Distance Annotation in ASP.NET Core PDF Viewer

14 Aug 20267 minutes to read

Distance is a measurement annotation used to measure the length between two points on a PDF page. Use it for precise reviews, markups, or engineering measurements.

Distance overview

Enable Distance Annotation

To enable Distance annotation, inject the following modules into the ASP.NET Core PDF Viewer:

<div style="width:100%;height:600px">
    <ejs-pdfviewer id="pdfviewer"
                   style="height:600px"
                   documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
                   resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib">
    </ejs-pdfviewer>
</div>

Add Distance Annotation

Add Distance Using the Toolbar

  1. Open the Annotation Toolbar.
  2. Select Measurement → Distance.
  3. Click to set the start point, then click again to set the end point.

Measurement toolbar

If Pan mode is active, choosing a measurement tool switches the viewer into the appropriate interaction mode for a smoother workflow.

Enable Distance Mode

Programmatically switch the viewer into Distance mode.

<script>
function enableDistanceMode() {
  var viewer = document.getElementById('pdfviewer').ej2_instances[0];
  viewer.annotation.setAnnotationMode('Distance');
}
</script>

Exit Distance Mode

<script>
function exitDistanceMode() {
  var viewer = document.getElementById('pdfviewer').ej2_instances[0];
  viewer.annotation.setAnnotationMode('None');
}
</script>

Add Distance Programmatically

Use the addAnnotation API to draw a Distance measurement by providing two vertexPoints.

<script>
function addDistance() {
  var viewer = document.getElementById('pdfviewer').ej2_instances[0];
  viewer.annotation.addAnnotation('Distance', {
    offset: { x: 200, y: 230 },
    pageNumber: 1,
    vertexPoints: [
      { x: 200, y: 230 },
      { x: 350, y: 230 }
    ]
  });
}
</script>

Customize Distance Appearance

Configure default properties using the Distance Settings property (for example, default fill color, stroke color, opacity).

<div style="width:100%;height:650px">
    <ejs-pdfviewer id="pdfviewer"
                   style="height:650px"
                   documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
                   resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib">
    </ejs-pdfviewer>
</div>
<script>
window.onload = function () {
  var viewer = document.getElementById('pdfviewer').ej2_instances[0];
  viewer.distanceSettings = { fillColor: 'blue', strokeColor: 'green', opacity: 0.6 };
}
</script>

Manage Distance (Move, Resize, Edit, Delete)

  • Move: Drag the measurement to reposition it.
  • Resize: Drag the end handles to adjust the length.

Edit Distance

Edit Distance (UI)

Change stroke color, thickness, and opacity using the annotation toolbar tools.

  • Edit the fill color using the Edit Color tool.
    Fill color
  • Edit the stroke color using the Edit Stroke Color tool.
    Stroke color
  • Edit the border thickness using the Edit Thickness tool.
    Thickness
  • Edit the opacity using the Edit Opacity tool.
    Opacity
  • Open Right Click → Properties for additional line-based options.
    Line properties

Edit Distance Programmatically

Update properties and call editAnnotation().

<script>
function editDistanceProgrammatically() {
  var viewer = document.getElementById('pdfviewer').ej2_instances[0];
  for (var i = 0; i < viewer.annotationCollection.length; i++) {
    var ann = viewer.annotationCollection[i];
    if (ann.subject === 'Distance calculation') {
      ann.strokeColor = '#0000FF';
      ann.thickness = 2;
      ann.opacity = 0.8;
      viewer.annotation.editAnnotation(ann);
      break;
    }
  }
}
</script>

Delete Distance Annotation

Delete Distance Annotation via UI (toolbar/context menu) or programmatically. For supported workflows and APIs, see Delete Annotation.

Set Default Properties During Initialization

Apply defaults for Distance using the distanceSettings property.

<PdfViewerComponent
  id="container"
  documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
  resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib"
  distanceSettings=
  style=
>
  <Inject services={[Toolbar, Annotation]} />
</PdfViewerComponent>

Set Properties While Adding Individual Annotation

Pass per-annotation values directly when calling addAnnotation.

<script>
function addStyledDistance() {
  var viewer = document.getElementById('pdfviewer').ej2_instances[0];
  viewer.annotation.addAnnotation('Distance', {
    offset: { x: 220, y: 260 },
    pageNumber: 1,
    vertexPoints: [
      { x: 220, y: 260 },
      { x: 360, y: 260 }
    ],
    strokeColor: '#059669',
    opacity: 0.9,
    fillColor: '#D1FAE5',
    thickness: 2
  });
}
</script>

Scale Ratio and Units

  • Use Scale Ratio from the context menu to set the actual-to-page scale.
    Scale ratio
  • Supported units include Inch, Millimeter, Centimeter, Point, Pica, Feet.
    Scale dialog

Set Default Scale Ratio During Initialization

Configure scale defaults using measurementSettings.

<div style="width:100%;height:650px">
    <ejs-pdfviewer id="pdfviewer"
                   style="height:650px"
                   documentPath="https://cdn.syncfusion.com/content/pdf/pdf-succinctly.pdf"
                   resourceUrl="https://cdn.syncfusion.com/ej2/31.2.2/dist/ej2-pdfviewer-lib">
    </ejs-pdfviewer>
</div>
<script>
var viewer = document.getElementById('pdfviewer').ej2_instances[0];
viewer.measurementSettings = { scaleRatio: 2, conversionUnit: 'cm', displayUnit: 'cm' };
</script>

Handle Distance Events

Listen to annotation life-cycle events (add/modify/select/remove). For the full list and parameters, see Annotation Events.

Export and Import

Distance measurements can be exported or imported with other annotations. For workflows and supported formats, see Export and Import annotations.

See Also