【OpenXml】Converting Pptx Dashed Borders to WPF Dashed Borders

1. Installing the OpenXML SDK

First, install the required NuGet package for the OpenXML SDK. We have open-sourced an OpenXML flattening layer for parsing pptx files. You can install it using either of the following methods:

• Via the NuGet Package Manager Console:

Install-Package dotnetCampus.DocumentFormat.OpenXml.Flatten -Version 2.0.0

• Via a csproj reference:

<PackageReference Include="dotnetCampus.DocumentFormat.OpenXml.Flatten" Version="2.0.0" />

2. Parsing the Pptx

Here I use the 7 types of straight lines in PPTX, each set to one of the 7 available dash types. The display effect in PPTX is as follows:

The parsing code is as follows, with the main logic part:

private void PptxToGeometry(string filePath)
{
    if (!File.Exists(filePath) || !filePath.EndsWith(".pptx", StringComparison.OrdinalIgnoreCase))
    {
        return;
    }

    var lines = new List<Line>();
    using var presentationDocument = PresentationDocument.Open(filePath, false);
    var presentationPart = presentationDocument.PresentationPart;
    var presentation = presentationPart?.Presentation;
    var slideIdList = presentation?.SlideIdList;
    if (slideIdList == null)
    {
        return;
    }
    foreach (var slideId in slideIdList.ChildElements.OfType<SlideId>())
    {
        var slidePart = (SlidePart)presentationPart.GetPartById(slideId.RelationshipId);
        var slide = slidePart.Slide;
        foreach (var shapeProperties in slide.Descendants<ShapeProperties>())
        {
            var presetGeometry = shapeProperties.GetFirstChild<PresetGeometry>();
            if (presetGeometry != null && presetGeometry.Preset.HasValue)
            {
                if (presetGeometry.Preset == ShapeTypeValues.StraightConnector1)
                {
                    var transform2D = shapeProperties.GetFirstChild<Transform2D>();
                    var extents = transform2D?.GetFirstChild<Extents>();
                    if (extents != null)
                    {
                        var width = new Emu(extents.Cx!.Value).ToPixel().Value;
                        var height = new Emu(extents.Cy!.Value).ToPixel().Value;


                        var presetDash = shapeProperties.GetFirstChild<Outline>()?.GetFirstChild<PresetDash>()?.Val;
                        var dashArray = GetDashArrayByPresetLineDashValues(presetDash);
                        var line = ConverterToGeometry( width, height, dashArray);
                        lines.Add(line);
                    }
                }
            }
        }
    }

    this.ListBox.ItemsSource = lines;
}

Method to map PPTX dash types to WPF dash arrays:

private DoubleCollection GetDashArrayByPresetLineDashValues(PresetLineDashValues presetLineDashValues)
{
    DoubleCollection dashStyle = presetLineDashValues switch
    {
        PresetLineDashValues.Solid => new(),
        PresetLineDashValues.Dot => new() { 0, 2 },
        PresetLineDashValues.Dash => new() { 3, 3 },
        PresetLineDashValues.LargeDash => new() { 8, 3 },
        PresetLineDashValues.DashDot => new() { 3, 3, 1, 3 },
        PresetLineDashValues.LargeDashDot => new() { 7.5, 3.5, 1, 3.5 },
        PresetLineDashValues.LargeDashDotDot => new() { 8, 3, 1, 3, 1, 3 },
        PresetLineDashValues.SystemDash => new() { 3, 1 },
        PresetLineDashValues.SystemDot => new() { 1, 1 },
        PresetLineDashValues.SystemDashDot => new() { 2, 2, 0, 2 },
        PresetLineDashValues.SystemDashDotDot => new() { 2, 2, 0, 2 },
        _ => new DoubleCollection()
    };
    return dashStyle;
}

Final method to draw the line:

private Line ConverterToGeometry(double width, double height, DoubleCollection dashDoubleCollection)
{
    var line = new Line
    {
        X1 = 0,
        Y1 = 0,
        X2 = width,
        Y2 = height,
        StrokeDashArray = dashDoubleCollection,
        Stroke = Stroke,
        StrokeThickness = StrokeThickness
    };
    return line;
}

Final effect:

We can see that the effect is very close. Of course, you can fine-tune the values to be more precise by simply adjusting the corresponding values in the GetDashArrayByPresetLineDashValues method.

3. Afterword

Actually, the OpenXML documentation provides the PresetDash values, roughly as follows:

However, these values do not correspond to the DoubleCollection used for setting dashes in WPF. Therefore, the mapping values above are all my own fine-tuning.

4. Source Code

BlogCodeSample/PptDashConverToWpfSample at main · ZhengDaoWang/BlogCodeSample