I realize this is late, but if you want to go pixel by pixel over an image, you're much better off using getscanline() or getsamples()

These fetch a partial or complete row from the image, which might not be suitable for your case (you're fetching columns), but might be for others who see this node.

In reply to Re: Using module Imager, how to convert scalar-color value to hex/rgba color value? by tonyc
in thread Using module Imager, how to convert scalar-color value to hex/rgba color value? by shortland

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