ResourceLoadingCallback

LoadOptions.ResourceLoadingCallback property

Allows to control how external resources (images, style sheets) are loaded when a document is imported from HTML, MHTML.

public IResourceLoadingCallback ResourceLoadingCallback { get; set; }

Examples

Shows how to handle external resources when loading Html documents.

public void LoadOptionsCallback()
{
    LoadOptions loadOptions = new LoadOptions();
    loadOptions.ResourceLoadingCallback = new HtmlLinkedResourceLoadingCallback();

    // When we load the document, our callback will handle linked resources such as CSS stylesheets and images.
    Document doc = new Document(MyDir + "Images.html", loadOptions);
    doc.Save(ArtifactsDir + "LoadOptions.LoadOptionsCallback.pdf");
}

/// <summary>
/// Prints the filenames of all external stylesheets and substitutes all images of a loaded html document.
/// </summary>
private class HtmlLinkedResourceLoadingCallback : IResourceLoadingCallback
{
    public ResourceLoadingAction ResourceLoading(ResourceLoadingArgs args)
    {
        switch (args.ResourceType)
        {
            case ResourceType.CssStyleSheet:
                Console.WriteLine($"External CSS Stylesheet found upon loading: {args.OriginalUri}");
                return ResourceLoadingAction.Default;
            case ResourceType.Image:
                Console.WriteLine($"External Image found upon loading: {args.OriginalUri}");

                const string newImageFilename = "Logo.jpg";
                Console.WriteLine($"\tImage will be substituted with: {newImageFilename}");

                Image newImage = Image.FromFile(ImageDir + newImageFilename);

                ImageConverter converter = new ImageConverter();
                byte[] imageBytes = (byte[])converter.ConvertTo(newImage, typeof(byte[]));
                args.SetData(imageBytes);

                return ResourceLoadingAction.UserProvided;
        }

        return ResourceLoadingAction.Default;
    }
}

See Also

LoadOptions.ProgressCallback LoadOptions.TempFolder