Add support for decoding 12 bits per pixel tiff's

src/ImageSharp/Formats/Tiff/Constants/TiffConstants.cs

@@ -96,10 +96,15 @@ namespace SixLabors.ImageSharp.Formats.Tiff.Constants
         public static readonly ushort[] BitsPerSample8Bit = { 8 };
 
         /// <summary>
-        /// The bits per sample for images with 8 bits for each color channel.
+        /// The bits per sample for color images with 8 bits for each color channel.
         /// </summary>
         public static readonly ushort[] BitsPerSampleRgb8Bit = { 8, 8, 8 };
 
+        /// <summary>
+        /// The bits per sample for color images with 4 bits for each color channel.
+        /// </summary>
+        public static readonly ushort[] BitsPerSampleRgb4Bit = { 4, 4, 4 };
+
         /// <summary>
         /// The list of mimetypes that equate to a tiff.
         /// </summary>

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/Rgb444TiffColor{TPixel}.cs

@@ -0,0 +1,60 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+using SixLabors.ImageSharp.Memory;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
+{
+    /// <summary>
+    /// Implements the 'RGB' photometric interpretation for 4 bits per color channel images.
+    /// </summary>
+    internal class Rgb444TiffColor<TPixel> : TiffBaseColorDecoder<TPixel>
+        where TPixel : unmanaged, IPixel<TPixel>
+    {
+        /// <inheritdoc/>
+        public override void Decode(ReadOnlySpan<byte> data, Buffer2D<TPixel> pixels, int left, int top, int width, int height)
+        {
+            var color = default(TPixel);
+
+            int offset = 0;
+
+            var bgra = default(Bgra4444);
+            for (int y = top; y < top + height; y++)
+            {
+                Span<TPixel> pixelRow = pixels.GetRowSpan(y);
+
+                for (int x = left; x < left + width; x += 2)
+                {
+                    byte r = (byte)((data[offset] & 0xF0) >> 4);
+                    byte g = (byte)(data[offset] & 0xF);
+                    offset++;
+                    byte b = (byte)((data[offset] & 0xF0) >> 4);
+
+                    bgra.PackedValue = ToBgraPackedValue(b, g, r);
+                    color.FromScaledVector4(bgra.ToScaledVector4());
+                    pixelRow[x] = color;
+                    if (x + 1 >= pixelRow.Length)
+                    {
+                        offset++;
+                        break;
+                    }
+
+                    r = (byte)(data[offset] & 0xF);
+                    offset++;
+                    g = (byte)((data[offset] & 0xF0) >> 4);
+                    b = (byte)(data[offset] & 0xF);
+                    offset++;
+
+                    bgra.PackedValue = ToBgraPackedValue(b, g, r);
+                    color.FromScaledVector4(bgra.ToScaledVector4());
+                    pixelRow[x + 1] = color;
+                }
+            }
+        }
+
+        private static ushort ToBgraPackedValue(byte b, byte g, byte r) => (ushort)(b | (g << 4) | (r << 8) | (0xF << 12));
+    }
+}

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/RgbPlanarTiffColor{TPixel}.cs

@@ -27,7 +27,6 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
         private readonly ushort bitsPerSampleB;
 
         public RgbPlanarTiffColor(ushort[] bitsPerSample)
-        /* : base(bitsPerSample, null) */
         {
             this.bitsPerSampleR = bitsPerSample[0];
             this.bitsPerSampleG = bitsPerSample[1];

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/TiffColorDecoderFactory{TPixel}.cs

@@ -57,6 +57,16 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
                     DebugGuard.IsTrue(colorMap == null, "colorMap");
                     return new RgbTiffColor<TPixel>(bitsPerSample);
 
+                case TiffColorType.Rgb444:
+                    DebugGuard.IsTrue(
+                        bitsPerSample.Length == 3
+                        && bitsPerSample[0] == 4
+                        && bitsPerSample[1] == 4
+                        && bitsPerSample[2] == 4,
+                        "bitsPerSample");
+                    DebugGuard.IsTrue(colorMap == null, "colorMap");
+                    return new Rgb444TiffColor<TPixel>();
+
                 case TiffColorType.Rgb888:
                     DebugGuard.IsTrue(
                         bitsPerSample.Length == 3

src/ImageSharp/Formats/Tiff/PhotometricInterpretation/TiffColorType.cs

@@ -63,6 +63,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff.PhotometricInterpretation
         /// </summary>
         Rgb888,
 
+        /// <summary>
+        /// RGB color image with 4 bits for each channel.
+        /// </summary>
+        Rgb444,
+
         /// <summary>
         /// RGB Full Color. Planar configuration of data.
         /// </summary>

src/ImageSharp/Formats/Tiff/TiffBitsPerPixel.cs

@@ -23,6 +23,13 @@ namespace SixLabors.ImageSharp.Formats.Tiff
         /// </summary>
         Bit8 = 8,
 
