Add overloads. Fix #1144

src/ImageSharp/Image.FromBytes.cs

@@ -37,6 +37,46 @@ namespace SixLabors.ImageSharp
             }
         }
 
+        /// <summary>
+        /// Reads the raw image information from the specified stream without fully decoding it.
+        /// </summary>
+        /// <param name="data">The byte array containing encoded image data to read the header from.</param>
+        /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
+        /// <returns>
+        /// The <see cref="IImageInfo"/> or null if suitable info detector not found.
+        /// </returns>
+        public static IImageInfo Identify(byte[] data) => Identify(data, out IImageFormat _);
+
+        /// <summary>
+        /// Reads the raw image information from the specified stream without fully decoding it.
+        /// </summary>
+        /// <param name="data">The byte array containing encoded image data to read the header from.</param>
+        /// <param name="format">The format type of the decoded image.</param>
+        /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
+        /// <returns>
+        /// The <see cref="IImageInfo"/> or null if suitable info detector not found.
+        /// </returns>
+        public static IImageInfo Identify(byte[] data, out IImageFormat format) => Identify(Configuration.Default, data, out format);
+
+        /// <summary>
+        /// Reads the raw image information from the specified stream without fully decoding it.
+        /// </summary>
+        /// <param name="config">The configuration.</param>
+        /// <param name="data">The byte array containing encoded image data to read the header from.</param>
+        /// <param name="format">The format type of the decoded image.</param>
+        /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
+        /// <returns>
+        /// The <see cref="IImageInfo"/> or null if suitable info detector is not found.
+        /// </returns>
+        public static IImageInfo Identify(Configuration config, byte[] data, out IImageFormat format)
+        {
+            config ??= Configuration.Default;
+            using (var stream = new MemoryStream(data))
+            {
+                return Identify(config, stream, out format);
+            }
+        }
+
         /// <summary>
         /// Load a new instance of <see cref="Image{Rgba32}"/> from the given encoded byte array.
         /// </summary>

src/ImageSharp/Image.FromFile.cs

@@ -31,13 +31,53 @@ namespace SixLabors.ImageSharp
         /// <returns>The mime type or null if none found.</returns>
         public static IImageFormat DetectFormat(Configuration config, string filePath)
         {
-            config = config ?? Configuration.Default;
+            config ??= Configuration.Default;
             using (Stream file = config.FileSystem.OpenRead(filePath))
             {
                 return DetectFormat(config, file);
             }
         }
 
+        /// <summary>
+        /// Reads the raw image information from the specified stream without fully decoding it.
+        /// </summary>
+        /// <param name="filePath">The image file to open and to read the header from.</param>
+        /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
+        /// <returns>
+        /// The <see cref="IImageInfo"/> or null if suitable info detector not found.
+        /// </returns>
+        public static IImageInfo Identify(string filePath) => Identify(filePath, out IImageFormat _);
+
+        /// <summary>
+        /// Reads the raw image information from the specified stream without fully decoding it.
+        /// </summary>
+        /// <param name="filePath">The image file to open and to read the header from.</param>
+        /// <param name="format">The format type of the decoded image.</param>
+        /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
+        /// <returns>
+        /// The <see cref="IImageInfo"/> or null if suitable info detector not found.
+        /// </returns>
+        public static IImageInfo Identify(string filePath, out IImageFormat format) => Identify(Configuration.Default, filePath, out format);
+
+        /// <summary>
+        /// Reads the raw image information from the specified stream without fully decoding it.
+        /// </summary>
+        /// <param name="config">The configuration.</param>
+        /// <param name="filePath">The image file to open and to read the header from.</param>
+        /// <param name="format">The format type of the decoded image.</param>
+        /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
+        /// <returns>
+        /// The <see cref="IImageInfo"/> or null if suitable info detector is not found.
+        /// </returns>
+        public static IImageInfo Identify(Configuration config, string filePath, out IImageFormat format)
+        {
+            config ??= Configuration.Default;
+            using (Stream file = config.FileSystem.OpenRead(filePath))
+            {
+                return Identify(config, file, out format);
+            }
+        }
+
         /// <summary>
         /// Create a new instance of the <see cref="Image"/> class from the given file.
         /// </summary>

src/ImageSharp/Image.FromStream.cs

@@ -34,7 +34,7 @@ namespace SixLabors.ImageSharp
             => WithSeekableStream(config, stream, s => InternalDetectFormat(s, config));
 
         /// <summary>
-        /// By reading the header on the provided stream this reads the raw image information.
+        /// Reads the raw image information from the specified stream without fully decoding it.
         /// </summary>
         /// <param name="stream">The image stream to read the header from.</param>
         /// <exception cref="NotSupportedException">Thrown if the stream is not readable.</exception>
@@ -44,7 +44,7 @@ namespace SixLabors.ImageSharp
         public static IImageInfo Identify(Stream stream) => Identify(stream, out IImageFormat _);
 
