Features/transparent and separation images

README.md

@@ -41,7 +41,10 @@ The PDF files created in this library are not fully PDF 1.7 compliant, because t
 This shortcoming shall be remedied when broader font support is implemented.
 
 ### Sample program images
-The sample project called *Synercoding.FileFormats.Pdf.ConsoleTester* uses multiple images. Those images were taken from [Pexels.com](https://www.pexels.com/royalty-free-images/) and are licensed under the [Pexels License](https://www.pexels.com/photo-license/).
+The sample project called *Synercoding.FileFormats.Pdf.ConsoleTester* uses multiple images. 
+Those images were taken from:
+- [Pexels.com](https://www.pexels.com/royalty-free-images/) and are licensed under the [Pexels License](https://www.pexels.com/photo-license/)
+- [FreePngImg.com](https://freepngimg.com/png/59872-jaguar-panther-royalty-free-cougar-black-cheetah) and are licensed under [Creative Commons (CC BY-NC 4.0)](https://creativecommons.org/licenses/by-nc/4.0/)
 
 ## Sample usage
 

samples/Synercoding.FileFormats.Pdf.ConsoleTester/Program.cs

@@ -1,3 +1,4 @@
+using SixLabors.ImageSharp.PixelFormats;
 using Synercoding.FileFormats.Pdf.Extensions;
 using Synercoding.FileFormats.Pdf.LowLevel.Colors;
 using Synercoding.FileFormats.Pdf.LowLevel.Colors.ColorSpaces;
@@ -63,7 +64,7 @@ public static void Main(string[] args)
                         });
 
                         using (var forestStream = File.OpenRead("Pexels_com/android-wallpaper-art-backlit-1114897.jpg"))
-                        using (var forestImage = SixLabors.ImageSharp.Image.Load(forestStream))
+                        using (var forestImage = SixLabors.ImageSharp.Image.Load<Rgba32>(forestStream))
                         {
                             var scale = (double)forestImage.Width / forestImage.Height;
 
@@ -81,7 +82,7 @@ public static void Main(string[] args)
                     page.TrimBox = trimBox;
 
                     using (var barrenStream = File.OpenRead("Pexels_com/arid-barren-desert-1975514.jpg"))
-                    using (var barrenImage = SixLabors.ImageSharp.Image.Load(barrenStream))
+                    using (var barrenImage = SixLabors.ImageSharp.Image.Load<Rgba32>(barrenStream))
                     {
                         var scale = (double)barrenImage.Width / barrenImage.Height;
 
@@ -175,7 +176,7 @@ public static void Main(string[] args)
                     page.TrimBox = trimBox;
 
                     using (var forestStream = File.OpenRead("Pexels_com/android-wallpaper-art-backlit-1114897.jpg"))
-                    using (var forestImage = SixLabors.ImageSharp.Image.Load(forestStream))
+                    using (var forestImage = SixLabors.ImageSharp.Image.Load<Rgba32>(forestStream))
                     {
                         var scale = (double)forestImage.Width / forestImage.Height;
 
@@ -187,7 +188,7 @@ public static void Main(string[] args)
                 });
 
             using (var blurStream = File.OpenRead("Pexels_com/4k-wallpaper-blur-bokeh-1484253.jpg"))
-            using (var blurImage = SixLabors.ImageSharp.Image.Load(blurStream))
+            using (var blurImage = SixLabors.ImageSharp.Image.Load<Rgba32>(blurStream))
             {
                 var reusedImage = writer.AddImage(blurImage);
 
@@ -226,6 +227,33 @@ public static void Main(string[] args)
                     });
                 });
             }
+
+            using (var pantherPngStream = File.OpenRead("FreePngImage_com/59872-jaguar-panther-royalty-free-cougar-black-cheetah.png"))
+            using (var pantherImage = SixLabors.ImageSharp.Image.Load<Rgba32>(pantherPngStream))
+            {
+                var pantherImg = writer.AddImage(pantherImage);
+                var transparentPanther = writer.AddSeparationImage(new Separation(LowLevel.PdfName.Get("White"), PredefinedColors.Yellow), pantherImage, GrayScaleMethod.AlphaChannel);
+
+                writer.AddPage(page =>
+                {
+                    page.MediaBox = mediaBox;
+                    page.TrimBox = trimBox;
+
+                    var scale = (double)transparentPanther.Width / transparentPanther.Height;
+                    var pantherSize = new Rectangle(0, 0, 216, 216 / scale, Unit.Millimeters);
+
+                    page.Content.AddImage(pantherImage, pantherSize);
+
+                    page.Content.WrapInState(pantherImage, (image, content) =>
+                    {
+                        content.SetExtendedGraphicsState(new ExtendedGraphicsState()
+                        {
+                            Overprint = true
+                        });
+                        content.AddImage(transparentPanther, pantherSize);
+                    });
+                });
+            }
         }
     }
 }

samples/Synercoding.FileFormats.Pdf.ConsoleTester/Synercoding.FileFormats.Pdf.ConsoleTester.csproj

