c# - 使用 Pdfium 将 PDF 页面渲染为位图

Question

我正在尝试Bitmap使用Pdfium将 PDF 页面转换为 .NET 。我想直接在 WPF 中使用它，所以不打算使用 WinForm 方法。当我尝试使用FPDF_RenderPage. 从我到现在从SDK和它的唯一 .NET 端口 ( PdfViewer ) 中学到的知识，有两种方法可以渲染到位图。

我想知道我是否在第一种方法中正确执行了这些步骤，特别是内存设备上下文，以及在第二种方法中正确地将本机位图带到 .NET 需要什么。

1. 通过FPDF_RenderPage提供内存设备上下文来使用

   var hMemDC = NativeMethods.CreateCompatibleDC(IntPtr.Zero);
   IntPtr hDC = NativeMethods.GetDC(IntPtr.Zero);
   
   // Create a bitmap for output 
   var hBitmap = NativeMethods.CreateCompatibleBitmap(hDC, width, height);
   
   // Select the bitmap into the memory DC 
   hBitmap = NativeMethods.SelectObject(hMemDC, hBitmap);
   
   IntPtr brush = NativeMethods.CreateSolidBrush((int)ColorTranslator.ToWin32(Color.White));
   NativeMethods.FillRgn(hMemDC, NativeMethods.CreateRectRgn(0, 0, width, height), brush);
   
   // _file is an instance of PdfFile from PdfViewer port
   // Now render the page onto the memory DC, which in turn changes the bitmap                 
   bool success = _file.RenderPDFPageToDC(
                page,
                hMemDC,
                (int)dpiX, (int)dpiY,
                bounds.X, bounds.Y, bounds.Width, bounds.Height,
                true /* fitToBounds */,
                true /* stretchToBounds */,
                true /* keepAspectRatio */,
                true /* centerInBounds */,
                true /* autoRotate */,
                forPrinting
           );
   
   hBitmap = NativeMethods.SelectObject(hMemDC, hBitmap);
   
   Bitmap myBitmap = Bitmap.FromHbitmap(hBitmap);
   

2. 使用FPDF_RenderPageBitmap

   IntPtr bitmapHandle = NativeMethods.FPDFBitmap_Create(bounds.Width, bounds.Height, 0);    
   
   // _file is an instance of PdfFile from PdfViewer port
   bool success = _file.RenderPDFPageToBitmap(
      page,
      bitmapHandle,
      (int)dpiX, (int)dpiY,
      bounds.X, bounds.Y, bounds.Width, bounds.Height,
      true /* fitToBounds */,
      true /* stretchToBounds */,
      true /* keepAspectRatio */,
      true /* centerInBounds */,
      true /* autoRotate */,
      forPrinting
   );                
   
   if (!success)
     throw new Win32Exception();
   else
   {
       byte[] bytes = new byte[bounds.Width * bounds.Height * 4];
       Marshal.Copy(bitmapHandle, bytes, 0, bytes.Length);
       bitmap = Convert_BGRA_TO_ARGB(bytes, bounds.Width, bounds.Height);
   }
   

// 将 BGRA 转换为 ARGB

    public Bitmap Convert_BGRA_TO_ARGB(byte[] DATA, int width, int height)
    {
        Bitmap Bm = new Bitmap(width, height, PixelFormat.Format32bppArgb);

        int index;
        for (int y = 0; y < height; y++)
        {
            for (int x = 0; x < width; x++)
            {
                // BGRA TO ARGB
                index = 4 * (x + (y * width));
                Color c = Color.FromArgb(
                     DATA[index + 3],
                    DATA[index + 2],
                    DATA[index + 1],
                    DATA[index + 0]);
                Bm.SetPixel(x, y, c);
            }
        }
        return Bm;
    }

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