Initial Commit towards WebP

src/ImageSharp/Formats/WebP/Readme.md

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+= WebP Format
+Reference implementation, specification and stuff like that:
+https://developers.google.com/speed/webp
+

src/ImageSharp/Formats/WebP/WebPConstants.cs

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+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Collections.Generic;
+
+namespace SixLabors.ImageSharp.Formats.WebP
+{
+    internal static class WebPConstants
+    {
+        /// <summary>
+        /// The list of file extensions that equate to WebP.
+        /// </summary>
+        public static readonly IEnumerable<string> FileExtensions = new[] { "webp" };
+
+        /// <summary>
+        /// The list of mimetypes that equate to a jpeg.
+        /// </summary>
+        public static readonly IEnumerable<string> MimeTypes = new[] { "image/webp", };
+    }
+}

src/ImageSharp/Formats/WebP/WebPDecoder.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace SixLabors.ImageSharp.Formats.WebP
+{
+    public sealed class WebPDecoder : IImageDecoder
+    {
+    }
+}

src/ImageSharp/Formats/WebP/WebPFormat.cs

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+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Collections.Generic;
+
+namespace SixLabors.ImageSharp.Formats.WebP
+{
+    /// <summary>
+    /// Registers the image encoders, decoders and mime type detectors for the WebP format
+    /// </summary>
+    public sealed class WebPFormat : IImageFormat<WebPMetadata>
+    {
+        /// <summary>
+        /// Gets the current instance.
+        /// </summary>
+        public static WebPFormat Instance { get; } = new WebPFormat();
+
+        /// <inheritdoc/>
+        public string Name => "WebP";
+
+        /// <inheritdoc/>
+        public string DefaultMimeType => "image/webp";
+
+        /// <inheritdoc/>
+        public IEnumerable<string> MimeTypes => WebPConstants.MimeTypes;
+
+        /// <inheritdoc/>
+        public IEnumerable<string> FileExtensions => WebPConstants.FileExtensions;
+
+        /// <inheritdoc/>
+        public WebPMetadata CreateDefaultFormatMetadata() => new WebPMetadata();
+    }
+}

src/ImageSharp/Formats/WebP/WebPImageFormatDetector.cs

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+using System;
+
+namespace SixLabors.ImageSharp.Formats.WebP
+{
+    /// <summary>
+    /// Detects WebP file headers
+    /// </summary>
+    public sealed class WebPImageFormatDetector : IImageFormatDetector
+    {
+        /// <inheritdoc />
+        public int HeaderSize => 12;
+
+        /// <inheritdoc />
+        public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+        {
+            return this.IsSupportedFileFormat(header) ? WebPFormat.Instance : null;
+        }
+
+        private bool IsSupportedFileFormat(ReadOnlySpan<byte> header)
+        {
+            return header.Length >= this.HeaderSize &&
+                   this.IsRiffContainer(header) &&
+                   this.IsWebPFile(header);
+        }
+
+        private bool IsRiffContainer(ReadOnlySpan<byte> header)
+        {
+            return header[0] == 0x52 && // R
+                   header[1] == 0x49 && // I
+                   header[2] == 0x46 && // F
+                   header[3] == 0x46; // F
+        }
+
+        private bool IsWebPFile(ReadOnlySpan<byte> header)
+        {
+            return header[8] == 0x57 && // W
+                   header[9] == 0x45 && // E
+                   header[10] == 0x42 && // B
+                   header[11] == 0x50; // P
+        }
+    }
+}

src/ImageSharp/Formats/WebP/WebPMetadata.cs

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+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+namespace SixLabors.ImageSharp.Formats.WebP
+{
+    /// <summary>
+    /// Provides WebP specific metadata information for the image.
+    /// </summary>
+    public class WebPMetadata : IDeepCloneable
+    {
+        /// <inheritdoc/>
+        public IDeepCloneable DeepClone() => throw new NotImplementedException();
+    }
+}