<s>
In	O
image	B-Algorithm
processing	I-Algorithm
,	O
the	O
grassfire	B-Algorithm
transform	I-Algorithm
is	O
the	O
computation	O
of	O
the	O
distance	O
from	O
a	O
pixel	O
to	O
the	O
border	O
of	O
a	O
region	O
.	O
</s>
<s>
It	O
can	O
be	O
described	O
as	O
"	O
setting	O
fire	O
"	O
to	O
the	O
borders	O
of	O
an	O
image	O
region	O
to	O
yield	O
descriptors	O
such	O
as	O
the	O
region	O
's	O
skeleton	B-Algorithm
or	O
medial	O
axis	O
.	O
</s>
<s>
A	O
region	O
's	O
skeleton	B-Algorithm
can	O
be	O
a	O
useful	O
descriptor	O
,	O
because	O
it	O
describes	O
things	O
such	O
as	O
the	O
symmetry	O
of	O
the	O
region	O
as	O
well	O
as	O
subparts	O
,	O
depressions	O
and	O
protrusions	O
.	O
</s>
<s>
In	O
the	O
grassfire	B-Algorithm
transform	I-Algorithm
,	O
the	O
skeleton	B-Algorithm
forms	O
at	O
the	O
points	O
in	O
the	O
region	O
where	O
the	O
"	O
fires	O
"	O
meet	O
.	O
</s>
<s>
Another	O
advantage	O
of	O
using	O
the	O
outcome	O
of	O
the	O
grassfire	B-Algorithm
transform	I-Algorithm
as	O
a	O
descriptor	O
is	O
that	O
it	O
is	O
invertible	O
.	O
</s>
<s>
Assuming	O
information	O
about	O
when	O
the	O
medial	O
axis	O
or	O
skeleton	B-Algorithm
is	O
created	O
by	O
meeting	O
waveforms	O
is	O
kept	O
,	O
then	O
the	O
skeleton	B-Algorithm
can	O
be	O
restored	O
by	O
radiating	O
outward	O
.	O
</s>
<s>
Of	O
course	O
there	O
are	O
several	O
other	O
algorithms	O
for	O
performing	O
the	O
grassfire	B-Algorithm
transform	I-Algorithm
.	O
</s>
<s>
It	O
is	O
important	O
to	O
note	O
that	O
the	O
most	O
intense	O
lines	O
make	O
up	O
the	O
skeleton	B-Algorithm
.	O
</s>
<s>
The	O
grassfire	B-Algorithm
transform	I-Algorithm
can	O
be	O
abstracted	O
to	O
suit	O
a	O
variety	O
of	O
computing	O
problems	O
.	O
</s>
<s>
This	O
includes	O
applications	O
in	O
energy	O
minimization	O
problems	O
such	O
as	O
those	O
handled	O
by	O
the	O
Viterbi	B-Algorithm
algorithm	I-Algorithm
,	O
max-product	O
belief	O
propagation	O
,	O
resource	O
allocation	O
,	O
and	O
in	O
optimal	O
control	O
methods	O
.	O
</s>
