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ScrubNScrubN
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Stronger username visibility adjustment against colored backgrounds (#1555)
* Fix hue adjust detection not wrapping around for extremely low/high hues * Increase username hue adjust threshold * Add test render case for ChatRenderer.AdjustColorVisibility * Add proper asserts to ColorVisibilityTests.RenderTestPattern * Forgot .Index() is .NET 7+
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2 files changed

+138
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lines changed

‎TwitchDownloaderCore.Tests/ToolTests/ColorVisibilityTests.cs‎

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Original file line numberDiff line numberDiff line change
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using System.Reflection;
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using System.Runtime.CompilerServices;
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using SkiaSharp;
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namespace TwitchDownloaderCore.Tests.ToolTests
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{
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// ReSharper disable once InconsistentNaming
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public class ColorVisibilityTests
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{
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// AdjustColorVisibility should be extracted and made public at some point, but for now just use reflection
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private static readonly MethodInfo AdjustVisibilityMethodInfo = typeof(ChatRenderer).GetMethod("AdjustColorVisibility", BindingFlags.NonPublic | BindingFlags.Static)!;
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private static readonly Func<SKColor, SKColor, SKColor> AdjustVisibilityDelegate = (Func<SKColor, SKColor, SKColor>)Delegate.CreateDelegate(typeof(Func<SKColor, SKColor, SKColor>), AdjustVisibilityMethodInfo);
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[Fact]
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public void RenderTestPattern()
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{
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const int HUE_LEN = 360; // Hue sweep length
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const int SAT_LEN = 100; // Sweep height
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const int TILE_W = HUE_LEN + 40; // Tile width
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const int TILE_H = SAT_LEN + 40; // Tile height
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const int TILE_X_OFFSET = (TILE_W - HUE_LEN) / 2; // Tile inner-sweep X offset
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const int TILE_Y_OFFSET = (TILE_H - SAT_LEN) / 2; // Tile inner-sweep Y offset
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var imageInfo = new SKImageInfo(TILE_W * 6, TILE_H * 2);
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using var bitmap = new SKBitmap(imageInfo);
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using var canvas = new SKCanvas(bitmap);
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using var paint = new SKPaint();
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paint.BlendMode = SKBlendMode.Src;
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var backgrounds = new[] { SKColors.Black, SKColors.White, SKColors.Gray, SKColors.Red, SKColors.Blue, SKColors.Lime };
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for (var i = 0; i < backgrounds.Length; i++)
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{
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var background = backgrounds[i];
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var tileStartX = TILE_W * i;
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DrawTile(tileStartX, TILE_H * 0, background, false); // Row 0 (reference)
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DrawTile(tileStartX, TILE_H * 1, background, true); // Row 1 (adjusted)
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background.ToHsv(out var bgHue, out var bgSat, out _);
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if (bgSat > 28)
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{
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AssertPixelMatrix(tileStartX, bgHue, background);
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}
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}
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// WriteDebugBitmap(bitmap);
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return;
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void DrawTile(int startX, int startY, SKColor background, bool adjust)
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{
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paint.Color = background;
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canvas.DrawRect(startX, startY, TILE_W, TILE_H, paint);
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// Hue sweep
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for (var x = 0; x < HUE_LEN; x++)
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for (var y = 0; y < SAT_LEN; y++)
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{
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var color = SKColor.FromHsv(x, y, 100);
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if (adjust) color = AdjustVisibilityDelegate(color, background);
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paint.Color = color;
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canvas.DrawPoint(TILE_X_OFFSET + startX + x, TILE_Y_OFFSET + startY + y, paint);
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}
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// Value sweep
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for (var x = startX + TILE_X_OFFSET - 3; x < startX + TILE_X_OFFSET; x++)
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for (var y = 0; y < SAT_LEN; y++)
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{
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var color = SKColor.FromHsv(0, 0, 100 - y);
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if (adjust) color = AdjustVisibilityDelegate(color, background);
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paint.Color = color;
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canvas.DrawPoint(x, TILE_Y_OFFSET + startY + y, paint);
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}
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}
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void AssertPixelMatrix(int startX, float bgHue, SKColor background)
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{
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const int MATRIX_W = 9;
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const int MATRIX_H = 9;
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for (var x = -MATRIX_W; x <= MATRIX_W; x++)
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for (var y = -MATRIX_H; y <= MATRIX_H; y++)
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{
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var x2 = x + (int)bgHue;
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if (x2 < 0) x2 += HUE_LEN;
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x2 %= HUE_LEN;
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var y2 = y + SAT_LEN / 2;
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if (y2 < 0) y2 += SAT_LEN;
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y2 %= SAT_LEN;
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var sourcePx = bitmap.GetPixel(
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TILE_X_OFFSET + startX + x2,
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TILE_Y_OFFSET + TILE_H * 0 + y2
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);
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var actualPx = bitmap.GetPixel(
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TILE_X_OFFSET + startX + x2,
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TILE_Y_OFFSET + TILE_H * 1 + y2
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);
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Assert.NotEqual(background, actualPx);
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Assert.NotEqual(sourcePx, actualPx);
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}
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}
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}
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private static void WriteDebugBitmap(SKBitmap bitmap, string nameSuffix = "Output", [CallerFilePath] string filePath = "", [CallerMemberName] string methodName = "")
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{
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using var fs = new FileStream($"{Path.GetFileNameWithoutExtension(filePath)}.{methodName}_{nameSuffix}.png", FileMode.Create);
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bitmap.Encode(fs, SKEncodedImageFormat.Png, 100);
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}
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}
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}

