Better exceptions for images with degenerate dimensions

src/ImageSharp/Common/Exceptions/ImageFormatException.cs

@@ -7,7 +7,7 @@ namespace SixLabors.ImageSharp
 {
     /// <summary>
     /// The exception that is thrown when the library tries to load
-    /// an image, which has an invalid format.
+    /// an image, which has format or content that is invalid or unsupported by ImageSharp.
     /// </summary>
     public class ImageFormatException : Exception
     {

src/ImageSharp/Formats/IImageDecoder.cs

@@ -18,6 +18,7 @@ namespace SixLabors.ImageSharp.Formats
         /// <param name="configuration">The configuration for the image.</param>
         /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
         /// <returns>The <see cref="Image{TPixel}"/>.</returns>
+        // TODO: Document ImageFormatExceptions (https://github.com/SixLabors/ImageSharp/issues/1110)
         Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             where TPixel : struct, IPixel<TPixel>;
 
@@ -27,6 +28,7 @@ namespace SixLabors.ImageSharp.Formats
         /// <param name="configuration">The configuration for the image.</param>
         /// <param name="stream">The <see cref="Stream"/> containing image data.</param>
         /// <returns>The <see cref="Image"/>.</returns>
+        // TODO: Document ImageFormatExceptions (https://github.com/SixLabors/ImageSharp/issues/1110)
         Image Decode(Configuration configuration, Stream stream);
     }
 }

src/ImageSharp/Formats/Jpeg/JpegDecoder.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System.IO;
+using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Jpeg
@@ -22,10 +23,19 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         {
             Guard.NotNull(stream, nameof(stream));
 
-            using (var decoder = new JpegDecoderCore(configuration, this))
+            using var decoder = new JpegDecoderCore(configuration, this);
+            try
             {
                 return decoder.Decode<TPixel>(stream);
             }
+            catch (InvalidMemoryOperationException ex)
+            {
+                (int w, int h) = (decoder.ImageWidth, decoder.ImageHeight);
+
+                // TODO: use InvalidImageContentException here, if we decide to define it
+                // https://github.com/SixLabors/ImageSharp/issues/1110
+                throw new ImageFormatException($"Can not decode the image having degenerate dimensions of {w}x{h}.", ex);
+            }
         }
 
         /// <inheritdoc />

src/ImageSharp/Memory/InvalidMemoryOperationException.cs

@@ -6,7 +6,8 @@ using System;
 namespace SixLabors.ImageSharp.Memory
 {
     /// <summary>
-    /// Exception thrown on invalid memory (allocation) requests.
+    /// Exception thrown when the library detects an invalid memory allocation request,
+    /// or an attempt has been made to use an invalidated <see cref="IMemoryGroup{T}"/>.
     /// </summary>
     public class InvalidMemoryOperationException : InvalidOperationException
     {

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

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using Microsoft.DotNet.RemoteExecutor;
+using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests.TestUtilities;
 using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
@@ -48,7 +49,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 
         [Theory]
         [WithFileCollection(nameof(UnrecoverableTestJpegs), PixelTypes.Rgba32)]
-        public void UnrecoverableImagesShouldThrowCorrectError<TPixel>(TestImageProvider<TPixel> provider)
+        public void UnrecoverableImage_Throws_ImageFormatException<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel> => Assert.Throws<ImageFormatException>(provider.GetImage);
     }
 }

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

@@ -105,6 +105,18 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                 appendPixelTypeToFileName: false);
         }
 
+        [Theory]
+        [WithFile(TestImages.Jpeg.Baseline.Floorplan, PixelTypes.Rgba32)]
+        [WithFile(TestImages.Jpeg.Progressive.Festzug, PixelTypes.Rgba32)]
+        public void DegenerateMemoryRequest_ShouldTranslateTo_ImageFormatException<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            provider.LimitAllocatorBufferCapacity(100);
+            ImageFormatException ex = Assert.Throws<ImageFormatException>(provider.GetImage);
+            this.Output.WriteLine(ex.Message);
+            Assert.IsType<InvalidMemoryOperationException>(ex.InnerException);
+        }
+
         // DEBUG ONLY!
         // The PDF.js output should be saved by "tests\ImageSharp.Tests\Formats\Jpg\pdfjs\jpeg-converter.htm"
         // into "\tests\Images\ActualOutput\JpegDecoderTests\"