Features/add decode array for separation image

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

@@ -226,33 +226,36 @@ public static void Main(string[] args)
                         context.Stroke();
                     });
                 });
-            }
-
-            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 =>
+                using (var pantherPngStream = File.OpenRead("FreePngImage_com/59872-jaguar-panther-royalty-free-cougar-black-cheetah.png"))
+                using (var pantherSixImage = SixLabors.ImageSharp.Image.Load<Rgba32>(pantherPngStream))
                 {
-                    page.MediaBox = mediaBox;
-                    page.TrimBox = trimBox;
+                    var pantherImg = writer.AddImage(pantherSixImage);
+                    var transparentPanther = writer.AddSeparationImage(new Separation(LowLevel.PdfName.Get("White"), PredefinedColors.Yellow), pantherSixImage, GrayScaleMethod.AlphaChannel, [0, 1]);
+
+                    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);
+                        var scale = (double)blurImage.Width / blurImage.Height;
+                        page.Content.AddImage(reusedImage, new Rectangle(0, 0, scale * 303, 303, Unit.Millimeters));
 
-                    page.Content.AddImage(pantherImage, pantherSize);
+                        scale = (double)transparentPanther.Width / transparentPanther.Height;
+                        var pantherSize = new Rectangle(0, 0, 216, 216 / scale, Unit.Millimeters);
 
-                    page.Content.WrapInState(pantherImage, (image, content) =>
-                    {
-                        content.SetExtendedGraphicsState(new ExtendedGraphicsState()
+                        page.Content.AddImage(pantherImg, pantherSize);
+
+                        page.Content.WrapInState(pantherSixImage, (image, content) =>
                         {
-                            Overprint = true
+                            content.SetExtendedGraphicsState(new ExtendedGraphicsState()
+                            {
+                                Overprint = true
+                            });
+                            content.AddImage(transparentPanther, pantherSize);
                         });
-                        content.AddImage(transparentPanther, pantherSize);
                     });
-                });
+                }
             }
         }
     }

src/Synercoding.FileFormats.Pdf/GrayScaleMethod.cs

@@ -24,5 +24,13 @@ public enum GrayScaleMethod
     /// <summary>
     /// Use the average of the Red, Green and Blue channels.
     /// </summary>
-    AverageOfRGBChannels
+    AverageOfRGBChannels,
+    /// <summary>
+    /// The constants defined by ITU-R BT.601 are 0.299 red + 0.587 green + 0.114 blue.
+    /// </summary>
+    BT601,
+    /// <summary>
+    /// The constants defined by ITU-R BT.709 are 0.2126 red + 0.7152 green + 0.0722 blue.
+    /// </summary>
+    BT709,
 }

src/Synercoding.FileFormats.Pdf/Image.cs

@@ -3,7 +3,6 @@
 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;
 
@@ -14,7 +13,7 @@ public class Image : IDisposable
 {
     private protected bool _disposed;
 
-    internal Image(PdfReference id, Stream jpgStream, int width, int height, ColorSpace colorSpace, Image? softMask, params StreamFilter[] filters)
+    internal Image(PdfReference id, Stream jpgStream, int width, int height, ColorSpace colorSpace, Image? softMask, double[]? decodeArray, params StreamFilter[] filters)
     {
         Reference = id;
 
@@ -23,13 +22,16 @@ internal Image(PdfReference id, Stream jpgStream, int width, int height, ColorSp
         RawStream = jpgStream;
         ColorSpace = colorSpace;
         SoftMask = softMask;
+        DecodeArray = decodeArray;
         Filters = filters;
     }
 
     internal Image? SoftMask { get; private set; }
 
     internal Stream RawStream { get; private set; }
 
+    internal double[]? DecodeArray { get; private set; }
+
     /// <summary>
     /// A pdf reference object that can be used to reference to this object
     /// </summary>
@@ -77,23 +79,46 @@ private static Stream _encodeToJpg(SixLabors.ImageSharp.Image image)
 
     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);
+        return new Image(tableBuilder.ReserveId(), _encodeToJpg(image), image.Width, image.Height, DeviceRGB.Instance, GetMask(tableBuilder, image), null, 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)
+        return _hasTransparancy(image)
+            ? new Image(tableBuilder.ReserveId(), AsImageByteStream(image, GrayScaleMethod.AlphaChannel), image.Width, image.Height, DeviceGray.Instance, null, null, StreamFilter.FlateDecode)
             : null;
     }
 
