Add basic colour-determining functionality

Seraphina/ColorHelper.cs

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+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Text;
+
+namespace Seraphina
+{
+    public static class ColorHelper
+    {
+        public static void ColorToHSV(Color color, out double hue, out double saturation, out double value)
+        {
+            int max = Math.Max(color.R, Math.Max(color.G, color.B));
+            int min = Math.Min(color.R, Math.Min(color.G, color.B));
+
+            hue = color.GetHue();
+            saturation = (max == 0) ? 0 : 1d - (1d * min / max);
+            value = max / 255d;
+        }
+
+        public static Color ColorFromHSV(double hue, double saturation = 1, double value = 1)
+        {
+            int hi = Convert.ToInt32(Math.Floor(hue / 60)) % 6;
+            double f = hue / 60 - Math.Floor(hue / 60);
+
+            value *= 255;
+            int v = Convert.ToInt32(value);
+            int p = Convert.ToInt32(value * (1 - saturation));
+            int q = Convert.ToInt32(value * (1 - f * saturation));
+            int t = Convert.ToInt32(value * (1 - (1 - f) * saturation));
+
+            return hi switch
+            {
+                0 => Color.FromArgb(v, t, p),
+                1 => Color.FromArgb(q, v, p),
+                2 => Color.FromArgb(p, v, t),
+                3 => Color.FromArgb(p, q, v),
+                4 => Color.FromArgb(t, p, v),
+                _ => Color.FromArgb(v, p, q),
+            };
+        }
+
+        /// <summary>
+        /// Gets a colour from the provided HSL values.
+        /// </summary>
+        /// <param name="hue">The hue, from 0 to 360.</param>
+        /// <param name="sat">The saturation, from 0 to 1.</param>
+        /// <param name="lightness">The lightness, from 0 to 1.</param>
+        /// <returns></returns>
+        public static Color ColorFromHSL(double hue, double sat = 1, double lightness = 0.5)
+        {
+            if (sat == 0)
+            {
+                int L = (int)lightness;
+                return Color.FromArgb(255, L, L, L);
+            }
+
+            double min, max, h;
+            h = hue / 360d;
+
+            max = lightness < 0.5d ? lightness * (1 + sat) : (lightness + sat) - (lightness * sat);
+            min = (lightness * 2d) - max;
+
+            return Color.FromArgb(255, (int)(255 * RGBChannelFromHue(min, max, h + 1 / 3d)),
+                                          (int)(255 * RGBChannelFromHue(min, max, h)),
+                                          (int)(255 * RGBChannelFromHue(min, max, h - 1 / 3d)));
+        }
+
+        static double RGBChannelFromHue(double m1, double m2, double h)
+        {
+            h = (h + 1d) % 1d;
+            if (h < 0) h += 1;
+            if (h * 6 < 1) return m1 + (m2 - m1) * 6 * h;
+            else if (h * 2 < 1) return m2;
+            else if (h * 3 < 2) return m1 + (m2 - m1) * 6 * (2d / 3d - h);
+            else return m1;
+
+        }
+    }
+}

Seraphina/PlayerHealthColor.cs

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+using Seraphina.Core;
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Text;
+
+namespace Seraphina
+{
+    public static class PlayerHealthColor
+    {
+
+        const int MinHp = 100;
+        const int MaxHp = 500;
+        const int HpDiff = MaxHp - MinHp;
+
+        const int MinHue = 100;
+        const int MaxHue = 300;
+        const int HueDiff = MaxHue - MinHue;
+        static readonly Color ZeroHp = Color.FromArgb(0, 255, 0, 0);
+        public static Color GetColor(HitPoint numerator, HitPoint denominator)
+        {
+            if (numerator <= 0) return ZeroHp; // Transparent red, for calculation consistency.
+            // XXX: Calculate the colour before rendering it transparent? Would it be a waste?
+
+            // Scale the HitPoint based on its percentage.
+            double pct = numerator.Value * 1.0 / denominator.Value;
+            if (denominator < MinHp)
+            {
+                return ColorHelper.ColorFromHSV(pct * 100);
+            }
+
+            // Scale the maximum hue by dividing anything over 100 by 2.
+            // ie 100 => 100, 200 => 150, 300 => 200, 500 => 300
+            var maxHue = ((denominator.Value - MinHp) / 2) + MinHp;
+
+            // Cap at 300 hue if max HitPoint is over 500 for some reason.
+            maxHue = Math.Min(MaxHue, maxHue);
+
+            var color = ColorHelper.ColorFromHSV(maxHue * pct);
+
+            return color;
+        }
+
+    }
+}

Seraphina/PlayerManaColor.cs

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+using Seraphina.Core;
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Text;
+
+namespace Seraphina
+{
+    public static class PlayerManaColor
+    {
+        // NOTE to more future self: change these around to tweak mana colour.
+        const double minLightness = 0.2;
+        const double maxLightness = 0.8;
+        const double range = maxLightness - minLightness;
+        const int BlueHue = 210;
+
+        public static Color GetColor(ManaPoint current, ManaPoint max)
+        {
+            // NOTE to future self:
+            // Mana could use HSL scale with blue.
+            // The L value coudl follow this formula, assuming 100 max mana:
+            //     (mana / 100 * 0.8) + 0.1
+            // Basically, get the mana percentage, multiply it by 80%,
+            // and add 0.1. This will Make the minimum lightness 0.1 and the max 0.9/
+            // This will leave some nice dark and light blues for the mana bar.
+
+            var pct = GetBrightnessValue(current, max);
+
+            return ColorHelper.ColorFromHSL(BlueHue, lightness: pct);
+        }
+
+        public static double GetBrightnessValue(ManaPoint num, ManaPoint denom)
+        {
+            var pct = num.Value * 1.0 / denom.Value;
+            pct *= range;
+            return pct + minLightness;
+        }
+    }
+}