@@ -15,4 +15,10 @@
     </None>
   </ItemGroup>
 
+  <ItemGroup>
+    <None Update="FreePngImage_com\*.png">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+  </ItemGroup>
+
 </Project>

src/Synercoding.FileFormats.Pdf/Extensions/IPageContentContextExtensions.cs

@@ -1,3 +1,4 @@
+using SixLabors.ImageSharp.PixelFormats;
 using Synercoding.FileFormats.Pdf.Internals;
 using Synercoding.FileFormats.Pdf.LowLevel.Colors.ColorSpaces;
 using Synercoding.FileFormats.Pdf.LowLevel.Text;
@@ -61,7 +62,7 @@ public static IPageContentContext AddImage(this IPageContentContext context, Sys
     /// <returns>The same <paramref name="context"/> to enable chaining operations.</returns>
     public static IPageContentContext AddImage(this IPageContentContext context, System.IO.Stream stream)
     {
-        using var image = SixLabors.ImageSharp.Image.Load(stream);
+        using var image = SixLabors.ImageSharp.Image.Load<Rgba32>(stream);
 
         return context.AddImage(image);
     }
@@ -73,7 +74,7 @@ public static IPageContentContext AddImage(this IPageContentContext context, Sys
     /// <param name="image">The image to place</param>
     /// <param name="matrix">The placement matrix to use</param>
     /// <returns>The same <paramref name="context"/> to enable chaining operations.</returns>
-    public static IPageContentContext AddImage(this IPageContentContext context, SixLabors.ImageSharp.Image image, Matrix matrix)
+    public static IPageContentContext AddImage(this IPageContentContext context, SixLabors.ImageSharp.Image<Rgba32> image, Matrix matrix)
     {
         return context.WrapInState((image, matrix), static (tuple, context) =>
         {
@@ -89,7 +90,7 @@ public static IPageContentContext AddImage(this IPageContentContext context, Six
     /// <param name="image">The image to place</param>
     /// <param name="rectangle">The rectangle of where to place the image.</param>
     /// <returns>The same <paramref name="context"/> to enable chaining operations.</returns>
-    public static IPageContentContext AddImage(this IPageContentContext context, SixLabors.ImageSharp.Image image, Rectangle rectangle)
+    public static IPageContentContext AddImage(this IPageContentContext context, SixLabors.ImageSharp.Image<Rgba32> image, Rectangle rectangle)
         => context.AddImage(image, rectangle.AsPlacementMatrix());
 
     /// <summary>
@@ -98,7 +99,7 @@ public static IPageContentContext AddImage(this IPageContentContext context, Six
     /// <param name="context">The context to add the image to.</param>
     /// <param name="image">The image to place</param>
     /// <returns>The same <paramref name="context"/> to enable chaining operations.</returns>
-    public static IPageContentContext AddImage(this IPageContentContext context, SixLabors.ImageSharp.Image image)
+    public static IPageContentContext AddImage(this IPageContentContext context, SixLabors.ImageSharp.Image<Rgba32> image)
     {
         var name = context.RawContentStream.Resources.AddImage(image);
 

src/Synercoding.FileFormats.Pdf/GrayScaleMethod.cs

@@ -0,0 +1,28 @@
+namespace Synercoding.FileFormats.Pdf;
+
+/// <summary>
+/// What method is used to generate a 1 component grayscale pixel byte array
+/// </summary>
+public enum GrayScaleMethod
+{
+    /// <summary>
+    /// Use the red channel
+    /// </summary>
+    RedChannel,
+    /// <summary>
+    /// Use the green channel
+    /// </summary>
+    GreenChannel,
+    /// <summary>
+    /// Use the blue channel
+    /// </summary>
+    BlueChannel,
+    /// <summary>
+    /// Use the alpha channel
+    /// </summary>
+    AlphaChannel,
+    /// <summary>
+    /// Use the average of the Red, Green and Blue channels.
+    /// </summary>
+    AverageOfRGBChannels
+}

src/Synercoding.FileFormats.Pdf/Image.cs

@@ -1,64 +1,33 @@
 using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
 using Synercoding.FileFormats.Pdf.LowLevel;
 using Synercoding.FileFormats.Pdf.LowLevel.Colors.ColorSpaces;
+using Synercoding.FileFormats.Pdf.LowLevel.XRef;
+using System.IO.Compression;
 
 namespace Synercoding.FileFormats.Pdf;
 
