hue = 5f / 18f * progress;
+            return Color.FromHsv((hue, 1f, 0.75f, 1f));
+        }
+
+        return InterpolateColorGaussian(Plasma, progress);
+    }
+
+    /// <summary>
+    /// Interpolates between multiple colors based on a gaussian distribution.
+    /// Taken from https://stackoverflow.com/a/26103117
+    /// </summary>
+    public static Color InterpolateColorGaussian(Color[] colors, double x)
+    {
+        double r = 0.0, g = 0.0, b = 0.0;
+        var total = 0f;
+        var step = 1.0 / (colors.Length - 1);
+        var mu = 0.0;
+        const double sigma2 = 0.035;
+
+        foreach(var color in colors)
+        {
+            var percent = Math.Exp(-(x - mu) * (x - mu) / (2.0 * sigma2)) / Math.Sqrt(2.0 * Math.PI * sigma2);
+            total += (float) percent;
+            mu += step;
+
+            r += color.R * percent;
+            g += color.G * percent;
+            b += color.B * percent;
+        }
+
+        return new Color((float) r / total, (float) g / total, (float) b / total);
+    }
+}