Add encoders that cannot be used.

src/ImageSharp/Formats/Bmp/BmpEncoder.cs

@@ -29,6 +29,15 @@ public sealed class BmpEncoder : QuantizingImageEncoder
     /// </summary>
     public bool SupportTransparency { get; init; }
 
+    /// <inheritdoc cref="BmpDecoderOptions.ProcessedAlphaMask"/>
+    internal bool ProcessedAlphaMask { get; init; }
+
+    /// <inheritdoc cref="BmpDecoderOptions.SkipFileHeader"/>
+    internal bool SkipFileHeader { get; init; }
+
+    /// <inheritdoc cref="BmpDecoderOptions.UseDoubleHeight"/>
+    internal bool UseDoubleHeight { get; init; }
+
     /// <inheritdoc/>
     protected override void Encode<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
     {

src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs

@@ -3,6 +3,7 @@
 
 using System.Buffers;
 using System.Buffers.Binary;
+using System.IO;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Common.Helpers;
@@ -11,6 +12,7 @@ using SixLabors.ImageSharp.Metadata;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
 using SixLabors.ImageSharp.Processing.Processors.Quantization;
+using static System.Net.Mime.MediaTypeNames;
 
 namespace SixLabors.ImageSharp.Formats.Bmp;
 
@@ -92,6 +94,15 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
     /// </summary>
     private readonly IPixelSamplingStrategy pixelSamplingStrategy;
 
+    /// <inheritdoc cref="BmpDecoderOptions.ProcessedAlphaMask"/>
+    private readonly bool processedAlphaMask;
+
+    /// <inheritdoc cref="BmpDecoderOptions.SkipFileHeader"/>
+    private readonly bool skipFileHeader;
+
+    /// <inheritdoc cref="BmpDecoderOptions.UseDoubleHeight"/>
+    private readonly bool isDoubleHeight;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="BmpEncoderCore"/> class.
     /// </summary>
@@ -104,6 +115,9 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
         this.quantizer = encoder.Quantizer ?? KnownQuantizers.Octree;
         this.pixelSamplingStrategy = encoder.PixelSamplingStrategy;
         this.infoHeaderType = encoder.SupportTransparency ? BmpInfoHeaderType.WinVersion4 : BmpInfoHeaderType.WinVersion3;
+        this.processedAlphaMask = encoder.ProcessedAlphaMask;
+        this.skipFileHeader = encoder.SkipFileHeader;
+        this.isDoubleHeight = encoder.UseDoubleHeight;
     }
 
     /// <summary>
@@ -154,11 +168,23 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
             _ => BmpInfoHeader.SizeV3
         };
 
-        BmpInfoHeader infoHeader = this.CreateBmpInfoHeader(image.Width, image.Height, infoHeaderSize, bpp, bytesPerLine, metadata, iccProfileData);
+        // for ico/cur encoder.
+        int height = image.Height;
+        if (this.isDoubleHeight)
+        {
+            height <<= 1;
+        }
+
+        BmpInfoHeader infoHeader = this.CreateBmpInfoHeader(image.Width, height, infoHeaderSize, bpp, bytesPerLine, metadata, iccProfileData);
 
         Span<byte> buffer = stackalloc byte[infoHeaderSize];
 
-        WriteBitmapFileHeader(stream, infoHeaderSize, colorPaletteSize, iccProfileSize, infoHeader, buffer);
+        // for ico/cur encoder.
+        if (!this.skipFileHeader)
+        {
+            WriteBitmapFileHeader(stream, infoHeaderSize, colorPaletteSize, iccProfileSize, infoHeader, buffer);
+        }
+
         this.WriteBitmapInfoHeader(stream, infoHeader, buffer, infoHeaderSize);
         this.WriteImage(configuration, stream, image);
         WriteColorProfile(stream, iccProfileData, buffer);
@@ -455,6 +481,11 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
         {
             this.Write8BitColor(configuration, stream, image, colorPalette);
         }
+
+        if (this.processedAlphaMask)
+        {
+            ProcessedAlphaMask(stream, image);
+        }
     }
 
