Coordinate conversion in the Flutter PDF viewer

PDF documents use a coordinate space that differs from the view coordinate space used by Flutter. The PDF coordinate system has its origin in the bottom-left corner with y values increasing upward, while Flutter view coordinates have their origin in the top-left corner with y values increasing downward.

Nutrient Flutter SDK provides coordinate conversion APIs on NutrientViewController(opens in a new tab) for mapping between these two coordinate spaces on Android and iOS.

Converting view coordinates to PDF coordinates

convertViewPointToPdfPoint converts a point from the view coordinate space to the PDF page coordinate space. The input point is in logical pixel coordinates relative to the upper-left corner of the rendered page:

NutrientViewController? controller;

NutrientView(
  documentPath: documentPath,
  onViewCreated: (NutrientViewController c) {
    controller = c;
  },
  onDocumentLoaded: (PdfDocument document) async {
    final pdfPoint = await controller?.convertViewPointToPdfPoint(
      0, // pageIndex (zero-based)
      const Offset(150.0, 300.0),
    );

    print('PDF coordinates: (${pdfPoint?.dx}, ${pdfPoint?.dy})');
  },
)

Converting PDF coordinates to view coordinates

convertPdfPointToViewPoint converts a point from the PDF page coordinate space to the view coordinate space. The returned Offset is in logical pixel coordinates relative to the upper-left corner of the rendered page:

final viewPoint = await controller.convertPdfPointToViewPoint(
  0, // pageIndex (zero-based)
  const Offset(72.0, 720.0),
);

print('View coordinates: (${viewPoint.dx}, ${viewPoint.dy})');

For more information about PDF coordinate spaces, refer to the web guide on coordinate spaces.