[NTG-context] Images centered on page

Hello, How can I center the image on a page? I want images to cover the page completely, and since they have proper size (roughly A4), I only need them to be centered. Now they are stuck to the top, leaving a gap on bottom (and same for left-right). I have the following script (note my Lua trick to process images in a batch). Image names are "Image00001.png" and so on. %engine=luatex \setuplayout [footer=0mm, header=0mm, topspace=0mm, backspace=0mm, leftmargin=0mm, rightmargin=0mm, location=middle, height=fit, width=fit] \starttext \startluacode for n = 1, 9 do tex.print(string.format("\\externalfigure[Image%05d.png]", n)); end \stopluacode \stoptext Best regards, Vyatcheslav