Don't force transparency

src/ImageSharp/PixelFormats/NamedColors{TPixel}.cs

@@ -746,10 +746,7 @@ namespace SixLabors.ImageSharp.PixelFormats
 
         private static TPixel[] GetPalette(Rgba32[] palette)
         {
-            // TODO: This should be the length only. 
-            // We need to fix and update tests/reference images.
-            // If someone wants transparency they should add it to the palette.
-            var converted = new TPixel[palette.Length + 1];
+            var converted = new TPixel[palette.Length];
 
             Span<byte> constantsBytes = MemoryMarshal.Cast<Rgba32, byte>(palette.AsSpan());
             PixelOperations<TPixel>.Instance.FromRgba32Bytes(

src/ImageSharp/Processing/KnownQuantizers.cs

@@ -12,26 +12,22 @@ namespace SixLabors.ImageSharp.Processing
     {
         /// <summary>
         /// Gets the adaptive Octree quantizer. Fast with good quality.
-        /// The quantizer only supports a single alpha value.
         /// </summary>
         public static IQuantizer Octree { get; } = new OctreeQuantizer();
 
         /// <summary>
         /// Gets the Xiaolin Wu's Color Quantizer which generates high quality output.
-        /// The quantizer supports multiple alpha values.
         /// </summary>
         public static IQuantizer Wu { get; } = new WuQuantizer();
 
         /// <summary>
         /// Gets the palette based quantizer consisting of web safe colors as defined in the CSS Color Module Level 4.
-        /// The quantizer supports a single alpha value.
         /// </summary>
         public static IQuantizer WebSafe { get; } = new WebSafePaletteQuantizer();
 
         /// <summary>
         /// Gets the palette based quantizer consisting of colors as defined in the original second edition of Werner’s Nomenclature of Colours 1821.
         /// The hex codes were collected and defined by Nicholas Rougeux <see href="https://www.c82.net/werner"/>
-        /// The quantizer supports a single alpha value.
         /// </summary>
         public static IQuantizer Werner { get; } = new WernerPaletteQuantizer();
     }

tests/ImageSharp.Tests/Quantization/QuantizedImageTests.cs

@@ -31,31 +31,6 @@ namespace SixLabors.ImageSharp.Tests
             Assert.True(wu.CreateFrameQuantizer<Rgba32>(this.Configuration).Dither);
         }
 
-        [Theory]
-        [WithFile(TestImages.Gif.Giphy, PixelTypes.Rgba32, true)]
-        [WithFile(TestImages.Gif.Giphy, PixelTypes.Rgba32, false)]
-        public void PaletteQuantizerYieldsCorrectTransparentPixel<TPixel>(
-            TestImageProvider<TPixel> provider,
-            bool dither)
-            where TPixel : struct, IPixel<TPixel>
-        {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                Assert.True(image[0, 0].Equals(default(TPixel)));
-
-                var quantizer = new WebSafePaletteQuantizer(dither);
-
-                foreach (ImageFrame<TPixel> frame in image.Frames)
-                {
-                    QuantizedFrame<TPixel> quantized =
-                        quantizer.CreateFrameQuantizer<TPixel>(this.Configuration).QuantizeFrame(frame);
-
-                    int index = this.GetTransparentIndex(quantized);
-                    Assert.Equal(index, quantized.GetPixelSpan()[0]);
-                }
-            }
-        }
-
         [Theory]
         [WithFile(TestImages.Gif.Giphy, PixelTypes.Rgba32, true)]
         [WithFile(TestImages.Gif.Giphy, PixelTypes.Rgba32, false)]

tests/Images/External

@@ -1 +1 @@
-Subproject commit f41ae0327a3ab21ab2388c32160bda67debcc082
+Subproject commit ed8a7b0b6fe1b2e2a7c822aa617103ae31192655