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using SkiaSharp;
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 SKColor GetFilteredColor(SKBitmap image)
{
var color = GetColor(image);
// 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.Red, color.Green, color.Blue);
if (luminosity < CutOffLuminosity)
{
color = new SKColor(
(byte)Math.Min(CutOffLuminosity + color.Red, byte.MaxValue),
(byte)Math.Min(CutOffLuminosity + color.Green, byte.MaxValue),
(byte)Math.Min(CutOffLuminosity + color.Blue, byte.MaxValue));
}
return color;
}
public static SKColor GetColor(SKBitmap 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;
#pragma warning disable IDE0059 // Unnecessary assignment
int xStep = w8 / ColorsPerLine;
int yStep = h8 / ColorsPerLine;
#pragma warning restore IDE0059
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;
SKColor pixel = buffer[offset];
byte cr = pixel.Red;
byte cg = pixel.Green;
byte cb = pixel.Blue;
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 new SKColor(bestCandidate.R, bestCandidate.G, bestCandidate.B);
}
public static SKColor[] GetBuffer(SKBitmap image)
{
var pixels = new SKColor[image.Width * image.Height];
for (int y = 0; y < image.Height; y++)
{
for (int x = 0; x < image.Width; x++)
{
pixels[x + y * image.Width] = image.GetPixel(x, y);
}
}
return pixels;
}
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);
}
}
}
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