Refactor ComposeSignaturePreviewPng to return Stream

Updated the `ComposeSignaturePreviewPng` method in the `IPdfPageImageRenderer` interface to return a `Stream` instead of a `byte[]` for improved memory efficiency when handling large image data.

- Added `ComposeSignaturePreviewPngBytes` extension method to convert the `Stream` to a `byte[]` for backward compatibility.
- Updated `PdfPageImageRenderer` to return a `Stream` and adjusted its internal logic to reset the `MemoryStream` position before returning.
- Modified `DevSignatureInkController` to use the `Stream`-based implementation for HTTP responses.
- Made minor formatting adjustments in `PdfPageImageRenderer`.

These changes optimize memory usage while maintaining compatibility with existing workflows that require `byte[]`.

EnvelopeGenerator.Application/Common/Interfaces/Doc/IPdfPageImageRenderer.cs

@@ -22,7 +22,7 @@ public interface IPdfPageImageRenderer
     /// </summary>
     /// <param name="element"></param>
     /// <returns></returns>
-    byte[] ComposeSignaturePreviewPng(ISignatureInkPayload element);
+    Stream ComposeSignaturePreviewPng(ISignatureInkPayload element);
 
     /// <summary>
     /// 
@@ -51,4 +51,16 @@ public static class PdfPageImageRendererExtensions
 
         return inkBytes;
     }
-}
+
+    public static byte[] ComposeSignaturePreviewPngBytes(this IPdfPageImageRenderer renderer, ISignatureInkPayload element)
+    {
+        using var stream = renderer.ComposeSignaturePreviewPng(element);
+
+        if (stream is MemoryStream memoryStream)
+            return memoryStream.ToArray();
+
+        using var copy = new MemoryStream();
+        stream.CopyTo(copy);
+        return copy.ToArray();
+    }
+}

EnvelopeGenerator.Infrastructure.Doc/PdfPageImageRenderer.cs

@@ -57,7 +57,7 @@ public class PdfPageImageRenderer : IPdfPageImageRenderer
         return Task.FromResult<IReadOnlyList<PdfPageImageDto>>(results);
     }
 
-    public byte[] ComposeSignaturePreviewPng(ISignatureInkPayload element)
+    public Stream ComposeSignaturePreviewPng(ISignatureInkPayload element)
     {
         const double sigW = 1.77 * 72;
         const double sigH = 1.96 * 72;
@@ -137,9 +137,10 @@ public class PdfPageImageRenderer : IPdfPageImageRenderer
 
         var renderOptions = PdfPageRenderingParameters.CreateWithResolution(400f);
         using DXBitmap bitmap = rasterProcessor.CreateDXBitmap(1, renderOptions);
-        using var pngStream = new MemoryStream();
+        var pngStream = new MemoryStream();
         bitmap.Save(pngStream, DXImageFormat.Png);
-        return pngStream.ToArray();
+        pngStream.Position = 0;
+        return pngStream;
     }
 
     private static System.Drawing.RectangleF FitImageContain(System.Drawing.RectangleF area, byte[] imageBytes)
@@ -176,4 +177,4 @@ public class PdfPageImageRenderer : IPdfPageImageRenderer
         return isJpeg;
     }
 
-}
+}

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/DevSignatureInkController.cs

@@ -90,8 +90,8 @@ public class DevSignatureInkController(
         if (!renderer.IsSupportedImageFormat(element.Ink!))
             return StatusCode(StatusCodes.Status415UnsupportedMediaType);
 
-        var composedBytes = renderer.ComposeSignaturePreviewPng(element);
-        return File(composedBytes, "image/png", $"signature-composed-{id}.png");
+        var composedStream = renderer.ComposeSignaturePreviewPng(element);
+        return File(composedStream, "image/png", $"signature-composed-{id}.png");
     }
 
     private bool IsEndpointEnabled()