// Load image from file
var image = PdfImage.FromFile("photo.jpg");

// Create figure structure with alt text
var figure = root.AddChild(StructureType.Figure,
    "Company logo on blue background");

// REQUIRED for PDF/UA: bounding box
figure.BBox = new[] {
    72.0, 500.0, 300.0, 680.0
};

// Tag the image content
page.BeginTaggedContent(figure);
page.AddImage(image, 72, 500, 228, 180);
page.EndTaggedContent();

// Scale to fit preserving aspect ratio
var photo = PdfImage.FromFile("landscape.jpg");
var photoFig = root.AddChild(StructureType.Figure,
    "Sunset over the ocean");
photoFig.BBox = new[] {
    72.0, 250.0, 472.0, 450.0
};
page.BeginTaggedContent(photoFig);
page.AddImageScaled(photo,
    72, 250, maxWidth: 400, maxHeight: 200);
page.EndTaggedContent();