update(PDF-2231): Address PR Review Feedbacks

Author: Sawraz-IS

IronSoftware.Drawing/IronSoftware.Drawing.Common.Tests/UnitTests/AnyBitmapFunctionality.cs

@@ -676,6 +676,23 @@ public void CreateMultiFrameTiffStream_Empty_Sequence_Throws()
             act.Should().Throw<ArgumentException>();
         }
 
+        [FactWithAutomaticDisplayName]
+        public void CreateMultiFrameTiffBytes_PreservesResolution_FromPixelsPerMeterSource()
+        {
+            const double dpi = 300d;
+            double pixelsPerMetre = dpi / 0.0254d; // 300 DPI expressed in pixels per metre
+
+            using var page = MakeBitmapWithResolution(220, 300, new Rgb24(40, 90, 160),
+                pixelsPerMetre, PixelResolutionUnit.PixelsPerMeter);
+
+            byte[] tiff = AnyBitmap.CreateMultiFrameTiffBytes(new[] { page });
+            var pages = ReadTiffDirectories(tiff);
+
+            pages.Should().ContainSingle();
+            ToDotsPerInch(pages[0].XResolution, pages[0].ResolutionUnit)
+                .Should().BeApproximately(dpi, 2d);
+        }
+
         [FactWithAutomaticDisplayName]
         public void CreateMultiFrameTiff_Preserves_Rgb24_Pixels()
         {
@@ -708,11 +725,17 @@ public void CreateMultiFrameTiff_Preserves_Rgb24_Pixels()
         }
 
         private static AnyBitmap CreateSolidBitmap(int width, int height, Rgb24 color, int dpi)
+        {
+            return MakeBitmapWithResolution(width, height, color, dpi, PixelResolutionUnit.PixelsPerInch);
+        }
+
+        private static AnyBitmap MakeBitmapWithResolution(int width, int height, Rgb24 color,
+            double resolution, PixelResolutionUnit unit)
         {
             var image = new SixLabors.ImageSharp.Image<Rgb24>(width, height, color);
-            image.Metadata.HorizontalResolution = dpi;
-            image.Metadata.VerticalResolution = dpi;
-            image.Metadata.ResolutionUnits = PixelResolutionUnit.PixelsPerInch;
+            image.Metadata.HorizontalResolution = resolution;
+            image.Metadata.VerticalResolution = resolution;
+            image.Metadata.ResolutionUnits = unit;
             return image;
         }
 

IronSoftware.Drawing/IronSoftware.Drawing.Common/AnyBitmap.cs

@@ -3420,10 +3420,20 @@ private static void InternalSaveAsMultiPageTiff(IEnumerable<Image> images, Strea
                             }
                             break;
                         case Image<Abgr32> imageAsFormat:
-                            imageAsFormat.CopyPixelDataTo(buffer);
+                            {
+                                // 4 bytes/pixel, but the bytes are A,B,G,R. The wrong sample
+                                // order for PHOTOMETRIC.RGB (which expects R,G,B,A). Convert to
+                                // Rgba32 so the channels are not written swapped.
+                                using var rgba = imageAsFormat.CloneAs<Rgba32>();
+                                rgba.CopyPixelDataTo(buffer);
+                            }
                             break;
                         case Image<Argb32> imageAsFormat:
-                            imageAsFormat.CopyPixelDataTo(buffer);
+                            {
+                                // Bytes are A,R,G,B; convert to Rgba32 for correct channel order.
+                                using var rgba = imageAsFormat.CloneAs<Rgba32>();
+                                rgba.CopyPixelDataTo(buffer);
+                            }
                             break;
                         case Image<Bgr24> imageAsFormat:
                             {
@@ -3435,7 +3445,12 @@ private static void InternalSaveAsMultiPageTiff(IEnumerable<Image> images, Strea
                             }
                             break;
                         case Image<Bgra32> imageAsFormat:
-                            imageAsFormat.CopyPixelDataTo(buffer);
+                            {
+                                // Bytes are B,G,R,A; convert to Rgba32 so they are not written
+                                // channel-swapped under PHOTOMETRIC.RGB.
+                                using var rgba = imageAsFormat.CloneAs<Rgba32>();
+                                rgba.CopyPixelDataTo(buffer);
+                            }
                             break;
                         default:
                             (image as Image<Rgba32>).CopyPixelDataTo(buffer);