1 files changed, 192 insertions, 0 deletions
diff --git a/src/Ryujinx.Ava/UI/Windows/IconColorPicker.cs b/src/Ryujinx.Ava/UI/Windows/IconColorPicker.cs
new file mode 100644
index 00000000..a4c6287f
--- /dev/null
+++ b/src/Ryujinx.Ava/UI/Windows/IconColorPicker.cs
@@ -0,0 +1,192 @@
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+using System;
+using System.Collections.Generic;
+
+namespace Ryujinx.Ava.UI.Windows
+{
+    static class IconColorPicker
+    {
+        private const int ColorsPerLine = 64;
+        private const int TotalColors = ColorsPerLine * ColorsPerLine;
+
+        private const int UvQuantBits = 3;
+        private const int UvQuantShift = BitsPerComponent - UvQuantBits;
+
+        private const int SatQuantBits = 5;
+        private const int SatQuantShift = BitsPerComponent - SatQuantBits;
+
+        private const int BitsPerComponent = 8;
+
+        private const int CutOffLuminosity = 64;
+
+        private readonly struct PaletteColor
+        {
+            public int Qck { get; }
+            public byte R { get; }
+            public byte G { get; }
+            public byte B { get; }
+
+            public PaletteColor(int qck, byte r, byte g, byte b)
+            {
+                Qck = qck;
+                R = r;
+                G = g;
+                B = b;
+            }
+        }
+
+        public static Color GetFilteredColor(Image<Bgra32> image)
+        {
+            var color = GetColor(image).ToPixel<Bgra32>();
+
+            // We don't want colors that are too dark.
+            // If the color is too dark, make it brighter by reducing the range
+            // and adding a constant color.
+            int luminosity = GetColorApproximateLuminosity(color.R, color.G, color.B);
+            if (luminosity < CutOffLuminosity)
+            {
+                color = Color.FromRgb(
+                    (byte)Math.Min(CutOffLuminosity + color.R, byte.MaxValue),
+                    (byte)Math.Min(CutOffLuminosity + color.G, byte.MaxValue),
+                    (byte)Math.Min(CutOffLuminosity + color.B, byte.MaxValue));
+            }
+
+            return color;
+        }
+
+        public static Color GetColor(Image<Bgra32> image)
+        {
+            var colors = new PaletteColor[TotalColors];
+
+            var dominantColorBin = new Dictionary<int, int>();
+
+            var buffer = GetBuffer(image);
+
+            int w = image.Width;
+
+            int w8 = w << 8;
+            int h8 = image.Height << 8;
+
+            int xStep = w8 / ColorsPerLine;
+            int yStep = h8 / ColorsPerLine;
+
+            int i = 0;
+            int maxHitCount = 0;
+
+            for (int y = 0; y < image.Height; y++)
+            {
+                int yOffset = y * image.Width;
+
+                for (int x = 0; x < image.Width && i < TotalColors; x++)
+                {
+                    int offset = x + yOffset;
+
+                    byte cb = buffer[offset].B;
+                    byte cg = buffer[offset].G;
+                    byte cr = buffer[offset].R;
+
+                    var qck = GetQuantizedColorKey(cr, cg, cb);
+
+                    if (dominantColorBin.TryGetValue(qck, out int hitCount))
+                    {
+                        dominantColorBin[qck] = hitCount + 1;
+
+                        if (maxHitCount < hitCount)
+                        {
+                            maxHitCount = hitCount;
+                        }
+                    }
+                    else
+                    {
+                        dominantColorBin.Add(qck, 1);
+                    }
+
+                    colors[i++] = new PaletteColor(qck, cr, cg, cb);
+                }
+            }
+
+            int highScore = -1;
+            PaletteColor bestCandidate = default;
+
+            for (i = 0; i < TotalColors; i++)
+            {
+                var score = GetColorScore(dominantColorBin, maxHitCount, colors[i]);
+
+                if (highScore < score)
+                {
+                    highScore = score;
+                    bestCandidate = colors[i];
+                }
+            }
+
+            return Color.FromRgb(bestCandidate.R, bestCandidate.G, bestCandidate.B);
+        }
+
+        public static Bgra32[] GetBuffer(Image<Bgra32> image)
+        {
+            return image.TryGetSinglePixelSpan(out var data) ? data.ToArray() : Array.Empty<Bgra32>();
+        }
+
+        private static int GetColorScore(Dictionary<int, int> dominantColorBin, int maxHitCount, PaletteColor color)
+        {
+            var hitCount = dominantColorBin[color.Qck];
+            var balancedHitCount = BalanceHitCount(hitCount, maxHitCount);
+            var quantSat = (GetColorSaturation(color) >> SatQuantShift) << SatQuantShift;
+            var value = GetColorValue(color);
+
+            // If the color is rarely used on the image,
+            // then chances are that theres a better candidate, even if the saturation value
+            // is high. By multiplying the saturation value with a weight, we can lower
+            // it if the color is almost never used (hit count is low).
+            var satWeighted = quantSat;
+            var satWeight = balancedHitCount << 5;
+            if (satWeight < 0x100)
+            {
+                satWeighted = (satWeighted * satWeight) >> 8;
+            }
+
+            // Compute score from saturation and dominance of the color.
+            // We prefer more vivid colors over dominant ones, so give more weight to the saturation.
+            var score = ((satWeighted << 1) + balancedHitCount) * value;
+
+            return score;
+        }
+
+        private static int BalanceHitCount(int hitCount, int maxHitCount)
+        {
+            return (hitCount << 8) / maxHitCount;
+        }
+
+        private static int GetColorApproximateLuminosity(byte r, byte g, byte b)
+        {
+            return (r + g + b) / 3;
+        }
+
+        private static int GetColorSaturation(PaletteColor color)
+        {
+            int cMax = Math.Max(Math.Max(color.R, color.G), color.B);
+
+            if (cMax == 0)
+            {
+                return 0;
+            }
+
+            int cMin = Math.Min(Math.Min(color.R, color.G), color.B);
+            int delta = cMax - cMin;
+            return (delta << 8) / cMax;
+        }
+
+        private static int GetColorValue(PaletteColor color)
+        {
+            return Math.Max(Math.Max(color.R, color.G), color.B);
+        }
+
+        private static int GetQuantizedColorKey(byte r, byte g, byte b)
+        {
+            int u = ((-38 * r - 74 * g + 112 * b + 128) >> 8) + 128;
+            int v = ((112 * r - 94 * g - 18 * b + 128) >> 8) + 128;
+            return (v >> UvQuantShift) | ((u >> UvQuantShift) << UvQuantBits);
+        }
+    }
+}