Charts to RichTextArea thru copy paste (Image or BufferedImage)

Hi,
My goal is to create a button to send Chart report to RichtextArea directly.
If i’m using Printscreen and paste it works smoothly. If i’m using export to jpg and using HTML Img src tag it works too.
Maybe I need to convert the Vaadin Chart to Image or BufferedImage and copy paste to RichtextArea but i don’t know how to perform cast chart to image and in VaadinBook it’s wrote :

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4.4.5. Stream Resources

Stream resources allow creating dynamic resource content. Charts are typical examples of dynamic images. To define a stream resource, you need to implement the StreamResource.StreamSource interface and its getStream() method. The method needs to return an InputStream from which the stream can be read
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Somebody helps me ?

Best regards
Herve