Handle incorrect colorspace metadata. Fix #882 (#885)

JimBobSquarePants · web-flow · commit 5a85ea72b552 · 2019-04-15T18:02:39.000+10:00
diff --git a/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs b/src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs
@@ -401,15 +401,14 @@ private JpegColorSpace DeduceJpegColorSpace()
 
             if (this.ComponentCount == 3)
             {
-                if (this.adobe.Equals(default) || this.adobe.ColorTransform == JpegConstants.Adobe.ColorTransformYCbCr)
-                {
-                    return JpegColorSpace.YCbCr;
-                }
-
-                if (this.adobe.ColorTransform == JpegConstants.Adobe.ColorTransformUnknown)
+                if (!this.adobe.Equals(default) && this.adobe.ColorTransform == JpegConstants.Adobe.ColorTransformUnknown)
                 {
                     return JpegColorSpace.RGB;
                 }
+
+                // Some images are poorly encoded and contain incorrect colorspace transform metadata.
+                // We ignore that and always fall back to the default colorspace.
+                return JpegColorSpace.YCbCr;
             }
 
             if (this.ComponentCount == 4)
@@ -419,7 +418,7 @@ private JpegColorSpace DeduceJpegColorSpace()
                     : JpegColorSpace.Cmyk;
             }
 
-            JpegThrowHelper.ThrowImageFormatException($"Unsupported color mode. Max components 4; found {this.ComponentCount}");
+            JpegThrowHelper.ThrowImageFormatException($"Unsupported color mode. Supported component counts 1, 3, and 4; found {this.ComponentCount}");
             return default;
         }
 
diff --git a/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Images.cs b/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.Images.cs
@@ -31,9 +31,12 @@ public partial class JpegDecoderTests
                 TestImages.Jpeg.Issues.ExifGetString750Load,
                 TestImages.Jpeg.Issues.ExifGetString750Transform,
 
-                // LibJpeg can open this despite the invalid desity units.
+                // LibJpeg can open this despite the invalid density units.
                 TestImages.Jpeg.Issues.Fuzz.ArgumentOutOfRangeException825B,
 
+                // LibJpeg can open this despite incorrect colorspace metadata.
+                TestImages.Jpeg.Issues.IncorrectColorspace855,
+
                 // High depth images
                 TestImages.Jpeg.Baseline.Testorig12bit,
             };
diff --git a/tests/ImageSharp.Tests/TestImages.cs b/tests/ImageSharp.Tests/TestImages.cs
@@ -175,6 +175,7 @@ public static class Issues
                 public const string ExifGetString750Transform = "Jpg/issues/issue750-exif-tranform.jpg";
                 public const string ExifGetString750Load = "Jpg/issues/issue750-exif-load.jpg";
                 public const string IncorrectQuality845 = "Jpg/issues/Issue845-Incorrect-Quality99.jpg";
+                public const string IncorrectColorspace855 = "Jpg/issues/issue855-incorrect-colorspace.jpg";
 
                 public static class Fuzz
                 {
diff --git a/tests/Images/External b/tests/Images/External
@@ -1 +1 @@
-Subproject commit 94b5a8e11b33ba62c15d1d03f1b8b721468764f1
+Subproject commit 802725dec2a6b1ca02f9e2f9a4c3f625583d0696
diff --git a/tests/Images/Input/Jpg/issues/issue855-incorrect-colorspace.jpg b/tests/Images/Input/Jpg/issues/issue855-incorrect-colorspace.jpg

Original file line number	Diff line number	Diff line change
`@@ -401,15 +401,14 @@ private JpegColorSpace DeduceJpegColorSpace()`
`401`	`401`
`402`	`402`	`if (this.ComponentCount == 3)`
`403`	`403`	`{`
`404`		`- if (this.adobe.Equals(default) \|\| this.adobe.ColorTransform == JpegConstants.Adobe.ColorTransformYCbCr)`
`405`		`- {`
`406`		`- return JpegColorSpace.YCbCr;`
`407`		`- }`
`408`		`-`
`409`		`- if (this.adobe.ColorTransform == JpegConstants.Adobe.ColorTransformUnknown)`
	`404`	`+ if (!this.adobe.Equals(default) && this.adobe.ColorTransform == JpegConstants.Adobe.ColorTransformUnknown)`
`410`	`405`	`{`
`411`	`406`	`return JpegColorSpace.RGB;`
`412`	`407`	`}`
	`408`	`+`
	`409`	`+ // Some images are poorly encoded and contain incorrect colorspace transform metadata.`
	`410`	`+ // We ignore that and always fall back to the default colorspace.`
	`411`	`+ return JpegColorSpace.YCbCr;`
`413`	`412`	`}`
`414`	`413`
`415`	`414`	`if (this.ComponentCount == 4)`
`@@ -419,7 +418,7 @@ private JpegColorSpace DeduceJpegColorSpace()`
`419`	`418`	`: JpegColorSpace.Cmyk;`
`420`	`419`	`}`
`421`	`420`
`422`		`- JpegThrowHelper.ThrowImageFormatException($"Unsupported color mode. Max components 4; found {this.ComponentCount}");`
	`421`	`+ JpegThrowHelper.ThrowImageFormatException($"Unsupported color mode. Supported component counts 1, 3, and 4; found {this.ComponentCount}");`
`423`	`422`	`return default;`
`424`	`423`	`}`
`425`	`424`
Original file line number	Diff line number	Diff line change
`@@ -175,6 +175,7 @@ public static class Issues`
`175`	`175`	`public const string ExifGetString750Transform = "Jpg/issues/issue750-exif-tranform.jpg";`
`176`	`176`	`public const string ExifGetString750Load = "Jpg/issues/issue750-exif-load.jpg";`
`177`	`177`	`public const string IncorrectQuality845 = "Jpg/issues/Issue845-Incorrect-Quality99.jpg";`
	`178`	`+ public const string IncorrectColorspace855 = "Jpg/issues/issue855-incorrect-colorspace.jpg";`
`178`	`179`
`179`	`180`	`public static class Fuzz`
`180`	`181`	`{`