From 29fed6500f56e75f9a933ebb00d8aef90969238e Mon Sep 17 00:00:00 2001
From: Sergiusz Zalewski <38229504+KeterSCP@users.noreply.github.com>
Date: Sun, 17 Dec 2023 13:12:56 +0100
Subject: [PATCH] Drawing of 24-bit DIB to png

---
 src/SharpEmf.Svg/BitmapUtils.cs               | 81 +++++++++++++++++++
 .../EmfBitmapRecordsHandlers.cs               |  9 +--
 src/SharpEmf.Svg/SharpEmf.Svg.csproj          |  5 ++
 src/SharpEmf/Extensions/StreamExtensions.cs   |  2 +
 4 files changed, 90 insertions(+), 7 deletions(-)
 create mode 100644 src/SharpEmf.Svg/BitmapUtils.cs

diff --git a/src/SharpEmf.Svg/BitmapUtils.cs b/src/SharpEmf.Svg/BitmapUtils.cs
new file mode 100644
index 0000000..2c55b9d
--- /dev/null
+++ b/src/SharpEmf.Svg/BitmapUtils.cs
@@ -0,0 +1,81 @@
+using SharpEmf.WmfTypes.Bitmap;
+using SkiaSharp;
+
+namespace SharpEmf.Svg;
+
+internal static class BitmapUtils
+{
+    public static unsafe string DibToPngBase64(byte[] dibData, BitmapInfoHeader bitmapHeader)
+    {
+        // TODO: this assumes that the DIB is 24-bit RGB, handle other cases
+
+        using var bitmap = new SKBitmap();
+
+        var width = bitmapHeader.Width;
+        var height = bitmapHeader.Height;
+
+        var rgbaData = DibToRgba(dibData, bitmapHeader);
+
+        fixed(byte* rgbaDataPtr = rgbaData)
+        {
+            var rgbaDataPtr2 = (IntPtr)rgbaDataPtr;
+            bitmap.InstallPixels(new SKImageInfo(width, height, SKColorType.Rgba8888, SKAlphaType.Unpremul), rgbaDataPtr2, width * 4);
+        }
+
+        using var pngData = bitmap.Encode(SKEncodedImageFormat.Png, 100);
+        var resultBase64Str = Convert.ToBase64String(pngData.Span);
+
+        return resultBase64Str;
+    }
+
+    public static unsafe byte[] DibToRgba(byte[] dibData, BitmapInfoHeader bitmapHeader)
+    {
+        var usedBytes = (ushort)bitmapHeader.BitCount / 8 * bitmapHeader.Width;
+        // DIB data is padded to the nearest DWORD (4-byte) boundary
+        var padding = RoundUpToNearestMultipleOf4(usedBytes) - usedBytes;
+
+        var rgbaStride = bitmapHeader.Width * 4;
+
+        byte[] rgbaData = new byte[rgbaStride * bitmapHeader.Height];
+
+        fixed (byte* dibDataPtr = dibData)
+        {
+            fixed (byte* rgbaDataPtr = rgbaData)
+            {
+                var dibDataPtr2 = dibDataPtr;
+                var rgbaDataPtr2 = rgbaDataPtr;
+
+                for (int y = 0; y < bitmapHeader.Height; y++)
+                {
+                    // Due to the fact that emf arrays after reading are reversed, padding skipping is done before the X-row loop
+                    // Bytes order in EMF file: B, G, R, PADDED, PADDED, B, G, R, PADDED, PADDED, ...
+                    // After reversing:         PADDED, PADDED, R, G, B, PADDED, PADDED, R, G, B, ...
+                    dibDataPtr2 += padding;
+
+                    for (int x = 0; x < bitmapHeader.Width; x++)
+                    {
+                        var r = *dibDataPtr2;
+                        var g = *(dibDataPtr2 + 1);
+                        var b = *(dibDataPtr2 + 2);
+                        const byte a = 0xFF;
+
+                        *rgbaDataPtr2 = r;
+                        *(rgbaDataPtr2 + 1) = g;
+                        *(rgbaDataPtr2 + 2) = b;
+                        *(rgbaDataPtr2 + 3) = a;
+
+                        dibDataPtr2 += 3;
+                        rgbaDataPtr2 += 4;
+                    }
+                }
+            }
+        }
+
+        return rgbaData;
+    }
+
+    private static int RoundUpToNearestMultipleOf4(int num)
+    {
+        return (num + 3) / 4 * 4;
+    }
+}
\ No newline at end of file
diff --git a/src/SharpEmf.Svg/RecordsProcessing/EmfBitmapRecordsHandlers.cs b/src/SharpEmf.Svg/RecordsProcessing/EmfBitmapRecordsHandlers.cs
index d8ec25b..513fab1 100644
--- a/src/SharpEmf.Svg/RecordsProcessing/EmfBitmapRecordsHandlers.cs
+++ b/src/SharpEmf.Svg/RecordsProcessing/EmfBitmapRecordsHandlers.cs
@@ -7,18 +7,13 @@ internal static class EmfBitmapRecordsHandlers
 {
     public static void HandleStretchDIBits(StringBuilder svgSb, EmfState state, EmrStretchDiBits stretchDiBits)
     {
-        // TODO: fix this
-        var bitmapBase64 = Convert.ToBase64String(stretchDiBits.BitsSrc);
-
-        var scalingForMapMode = state.GetScalingForCurrentMapMode();
-        var scaleMatrix = $"matrix({scalingForMapMode.X},0,0,{scalingForMapMode.Y},0,0)";
+        var bitmapBase64 = BitmapUtils.DibToPngBase64(stretchDiBits.BitsSrc, stretchDiBits.BmiHeader);
 
