Add tests for tiff encoder options

src/ImageSharp/Formats/Tiff/Compression/T4BitReader.cs

@@ -6,7 +6,6 @@ using System.Buffers;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
-using SixLabors.ImageSharp.Formats.Experimental.Tiff.Utils;
 using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp.Formats.Experimental.Tiff.Compression

src/ImageSharp/Formats/Tiff/Compression/T4BitWriter.cs

@@ -314,9 +314,10 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff.Compression
             }
 
             // Write the compressed data to the stream.
-            stream.Write(compressedData.Slice(0, this.bytePosition));
+            int bytesToWrite = this.bitPosition != 0 ? this.bytePosition + 1 : this.bytePosition;
+            stream.Write(compressedData.Slice(0, bytesToWrite));
 
-            return this.bytePosition;
+            return bytesToWrite;
         }
 
         private void WriteEndOfLine(Span<byte> compressedData)

src/ImageSharp/Formats/Tiff/TiffEncoderCore.cs

@@ -426,6 +426,11 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
 
         private ushort GetCompressionType()
         {
+            if (this.CompressionType == TiffEncoderCompression.Deflate && this.Mode == TiffEncodingMode.Default)
+            {
+                return (ushort)TiffCompression.Deflate;
+            }
+
             if (this.CompressionType == TiffEncoderCompression.Deflate && this.Mode == TiffEncodingMode.Rgb)
             {
                 return (ushort)TiffCompression.Deflate;
@@ -436,6 +441,11 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff
                 return (ushort)TiffCompression.Lzw;
             }
 
+            if (this.CompressionType == TiffEncoderCompression.PackBits && this.Mode == TiffEncodingMode.Default)
+            {
+                return (ushort)TiffCompression.PackBits;
+            }
+
             if (this.CompressionType == TiffEncoderCompression.PackBits && this.Mode == TiffEncodingMode.Rgb)
             {
                 return (ushort)TiffCompression.PackBits;

src/ImageSharp/Formats/Tiff/Utils/TiffWriter.cs

@@ -764,7 +764,7 @@ namespace SixLabors.ImageSharp.Formats.Experimental.Tiff.Utils
             where TPixel : unmanaged, IPixel<TPixel>
         {
             // Worst case is that the actual compressed data is larger then the input data. In this case we need 1 additional byte per 127 bits.
-            int additionalBytes = (image.Width / 127) + 1;
+            int additionalBytes = (image.Width / 127) + 2;
             int compressedRowBytes = (image.Width / 8) + additionalBytes;
             using IManagedByteBuffer compressedRow = this.memoryAllocator.AllocateManagedByteBuffer(compressedRowBytes, AllocationOptions.Clean);
             Span<byte> compressedRowSpan = compressedRow.GetSpan();

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

@@ -5,6 +5,7 @@ using System.IO;
 
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.Formats.Experimental.Tiff;
+using SixLabors.ImageSharp.Formats.Experimental.Tiff.Constants;
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
 using SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs;
@@ -23,11 +24,50 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
         public static readonly TheoryData<string, TiffBitsPerPixel> TiffBitsPerPixelFiles =
             new TheoryData<string, TiffBitsPerPixel>
             {
-                { TestImages.Tiff.Calliphora_BiColorUncompressed, TiffBitsPerPixel.Pixel1 },
-                { TestImages.Tiff.GrayscaleUncompressed, TiffBitsPerPixel.Pixel8 },
-                { TestImages.Tiff.RgbUncompressed, TiffBitsPerPixel.Pixel24 },
+                { Calliphora_BiColorUncompressed, TiffBitsPerPixel.Pixel1 },
+                { GrayscaleUncompressed, TiffBitsPerPixel.Pixel8 },
+                { RgbUncompressed, TiffBitsPerPixel.Pixel24 },
             };
 