 /// <summary>
 /// Class representing an image inside a pdf
 /// </summary>
-public sealed class Image : IDisposable
+public class Image : IDisposable
 {
-    private bool _disposed;
+    private protected bool _disposed;
 
-    internal Image(PdfReference id, SixLabors.ImageSharp.Image image)
-    {
-        Reference = id;
-
-        var ms = new MemoryStream();
-        image.SaveAsJpeg(ms, new SixLabors.ImageSharp.Formats.Jpeg.JpegEncoder()
-        {
-            Quality = 100,
-            ColorType = SixLabors.ImageSharp.Formats.Jpeg.JpegEncodingColor.YCbCrRatio444
-        });
-        Width = image.Width;
-        Height = image.Height;
-        ColorSpace = DeviceRGB.Instance.Name;
-        DecodeArray = new double[] { 0, 1, 0, 1, 0, 1 };
-        ms.Position = 0;
-        RawStream = ms;
-    }
-
-    internal Image(PdfReference id, Stream jpgStream, int width, int height, ColorSpace colorSpace)
-    {
-        Reference = id;
-
-        Width = width;
-        Height = height;
-        RawStream = jpgStream;
-
-        var (csName, decodeArray) = colorSpace switch
-        {
-            DeviceCMYK cmyk => (cmyk.Name, new double[] { 0, 1, 0, 1, 0, 1, 0, 1 }),
-            DeviceRGB rgb => (rgb.Name, new double[] { 0, 1, 0, 1, 0, 1 }),
-            _ => throw new ArgumentOutOfRangeException(nameof(colorSpace), $"The provided color space {colorSpace} is currently not supported.")
-        };
-
-        ColorSpace = csName;
-        DecodeArray = decodeArray;
-    }
-
-    internal Image(PdfReference id, Stream jpgStream, int width, int height, PdfName colorSpace, double[] decodeArray)
+    internal Image(PdfReference id, Stream jpgStream, int width, int height, ColorSpace colorSpace, Image? softMask, params StreamFilter[] filters)
     {
         Reference = id;
 
         Width = width;
         Height = height;
         RawStream = jpgStream;
         ColorSpace = colorSpace;
-        DecodeArray = decodeArray;
+        SoftMask = softMask;
+        Filters = filters;
     }
 
+    internal Image? SoftMask { get; private set; }
+
     internal Stream RawStream { get; private set; }
 
     /// <summary>
@@ -79,12 +48,9 @@ internal Image(PdfReference id, Stream jpgStream, int width, int height, PdfName
     /// <summary>
     /// The name of the colorspace used in this <see cref="Image"/>
     /// </summary>
-    public PdfName ColorSpace { get; }
+    public ColorSpace ColorSpace { get; }
 
-    /// <summary>
-    /// The decode array used in this <see cref="Image"/>
-    /// </summary>
-    public double[] DecodeArray { get; }
+    internal StreamFilter[] Filters { get; } = Array.Empty<StreamFilter>();
 
