  Complementary to conventional and phase X-ray radiography, dark-field imaging
has become central in visualizing diffusive scattering signal due to the
spatially-unresolved texture within an object. To date most
diffusive-dark-field retrieval methods require either the acquisition of
multiple images at the cost of higher radiation dose or significant amounts of
computational memory and time. In this work, a simple method of X-ray diffusive
dark-field retrieval is presented, applicable to any single-mask imaging setup,
with only one exposure of the sample. The approach, which is based on a model
of geometric and diffusive reverse-flow conservation, is implicit and
non-iterative. This numerically fast methodology is applied to experimental
X-ray images acquired using both a random mask and a grid mask, giving high
quality reconstructions that are very stable in the presence of noise. The
method should be useful for high-speed imaging and/or imaging with low-flux
sources.
