Fix reviewed issues

Author: JimBobSquarePants

src/ImageSharp/Color/Color.cs

@@ -105,7 +105,7 @@ public static Color FromPixel<TPixel>(TPixel source)
     public static void FromScaledVector(ReadOnlySpan<Vector4> source, Span<Color> destination)
     {
         Guard.DestinationShouldNotBeTooShort(source, destination, nameof(destination));
-        for (int i = 0; i < destination.Length; i++)
+        for (int i = 0; i < source.Length; i++)
         {
             destination[i] = FromScaledVector(source[i]);
         }
@@ -127,14 +127,14 @@ public static void FromPixel<TPixel>(ReadOnlySpan<TPixel> source, Span<Color> de
         PixelTypeInfo info = TPixel.GetPixelTypeInfo();
         if (info.ComponentInfo.HasValue && info.ComponentInfo.Value.GetMaximumComponentPrecision() <= (int)PixelComponentBitDepth.Bit32)
         {
-            for (int i = 0; i < destination.Length; i++)
+            for (int i = 0; i < source.Length; i++)
             {
                 destination[i] = FromScaledVector(source[i].ToScaledVector4());
             }
         }
         else
         {
-            for (int i = 0; i < destination.Length; i++)
+            for (int i = 0; i < source.Length; i++)
             {
                 destination[i] = new Color(source[i]);
             }

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/PaletteTiffColor{TPixel}.cs

@@ -19,7 +19,9 @@ internal class PaletteTiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
     private readonly ushort bitsPerSample1;
     private readonly TiffExtraSampleType? extraSamplesType;
 
-    private readonly Vector4[] paletteVectors;
+    private readonly Vector4[] vectorPallete;
+    private readonly TPixel[] pixelPalette;
+
     private readonly float alphaScale;
     private readonly bool hasAlpha;
     private Color[]? paletteColors;
@@ -41,7 +43,7 @@ public PaletteTiffColor(TiffBitsPerSample bitsPerSample, ushort[] colorMap, Tiff
         int colorCount = 1 << this.bitsPerSample0;
 
         // TIFF PaletteColor uses ColorMap (tag 320 / 0x0140) which is RGB-only (no alpha).
-        this.paletteVectors = GeneratePaletteVectors(colorMap, colorCount);
+        this.vectorPallete = GenerateVectorPalette(colorMap, colorCount);
 
         // ExtraSamples (tag 338 / 0x0152) describes extra per-pixel samples stored in the image data stream.
         // For PaletteColor, any alpha is per pixel (stored alongside the index), not per palette entry.
@@ -54,10 +56,16 @@ public PaletteTiffColor(TiffBitsPerSample bitsPerSample, ushort[] colorMap, Tiff
         {
             ulong alphaMax = (1UL << this.bitsPerSample1) - 1;
             this.alphaScale = alphaMax > 0 ? 1f / alphaMax : 1f;
+            this.pixelPalette = [];
+        }
+        else
+        {
+            // Pre-generate pixel palette for non-alpha case for performance.
+            this.pixelPalette = GeneratePixelPalette(colorMap, colorCount);
         }
     }
 
-    public Color[] PaletteColors => this.paletteColors ??= GenerateColorPalette(this.paletteVectors);
+    public Color[] PaletteColors => this.paletteColors ??= GenerateColorPalette(this.vectorPallete);
 
     /// <inheritdoc/>
     public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)
@@ -66,7 +74,7 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
 
         if (this.hasAlpha)
         {
-            Color[] colors = this.paletteColors ??= GenerateColorPalette(this.paletteVectors);
+            Color[] colors = this.paletteColors ??= GenerateColorPalette(this.vectorPallete);
 
             // NOTE: ExtraSamples may report "AssociatedAlphaData". For PaletteColor, the stored color sample is the
             // palette index, not per-pixel RGB components, so the premultiplication concept is not representable
@@ -81,18 +89,19 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                     float alpha = bitReader.ReadBits(this.bitsPerSample1) * this.alphaScale;
 
                     // Defensive guard against malformed streams.
-                    if ((uint)index >= (uint)this.paletteVectors.Length)
+                    if ((uint)index >= (uint)this.vectorPallete.Length)
                     {
                         index = 0;
                     }
 
-                    Vector4 color = this.paletteVectors[index];
+                    Vector4 color = this.vectorPallete[index];
                     color.W = alpha;
 
                     pixelRow[x] = TPixel.FromScaledVector4(color);
 
                     // Best-effort palette update for downstream conversions.
                     // This is intentionally "last writer wins" with no per-pixel branch.
+                    // Performance is not an issue here since the constructor performs no actual transformations.
                     colors[index] = Color.FromScaledVector(color);
                 }
 
@@ -110,19 +119,19 @@ public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, in
                 int index = bitReader.ReadBits(this.bitsPerSample0);
 
                 // Defensive guard against malformed streams.
-                if ((uint)index >= (uint)this.paletteVectors.Length)
+                if ((uint)index >= (uint)this.pixelPalette.Length)
                 {
                     index = 0;
                 }
 
-                pixelRow[x] = TPixel.FromScaledVector4(this.paletteVectors[index]);
+                pixelRow[x] = this.pixelPalette[index];
             }
 
             bitReader.NextRow();
         }
     }
 
-    private static Vector4[] GeneratePaletteVectors(ushort[] colorMap, int colorCount)
+    private static Vector4[] GenerateVectorPalette(ushort[] colorMap, int colorCount)
     {
         Vector4[] palette = new Vector4[colorCount];
 
@@ -141,6 +150,25 @@ private static Vector4[] GeneratePaletteVectors(ushort[] colorMap, int colorCoun
         return palette;
     }
 
+    private static TPixel[] GeneratePixelPalette(ushort[] colorMap, int colorCount)
+    {
+        TPixel[] palette = new TPixel[colorCount];
+
+        const int rOffset = 0;
+        int gOffset = colorCount;
+        int bOffset = colorCount * 2;
+
+        for (int i = 0; i < palette.Length; i++)
+        {
+            float r = colorMap[rOffset + i] * InvMax;
+            float g = colorMap[gOffset + i] * InvMax;
+            float b = colorMap[bOffset + i] * InvMax;
+            palette[i] = TPixel.FromScaledVector4(new Vector4(r, g, b, 1f));
+        }
+
+        return palette;
+    }
+
     private static Color[] GenerateColorPalette(Vector4[] palette)
     {
         Color[] colors = new Color[palette.Length];

src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs

@@ -407,7 +407,7 @@ private static void ParseColorType(this TiffDecoderCore options, ExifProfile exi
                 if (exifProfile.TryGetValue(ExifTag.ColorMap, out IExifValue<ushort[]> value))
                 {
                     options.ColorMap = value.Value;
-                    if (options.BitsPerSample.Channels != 1)
+                    if (options.BitsPerSample.Channels is not 1 and not 2)
                     {
                         TiffThrowHelper.ThrowNotSupported("The number of samples in the TIFF BitsPerSample entry is not supported.");
                     }

src/ImageSharp/Formats/Tiff/TiffFrameMetadata.cs

@@ -33,7 +33,11 @@ private TiffFrameMetadata(TiffFrameMetadata other)
         this.InkSet = other.InkSet;
         this.EncodingWidth = other.EncodingWidth;
         this.EncodingHeight = other.EncodingHeight;
-        this.LocalColorTable = other.LocalColorTable;
+
+        if (other.LocalColorTable?.Length > 0)
+        {
+            this.LocalColorTable = other.LocalColorTable.Value.ToArray();
+        }
     }
 
     /// <summary>