Smoother Freehand Annotations

Product: WebViewer

Product Version: 8.5.0


when creating Freehand-Annotations in the WebViewer it always looks a little bit spidery compared to the native Handwriting on iOS.

As smaller the writing are, the more hard it is to read. As we are using the WebViewer extensive and Freehand Annotations are a big part of our daily use, i’m wondering if there’s a way to improve this behavior.

See the Attached examples:

  • Test_PDFTronDemo.pdf - Here i used the Online-Demo of your Website
  • Test_Prod.pdf - Here i used the WebViewer within our Application
  • Test_iPad.pdf - Here i used the native iOS-PDF-Viewer. As you can see, the Handwriting there is much smoother compared to the previous examples.

Test_PDFTronDemo.pdf (645.2 KB)
Test_Prod.pdf (645.4 KB)
Test_iPad.pdf (728.4 KB)

Thanks in advance


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Hello chris,

Some options that might be able help with FreeHand annotations could be:

​Let us know if this helps!

Best Regards,
Carlo Mendoza
Software Developer
PDFTron Systems, Inc.

Hello Carlo,

thank you for your answer. I tried both of the options, but neither of them made a difference.

With simplyfyPen there was no difference at all.

Increasing the resolution made the problem even worse, as writing with the Apple Pencil are even more delayed.

Here’s a Screenshot, zoomed in into the PDF, that i annotated with PDFViewer. At 1 and 2 for example the lines are very squiggly. The Problem is, that when there is much Text written by hand on the iPad, it get’s very hard to read :frowning:

And here’s another Screenshot, that i made with the files app on the iPad, here everything looks much smoother:

Best Regards


Hello chris,

Just wanted to clarify, when you tried using simplifyPen were you using code similar to this?

window.instance.Core.documentViewer.getTool('AnnotationCreateFreeHand').simplifyPen = true;

Another trick that might help the lines look less jagged could be using a slightly higher stroke size for the Free Hand Annotation Tool. It might also take a combination of all these things to try and customize the viewer and the Free Hand tool to get to a more desirable smoothness.

Best Regards,
Carlo Mendoza
Software Developer
PDFTron Systems, Inc.

Hello Carlo,

thanks again for your answer. Looks like i did it the wrong way:

this.webviewer.instance.Core.Tools.FreeHandCreateTool.prototype.simplifyPen = true;

Now i made it as you mentioned. The result is slightly better. The Problem with simplyfyPen and setCanvasMultiplier, is that with both options the Performance get a little bit worser (even on an iPad Air 4th Gen, which should have enough CPU-Power). Writing is a little bit “tough”.

For now, i deploy a new Version with simplifyPen activated and hope, this is sufficient for our users. Either way, maybe this is considered as enhancement for a future release :slight_smile:

Best regards