Source pixel while zooming

Hello,

Currently, I can get the source pixel (x,y) by doing below. When zooming in or out, the pixel value changes. How can I grab the correct pixel point from the source image whether I'm zoomed in or out.

Thanks in advance!

Josh

 def getPixel(self, event):
    pointer = event.pointer()
    sourcePixel = rv.commands.sourceAtPixel(pointer)[0]
    px = sourcePixel['px']
    py = sourcePixel['py']