     /// <inheritdoc />
     public void Dispose()
@@ -95,4 +61,74 @@ public void Dispose()
             _disposed = true;
         }
     }
+
+    private static Stream _encodeToJpg(SixLabors.ImageSharp.Image image)
+    {
+        var ms = new MemoryStream();
+        image.SaveAsJpeg(ms, new SixLabors.ImageSharp.Formats.Jpeg.JpegEncoder()
+        {
+            Quality = 100,
+            ColorType = SixLabors.ImageSharp.Formats.Jpeg.JpegEncodingColor.YCbCrRatio444
+        });
+        ms.Position = 0;
+
+        return ms;
+    }
+
+    internal static Image Get(TableBuilder tableBuilder, Image<Rgba32> image)
+    {
+        return new Image(tableBuilder.ReserveId(), _encodeToJpg(image), image.Width, image.Height, DeviceRGB.Instance, GetMask(tableBuilder, image), StreamFilter.DCTDecode);
+    }
+
+    internal static Image? GetMask(TableBuilder tableBuilder, Image<Rgba32> image)
+    {
+        var hasTrans = image.Metadata.TryGetPngMetadata(out var pngMeta)
+            &&
+            (
+                pngMeta.ColorType == SixLabors.ImageSharp.Formats.Png.PngColorType.RgbWithAlpha
+                || pngMeta.ColorType == SixLabors.ImageSharp.Formats.Png.PngColorType.GrayscaleWithAlpha
+            );
+
+        return hasTrans
+            ? new Image(tableBuilder.ReserveId(), AsImageByteStream(image, GrayScaleMethod.AlphaChannel), image.Width, image.Height, DeviceGray.Instance, null, StreamFilter.FlateDecode)
+            : null;
+    }
+
+    internal static Stream AsImageByteStream(Image<Rgba32> image, GrayScaleMethod grayScaleMethod)
+    {
+        using (var byteStream = new MemoryStream())
+        {
+            image.ProcessPixelRows(accessor =>
+            {
+                for (int y = 0; y < accessor.Height; y++)
+                {
+                    var pixelRow = accessor.GetRowSpan(y);
+
+                    // pixelRow.Length has the same value as accessor.Width,
+                    // but using pixelRow.Length allows the JIT to optimize away bounds checks:
+                    for (int x = 0; x < pixelRow.Length; x++)
+                    {
+                        // Get a reference to the pixel at position x
+                        ref Rgba32 pixel = ref pixelRow[x];
+
+                        var pixelValue = grayScaleMethod switch
+                        {
+                            GrayScaleMethod.AlphaChannel => pixel.A,
+                            GrayScaleMethod.RedChannel => pixel.R,
+                            GrayScaleMethod.GreenChannel => pixel.G,
+                            GrayScaleMethod.BlueChannel => pixel.B,
+                            GrayScaleMethod.AverageOfRGBChannels => (byte)( ( pixel.R + pixel.G + pixel.B ) / 3 ),
+                            _ => throw new NotImplementedException()
+                        };
+
+                        byteStream.WriteByte(pixelValue);
+                    }
+                }
+            });
+
+            byteStream.Position = 0;
+
+            return PdfWriter.FlateEncode(byteStream);
+        }
+    }
 }

src/Synercoding.FileFormats.Pdf/LowLevel/Extensions/StreamFilterExtensions.cs

@@ -7,6 +7,7 @@ public static PdfName ToPdfName(this StreamFilter streamFilter)
         return streamFilter switch
         {
             StreamFilter.DCTDecode => PdfName.Get("DCTDecode"),
+            StreamFilter.FlateDecode => PdfName.Get("FlateDecode"),
             _ => throw new NotImplementedException(),
         };
     }

src/Synercoding.FileFormats.Pdf/LowLevel/Internal/PageResources.cs

@@ -1,3 +1,4 @@
+using SixLabors.ImageSharp.PixelFormats;
 using Synercoding.FileFormats.Pdf.Internals;
 using Synercoding.FileFormats.Pdf.LowLevel.Colors.ColorSpaces;
 using Synercoding.FileFormats.Pdf.LowLevel.Text;
@@ -56,25 +57,14 @@ public PdfName AddJpgUnsafe(System.IO.Stream jpgStream, int originalWidth, int o
     {
         var id = _tableBuilder.ReserveId();
 
-        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace);
+        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace, null, StreamFilter.DCTDecode);
 
         return AddImage(pdfImage);
     }
 
-    public PdfName AddJpgUnsafe(System.IO.Stream jpgStream, int originalWidth, int originalHeight, PdfName colorSpace, double[] decodeArray)
+    public PdfName AddImage(SixLabors.ImageSharp.Image<Rgba32> image)
     {
-        var id = _tableBuilder.ReserveId();
-
-        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace, decodeArray);
-
-        return AddImage(pdfImage);
-    }
-
-    public PdfName AddImage(SixLabors.ImageSharp.Image image)
-    {
-        var id = _tableBuilder.ReserveId();
-
-        var pdfImage = new Image(id, image);
+        var pdfImage = Image.Get(_tableBuilder, image);
 
         return AddImage(pdfImage);
     }
@@ -108,7 +98,7 @@ internal PdfName AddSeparation(Separation separation)
 
         var key = PREFIX_SEPARATION + System.Threading.Interlocked.Increment(ref _separationCounter).ToString().PadLeft(6, '0');
         var name = PdfName.Get(key);
-        _separations[separation] = (name, _tableBuilder.ReserveId());
+        _separations[separation] = (name, _tableBuilder.GetSeparationId(separation));
 
         return name;
     }