     /// <summary>
@@ -572,6 +603,11 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
                 stream.WriteByte(0);
             }
         }
+
+        if (this.processedAlphaMask)
+        {
+            ProcessedAlphaMask(stream, image);
+        }
     }
 
     /// <summary>
@@ -629,6 +665,11 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
                 stream.WriteByte(0);
             }
         }
+
+        if (this.processedAlphaMask)
+        {
+            ProcessedAlphaMask(stream, image);
+        }
     }
 
     /// <summary>
@@ -679,6 +720,11 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
                 stream.WriteByte(0);
             }
         }
+
+        if (this.processedAlphaMask)
+        {
+            ProcessedAlphaMask(stream, image);
+        }
     }
 
     /// <summary>
@@ -722,4 +768,35 @@ internal sealed class BmpEncoderCore : IImageEncoderInternals
 
         stream.WriteByte(indices);
     }
+
+    private static void ProcessedAlphaMask<TPixel>(Stream stream, Image<TPixel> image)
+         where TPixel : unmanaged, IPixel<TPixel>
+    {
+        Rgba32 rgba = default;
+        int arrayWidth = image.Width / 8;
+        int padding = arrayWidth % 4;
+        if (padding is not 0)
+        {
+            padding = 4 - padding;
+        }
+
+        Span<byte> mask = stackalloc byte[arrayWidth];
+        for (int y = image.Height - 1; y >= 0; y--)
+        {
+            mask.Clear();
+            for (int x = 0; x < image.Width; x++)
+            {
+                int bit = x % 8;
+                int i = x / 8;
+                TPixel pixel = image[x, y];
+                pixel.ToRgba32(ref rgba);
+                if (rgba.A is not 0)
+                {
+                    mask[i] &= unchecked((byte)(0b10000000 >> bit));
+                }
+            }
+
+            stream.Write(mask);
+        }
+    }
 }

src/ImageSharp/Formats/Cur/CurConfigurationModule.cs

@@ -13,8 +13,7 @@ public sealed class CurConfigurationModule : IImageFormatConfigurationModule
     /// <inheritdoc/>
     public void Configure(Configuration configuration)
     {
-        // TODO: CurEncoder
+        configuration.ImageFormatsManager.SetEncoder(CurFormat.Instance, new CurEncoder());
-        // configuration.ImageFormatsManager.SetEncoder(CurFormat.Instance, new CurEncoder());
         configuration.ImageFormatsManager.SetDecoder(CurFormat.Instance, CurDecoder.Instance);
         configuration.ImageFormatsManager.AddImageFormatDetector(new IconImageFormatDetector());
     }

src/ImageSharp/Formats/Cur/CurEncoder.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Cur;
+
+/// <summary>
+/// Image encoder for writing an image to a stream as a Windows Cursor.
+/// </summary>
+public sealed class CurEncoder : QuantizingImageEncoder
+{
+    /// <inheritdoc/>
+    protected override void Encode<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
+    {
+        CurEncoderCore encoderCore = new();
+        encoderCore.Encode(image, stream, cancellationToken);
+    }
+}

src/ImageSharp/Formats/Cur/CurEncoderCore.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Icon;
+
+namespace SixLabors.ImageSharp.Formats.Cur;
+
+internal sealed class CurEncoderCore : IconEncoderCore
+{
+    protected override void GetHeader(in Image image)
+    {
+        this.FileHeader = new(IconFileType.ICO, (ushort)image.Frames.Count);
+        this.Entries = image.Frames.Select(i =>
+        {
+            CurFrameMetadata metadata = i.Metadata.GetCurMetadata();
+            return metadata.ToIconDirEntry();
+        }).ToArray();
+    }
+}

