Convert DetectFormat to the Try pattern

src/ImageSharp/Image.FromBytes.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Diagnostics.CodeAnalysis;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -15,18 +16,20 @@ public abstract partial class Image
     /// By reading the header on the provided byte span this calculates the images format.
     /// </summary>
     /// <param name="data">The byte span 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)
-        => DetectFormat(DecoderOptions.Default, data);
+    /// <param name="format">The format or null if none found.</param>
+    /// <returns>returns true when format was detected otherwise false.</returns>
+    public static bool TryDetectFormat(ReadOnlySpan<byte> data, [NotNullWhen(true)] out IImageFormat? format)
+        => TryDetectFormat(DecoderOptions.Default, data, out format);
 
     /// <summary>
     /// By reading the header on the provided byte span this calculates the images format.
     /// </summary>
     /// <param name="options">The general decoder options.</param>
     /// <param name="data">The byte span containing encoded image data to read the header from.</param>
+    /// <param name="format">The mime type or null if none found.</param>
     /// <exception cref="ArgumentNullException">The options are null.</exception>
-    /// <returns>The mime type or null if none found.</returns>
-    public static IImageFormat? DetectFormat(DecoderOptions options, ReadOnlySpan<byte> data)
+    /// <returns>returns true when format was detected otherwise false.</returns>
+    public static bool TryDetectFormat(DecoderOptions options, ReadOnlySpan<byte> data, [NotNullWhen(true)] out IImageFormat? format)
     {
         Guard.NotNull(options, nameof(options.Configuration));
 
@@ -34,18 +37,20 @@ public abstract partial class Image
         int maxHeaderSize = configuration.MaxHeaderSize;
         if (maxHeaderSize <= 0)
         {
-            return null;
+            format = null;
+            return false;
         }
 
         foreach (IImageFormatDetector detector in configuration.ImageFormatsManager.FormatDetectors)
         {
-            if (detector.TryDetectFormat(data, out IImageFormat? f))
+            if (detector.TryDetectFormat(data, out format))
             {
-                return f;
+                return true;
             }
         }
 
-        return default;
+        format = default;
+        return false;
     }
 
     /// <summary>

src/ImageSharp/Image.FromFile.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Diagnostics.CodeAnalysis;
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -15,23 +16,25 @@ public abstract partial class Image
     /// By reading the header on the provided file this calculates the images mime type.
     /// </summary>
     /// <param name="filePath">The image file to open and to read the header from.</param>
-    /// <returns>The mime type or null if none found.</returns>
-    public static IImageFormat DetectFormat(string filePath)
-        => DetectFormat(DecoderOptions.Default, filePath);
+    /// <param name="format">The mime type or null if none found.</param>
+    /// <returns>returns true when format was detected otherwise false.</returns>
+    public static bool TryDetectFormat(string filePath, [NotNullWhen(true)] out IImageFormat? format)
+        => TryDetectFormat(DecoderOptions.Default, filePath, out format);
 
     /// <summary>
     /// By reading the header on the provided file this calculates the images mime type.
     /// </summary>
     /// <param name="options">The general decoder options.</param>
     /// <param name="filePath">The image file to open and to read the header from.</param>
+    /// <param name="format">The mime type or null if none found.</param>
     /// <exception cref="ArgumentNullException">The configuration is null.</exception>
-    /// <returns>The mime type or null if none found.</returns>
-    public static IImageFormat DetectFormat(DecoderOptions options, string filePath)
+    /// <returns>returns true when format was detected otherwise false.</returns>
+    public static bool TryDetectFormat(DecoderOptions options, string filePath, [NotNullWhen(true)] out IImageFormat? format)
     {
         Guard.NotNull(options, nameof(options));
 
         using Stream file = options.Configuration.FileSystem.OpenRead(filePath);
-        return DetectFormat(options, file);
+        return TryDetectFormat(options, file, out format);
     }
 
     /// <summary>

src/ImageSharp/Image.FromStream.cs

@@ -19,23 +19,28 @@ public abstract partial class Image
     /// By reading the header on the provided stream this calculates the images format type.
     /// </summary>
     /// <param name="stream">The image stream to read the header from.</param>
+    /// <param name="format">The format type or null if none found.</param>
     /// <exception cref="ArgumentNullException">The stream is null.</exception>
     /// <exception cref="NotSupportedException">The stream is not readable.</exception>
-    /// <returns>The format type or null if none found.</returns>
-    public static IImageFormat DetectFormat(Stream stream)
-        => DetectFormat(DecoderOptions.Default, stream);
+    /// <returns>returns true when format was detected otherwise false.</returns>
+    public static bool TryDetectFormat(Stream stream, [NotNullWhen(true)] out IImageFormat? format)
+        => TryDetectFormat(DecoderOptions.Default, stream, out format);
 
