What's the fastest way to set the pixels of a Picture object?

[Marco_Hof]

2). One of the key operations needed when viewing medical images is the ability to “re-window” in realtime. Essentially, this means adjusting the pixel value of the pixels in the image to be within a certain threshold.

Can you clarify what “re-window” means in real-world?
Is the user resizing the image? Is it moved around? Refreshed? Another drawn on top of it?