Throw InvalidDataException when Skia cannot decode an image

src/BlurHashSharp.SkiaSharp/BlurHashEncoder.cs

@@ -15,9 +15,10 @@ public static class BlurHashEncoder
         /// <param name="yComponent">The number y components.</param>
         /// <param name="stream">The IO stream of an encoded image.</param>
         /// <returns>BlurHash representation of the image.</returns>
+        /// <exception cref="InvalidDataException">The image is in an unsupported format or could not be decoded.</exception>
         public static string Encode(int xComponent, int yComponent, Stream stream)
         {
-            using (SKCodec codec = SKCodec.Create(stream))
+            using (SKCodec codec = CreateCodec(stream))
             {
                 return Encode(xComponent, yComponent, codec);
             }
@@ -30,9 +31,11 @@ public static string Encode(int xComponent, int yComponent, Stream stream)
         /// <param name="yComponent">The number y components.</param>
         /// <param name="filename">The path to an encoded image on the file system.</param>
         /// <returns>BlurHash representation of the image.</returns>
+        /// <exception cref="FileNotFoundException">The file does not exist.</exception>
+        /// <exception cref="InvalidDataException">The image is in an unsupported format or could not be decoded.</exception>
         public static string Encode(int xComponent, int yComponent, string filename)
         {
-            using (SKCodec codec = SKCodec.Create(filename))
+            using (SKCodec codec = CreateCodec(filename))
             {
                 return Encode(xComponent, yComponent, codec);
             }
@@ -49,7 +52,7 @@ internal static string Encode(int xComponent, int yComponent, SKCodec codec)
                 ColorSpace = SKColorSpace.CreateSrgb()
             };
 
-            using (SKBitmap bitmap = SKBitmap.Decode(codec, newInfo))
+            using (SKBitmap bitmap = DecodeBitmap(codec, newInfo))
             {
                 return EncodeInternal(xComponent, yComponent, bitmap);
             }
@@ -64,9 +67,10 @@ internal static string Encode(int xComponent, int yComponent, SKCodec codec)
         /// <param name="maxWidth">The maximum width to resize the image to.</param>
         /// <param name="maxHeight">The maximum height to resize the image to.</param>
         /// <returns>BlurHash representation of the image.</returns>
+        /// <exception cref="InvalidDataException">The image is in an unsupported format or could not be decoded.</exception>
         public static string Encode(int xComponent, int yComponent, Stream stream, int maxWidth, int maxHeight)
         {
-            using (SKCodec codec = SKCodec.Create(stream))
+            using (SKCodec codec = CreateCodec(stream))
             {
                 return Encode(xComponent, yComponent, codec, maxWidth, maxHeight);
             }
@@ -81,9 +85,11 @@ public static string Encode(int xComponent, int yComponent, Stream stream, int m
         /// <param name="maxWidth">The maximum width to resize the image to.</param>
         /// <param name="maxHeight">The maximum height to resize the image to.</param>
         /// <returns>BlurHash representation of the image.</returns>
+        /// <exception cref="FileNotFoundException">The file does not exist.</exception>
+        /// <exception cref="InvalidDataException">The image is in an unsupported format or could not be decoded.</exception>
         public static string Encode(int xComponent, int yComponent, string filename, int maxWidth, int maxHeight)
         {
-            using (SKCodec codec = SKCodec.Create(filename))
+            using (SKCodec codec = CreateCodec(filename))
             {
                 return Encode(xComponent, yComponent, codec, maxWidth, maxHeight);
             }
@@ -111,7 +117,7 @@ internal static string Encode(int xComponent, int yComponent, SKCodec codec, int
                 ColorSpace = SKColorSpace.CreateSrgb()
             };
 
-            using (SKBitmap bitmap = SKBitmap.Decode(codec, newInfo))
+            using (SKBitmap bitmap = DecodeBitmap(codec, newInfo))
             {
                 if (scaleFactor == 0f)
                 {
@@ -129,6 +135,25 @@ internal static string Encode(int xComponent, int yComponent, SKCodec codec, int
             }
         }
 