     /// <summary>
     /// By reading the header on the provided stream this calculates the images format type.
     /// </summary>
     /// <param name="options">The general decoder options.</param>
     /// <param name="stream">The image stream to read the header from.</param>
+    /// <param name="format">The format type or null if none found.</param>
     /// <exception cref="ArgumentNullException">The options are null.</exception>
     /// <exception cref="ArgumentNullException">The stream is null.</exception>
     /// <exception cref="NotSupportedException">The stream is not readable.</exception>
-    /// <returns>The format type or null if none found.</returns>
-    public static IImageFormat DetectFormat(DecoderOptions options, Stream stream)
-        => WithSeekableStream(options, stream, s => InternalDetectFormat(options.Configuration, s));
+    /// <returns>returns true when format was detected otherwise false.</returns>
+    public static bool TryDetectFormat(DecoderOptions options, Stream stream, [NotNullWhen(true)] out IImageFormat? format)
+    {
+        format = WithSeekableStream(options, stream, s => InternalDetectFormat(options.Configuration, s));
+        return format != null;
+    }
 
     /// <summary>
     /// By reading the header on the provided stream this calculates the images format type.

tests/ImageSharp.Tests/Formats/ImageFormatManagerTests.cs

@@ -122,7 +122,13 @@ public class ImageFormatManagerTests
 
         byte[] invalidImage = { 1, 2, 3 };
 
-        Assert.Equal(Image.DetectFormat(jpegImage), JpegFormat.Instance);
-        Assert.True(Image.DetectFormat(invalidImage) is null);
+        bool resultValidImage = Image.TryDetectFormat(jpegImage, out IImageFormat format);
+
+        bool resultInvalidImage = Image.TryDetectFormat(invalidImage, out IImageFormat formatInvalid);
+
+        Assert.True(resultValidImage);
+        Assert.Equal(format, JpegFormat.Instance);
+        Assert.False(resultInvalidImage);
+        Assert.True(formatInvalid is null);
     }
 }

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

@@ -34,8 +34,9 @@ public partial class ImageTests
         [Fact]
         public void FromBytes_GlobalConfiguration()
         {
-            IImageFormat type = Image.DetectFormat(this.ActualImageSpan);
+            bool result = Image.TryDetectFormat(this.ActualImageSpan, out IImageFormat type);
 
+            Assert.True(result);
             Assert.Equal(ExpectedGlobalFormat, type);
         }
 
@@ -47,15 +48,18 @@ public partial class ImageTests
                 Configuration = this.LocalConfiguration
             };
 
-            IImageFormat type = Image.DetectFormat(options, this.ByteArray);
+            bool result = Image.TryDetectFormat(options, this.ByteArray, out IImageFormat type);
 
+            Assert.True(result);
             Assert.Equal(this.LocalImageFormat, type);
         }
 
         [Fact]
         public void FromFileSystemPath_GlobalConfiguration()
         {
-            IImageFormat type = Image.DetectFormat(ActualImagePath);
+            bool result = Image.TryDetectFormat(ActualImagePath, out IImageFormat type);
+
+            Assert.True(result);
             Assert.Equal(ExpectedGlobalFormat, type);
         }
 
@@ -67,7 +71,9 @@ public partial class ImageTests
                 Configuration = this.LocalConfiguration
             };
 
-            IImageFormat type = Image.DetectFormat(options, this.MockFilePath);
+            bool result = Image.TryDetectFormat(options, this.MockFilePath, out IImageFormat type);
+
+            Assert.True(result);
             Assert.Equal(this.LocalImageFormat, type);
         }
 
@@ -76,7 +82,9 @@ public partial class ImageTests
         {
             using (var stream = new MemoryStream(this.ActualImageBytes))
             {
-                IImageFormat type = Image.DetectFormat(stream);
+                bool result = Image.TryDetectFormat(stream, out IImageFormat type);
+
+                Assert.True(result);
                 Assert.Equal(ExpectedGlobalFormat, type);
             }
         }
@@ -89,7 +97,9 @@ public partial class ImageTests
                 Configuration = this.LocalConfiguration
             };
 
-            IImageFormat type = Image.DetectFormat(options, this.DataStream);
+            bool result = Image.TryDetectFormat(options, this.DataStream, out IImageFormat type);
+
+            Assert.True(result);
             Assert.Equal(this.LocalImageFormat, type);
         }
 
@@ -101,7 +111,9 @@ public partial class ImageTests
                 Configuration = new()
             };
 
-            IImageFormat type = Image.DetectFormat(options, this.DataStream);
+            bool result = Image.TryDetectFormat(options, this.DataStream, out IImageFormat type);
+
+            Assert.False(result);
             Assert.Null(type);
         }