MakeTransparentBlack is now a png encoder option

src/ImageSharp/Formats/Png/IPngEncoderOptions.cs

@@ -62,5 +62,10 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// Gets the optimize method.
         /// </summary>
         PngChunkFilter? ChunkFilter { get; }
+
+        /// <summary>
+        /// Gets a value indicating whether fully transparent pixels should be converted to black pixels.
+        /// </summary>
+        bool MakeTransparentBlack { get; }
     }
 }

src/ImageSharp/Formats/Png/PngChunkFilter.cs

@@ -36,11 +36,6 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// </summary>
         ExcludeTextChunks = 1 << 3,
 
-        /// <summary>
-        /// Make fully transparent pixels black.
-        /// </summary>
-        MakeTransparentBlack = 16,
-
         /// <summary>
         /// All possible optimizations.
         /// </summary>

src/ImageSharp/Formats/Png/PngEncoder.cs

@@ -67,6 +67,11 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// </summary>
         public PngChunkFilter? ChunkFilter { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether fully transparent pixels should be converted to black pixels.
+        /// </summary>
+        public bool MakeTransparentBlack { get; set; }
+
         /// <summary>
         /// Encodes the image to the specified stream from the <see cref="Image{TPixel}"/>.
         /// </summary>

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -7,7 +7,7 @@ using System.Buffers.Binary;
 using System.IO;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Advanced;
+
 using SixLabors.ImageSharp.Formats.Png.Chunks;
 using SixLabors.ImageSharp.Formats.Png.Filters;
 using SixLabors.ImageSharp.Formats.Png.Zlib;
@@ -145,7 +145,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             PngMetadata pngMetadata = metadata.GetFormatMetadata(PngFormat.Instance);
             PngEncoderOptionsHelpers.AdjustOptions<TPixel>(this.options, pngMetadata, out this.use16Bit, out this.bytesPerPixel);
             IndexedImageFrame<TPixel> quantized;
-            if (((this.options.ChunkFilter ?? PngChunkFilter.None) & PngChunkFilter.MakeTransparentBlack) == PngChunkFilter.MakeTransparentBlack)
+            if (this.options.MakeTransparentBlack)
             {
                 using (Image<TPixel> tempImage = image.Clone())
                 {

src/ImageSharp/Formats/Png/PngEncoderOptions.cs

@@ -30,6 +30,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             this.Threshold = source.Threshold;
             this.InterlaceMethod = source.InterlaceMethod;
             this.ChunkFilter = source.ChunkFilter;
+            this.MakeTransparentBlack = source.MakeTransparentBlack;
         }
 
         /// <summary>
@@ -84,5 +85,8 @@ namespace SixLabors.ImageSharp.Formats.Png
         /// Gets or sets a the optimize method.
         /// </summary>
         public PngChunkFilter? ChunkFilter { get; set; }
+
+        /// <inheritdoc/>
+        public bool MakeTransparentBlack { get; set; }
     }
 }