+        [Theory]
+        [InlineData(TiffEncodingMode.Default, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel24, TiffCompression.None)]
+        [InlineData(TiffEncodingMode.Rgb, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel24, TiffCompression.None)]
+        [InlineData(TiffEncodingMode.ColorPalette, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel8, TiffCompression.None)]
+        [InlineData(TiffEncodingMode.Gray, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel8, TiffCompression.None)]
+        [InlineData(TiffEncodingMode.BiColor, TiffEncoderCompression.None, TiffBitsPerPixel.Pixel1, TiffCompression.None)]
+        [InlineData(TiffEncodingMode.Default, TiffEncoderCompression.Deflate, TiffBitsPerPixel.Pixel24, TiffCompression.Deflate)]
+        [InlineData(TiffEncodingMode.Rgb, TiffEncoderCompression.Deflate, TiffBitsPerPixel.Pixel24, TiffCompression.Deflate)]
+        [InlineData(TiffEncodingMode.ColorPalette, TiffEncoderCompression.Deflate, TiffBitsPerPixel.Pixel8, TiffCompression.Deflate)]
+        [InlineData(TiffEncodingMode.Gray, TiffEncoderCompression.Deflate, TiffBitsPerPixel.Pixel8, TiffCompression.Deflate)]
+        [InlineData(TiffEncodingMode.BiColor, TiffEncoderCompression.Deflate, TiffBitsPerPixel.Pixel1, TiffCompression.Deflate)]
+        [InlineData(TiffEncodingMode.Default, TiffEncoderCompression.PackBits, TiffBitsPerPixel.Pixel24, TiffCompression.PackBits)]
+        [InlineData(TiffEncodingMode.Rgb, TiffEncoderCompression.PackBits, TiffBitsPerPixel.Pixel24, TiffCompression.PackBits)]
+        [InlineData(TiffEncodingMode.ColorPalette, TiffEncoderCompression.PackBits, TiffBitsPerPixel.Pixel8, TiffCompression.PackBits)]
+        [InlineData(TiffEncodingMode.Gray, TiffEncoderCompression.PackBits, TiffBitsPerPixel.Pixel8, TiffCompression.PackBits)]
+        [InlineData(TiffEncodingMode.BiColor, TiffEncoderCompression.PackBits, TiffBitsPerPixel.Pixel1, TiffCompression.PackBits)]
+        [InlineData(TiffEncodingMode.Rgb, TiffEncoderCompression.Lzw, TiffBitsPerPixel.Pixel24, TiffCompression.Lzw)]
+        [InlineData(TiffEncodingMode.ColorPalette, TiffEncoderCompression.Lzw, TiffBitsPerPixel.Pixel8, TiffCompression.Lzw)]
+        [InlineData(TiffEncodingMode.Gray, TiffEncoderCompression.Lzw, TiffBitsPerPixel.Pixel8, TiffCompression.Lzw)]
+        [InlineData(TiffEncodingMode.BiColor, TiffEncoderCompression.CcittGroup3Fax, TiffBitsPerPixel.Pixel1, TiffCompression.CcittGroup3Fax)]
+        [InlineData(TiffEncodingMode.BiColor, TiffEncoderCompression.ModifiedHuffman, TiffBitsPerPixel.Pixel1, TiffCompression.Ccitt1D)]
+        public void EncoderOptions_Work(TiffEncodingMode mode, TiffEncoderCompression compression, TiffBitsPerPixel expectedBitsPerPixel, TiffCompression expectedCompression)
+        {
+            // arrange
+            var tiffEncoder = new TiffEncoder { Mode = mode, Compression = compression };
+            Image input = new Image<Rgb24>(10, 10);
+            using var memStream = new MemoryStream();
+
+            // act
+            input.Save(memStream, tiffEncoder);
+
+            // assert
+            memStream.Position = 0;
+            using var output = Image.Load<Rgba32>(memStream);
+            TiffMetadata meta = output.Metadata.GetTiffMetadata();
+            Assert.Equal(expectedBitsPerPixel, meta.BitsPerPixel);
+            Assert.Equal(expectedCompression, meta.Compression);
+        }
+
         [Theory]
         [MemberData(nameof(TiffBitsPerPixelFiles))]
         public void TiffEncoder_PreserveBitsPerPixel(string imagePath, TiffBitsPerPixel expectedBitsPerPixel)