Clamp JPEG quality estimation results.

Signed-off-by: antonfirsov <antonfir@gmail.com>

src/ImageSharp/Formats/Jpeg/Components/Quantization.cs

@@ -147,7 +147,7 @@ public static int EstimateQuality(ref Block8x8F table, ReadOnlySpan<byte> target
                 quality = (int)Math.Round(5000.0 / sumPercent);
             }
 
-            return quality;
+        return Numerics.Clamp(quality, MinQualityFactor, MaxQualityFactor);
         }
 
         /// <summary>

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

@@ -10,6 +10,7 @@
 using SixLabors.ImageSharp.Metadata.Profiles.Exif;
 using SixLabors.ImageSharp.Metadata.Profiles.Icc;
 using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Processing;
 
 using Xunit;
 
@@ -361,6 +362,32 @@ public void EncodedStringTags_Read()
             {
                 ExifProfile exif = image.Metadata.ExifProfile;
                 VerifyEncodedStrings(exif);
+    }
+
+    // https://github.com/SixLabors/ImageSharp/issues/2758
+    [Theory]
+    [WithFile(TestImages.Jpeg.Issues.Issue2758, PixelTypes.L8)]
+    public void Issue2758_DecodeWorks<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        using Image<TPixel> image = provider.GetImage(JpegDecoder.Instance);
+
+        Assert.Equal(59787, image.Width);
+        Assert.Equal(511, image.Height);
+
+        JpegMetadata meta = image.Metadata.GetJpegMetadata();
+
+        // Quality determination should be between 1-100.
+        Assert.Equal(15, meta.LuminanceQuality);
+        Assert.Equal(1, meta.ChrominanceQuality);
+
+        // We want to test the encoder to ensure the determined values can be encoded but not by encoding
+        // the full size image as it would be too slow.
+        // We will crop the image to a smaller size and then encode it.
+        image.Mutate(x => x.Crop(new(0, 0, 100, 100)));
+
+        using MemoryStream ms = new();
+        image.Save(ms, new JpegEncoder());
             }
         }
 

tests/ImageSharp.Tests/TestImages.cs

@@ -269,6 +269,7 @@ public static class Issues
                 public const string ValidExifArgumentNullExceptionOnEncode = "Jpg/issues/Issue2087-exif-null-reference-on-encode.jpg";
                 public const string Issue2133DeduceColorSpace = "Jpg/issues/Issue2133.jpg";
                 public const string HangBadScan = "Jpg/issues/Hang_C438A851.jpg";
+            public const string Issue2758 = "Jpg/issues/issue-2758.jpg";
 
                 public static class Fuzz
                 {