ABCpdf .NET PDF Component Documentation - RenderOperation Save Function. Renders and saves a page.

Here we render all the pages of the doc using 10 threads at a time. We alternate rendering format between jpg and tiff. We also alternate resolution between 150 and 300 dpi. Note how the RenderingOperation is created in the constructor of TheRenderingWorker. This is because at this point a copy of the rendering options is made. Had we created the RenderingOperation in DoWork, we would have picked up only the last doc.Rendering.DotsPerInch, because the threads are started in the following loop. Also note how we dispose the operation in DoWork, to release resources stored on the native side (the copy of the rendering options basically).

using var doc = new Doc();
doc.Read(Server.MapPath("spaceshuttle.pdf"));
string[] xts = { ".jpg", ".tif" };
int[] dpis = { 150, 300 };
var threads = new Thread[10];
int pageNum = 1, pageCount = doc.PageCount;
while (pageNum <= pageCount) {
  int count = 0;
  while (count < threads.Length && pageNum <= pageCount) {
    doc.Rendering.DotsPerInch = dpis[(pageNum - 1) % 2];
    doc.PageNumber = pageNum;
    string path = Server.MapPath($"ABCpdf{pageNum}{xts[(pageNum - 1) % 2]}");


    threads[count] = new Thread(new RenderingWorker(doc, path).DoWork);
    ++count;
    ++pageNum;
  }
  for (int i = 0; i < count; ++i)
    threads[i].Start();
  for (int i = 0; i < count; ++i)
    threads[i].Join();
}

Using doc As New Doc()
  doc.Read(Server.MapPath("spaceshuttle.pdf"))
  Dim theExts As String() = {".jpg", ".tif"}
  Dim theDpis As Integer() = {150, 300}
  Dim threadList As Thread() = New Thread(9) {}
  Dim pageNum As Integer = 1, pageCount As Integer = doc.PageCount
  While pageNum <= pageCount
    Dim count As Integer = 0
    While count < threadList.Length AndAlso pageNum <= pageCount
      doc.Rendering.DotsPerInch = theDpis((pageNum - 1) Mod 2)
      doc.PageNumber = pageNum
      Dim path As String = Server.MapPath($"ABCpdf{pageNum}{theExts[(pageNum - 1) % 2]}")


      threadList(count) = New Thread(New RenderingWorker(doc, path).DoWork)
      System.Threading.Interlocked.Increment(count)
      System.Threading.Interlocked.Increment(pageNum)
    End While
    Dim i As Integer = 0
    While i < count
      threadList(i).Start()
      System.Threading.Interlocked.Increment(i)
    End While
    Dim i As Integer = 0
    While i < count
      threadList(i).Join()
      System.Threading.Interlocked.Increment(i)
    End While
  End While
End Using

class RenderingWorker {
  private string mPath;
  private RenderOperation mOp;

  public RenderingWorker(Doc inDoc, string inPath) {
    mPath = inPath;
    mOp = new RenderOperation(inDoc);
  }

  public void DoWork() {
    mOp.Save(mPath);
    mOp.Dispose();
  }
}

Private Class RenderingWorker
  Private mPath As String
  Private mOp As RenderOperation

  Public Sub New(inDoc As Doc, inPath As String)
    mPath = inPath
    mOp = New RenderOperation(inDoc)
  End Sub

  Public Sub DoWork()
    mOp.Save(mPath)
    mOp.Dispose()
  End Sub
End Class