+    private static bool _hasTransparancy(Image<Rgba32> image)
+    {
+        if( image.Metadata.TryGetPngMetadata(out var pngMeta))
+        {
+            if (pngMeta.ColorType == SixLabors.ImageSharp.Formats.Png.PngColorType.RgbWithAlpha)
+                return true;
+            if (pngMeta.ColorType == SixLabors.ImageSharp.Formats.Png.PngColorType.GrayscaleWithAlpha)
+                return true;
+        }
+
+        bool hasTransparancy = false;
+        image.ProcessPixelRows(accessor =>
+        {
+            for (int y = 0; y < accessor.Height; y++)
+            {
+                var row = accessor.GetRowSpan(y);
+                for (int x = 0; x < row.Length; x++)
+                {
+                    ref Rgba32 pixel = ref row[x];
+                    if (pixel.A != 0xFF)
+                    {
+                        hasTransparancy = true;
+                        return;
+                    }
+                }
+            }
+        });
+        return hasTransparancy;
+    }
+
     internal static Stream AsImageByteStream(Image<Rgba32> image, GrayScaleMethod grayScaleMethod)
     {
         using (var byteStream = new MemoryStream())
@@ -118,6 +143,8 @@ internal static Stream AsImageByteStream(Image<Rgba32> image, GrayScaleMethod gr
                             GrayScaleMethod.GreenChannel => pixel.G,
                             GrayScaleMethod.BlueChannel => pixel.B,
                             GrayScaleMethod.AverageOfRGBChannels => (byte)( ( pixel.R + pixel.G + pixel.B ) / 3 ),
+                            GrayScaleMethod.BT601 => (byte)( ( pixel.R * 0.299 ) + ( pixel.G * 0.587 ) + ( pixel.B * 0.114 ) ),
+                            GrayScaleMethod.BT709 => (byte)( ( pixel.R * 0.2126 ) + ( pixel.G * 0.7152 ) + ( pixel.B * 0.0722 ) ),
                             _ => throw new NotImplementedException()
                         };
 

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

@@ -57,7 +57,7 @@ public PdfName AddJpgUnsafe(System.IO.Stream jpgStream, int originalWidth, int o
     {
         var id = _tableBuilder.ReserveId();
 
-        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace, null, StreamFilter.DCTDecode);
+        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace, null, null, StreamFilter.DCTDecode);
 
         return AddImage(pdfImage);
     }

src/Synercoding.FileFormats.Pdf/LowLevel/ObjectStream.cs

@@ -103,7 +103,7 @@ public ObjectStream Write(Image image)
                 .Write(PdfName.Get("Width"), image.Width)
                 .Write(PdfName.Get("Height"), image.Height)
                 .Write(PdfName.Get("BitsPerComponent"), 8)
-                .Write(PdfName.Get("Decode"), _decodeArray(image.ColorSpace))
+                .Write(PdfName.Get("Decode"), image.DecodeArray ?? _decodeArray(image.ColorSpace))
                 .WriteIfNotNull(PdfName.Get("SMask"), image.SoftMask?.Reference);
 
 

src/Synercoding.FileFormats.Pdf/PdfWriter.cs

@@ -167,18 +167,25 @@ public Image AddImage(Image<Rgba32> image)
     /// <param name="separation">The <see cref="Separation"/> to use.</param>
     /// <param name="image">The image to use.</param>
     /// <param name="grayScaleMethod">The <see cref="GrayScaleMethod"/> to use.</param>
+    /// <param name="decodeArray">Optional decode array to use, default value is <c>[ 0.0 1.0 ]</c></param>
     /// <returns>The SeparationImage reference that can be used in pages</returns>
-    public Image AddSeparationImage(Separation separation, Image<Rgba32> image, GrayScaleMethod grayScaleMethod)
+    public Image AddSeparationImage(Separation separation, Image<Rgba32> image, GrayScaleMethod grayScaleMethod, double[]? decodeArray = null)
     {
         _throwWhenEndingWritten();
 
+        decodeArray ??= new double[] { 0, 1 };
+        if(decodeArray.Length != 2)
+            throw new ArgumentOutOfRangeException(nameof(decodeArray), "Length of decode array for separation images should be 2.");
+        if (decodeArray.Any(v => v < 0 || v > 1))
+            throw new ArgumentOutOfRangeException(nameof(decodeArray), "All values of the decode array should be between 0 and 1.");
+
         var id = _tableBuilder.ReserveId();
 
         var mask = Image.GetMask(_tableBuilder, image);
 
         var imageStream = Image.AsImageByteStream(image, grayScaleMethod);
 
-        var pdfImage = new Image(id, imageStream, image.Width, image.Height, separation, mask, StreamFilter.FlateDecode);
+        var pdfImage = new Image(id, imageStream, image.Width, image.Height, separation, mask, decodeArray, StreamFilter.FlateDecode);
 
         _objectStream.Write(pdfImage);
 
@@ -202,7 +209,7 @@ public Image AddJpgUnsafe(Stream jpgStream, int originalWidth, int originalHeigh
 
         var id = _tableBuilder.ReserveId();
 
-        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace, null, StreamFilter.DCTDecode);
+        var pdfImage = new Image(id, jpgStream, originalWidth, originalHeight, colorSpace, null, null, StreamFilter.DCTDecode);
 
         _objectStream.Write(pdfImage);