Note that one could also do "area mapping" with nearest neighbor instead of 4-pixel interpolation (if speed is more important than smoothness) to avoid the whit

Note that one could also do "area mapping" with nearest neighbor instead of 4-pixel interpolation (if speed is more important than smoothness) to avoid the white dots. This is the most obvious "naive" approach to me -- basically the same cost as the white dots approach (loop over every destination pixel just once, grab just one pixel from source) but with some repeated neighboring pixels instead of missing information.