make converter public and add separation color space

src/UglyToad.PdfPig.Tests/PublicApiScannerTests.cs

@@ -103,6 +103,13 @@
                 "UglyToad.PdfPig.Graphics.Colors.GrayColor",
                 "UglyToad.PdfPig.Graphics.Colors.IColor",
                 "UglyToad.PdfPig.Graphics.Colors.RGBColor",
+                "UglyToad.PdfPig.Graphics.Colors.ColorSpaceDetails",
+                "UglyToad.PdfPig.Graphics.Colors.DeviceGrayColorSpaceDetails",
+                "UglyToad.PdfPig.Graphics.Colors.DeviceRgbColorSpaceDetails",
+                "UglyToad.PdfPig.Graphics.Colors.DeviceCmykColorSpaceDetails",
+                "UglyToad.PdfPig.Graphics.Colors.IndexedColorSpaceDetails",
+                "UglyToad.PdfPig.Graphics.Colors.SeparationColorSpaceDetails",
+                "UglyToad.PdfPig.Graphics.Colors.UnsupportedColorSpaceDetails",
                 "UglyToad.PdfPig.Graphics.Core.LineCapStyle",
                 "UglyToad.PdfPig.Graphics.Core.LineDashPattern",
                 "UglyToad.PdfPig.Graphics.Core.LineJoinStyle",
@@ -187,6 +194,7 @@
                 "UglyToad.PdfPig.Graphics.Operations.TextState.Type3SetGlyphWidth",
                 "UglyToad.PdfPig.Graphics.Operations.TextState.Type3SetGlyphWidthAndBoundingBox",
                 "UglyToad.PdfPig.Graphics.TextMatrices",
+                "UglyToad.PdfPig.Images.ColorSpaceDetailsByteConverter",
                 "UglyToad.PdfPig.Logging.ILog",
                 "UglyToad.PdfPig.Outline.Bookmarks",
                 "UglyToad.PdfPig.Outline.BookmarkNode",

src/UglyToad.PdfPig/Graphics/Colors/ColorSpaceDetails.cs

@@ -2,6 +2,8 @@
 {
     using System;
     using System.Collections.Generic;
+    using PdfPig.Core;
+    using Tokens;
 
     /// <summary>
     /// Contains more document-specific information about the <see cref="ColorSpace"/>.
@@ -112,6 +114,59 @@
         }
     }
 
+    /// <summary>
+    /// A Separation color space provides a means for specifying the use of additional colorants or
+    /// for isolating the control of individual color components of a device color space for a subtractive device.
+    /// When such a space is the current color space, the current color is a single-component value, called a tint,
+    /// that controls the application of the given colorant or color components only.
+    /// </summary>
+    public class SeparationColorSpaceDetails : ColorSpaceDetails
+    {
+        /// <summary>
+        /// Specifies the name of the colorant that this Separation color space is intended to represent.
+        /// </summary>
+        /// <remarks>
+        /// <para>
+        /// The special colorant name All refers collectively to all colorants available on an output device,
+        /// including those for the standard process colorants.
+        /// </para>
+        /// <para>
+        /// The special colorant name None never produces any visible output.
+        /// Painting operations in a Separation space with this colorant name have no effect on the current page.
+        /// </para>
+        /// </remarks>
+        public NameToken Name { get; }
+
+        /// <summary>
+        /// If the colorant name associated with a Separation color space does not correspond to a colorant available on the device,
+        /// the application arranges for subsequent painting operations to be performed in an alternate color space.
+        /// The intended colors can be approximated by colors in a device or CIE-based color space
+        /// which are then rendered with the usual primary or process colorants.
+        /// </summary>
+        public ColorSpaceDetails AlternateColorSpaceDetails { get; }
+
+        /// <summary>
+        /// During subsequent painting operations, an application calls this function to transform a tint value into
+        /// color component values in the alternate color space.
+        /// The function is called with the tint value and must return the corresponding color component values.
+        /// That is, the number of components and the interpretation of their values depend on the <see cref="AlternateColorSpaceDetails"/>.
+        /// </summary>
+        public Union<DictionaryToken, StreamToken> TintFunction { get; }
+
+        /// <summary>
+        /// Create a new <see cref="SeparationColorSpaceDetails"/>.
+        /// </summary>
+        public SeparationColorSpaceDetails(NameToken name,
+            ColorSpaceDetails alternateColorSpaceDetails,
+            Union<DictionaryToken, StreamToken> tintFunction)
+            : base(ColorSpace.Separation)
+        {
+            Name = name;
+            AlternateColorSpaceDetails = alternateColorSpaceDetails;
+            TintFunction = tintFunction;
+        }
+    }
+
     /// <summary>
     /// A ColorSpace which the PdfPig library does not currently support. Please raise a PR if you need support for this ColorSpace.
     /// </summary>

src/UglyToad.PdfPig/Images/ColorSpaceDetailsByteConverter.cs

@@ -3,12 +3,33 @@
     using System;
     using System.Collections.Generic;
     using System.Linq;
+    using Content;
+    using Core;
     using Graphics.Colors;
 
