feat(sender-editor): add PDF page rendering pipeline

EnvelopeGenerator.Infrastructure.Doc/PdfPageImageRenderer.cs

@@ -0,0 +1,57 @@
+using DevExpress.Drawing;
+using DevExpress.Pdf;
+using EnvelopeGenerator.Application.Common.Dto;
+using EnvelopeGenerator.Application.Common.Interfaces.Doc;
+
+namespace EnvelopeGenerator.Infrastructure.Doc;
+
+public class PdfPageImageRenderer : IPdfPageImageRenderer
+{
+    private const float RenderDpi = 110f;
+
+    public Task<IReadOnlyList<PdfPageImageDto>> RenderPagesAsImagesAsync(byte[] pdfBytes, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(pdfBytes);
+
+        if (pdfBytes.Length == 0)
+            return Task.FromResult<IReadOnlyList<PdfPageImageDto>>(Array.Empty<PdfPageImageDto>());
+
+        using var stream = new MemoryStream(pdfBytes, writable: false);
+        using var processor = new PdfDocumentProcessor();
+        processor.LoadDocument(stream);
+
+        var pages = processor.Document.Pages;
+        if (pages.Count == 0)
+            return Task.FromResult<IReadOnlyList<PdfPageImageDto>>(Array.Empty<PdfPageImageDto>());
+
+        var renderOptions = PdfPageRenderingParameters.CreateWithResolution(RenderDpi);
+        var results = new List<PdfPageImageDto>(pages.Count);
+
+        for (var i = 0; i < pages.Count; i++)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+
+            var pageNumber = i + 1;
+            var page = pages[i];
+            var cropBox = page.CropBox;
+
+            using DXBitmap bitmap = processor.CreateDXBitmap(pageNumber, renderOptions);
+            using var imageStream = new MemoryStream();
+            bitmap.Save(imageStream, DXImageFormat.Png);
+
+            var dataUrl = $"data:image/png;base64,{Convert.ToBase64String(imageStream.ToArray())}";
+
+            results.Add(new PdfPageImageDto
+            {
+                PageNumber = pageNumber,
+                WidthPt = cropBox.Width,
+                HeightPt = cropBox.Height,
+                WidthPx = bitmap.Width,
+                HeightPx = bitmap.Height,
+                ImageDataUrl = dataUrl
+            });
+        }
+
+        return Task.FromResult<IReadOnlyList<PdfPageImageDto>>(results);
+    }
+}