+        /// <summary>
+        /// 14 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>
+        Bit12 = 12,
+
         /// <summary>
         /// 24 bits per pixel. One byte for each color channel.
         /// </summary>

src/ImageSharp/Formats/Tiff/TiffBitsPerSample.cs

@@ -28,6 +28,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff
         /// </summary>
         Bit8 = 8,
 
+        /// <summary>
+        /// Twelve bits per sample, each channel has 4 bits.
+        /// </summary>
+        Bit12 = 12,
+
         /// <summary>
         /// 24 bits per sample, each color channel has 8 Bits.
         /// </summary>

src/ImageSharp/Formats/Tiff/TiffBitsPerSampleExtensions.cs

@@ -23,6 +23,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     return TiffConstants.BitsPerSample4Bit;
                 case TiffBitsPerSample.Bit8:
                     return TiffConstants.BitsPerSample8Bit;
+                case TiffBitsPerSample.Bit12:
+                    return TiffConstants.BitsPerSampleRgb4Bit;
                 case TiffBitsPerSample.Bit24:
                     return TiffConstants.BitsPerSampleRgb8Bit;
 
@@ -48,6 +50,13 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                         return TiffBitsPerSample.Bit24;
                     }
 
+                    if (bitsPerSample[0] == TiffConstants.BitsPerSampleRgb4Bit[0] &&
+                        bitsPerSample[1] == TiffConstants.BitsPerSampleRgb4Bit[1] &&
+                        bitsPerSample[2] == TiffConstants.BitsPerSampleRgb4Bit[2])
+                    {
+                        return TiffBitsPerSample.Bit12;
+                    }
+
                     break;
 
                 case 1:

src/ImageSharp/Formats/Tiff/TiffDecoderCore.cs

@@ -294,7 +294,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                 int top = rowsPerStrip * stripIndex;
                 if (top + stripHeight > frame.Height)
                 {
-                    // Make sure we ignore any strips that are not needed for the image (if too many are present)
+                    // Make sure we ignore any strips that are not needed for the image (if too many are present).
                     break;
                 }
 

src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Linq;
 using SixLabors.ImageSharp.Formats.Tiff.Compression;
 using SixLabors.ImageSharp.Formats.Tiff.Constants;
@@ -179,7 +180,18 @@ namespace SixLabors.ImageSharp.Formats.Tiff
 
                     if (options.PlanarConfiguration == TiffPlanarConfiguration.Chunky)
                     {
-                        options.ColorType = options.BitsPerSample == TiffBitsPerSample.Bit24 ? TiffColorType.Rgb888 : TiffColorType.Rgb;
+                        switch (options.BitsPerSample)
+                        {
+                            case TiffBitsPerSample.Bit24:
+                                options.ColorType = TiffColorType.Rgb888;
+                                break;
+                            case TiffBitsPerSample.Bit12:
+                                options.ColorType = TiffColorType.Rgb444;
+                                break;
+                            default:
+                                TiffThrowHelper.ThrowNotSupported("Bits per sample is nut supported.");
+                                break;
+                        }
                     }
                     else
                     {
@@ -274,8 +286,9 @@ namespace SixLabors.ImageSharp.Formats.Tiff
             TiffBitsPerPixel.Bit1 => TiffBitsPerSample.Bit1,
             TiffBitsPerPixel.Bit4 => TiffBitsPerSample.Bit4,
             TiffBitsPerPixel.Bit8 => TiffBitsPerSample.Bit8,
+            TiffBitsPerPixel.Bit12 => TiffBitsPerSample.Bit12,
             TiffBitsPerPixel.Bit24 => TiffBitsPerSample.Bit24,
-            _ => TiffBitsPerSample.Bit24,
+            _ => throw new NotSupportedException("The bits per pixel are not supported"),
         };
     }
 }

src/ImageSharp/Formats/Tiff/TiffEncoderCore.cs

@@ -306,7 +306,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     case TiffBitsPerPixel.Bit1:
                         if (compression == TiffCompression.Ccitt1D || compression == TiffCompression.CcittGroup3Fax || compression == TiffCompression.CcittGroup4Fax)
                         {
-                            // The “normal” PhotometricInterpretation for bilevel CCITT compressed data is WhiteIsZero.
+                            // The “normal” PhotometricInterpretation for bilevel CCITT compressed data is WhiteIsZero.
                             this.SetEncoderOptions(bitsPerPixel, TiffPhotometricInterpretation.WhiteIsZero, compression, TiffPredictor.None);
                             break;
                         }
@@ -319,6 +319,10 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     case TiffBitsPerPixel.Bit8:
                         this.SetEncoderOptions(bitsPerPixel, photometricInterpretation ?? TiffPhotometricInterpretation.BlackIsZero, compression, predictor);
                         break;
+                    case TiffBitsPerPixel.Bit12:
+                        // Encoding 12 bits per pixel is not yet supported. Default to 24 bits.
+                        this.SetEncoderOptions(TiffBitsPerPixel.Bit24, TiffPhotometricInterpretation.Rgb, compression, TiffPredictor.None);
+                        break;
                     default:
                         this.SetEncoderOptions(bitsPerPixel, TiffPhotometricInterpretation.Rgb, compression, predictor);
                         break;

src/ImageSharp/Formats/Tiff/TiffEncoderEntriesCollector.cs

@@ -66,8 +66,8 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     Value = SoftwareValue
                 };
 
-                this.collector.Add(width);
-                this.collector.Add(height);
+                this.collector.AddOrReplace(width);
+                this.collector.AddOrReplace(height);
 
                 this.ProcessResolution(image.Metadata, rootFrameExifProfile);
                 this.ProcessProfiles(image.Metadata, rootFrameExifProfile, rootFrameXmpBytes);
@@ -227,7 +227,6 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     exifProfile.RemoveValue(ExifTag.IccProfile);
                 }
 
-                TiffMetadata tiffMetadata = imageMetadata.GetTiffMetadata();
                 if (xmpProfile != null)
                 {
                     var xmp = new ExifByteArray(ExifTagValue.XMP, ExifDataType.Byte)
@@ -252,6 +251,11 @@ namespace SixLabors.ImageSharp.Formats.Tiff
 
             public void Process(TiffEncoderCore encoder)
             {
+                var planarConfig = new ExifShort(ExifTagValue.PlanarConfiguration)
+                {
+                    Value = (ushort)TiffPlanarConfiguration.Chunky
+                };
+
                 var samplesPerPixel = new ExifLong(ExifTagValue.SamplesPerPixel)
                 {
                     Value = GetSamplesPerPixel(encoder)
@@ -274,6 +278,7 @@ namespace SixLabors.ImageSharp.Formats.Tiff
                     Value = (ushort)encoder.PhotometricInterpretation
                 };
 
+                this.collector.AddOrReplace(planarConfig);
                 this.collector.AddOrReplace(samplesPerPixel);
                 this.collector.AddOrReplace(bitPerSample);
                 this.collector.AddOrReplace(compression);

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

@@ -105,6 +105,18 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
             }
         }
 
+        [Theory]
+        [WithFile(FlowerRgb444Contiguous, PixelTypes.Rgba32)]
+        [WithFile(FlowerRgb444Planar, PixelTypes.Rgba32)]
+        public void TiffDecoder_CanDecode_12Bit<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            if (TestEnvironment.IsWindows)
+            {
+                TestTiffDecoder(provider, new SystemDrawingReferenceDecoder());
+            }
+        }
+
         [Theory]
         [WithFile(GrayscaleDeflateMultistrip, PixelTypes.Rgba32)]
         [WithFile(RgbDeflateMultistrip, PixelTypes.Rgba32)]

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

@@ -288,10 +288,13 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tiff
             Assert.Equal("This is Изготовитель камеры", exifProfileInput.GetValue(ExifTag.Make).Value);
             Assert.Equal("This is Авторские права", exifProfileInput.GetValue(ExifTag.Copyright).Value);
 
-            Assert.Equal(exifProfileInput.Values.Count, encodedImageExifProfile.Values.Count);
             Assert.Equal(exifProfileInput.GetValue(ExifTag.ImageDescription).Value, encodedImageExifProfile.GetValue(ExifTag.ImageDescription).Value);
             Assert.Equal(exifProfileInput.GetValue(ExifTag.Make).Value, encodedImageExifProfile.GetValue(ExifTag.Make).Value);
             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(exifProfileInput.Values.Count + 1, encodedImageExifProfile.Values.Count);
         }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -560,6 +560,8 @@ namespace SixLabors.ImageSharp.Tests
             public const string RgbPaletteDeflate = "Tiff/rgb_palette_deflate.tiff";
             public const string Flower4BitPalette = "Tiff/flower-palette-04.tiff";
             public const string Flower4BitPaletteGray = "Tiff/flower-minisblack-04.tiff";
+            public const string FlowerRgb444Contiguous = "Tiff/flower-rgb-contig-04.tiff";
+            public const string FlowerRgb444Planar = "Tiff/flower-rgb-planar-04.tiff";
 
             public const string SmallRgbDeflate = "Tiff/rgb_small_deflate.tiff";
             public const string SmallRgbLzw = "Tiff/rgb_small_lzw.tiff";

tests/Images/Input/Tiff/flower-rgb-contig-04.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:96c4c1dfc23a0d9e5c6189717647fa117b08aac9a40c63e3945d3e674df4c3c6
+size 5049

tests/Images/Input/Tiff/flower-rgb-planar-04.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ca4434aa1a8c52654b20596c7c428c9016e089de75c29dc6ddcd32708874005c
+size 5117