-    internal static class ColorSpaceDetailsByteConverter
+    /// <summary>
+    /// Utility for working with the bytes in <see cref="IPdfImage"/>s and converting according to their <see cref="ColorSpaceDetails"/>.s
+    /// </summary>
+    public static class ColorSpaceDetailsByteConverter
     {
+        /// <summary>
+        /// Converts the output bytes (if available) of <see cref="IPdfImage.TryGetBytes"/>
+        /// to actual pixel values using the <see cref="IPdfImage.ColorSpaceDetails"/>. For most images this doesn't
+        /// change the data but for <see cref="ColorSpace.Indexed"/> it will convert the bytes which are indexes into the
+        /// real pixel data into the real pixel data.
+        /// </summary>
         public static byte[] Convert(ColorSpaceDetails details, IReadOnlyList<byte> decoded)
         {
+            if (decoded == null)
+            {
+                return EmptyArray<byte>.Instance;
+            }
+
+            if (details == null)
+            {
+                return decoded.ToArray();
+            }
+
             switch (details)
             {
                 case IndexedColorSpaceDetails indexed:
@@ -41,7 +62,7 @@
                     transformer = x =>
                     {
                         var r = new byte[4];
-                        for (int i = 0; i < 4; i++)
+                        for (var i = 0; i < 4; i++)
                         {
                             r[i] = indexed.ColorTable[x * 4 + i];
                         }
@@ -52,7 +73,7 @@
                     multiplier = 4;
                     break;
                 case ColorSpace.DeviceGray:
-                    transformer = x => new[] {indexed.ColorTable[x]};
+                    transformer = x => new[] { indexed.ColorTable[x] };
                     multiplier = 1;
                     break;
             }

src/UglyToad.PdfPig/Util/ColorSpaceDetailsParser.cs

@@ -2,6 +2,7 @@
 {
     using System.Collections.Generic;
     using Content;
+    using Core;
     using Filters;
     using Graphics.Colors;
     using Parser.Parts;
@@ -135,10 +136,11 @@
                         && baseColorSpaceArrayToken.Length > 0 && baseColorSpaceArrayToken[0] is NameToken baseColorSpaceArrayNameToken
                         && ColorSpaceMapper.TryMap(baseColorSpaceArrayNameToken, resourceStore, out var baseColorSpaceArrayColorSpace))
                         {
-                            var pseudoImageDictionary = new DictionaryToken(new Dictionary<NameToken, IToken>
+                            var pseudoImageDictionary = new DictionaryToken(
-                        {
+                                new Dictionary<NameToken, IToken>
-                            {NameToken.ColorSpace, baseColorSpaceArrayToken}
+                                {
-                        });
+                                    {NameToken.ColorSpace, baseColorSpaceArrayToken}
+                                });
 
                             baseDetails = GetColorSpaceDetails(
                                 baseColorSpaceArrayColorSpace,
@@ -189,7 +191,79 @@
                 case ColorSpace.Pattern:
                     return UnsupportedColorSpaceDetails.Instance;
                 case ColorSpace.Separation:
-                    return UnsupportedColorSpaceDetails.Instance;
+                    {
+                        if (!imageDictionary.TryGet(NameToken.ColorSpace, scanner, out ArrayToken colorSpaceArray)
+                            || colorSpaceArray.Length != 4)
+                        {
+                            // Error instead?
+                            return UnsupportedColorSpaceDetails.Instance;
+                        }
+
+                        if (!DirectObjectFinder.TryGet(colorSpaceArray[0], scanner, out NameToken separationColorSpaceNameToken)
+                            || !separationColorSpaceNameToken.Equals(NameToken.Separation))
+                        {
+                            return UnsupportedColorSpaceDetails.Instance;
+                        }
+
+                        if (!DirectObjectFinder.TryGet(colorSpaceArray[1], scanner, out NameToken separationNameToken))
+                        {
+                            return UnsupportedColorSpaceDetails.Instance;
+                        }
+
+                        ColorSpaceDetails alternateColorSpaceDetails;
+                        if (DirectObjectFinder.TryGet(colorSpaceArray[2], scanner, out NameToken alternateNameToken)
+                            && ColorSpaceMapper.TryMap(alternateNameToken, resourceStore, out var baseColorSpaceName))
+                        {
+                            alternateColorSpaceDetails = GetColorSpaceDetails(
+                                baseColorSpaceName,
+                                imageDictionary,
+                                scanner,
+                                resourceStore,
+                                filterProvider,
+                                true);
+                        }
+                        else if (DirectObjectFinder.TryGet(colorSpaceArray[2], scanner, out ArrayToken alternateArrayToken)
+                        && alternateArrayToken.Length > 0
+                        && alternateArrayToken[0] is NameToken alternateColorSpaceNameToken
+                        && ColorSpaceMapper.TryMap(alternateColorSpaceNameToken, resourceStore, out var alternateArrayColorSpace))
+                        {
+                            var pseudoImageDictionary = new DictionaryToken(
+                                new Dictionary<NameToken, IToken>
+                                {
+                                {NameToken.ColorSpace, alternateArrayToken}
+                                });
+
+                            alternateColorSpaceDetails = GetColorSpaceDetails(
+                                alternateArrayColorSpace,
+                                pseudoImageDictionary,
+                                scanner,
+                                resourceStore,
+                                filterProvider,
+                                true);
+                        }
+                        else
+                        {
+                            return UnsupportedColorSpaceDetails.Instance;
+                        }
+
+                        Union<DictionaryToken, StreamToken> functionTokensUnion;
+                        var func = colorSpaceArray[3];
+
+                        if (DirectObjectFinder.TryGet(func, scanner, out DictionaryToken functionDictionary))
+                        {
+                            functionTokensUnion = Union<DictionaryToken, StreamToken>.One(functionDictionary);
+                        }
+                        else if (DirectObjectFinder.TryGet(func, scanner, out StreamToken functionStream))
+                        {
+                            functionTokensUnion = Union<DictionaryToken, StreamToken>.Two(functionStream);
+                        }
+                        else
+                        {
+                            return UnsupportedColorSpaceDetails.Instance;
+                        }
+
+                        return new SeparationColorSpaceDetails(separationNameToken, alternateColorSpaceDetails, functionTokensUnion);
+                    }
                 case ColorSpace.DeviceN:
                     return UnsupportedColorSpaceDetails.Instance;
                 default: