<s>
Adam7	B-Algorithm
is	O
an	O
interlacing	O
algorithm	O
for	O
raster	B-Algorithm
images	I-Algorithm
,	O
best	O
known	O
as	O
the	O
interlacing	O
scheme	O
optionally	O
used	O
in	O
PNG	O
images	O
.	O
</s>
<s>
An	O
Adam7	B-Algorithm
interlaced	O
image	O
is	O
broken	O
into	O
seven	O
subimages	O
,	O
which	O
are	O
defined	O
by	O
replicating	O
this	O
8×8	O
pattern	O
across	O
the	O
full	O
image	O
.	O
</s>
<s>
Adam7	B-Algorithm
uses	O
seven	O
passes	O
and	O
operates	O
in	O
both	O
dimensions	O
,	O
compared	O
to	O
only	O
four	O
passes	O
in	O
the	O
vertical	O
dimension	O
used	O
by	O
GIF	O
.	O
</s>
<s>
This	O
means	O
that	O
an	O
approximation	O
of	O
the	O
entire	O
image	O
can	O
be	O
perceived	O
much	O
more	O
quickly	O
in	O
the	O
early	O
passes	O
,	O
particularly	O
if	O
interpolation	O
algorithms	O
such	O
as	O
bicubic	B-Algorithm
interpolation	I-Algorithm
are	O
used	O
.	O
</s>
<s>
Adam7	B-Algorithm
is	O
named	O
after	O
Adam	O
M	O
.	O
Costello	O
,	O
who	O
suggested	O
the	O
method	O
on	O
February	O
2	O
,	O
1995	O
,	O
and	O
after	O
the	O
seven	O
steps	O
involved	O
.	O
</s>
<s>
Alternative	O
speculative	O
proposals	O
at	O
the	O
time	O
included	O
square	O
spiral	O
interlacing	O
and	O
using	O
Peano	B-Algorithm
curves	I-Algorithm
,	O
but	O
these	O
were	O
rejected	O
as	O
being	O
overcomplicated	O
.	O
</s>
<s>
Adam7	B-Algorithm
is	O
a	O
multiscale	O
model	O
of	O
the	O
data	O
,	O
similar	O
to	O
a	O
discrete	O
wavelet	O
transform	O
with	O
Haar	O
wavelets	O
,	O
though	O
it	O
starts	O
from	O
an	O
8×8	O
block	O
,	O
and	O
downsamples	B-Algorithm
the	O
image	O
,	O
rather	O
than	O
decimating	B-Algorithm
(	O
low-pass	B-Algorithm
filtering	I-Algorithm
,	O
then	O
downsampling	B-Algorithm
)	O
.	O
</s>
<s>
It	O
thus	O
offers	O
worse	O
frequency	O
behavior	O
,	O
showing	O
artifacts	O
(	O
pixelation	B-Algorithm
)	O
at	O
the	O
early	O
stages	O
,	O
in	O
return	O
for	O
simpler	O
implementation	O
.	O
</s>
<s>
Adam7	B-Algorithm
arises	O
from	O
iteration	O
of	O
the	O
following	O
pattern	O
:	O
</s>
<s>
Iterating	O
again	O
yields	O
the	O
7-pass	O
Adam7	B-Algorithm
scheme	O
,	O
where	O
the	O
first	O
pass	O
(	O
1/8	O
)	O
2	O
=	O
1/64	O
(	O
1.5625	O
%	O
)	O
of	O
the	O
image	O
.	O
</s>