‎TwitchDownloaderCore/ChatRenderer.cs‎

Lines changed: 25 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -1543,16 +1543,31 @@ private static SKColor AdjustColorVisibility(SKColor foreground, SKColor backgro
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// Adjust hue on colored backgrounds
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if (bgSat > 28 && fgSat > 28)
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{
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var hueDiff = fgHue - bgHue;
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const int HUE_THRESHOLD = 25;
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if (Math.Abs(hueDiff) < HUE_THRESHOLD)
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{
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var diffSign = hueDiff < 0 ? -1 : 1; // Math.Sign returns 1, -1, or 0. We only want 1 or -1.
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fgHue = bgHue + HUE_THRESHOLD * diffSign;
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if (fgHue < 0) fgHue += 360;
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fgHue %= 360;
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}
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const float HUE_WIDTH = 360;
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const int ADJUST_THRESHOLD = 35;
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Debug.Assert(ADJUST_THRESHOLD < HUE_WIDTH / 2);
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// Compute computer lower and higher hue diff to ensure we wrap around for reds
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// hue: [||||||||||]
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// not red: [ ^ ] ^
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// upper red: ^ [ ^ ]
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// lower red: [^ ]^
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var hueDiff1 = fgHue - (bgHue > HUE_WIDTH / 2 ? bgHue - HUE_WIDTH : bgHue);
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var hueDiff2 = fgHue - (bgHue > HUE_WIDTH / 2 ? bgHue : bgHue + HUE_WIDTH);
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// Take smallest diff, or skip if both are >ADJUST_THRESHOLD
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float hueDiff;
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if (Math.Abs(hueDiff1) <= ADJUST_THRESHOLD) hueDiff = hueDiff1;
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else if (Math.Abs(hueDiff2) <= ADJUST_THRESHOLD) hueDiff = hueDiff2;
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else goto SkipHueAdjust;
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var diffSign = hueDiff < 0 ? -1 : 1; // Math.Sign returns 1, -1, or 0. We only want 1 or -1.
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fgHue = bgHue + ADJUST_THRESHOLD * diffSign;
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if (fgHue < 0) fgHue += HUE_WIDTH;
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fgHue %= HUE_WIDTH;
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SkipHueAdjust: ;
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}
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return SKColor.FromHsl(fgHue, Math.Min(fgSat, 90), fgLight);

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