+        private static SKCodec CreateCodec(Stream stream)
+            => SKCodec.Create(stream)
+                ?? throw new InvalidDataException("The stream does not contain an image in a format supported by SkiaSharp.");
+
+        private static SKCodec CreateCodec(string filename)
+        {
+            if (!File.Exists(filename))
+            {
+                throw new FileNotFoundException("The image file could not be found.", filename);
+            }
+
+            return SKCodec.Create(filename)
+                ?? throw new InvalidDataException($"The file '{filename}' does not contain an image in a format supported by SkiaSharp.");
+        }
+
+        private static SKBitmap DecodeBitmap(SKCodec codec, SKImageInfo info)
+            => SKBitmap.Decode(codec, info)
+                ?? throw new InvalidDataException("The image could not be decoded; the data is corrupt or truncated.");
+
         internal static string EncodeInternal(int xComponent, int yComponent, SKBitmap bitmap)
             => CoreBlurHashEncoder.Encode(xComponent, yComponent, bitmap.Width, bitmap.Height, bitmap.GetPixelSpan(), bitmap.RowBytes, PixelFormat.RGB888x);
     }

tests/BlurHashSharp.SkiaSharp.Tests/BlurHashEncoderInvalidInputTests.cs

@@ -0,0 +1,89 @@
+using System;
+using System.IO;
+using Xunit;
+
+namespace BlurHashSharp.SkiaSharp.Tests
+{
+    public class BlurHashEncoderInvalidInputTests
+    {
+        // A 64x96 progressive JPEG cut off half way through its first scan: Skia reads the header
+        // and creates a codec, but decoding the pixels fails with InvalidInput.
+        private static readonly string TruncatedImagePath = Path.Join(AppContext.BaseDirectory, "TestData", "truncated-progressive.jpg");
+
+        private static byte[] UnrecognizedData()
+        {
+            var data = new byte[2048];
+            for (int i = 0; i < data.Length; i++)
+            {
+                data[i] = (byte)i;
+            }
+
+            return data;
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Encode_UnrecognizedStream_ThrowsInvalidDataException(bool resize)
+        {
+            using var stream = new MemoryStream(UnrecognizedData());
+
+            Assert.Throws<InvalidDataException>(() => resize
+                ? BlurHashEncoder.Encode(4, 3, stream, 128, 128)
+                : BlurHashEncoder.Encode(4, 3, stream));
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Encode_UnrecognizedFile_ThrowsInvalidDataException(bool resize)
+        {
+            var path = Path.Join(Path.GetTempPath(), Path.GetRandomFileName() + ".jpg");
+            File.WriteAllBytes(path, UnrecognizedData());
+            try
+            {
+                Assert.Throws<InvalidDataException>(() => resize
+                    ? BlurHashEncoder.Encode(4, 3, path, 128, 128)
+                    : BlurHashEncoder.Encode(4, 3, path));
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Encode_TruncatedStream_ThrowsInvalidDataException(bool resize)
+        {
+            using var stream = File.OpenRead(TruncatedImagePath);
+
+            Assert.Throws<InvalidDataException>(() => resize
+                ? BlurHashEncoder.Encode(4, 3, stream, 32, 32)
+                : BlurHashEncoder.Encode(4, 3, stream));
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Encode_TruncatedFile_ThrowsInvalidDataException(bool resize)
+        {
+            Assert.Throws<InvalidDataException>(() => resize
+                ? BlurHashEncoder.Encode(4, 3, TruncatedImagePath, 32, 32)
+                : BlurHashEncoder.Encode(4, 3, TruncatedImagePath));
+        }
+
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void Encode_MissingFile_ThrowsFileNotFoundException(bool resize)
+        {
+            var path = Path.Join(Path.GetTempPath(), Path.GetRandomFileName() + ".png");
+
+            Assert.Throws<FileNotFoundException>(() => resize
+                ? BlurHashEncoder.Encode(4, 3, path, 128, 128)
+                : BlurHashEncoder.Encode(4, 3, path));
+        }
+    }
+}

tests/BlurHashSharp.SkiaSharp.Tests/BlurHashSharp.SkiaSharp.Tests.csproj

@@ -18,6 +18,10 @@
     <PackageReference Include="SkiaSharp.NativeAssets.Linux" Version="3.119.2" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Include="TestData/**" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="../../src/BlurHashSharp.SkiaSharp/BlurHashSharp.SkiaSharp.csproj" />
   </ItemGroup>