Unable to render pdf page as the ImageContext wasn't created with an IPdfRenderer.

[nataz77]

Hi!

I don't think this is a bug but more something I'm doing wrong with my code.
I have a bunch of PDFs that are rotated upside down. I would normally use NAPS2 and do it manually, but I wanted to look for a way to automate it, and re-run OCR on top of it afterwards.

Using Naps2.Sdk, the PDF import/export and the OCR libs here's a piece of code I've been experimenting with:

using NAPS2.Images;
using NAPS2.Images.Gdi;
using NAPS2.Images.Transforms;
using NAPS2.Ocr;
using NAPS2.Pdf;
using NAPS2.Scan;

...

using ScanningContext scanningContext = new (new GdiImageContext());
scanningContext.OcrEngine = TesseractOcrEngine.Bundled(@"pathtotraineddata");
PdfImporter pdfImporter = new(scanningContext);
List<ProcessedImage> images = [];
List<ProcessedImage> rotated = [];

await foreach (ProcessedImage image in pdfImporter.Import(pdfPath))
{
    images.Add(image);
}
// if i merge the two foreach adding directly the image.WithTransform to the images list the result is the same
foreach(ProcessedImage image in images)
{
      rotated.Add(image.WithTransform(new RotationTransform(180)));
}

PdfExporter pdfExporter = new(scanningContext);
await pdfExporter.Export(outputPath, rotated, ocrParams: new OcrParams("ita", OcrMode.Best));

Everything seems to be working, except when calling the pdfExporter.Export I get:

System.AggregateException: One or more errors occurred. (One or more errors occurred. (One or more errors occurred. (One or more errors occurred. (Unable to render pdf page as the ImageContext wasn't created with an IPdfRenderer.))))
 ---> System.AggregateException: One or more errors occurred. (One or more errors occurred. (One or more errors occurred. (Unable to render pdf page as the ImageContext wasn't created with an IPdfRenderer.)))
 ---> System.AggregateException: One or more errors occurred. (One or more errors occurred. (Unable to render pdf page as the ImageContext wasn't created with an IPdfRenderer.))
 ---> System.AggregateException: One or more errors occurred. (Unable to render pdf page as the ImageContext wasn't created with an IPdfRenderer.)
 ---> System.InvalidOperationException: Unable to render pdf page as the ImageContext wasn't created with an IPdfRenderer.
   at NAPS2.Images.ImageContext.MaybeRenderPdf(ImageMemoryStorage memoryStorage, IMemoryImage& renderedPdf)
   at NAPS2.Images.ImageContext.RenderFromStorage(IImageStorage storage)
   at NAPS2.Images.ImageContext.Render(IRenderableImage image)
   at NAPS2.Images.ImageExtensions.Render(IRenderableImage image)
   at NAPS2.Pdf.PdfExporter.GetRenderedImageOrDirectJpegEmbedder(PageExportState state)
   at NAPS2.Pdf.PdfExporter.RenderStep(PageExportState state)
   at System.Threading.Tasks.Dataflow.TransformBlock`2.ProcessMessage(Func`2 transform, KeyValuePair`2 messageWithId)
   at System.Threading.Tasks.Dataflow.Internal.TargetCore`1.ProcessMessagesLoopCore()
   --- End of inner exception stack trace ---
   --- End of inner exception stack trace ---
   --- End of inner exception stack trace ---
   --- End of inner exception stack trace ---
   at NAPS2.Threading.Pipeline.PipelineStep`1.Run()
   at NAPS2.Pdf.PdfExporter.<>c__DisplayClass5_0.<<Export>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at NAPS2.Pdf.PdfExporter.Export(OutputPathOrStream output, ICollection`1 images, PdfExportParams exportParams, OcrParams ocrParams, ProgressHandler progress)
  at ConsoleApp14.Test.Services.OcrService.RotateAndProcessDocument(String pdfPath, String outputPath)

If I remove the transform, the export works correctly, so I'm sure I'm using the transform the wrong way.
What would be the best way to apply a transform to a pre-existing PDF and export it again?

I am very thankful and appreciate any help on this issue!

[cyanfish]

Try with the latest SDK version 0.3.0.

[nataz77]

It worked!
There was a conflict as I was fiddling around with PdfSharpCore too, but removing that everything worked.

Thanks for the help