In the usual workflow Enblend and Enfuse generate the blending and
fusing masks according to the command-line options and the input
images and then they immediately use these masks for blending or
fusing the output image.

Sometimes more control over the masks is needed or wanted.  To this
end, both applications provide the option pair @option{--load-masks}
and @option{--save-masks}.  @xref{Invocation}, for detailed
explanations of both options.  With the help of these options the
processing can be broken up into two steps:

@table @asis
@item Save masks with @option{--save-masks}.
Generate masks and save them into image files.

Avoid option@tie{}@option{--output} unless the blended or fused image
at this point is necessary.
@item Load masks with @option{--load-masks}.
Load masks from files and then blend or fuse the final image with the
help of the loaded masks.
@end table

In between these two steps the user may apply whatever transformation
to the mask files, as long as their geometries and offsets remain the
same.  Thus the ``Combine Images'' box of
@ref{Figure:photographic-workflow} becomes three activities as is
depicted in @ref{Figure:external-mask-workflow}.

@float Figure,Figure:external-mask-workflow
@vimage{external-mask-workflow}

@caption{Workflow for externally modified masks.}

@shortcaption{External masks workflow}

@cindex workflow, external masks
@end float

To further optimize this kind of workflow, both Enblend and Enfuse
stop after mask generation if option@tie{}@option{--save-masks} is
given, but @emph{no output file} is specified with the
@option{--output} option.  This way the time for pyramid generation,
blending, fusing, and writing the final image to disk is saved, as
well as no output image gets generated.

Note that options@tie{}@option{--save-masks} and @option{--load-masks}
cannot be used simultaneously.