         var x = stretchDiBits.XDest;
         var y = stretchDiBits.YDest;
         var width = stretchDiBits.CXDest;
         var height = stretchDiBits.CYDest;
 
-
-        svgSb.AppendLine($"<image transform=\"{scaleMatrix}\" x=\"{x}\" y=\"{y}\" width=\"{width}\" height=\"{height}\" xlink:href=\"data:image/bmp;base64,{bitmapBase64}\" />");
+        svgSb.AppendLine($"<image x=\"{x}\" y=\"{y}\" width=\"{width}\" height=\"{height}\" href=\"data:image/png;base64,{bitmapBase64}\" />");
     }
 }
\ No newline at end of file
diff --git a/src/SharpEmf.Svg/SharpEmf.Svg.csproj b/src/SharpEmf.Svg/SharpEmf.Svg.csproj
index 34e08d0..e1c1937 100644
--- a/src/SharpEmf.Svg/SharpEmf.Svg.csproj
+++ b/src/SharpEmf.Svg/SharpEmf.Svg.csproj
@@ -4,10 +4,15 @@
         <TargetFramework>net8.0</TargetFramework>
         <ImplicitUsings>enable</ImplicitUsings>
         <Nullable>enable</Nullable>
+        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     </PropertyGroup>
 
     <ItemGroup>
       <ProjectReference Include="..\SharpEmf\SharpEmf.csproj" />
     </ItemGroup>
 
+    <ItemGroup>
+      <PackageReference Include="SkiaSharp" Version="2.88.6" />
+    </ItemGroup>
+
 </Project>
diff --git a/src/SharpEmf/Extensions/StreamExtensions.cs b/src/SharpEmf/Extensions/StreamExtensions.cs
index 7aca345..cad631b 100644
--- a/src/SharpEmf/Extensions/StreamExtensions.cs
+++ b/src/SharpEmf/Extensions/StreamExtensions.cs
@@ -75,6 +75,8 @@ internal static byte[] ReadByteArray(this Stream stream, int length)
 
         var buffer = new byte[length];
         stream.ReadExactly(buffer);
+        buffer.AsSpan().Reverse();
+
         return buffer;
     }