How do I make a snapshot of a part of a PDF Page ?

Q: I would like to know if it's possible to make a snapshot of a part
of a PDF Page.
I have charts in a page, but it is not considered as an image. So, i
can't export it like any other image.
Is there a way to export each charts of a page in a JPG format ?
Something like doing a snapShot ?
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A: You could set a crop box on the page (page.SetCropBox(rect)) before
using PDFDraw to render the page. This is show in the last code
snippet (example 5) in PDFDraw sample project:
  http://www.pdftron.com/pdfnet/samplecode.html#PDFDraw