src/ImageSharp/Formats/Ico/IcoConfigurationModule.cs

@@ -13,8 +13,7 @@ public sealed class IcoConfigurationModule : IImageFormatConfigurationModule
     /// <inheritdoc/>
     public void Configure(Configuration configuration)
     {
-        // TODO: IcoEncoder
+        configuration.ImageFormatsManager.SetEncoder(IcoFormat.Instance, new IcoEncoder());
-        // configuration.ImageFormatsManager.SetEncoder(IcoFormat.Instance, new IcoEncoder());
         configuration.ImageFormatsManager.SetDecoder(IcoFormat.Instance, IcoDecoder.Instance);
         configuration.ImageFormatsManager.AddImageFormatDetector(new IconImageFormatDetector());
     }

src/ImageSharp/Formats/Ico/IcoEncoder.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Ico;
+
+/// <summary>
+/// Image encoder for writing an image to a stream as a Windows Icon.
+/// </summary>
+public sealed class IcoEncoder : QuantizingImageEncoder
+{
+    /// <inheritdoc/>
+    protected override void Encode<TPixel>(Image<TPixel> image, Stream stream, CancellationToken cancellationToken)
+    {
+        IcoEncoderCore encoderCore = new();
+        encoderCore.Encode(image, stream, cancellationToken);
+    }
+}

src/ImageSharp/Formats/Ico/IcoEncoderCore.cs

@@ -0,0 +1,19 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Icon;
+
+namespace SixLabors.ImageSharp.Formats.Ico;
+
+internal sealed class IcoEncoderCore : IconEncoderCore
+{
+    protected override void GetHeader(in Image image)
+    {
+        this.FileHeader = new(IconFileType.ICO, (ushort)image.Frames.Count);
+        this.Entries = image.Frames.Select(i =>
+        {
+            IcoFrameMetadata metadata = i.Metadata.GetIcoMetadata();
+            return metadata.ToIconDirEntry();
+        }).ToArray();
+    }
+}

src/ImageSharp/Formats/Icon/IconAssert.cs

@@ -32,4 +32,18 @@ internal class IconAssert
 
         return v;
     }
+
+    internal static byte Is1ByteSize(int i)
+    {
+        if (i is 256)
+        {
+            return 0;
+        }
+        else if (i > byte.MaxValue)
+        {
+            throw new FormatException("Image size Too Large.");
+        }
+
+        return (byte)i;
+    }
 }

src/ImageSharp/Formats/Icon/IconDir.cs

@@ -25,4 +25,7 @@ internal struct IconDir(ushort reserved, IconFileType type, ushort count)
 
     public static IconDir Parse(in ReadOnlySpan<byte> data)
         => MemoryMarshal.Cast<byte, IconDir>(data)[0];
+
+    public unsafe void WriteTo(in Stream stream)
+        => stream.Write(MemoryMarshal.Cast<IconDir, byte>([this]));
 }

src/ImageSharp/Formats/Icon/IconDirEntry.cs

@@ -28,4 +28,7 @@ internal struct IconDirEntry
 
     public static IconDirEntry Parse(in ReadOnlySpan<byte> data)
         => MemoryMarshal.Cast<byte, IconDirEntry>(data)[0];
+
+    public unsafe void WriteTo(in Stream stream)
+        => stream.Write(MemoryMarshal.Cast<IconDirEntry, byte>([this]));
 }