         /// <summary>
-        /// By reading the header on the provided stream this reads the raw image information.
+        /// Reads the raw image information from the specified stream without fully decoding it.
         /// </summary>
         /// <param name="stream">The image stream to read the header from.</param>
         /// <param name="format">The format type of the decoded image.</param>

tests/ImageSharp.Tests/Image/ImageTests.Identify.cs

@@ -0,0 +1,99 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.IO;
+using SixLabors.ImageSharp.Formats;
+
+using Xunit;
+
+// ReSharper disable InconsistentNaming
+namespace SixLabors.ImageSharp.Tests
+{
+    public partial class ImageTests
+    {
+        /// <summary>
+        /// Tests the <see cref="Image"/> class.
+        /// </summary>
+        public class Identify : ImageLoadTestBase
+        {
+            private static readonly string ActualImagePath = TestFile.GetInputFileFullPath(TestImages.Bmp.F);
+
+            private byte[] ActualImageBytes => TestFile.Create(TestImages.Bmp.F).Bytes;
+
+            private byte[] ByteArray => this.DataStream.ToArray();
+
+            private IImageInfo LocalImageInfo => this.localImageInfoMock.Object;
+
+            private IImageFormat LocalImageFormat => this.localImageFormatMock.Object;
+
+            private static readonly IImageFormat ExpectedGlobalFormat =
+                Configuration.Default.ImageFormatsManager.FindFormatByFileExtension("bmp");
+
+            [Fact]
+            public void FromBytes_GlobalConfiguration()
+            {
+                IImageInfo info = Image.Identify(this.ActualImageBytes, out IImageFormat type);
+
+                Assert.NotNull(info);
+                Assert.Equal(ExpectedGlobalFormat, type);
+            }
+
+            [Fact]
+            public void FromBytes_CustomConfiguration()
+            {
+                IImageInfo info = Image.Identify(this.LocalConfiguration, this.ByteArray, out IImageFormat type);
+
+                Assert.Equal(this.LocalImageInfo, info);
+                Assert.Equal(this.LocalImageFormat, type);
+            }
+
+            [Fact]
+            public void FromFileSystemPath_GlobalConfiguration()
+            {
+                IImageInfo info = Image.Identify(ActualImagePath, out IImageFormat type);
+
+                Assert.NotNull(info);
+                Assert.Equal(ExpectedGlobalFormat, type);
+            }
+
+            [Fact]
+            public void FromFileSystemPath_CustomConfiguration()
+            {
+                IImageInfo info = Image.Identify(this.LocalConfiguration, this.MockFilePath, out IImageFormat type);
+
+                Assert.Equal(this.LocalImageInfo, info);
+                Assert.Equal(this.LocalImageFormat, type);
+            }
+
+            [Fact]
+            public void FromStream_GlobalConfiguration()
+            {
+                using (var stream = new MemoryStream(this.ActualImageBytes))
+                {
+                    IImageInfo info = Image.Identify(stream, out IImageFormat type);
+
+                    Assert.NotNull(info);
+                    Assert.Equal(ExpectedGlobalFormat, type);
+                }
+            }
+
+            [Fact]
+            public void FromStream_CustomConfiguration()
+            {
+                IImageInfo info = Image.Identify(this.LocalConfiguration, this.DataStream, out IImageFormat type);
+
+                Assert.Equal(this.LocalImageInfo, info);
+                Assert.Equal(this.LocalImageFormat, type);
+            }
+
+            [Fact]
+            public void WhenNoMatchingFormatFound_ReturnsNull()
+            {
+                IImageInfo info = Image.Identify(new Configuration(), this.DataStream, out IImageFormat type);
+
+                Assert.Null(info);
+                Assert.Null(type);
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/Image/ImageTests.ImageLoadTestBase.cs

@@ -26,6 +26,8 @@ namespace SixLabors.ImageSharp.Tests
 
             protected Mock<IImageFormat> localImageFormatMock;
 
+            protected Mock<IImageInfo> localImageInfoMock;
+
             protected readonly string MockFilePath = Guid.NewGuid().ToString();
 
             internal readonly Mock<IFileSystem> LocalFileSystemMock = new Mock<IFileSystem>();
@@ -53,9 +55,12 @@ namespace SixLabors.ImageSharp.Tests
                 this.localStreamReturnImageRgba32 = new Image<Rgba32>(1, 1);
                 this.localStreamReturnImageAgnostic = new Image<Bgra4444>(1, 1);
 
+                this.localImageInfoMock = new Mock<IImageInfo>();
                 this.localImageFormatMock = new Mock<IImageFormat>();
 
-                this.localDecoder = new Mock<IImageDecoder>();
+                var detector = new Mock<IImageInfoDetector>();
+                detector.Setup(x => x.Identify(It.IsAny<Configuration>(), It.IsAny<Stream>())).Returns(this.localImageInfoMock.Object);
+                this.localDecoder = detector.As<IImageDecoder>();
                 this.localMimeTypeDetector = new MockImageFormatDetector(this.localImageFormatMock.Object);
 
                 this.localDecoder.Setup(x => x.Decode<Rgba32>(It.IsAny<Configuration>(), It.IsAny<Stream>()))
@@ -80,9 +85,7 @@ namespace SixLabors.ImageSharp.Tests
                         })
                     .Returns(this.localStreamReturnImageAgnostic);
 
-                this.LocalConfiguration = new Configuration
-                                              {
-                                              };
+                this.LocalConfiguration = new Configuration();
                 this.LocalConfiguration.ImageFormatsManager.AddImageFormatDetector(this.localMimeTypeDetector);
                 this.LocalConfiguration.ImageFormatsManager.SetDecoder(this.localImageFormatMock.Object, this.localDecoder.Object);