ReadOnlySpan<byte> overloads for Image.DetectFormat()

src/ImageSharp/Image.FromBytes.cs

@@ -175,6 +175,33 @@ namespace SixLabors.ImageSharp
 
 #if !NETSTANDARD1_1
 
+        /// <summary>
+        /// By reading the header on the provided byte array this calculates the images format.
+        /// </summary>
+        /// <param name="data">The byte array containing encoded image data to read the header from.</param>
+        /// <returns>The format or null if none found.</returns>
+        public static IImageFormat DetectFormat(ReadOnlySpan<byte> data)
+        {
+            return DetectFormat(Configuration.Default, data);
+        }
+
+        /// <summary>
+        /// By reading the header on the provided byte array this calculates the images format.
+        /// </summary>
+        /// <param name="config">The configuration.</param>
+        /// <param name="data">The byte array containing encoded image data to read the header from.</param>
+        /// <returns>The mime type or null if none found.</returns>
+        public static unsafe IImageFormat DetectFormat(Configuration config, ReadOnlySpan<byte> data)
+        {
+            fixed (byte* ptr = &data.GetPinnableReference())
+            {
+                using (var stream = new UnmanagedMemoryStream(ptr, data.Length))
+                {
+                    return DetectFormat(config, stream);
+                }
+            }
+        }
+
         /// <summary>
         /// Load a new instance of <see cref="Image{Rgba32}"/> from the given encoded byte span.
         /// </summary>

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

@@ -33,18 +33,27 @@ namespace SixLabors.ImageSharp.Tests
             private static readonly IImageFormat ExpectedGlobalFormat =
                 Configuration.Default.ImageFormatsManager.FindFormatByFileExtension("bmp");
 
-            [Fact]
-            public void FromBytes_GlobalConfiguration()
+            [Theory]
+            [InlineData(false)]
+            [InlineData(true)]
+            public void FromBytes_GlobalConfiguration(bool useSpan)
             {
-                IImageFormat type = Image.DetectFormat(this.ActualImageBytes);
-                
+                IImageFormat type = useSpan
+                                        ? Image.DetectFormat(this.ActualImageSpan)
+                                        : Image.DetectFormat(this.ActualImageBytes);
+
                 Assert.Equal(ExpectedGlobalFormat, type);
             }
 
-            [Fact]
-            public void FromBytes_CustomConfiguration()
+            [Theory]
+            [InlineData(false)]
+            [InlineData(true)]
+            public void FromBytes_CustomConfiguration(bool useSpan)
             {
-                IImageFormat type = Image.DetectFormat(this.LocalConfiguration, this.ByteArray);
+                IImageFormat type = useSpan
+                                        ? Image.DetectFormat(this.LocalConfiguration, this.ByteArray.AsSpan())
+                                        : Image.DetectFormat(this.LocalConfiguration, this.ByteArray);
+
                 Assert.Equal(this.LocalImageFormat, type);
             }