From 7077473d71bff5029841bd51245d11c085e3900e Mon Sep 17 00:00:00 2001
From: Dmitry Pentin <riotbr3aker@gmail.com>
Date: Fri, 16 Jul 2021 12:57:12 +0300
Subject: [PATCH] Decoupled mcu size from the decoder, fixed SOF component
 bytes length check

---
 .../Formats/Jpeg/Components/Decoder/JpegFrame.cs   |  5 +++++
 src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs     | 14 +++-----------
 .../Formats/Jpg/ParseStreamTests.cs                |  6 +++---
 3 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegFrame.cs b/src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegFrame.cs
index 4baaab3868..b8f88cfe0e 100644
--- a/src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegFrame.cs
+++ b/src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegFrame.cs
@@ -89,6 +89,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// </summary>
         public int McusPerColumn { get; set; }
 
+        /// <summary>
+        /// Gets the mcu size of the image.
+        /// </summary>
+        public Size McuSize => new Size(this.McusPerLine, this.McusPerColumn);
+
         /// <summary>
         /// Gets the color depth, in number of bits per pixel.
         /// </summary>
diff --git a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
index 04495f1721..3c48aabee0 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
@@ -112,11 +112,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         /// <inheritdoc/>
         Size IImageDecoderInternals.Dimensions => this.Frame.PixelSize;
 
-        /// <summary>
-        /// Gets the number of MCU blocks in the image as <see cref="Size"/>.
-        /// </summary>
-        public Size ImageSizeInMCU { get; private set; }
-
         /// <summary>
         /// Gets a value indicating whether the metadata should be ignored when the image is being decoded.
         /// </summary>
@@ -834,6 +829,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
             byte componentCount = this.temp[5];
             this.ColorSpace = this.DeduceJpegColorSpace(componentCount);
 
+            this.Metadata.GetJpegMetadata().ColorType = this.ColorSpace == JpegColorSpace.Grayscale ? JpegColorType.Luminance : JpegColorType.YCbCr;
+
             this.Frame = new JpegFrame
             {
                 Extended = frameMarker.Marker == JpegConstants.Markers.SOF1,
@@ -844,14 +841,12 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 ComponentCount = componentCount
             };
 
-            this.Metadata.GetJpegMetadata().ColorType = this.ColorSpace == JpegColorSpace.Grayscale ? JpegColorType.Luminance : JpegColorType.YCbCr;
-
             if (!metadataOnly)
             {
                 remaining -= length;
 
                 const int componentBytes = 3;
-                if (remaining > componentCount * componentBytes)
+                if (remaining != componentCount * componentBytes)
                 {
                     JpegThrowHelper.ThrowBadMarker("SOFn", remaining);
                 }
@@ -894,9 +889,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
                 this.Frame.MaxVerticalFactor = maxV;
                 this.Frame.InitComponents();
 
-                this.ImageSizeInMCU = new Size(this.Frame.McusPerLine, this.Frame.McusPerColumn);
-
-                // This can be injected in SOF marker callback
                 this.scanDecoder.InjectFrameData(this.Frame, this);
             }
         }
diff --git a/tests/ImageSharp.Tests/Formats/Jpg/ParseStreamTests.cs b/tests/ImageSharp.Tests/Formats/Jpg/ParseStreamTests.cs
index 2162ee13c6..e1307d3fc6 100644
--- a/tests/ImageSharp.Tests/Formats/Jpg/ParseStreamTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Jpg/ParseStreamTests.cs
@@ -48,7 +48,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 
                 Size expectedSizeInBlocks = decoder.ImageSizeInPixels.DivideRoundUp(8);
 
-                Assert.Equal(expectedSizeInBlocks, decoder.ImageSizeInMCU);
+                Assert.Equal(expectedSizeInBlocks, decoder.Frame.McuSize);
 
                 var uniform1 = new Size(1, 1);
                 JpegComponent c0 = decoder.Components[0];
@@ -70,7 +70,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
             using (JpegDecoderCore decoder = JpegFixture.ParseJpegStream(imageFile))
             {
                 sb.AppendLine(imageFile);
-                sb.AppendLine($"Size:{decoder.ImageSizeInPixels} MCU:{decoder.ImageSizeInMCU}");
+                sb.AppendLine($"Size:{decoder.ImageSizeInPixels} MCU:{decoder.Frame.McuSize}");
                 JpegComponent c0 = decoder.Components[0];
                 JpegComponent c1 = decoder.Components[1];
 
@@ -115,7 +115,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 
                 var uniform1 = new Size(1, 1);
 
-                Size expectedLumaSizeInBlocks = decoder.ImageSizeInMCU.MultiplyBy(fLuma);
+                Size expectedLumaSizeInBlocks = decoder.Frame.McuSize.MultiplyBy(fLuma);
 
                 Size divisor = fLuma.DivideBy(fChroma);