From Xojo Documentation
Supported PlatformsProject Types: Web Platforms: macOS, Windows, Linux
Creates a picture that can be used by the web browser, either for display or downloading.
Converting Picture to WebPicture gives you a PNG encoded image. For better performance avoid converting from WebPicture to Picture in your application and keep original Picture object.
Unlike WebFile, WebPicture defaults the session property to the session which it was created in.
Convert a Picture, created at runtime to a WebPicture to display using a WebImageViewer:
p.Graphics.DrawingColor = Color.Blue
p.Graphics.FillRectangle(10, 10, 50, 50)
Var wp As WebPicture = p
ImageViewer1.Picture = wp