+(defun pixel-size (format-spec)
+ "Return pixel size in micrometers."
+ (let ((pixel-dim (pixel-dimensions format-spec))
+ (imager-dim (imager-dimensions format-spec)))
+ (values (* 1000 (/ (car imager-dim) (car pixel-dim)))
+ (* 1000 (/ (cdr imager-dim) (cdr pixel-dim))))))