Make JFIF marker optional

src/ImageSharp/Formats/Jpeg/Components/Decoder/JFifMarker.cs

@@ -73,8 +73,7 @@ internal readonly struct JFifMarker : IEquatable<JFifMarker>
     {
         // Some images incorrectly use JFXX as the App0 marker (Issue 2478)
         if (ProfileResolver.IsProfile(bytes, ProfileResolver.JFifMarker)
-            || ProfileResolver.IsProfile(bytes, ProfileResolver.JFxxMarker)
-            || ProfileResolver.IsProfile(bytes, ProfileResolver.OSQidMaker))
+            || ProfileResolver.IsProfile(bytes, ProfileResolver.JFxxMarker))
         {
             byte majorVersion = bytes[5];
             byte minorVersion = bytes[6];

src/ImageSharp/Formats/Jpeg/Components/Decoder/ProfileResolver.cs

@@ -24,14 +24,6 @@ internal static class ProfileResolver
         (byte)'J', (byte)'F', (byte)'X', (byte)'X', (byte)'\0'
     };
 
-    /// <summary>
-    /// Gets the \n[ID or 10 91 73 68 32 specific markers.
-    /// </summary>
-    public static ReadOnlySpan<byte> OSQidMaker => new[]
-    {
-        (byte)'\n', (byte)'[', (byte)'I', (byte)'D', (byte)' '
-    };
-
     /// <summary>
     /// Gets the ICC specific markers.
     /// </summary>

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -753,10 +753,7 @@ internal sealed class JpegDecoderCore : IRawJpegData, IImageDecoderInternals
         Span<byte> temp = stackalloc byte[2 * 16 * 4];
 
         stream.Read(temp, 0, JFifMarker.Length);
-        if (!JFifMarker.TryParse(temp, out this.jFif))
-        {
-            JpegThrowHelper.ThrowNotSupportedException("Unknown App0 Marker - Expected JFIF.");
-        }
+        _ = JFifMarker.TryParse(temp, out this.jFif);
 
         remaining -= JFifMarker.Length;
 

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs

@@ -330,7 +330,7 @@ public partial class JpegDecoderTests
     [Theory]
     [WithFile(TestImages.Jpeg.Issues.Issue2564, PixelTypes.Rgba32)]
     public void Issue2564_DecodeWorks<TPixel>(TestImageProvider<TPixel> provider)
-    where TPixel : unmanaged, IPixel<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
     {
         using Image<TPixel> image = provider.GetImage(JpegDecoder.Instance);
         image.DebugSave(provider);