SixLabors · JimBobSquarePants · Nov 25, 2023 · Nov 24, 2023
diff --git a/src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs b/src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs
@@ -139,8 +139,8 @@ public static bool VerifyAndParse(this TiffDecoderCore options, ExifProfile exif
            options.OldJpegCompressionStartOfImageMarker = jpegInterchangeFormatValue.Value;
        }

-        options.ParseColorType(exifProfile);
        options.ParseCompression(frameMetadata.Compression, exifProfile);
+        options.ParseColorType(exifProfile);

        bool isTiled = VerifyRequiredFieldsArePresent(exifProfile, frameMetadata, options.PlanarConfiguration);

@@ -194,7 +194,9 @@ private static bool VerifyRequiredFieldsArePresent(ExifProfile exifProfile, Tiff
            }
        }

-        if (frameMetadata.BitsPerPixel == null)
+        // For BiColor compressed images, the BitsPerPixel value will be set explicitly to 1, so we don't throw in those cases.
+        // See: https://github.com/SixLabors/ImageSharp/issues/2587
+        if (frameMetadata.BitsPerPixel == null && !IsBiColorCompression(frameMetadata.Compression))
        {
            TiffThrowHelper.ThrowNotSupported("The TIFF BitsPerSample entry is missing which is required to decode the image!");
        }
@@ -570,6 +572,11 @@ private static void ParseCompression(this TiffDecoderCore options, TiffCompressi
                    options.FaxCompressionOptions = FaxCompressionOptions.None;
                }

+                // Some encoders do not set the BitsPerSample correctly, so we set those values here to the required values:
+                // https://github.com/SixLabors/ImageSharp/issues/2587
+                options.BitsPerSample = new TiffBitsPerSample(1, 0, 0);
+                options.BitsPerPixel = 1;
+
                break;
            }

@@ -585,12 +592,18 @@ private static void ParseCompression(this TiffDecoderCore options, TiffCompressi
                    options.FaxCompressionOptions = FaxCompressionOptions.None;
                }

+                options.BitsPerSample = new TiffBitsPerSample(1, 0, 0);
+                options.BitsPerPixel = 1;
+
                break;
            }

            case TiffCompression.Ccitt1D:
            {
                options.CompressionType = TiffDecoderCompressionType.HuffmanRle;
+                options.BitsPerSample = new TiffBitsPerSample(1, 0, 0);
+                options.BitsPerPixel = 1;
+
                break;
            }

@@ -645,4 +658,15 @@ private static void ParseCompression(this TiffDecoderCore options, TiffCompressi
            }
        }
    }
+
+    private static bool IsBiColorCompression(TiffCompression? compression)
+    {
+        if (compression is TiffCompression.Ccitt1D or TiffCompression.CcittGroup3Fax or
+            TiffCompression.CcittGroup4Fax)
+        {
+            return true;
+        }
+
+        return false;
+    }
 }
diff --git a/tests/ImageSharp.Tests/Formats/Tiff/TiffDecoderTests.cs b/tests/ImageSharp.Tests/Formats/Tiff/TiffDecoderTests.cs
@@ -665,6 +665,12 @@ public void TiffDecoder_CanDecode_Fax4CompressedWithStrips<TPixel>(TestImageProv
    public void TiffDecoder_CanDecode_TiledWithNonEqualWidthAndHeight<TPixel>(TestImageProvider<TPixel> provider)
        where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);

+    // https://github.com/SixLabors/ImageSharp/issues/2587
+    [Theory]
+    [WithFile(Issues2587, PixelTypes.Rgba32)]
+    public void TiffDecoder_CanDecode_BiColorWithMissingBitsPerSample<TPixel>(TestImageProvider<TPixel> provider)
+        where TPixel : unmanaged, IPixel<TPixel> => TestTiffDecoder(provider);
+
    [Theory]
    [WithFile(JpegCompressedGray0000539558, PixelTypes.Rgba32)]
    public void TiffDecoder_ThrowsException_WithCircular_IFD_Offsets<TPixel>(TestImageProvider<TPixel> provider)

diff --git a/tests/ImageSharp.Tests/TestImages.cs b/tests/ImageSharp.Tests/TestImages.cs
@@ -992,6 +992,7 @@ public static class Tiff
        public const string Issues2149 = "Tiff/Issues/Group4CompressionWithStrips.tiff";
        public const string Issues2255 = "Tiff/Issues/Issue2255.png";
        public const string Issues2435 = "Tiff/Issues/Issue2435.tiff";
+        public const string Issues2587 = "Tiff/Issues/Issue2587.tiff";
        public const string JpegCompressedGray0000539558 = "Tiff/Issues/JpegCompressedGray-0000539558.tiff";
        public const string Tiled0000023664 = "Tiff/Issues/tiled-0000023664.tiff";


diff --git a/tests/Images/Input/Tiff/Issues/Issue2587.tiff b/tests/Images/Input/Tiff/Issues/Issue2587.tiff