Add test for encode and reload planar tiff

src/ImageSharp/Formats/Tiff/TiffBitsPerPixel.cs

@@ -24,7 +24,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
         Bit8 = 8,
 
         /// <summary>
-        /// 14 bits per pixel. 4 bit for each color channel.
+        /// 12 bits per pixel. 4 bit for each color channel.
         ///
         /// Note: The TiffEncoder does not yet support 4 bits per color channel and will default to 24 bits per pixel.
         /// </summary>

tests/ImageSharp.Tests/Formats/Tiff/TiffEncoderTests.cs

@@ -248,6 +248,12 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
             Assert.Equal(expectedCompression, frameMetaData.Compression);
         }
 
+        // This makes sure, that when decoding a planar tiff, the planar configuration is not carried over to the encoded image.
+        [Theory]
+        [WithFile(FlowerRgb444Planar, PixelTypes.Rgba32)]
+        public void TiffEncoder_EncodePlanar_AndReload_Works<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel> => TestTiffEncoderCore(provider, TiffBitsPerPixel.Bit24, TiffPhotometricInterpretation.Rgb, imageDecoder: new TiffDecoder());
+
         [Theory]
         [WithFile(Calliphora_RgbUncompressed, PixelTypes.Rgba32)]
         public void TiffEncoder_EncodeRgb_Works<TPixel>(TestImageProvider<TPixel> provider)

tests/ImageSharp.Tests/Formats/Tiff/TiffMetadataTests.cs

@@ -293,7 +293,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
             Assert.Equal(exifProfileInput.GetValue(ExifTag.Copyright).Value, encodedImageExifProfile.GetValue(ExifTag.Copyright).Value);
 
             // Note that the encoded profile has PlanarConfiguration explicitly set, which is missing in the original image profile.
-            Assert.Equal((ushort)TiffPlanarConfiguration.Chunky, encodedImageExifProfile.GetValue(ExifTag.PlanarConfiguration).Value);
+            Assert.Equal((ushort)TiffPlanarConfiguration.Chunky, encodedImageExifProfile.GetValue(ExifTag.PlanarConfiguration)?.Value);
             Assert.Equal(exifProfileInput.Values.Count + 1, encodedImageExifProfile.Values.Count);
         }
     }