src/ImageSharp/Formats/Icon/IconEncoderCore.cs

@@ -0,0 +1,69 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Diagnostics.CodeAnalysis;
+using SixLabors.ImageSharp.Formats.Bmp;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Formats.Icon;
+
+internal abstract class IconEncoderCore : IImageEncoderInternals
+{
+    protected IconDir FileHeader { get; set; }
+
+    protected IconDirEntry[]? Entries { get; set; }
+
+    public void Encode<TPixel>(
+        Image<TPixel> image,
+        Stream stream,
+        CancellationToken cancellationToken)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        Guard.NotNull(image, nameof(image));
+        Guard.NotNull(stream, nameof(stream));
+
+        IconAssert.CanSeek(stream);
+
+        // Stream may not at 0.
+        long basePosition = stream.Position;
+        this.GetHeader(image);
+
+        int dataOffset = IconDir.Size + (IconDirEntry.Size * this.Entries.Length);
+        _ = stream.Seek(dataOffset, SeekOrigin.Current);
+
+        for (int i = 0; i < image.Frames.Count; i++)
+        {
+            ImageFrame<TPixel> frame = image.Frames[i];
+            this.Entries[i].ImageOffset = (uint)stream.Position;
+            Image<TPixel> img = new(Configuration.Default, frame.PixelBuffer, new());
+
+            // Note: this encoder are not supported PNG Data.
+            BmpEncoder encoder = new()
+            {
+                ProcessedAlphaMask = true,
+                UseDoubleHeight = true,
+                SkipFileHeader = true,
+                SupportTransparency = false,
+                BitsPerPixel = this.Entries[i].BitCount is 0
+                    ? BmpBitsPerPixel.Pixel8
+                    : (BmpBitsPerPixel?)this.Entries[i].BitCount
+            };
+
+            encoder.Encode(img, stream);
+            this.Entries[i].BytesInRes = this.Entries[i].ImageOffset - (uint)stream.Position;
+        }
+
+        long endPosition = stream.Position;
+        _ = stream.Seek(basePosition, SeekOrigin.Begin);
+        this.FileHeader.WriteTo(stream);
+        foreach (IconDirEntry entry in this.Entries)
+        {
+            entry.WriteTo(stream);
+        }
+
+        _ = stream.Seek(endPosition, SeekOrigin.Begin);
+    }
+
+    [MemberNotNull(nameof(Entries))]
+    protected abstract void GetHeader(in Image image);
+}

src/ImageSharp/Metadata/ImageMetadata.cs

@@ -215,6 +215,7 @@ public sealed class ImageMetadata : IDeepCloneable<ImageMetadata>
         metadata = default;
         return false;
     }
+
     internal void SetFormatMetadata<TFormatMetadata>(IImageFormat<TFormatMetadata> key, TFormatMetadata value)
         where TFormatMetadata : class, IDeepCloneable
         => this.formatMetadata[key] = value;

tests/ImageSharp.Tests/Formats/Icon/Cur/CurEncoderTests.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Cur;
+using SixLabors.ImageSharp.PixelFormats;
+using static SixLabors.ImageSharp.Tests.TestImages.Cur;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Icon.Cur;
+
+[Trait("Format", "Cur")]
+public class CurEncoderTests
+{
+    private static CurEncoder CurEncoder => new();
+
+    public static readonly TheoryData<string> Files = new()
+    {
+        { WindowsMouse },
+    };
+
+    [Theory]
+    [MemberData(nameof(Files))]
+    public void Encode(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using Image<Rgba32> input = testFile.CreateRgba32Image();
+        using MemoryStream memStream = new();
+        input.Save(memStream, CurEncoder);
+
+        memStream.Seek(0, SeekOrigin.Begin);
+        CurDecoder.Instance.Decode(new(), memStream);
+    }
+}

tests/ImageSharp.Tests/Formats/Icon/Ico/IcoEncoderTests.cs

@@ -0,0 +1,32 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Ico;
+using SixLabors.ImageSharp.PixelFormats;
+using static SixLabors.ImageSharp.Tests.TestImages.Ico;
+
+namespace SixLabors.ImageSharp.Tests.Formats.Icon.Ico;
+
+[Trait("Format", "Icon")]
+public class IcoEncoderTests
+{
+    private static IcoEncoder CurEncoder => new();
+
+    public static readonly TheoryData<string> Files = new()
+    {
+        { Flutter },
+    };
+
+    [Theory]
+    [MemberData(nameof(Files))]
+    public void Encode(string imagePath)
+    {
+        TestFile testFile = TestFile.Create(imagePath);
+        using Image<Rgba32> input = testFile.CreateRgba32Image();
+        using MemoryStream memStream = new();
+        input.Save(memStream, CurEncoder);
+
+        memStream.Seek(0, SeekOrigin.Begin);
+        IcoDecoder.Instance.Decode(new(), memStream);
+    }
+}