SetDirectory["C:\\drorbn\\Talks\\Goettingen-1004"]

img=Import["Hilbert_256.png"]

Dimensions[im=img[[1]] /. {x_,x_,x_} :> x]

GraphicsArray[Partition[
Table[
bs=2^(8-k);
ps = Graphics[
Raster[Reverse[Total[Partition[im, {bs,bs}], {3,4}]/bs^2/255.]
],
ImageSize -> 256, ImagePadding -> None, PlotRangePadding -> None
];
Export["Hilbert-"<>ToString[k]<>".png", ps];
ps,
{k,0,7}
],2]]

256*8+64*7