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INT
52h,
Function
D
-
Get
Pixels
Entry:
AH
=
D
(function
code)
Exit:
AL=
pixel
states (see description
below)
BL = number
of pixels
returned
This
routine returns
a
byte
in
AL
representing the
state
of
the pixels
at
and
to
the
right
of
the
pixel
addressed by
the graphics cursor.
Bit
7
(MSB)
of
AL
corresponds
to
the
pixel
addressed
by
the
graphics
cursor,
bit
6 corresponds
to
the
pixel
immediately
to
its
right,
and
so
on.
Normally
this
routine returns
8
pixels
so
BL
contains
8.
However,
if
the
right
screen
edge
is
encountered
prior to getting
8
pixels,
the
count
in
BL
is
less
than 8
and
the
unused
low order
bits
of
AL
are undefined.
Normally
this
routine
leaves the graphics cursor
pointing
to
the
first
pixel
to
the
right
of
the
last
pixel
returned.
However,
if
the
last
pixel
returned
is
the rightmost
pixel of
the screen, the
graphics cursor
is left
pointing to
it
rather
than
pointing
beyond
the
right
edge
of
the screen.
This
is
a speed
critical
routine,
it
should be
coded
accordingly.
INT 52h, Function
E
-
Put
Pixels
Entry:
AH =
E
(function
code)
AL
=
pixel
data
BH
=
operation
code
-
Off
1
-
On
2
-
XOR
3
-
AND
4
-
OR
BL = number
of
pixels to affect
1
through
8,
inclusive
Exit:
No
registers specified
This
routine affects the states
of
BL
pixels
at
and
to
the
right
of
the graphics
cursor.
Operation
code
performs a
logical
NOT
on
the
pixel
data
in
AL,
and
then sets the
appropriate
screen
pixels
accordingly.
Operation
code
1
simply
sets the appropriate
screen
pixels
to
the
pixel
data contained
rn
AL.
Operation
codes
2, 3,
and 4
perform
the
following steps:
1.
Read
the current state
of
the affected pixels
from
the screen.
2.
Perform the
specified
logical
operation
on
the
data obtained
in
step
1
and
the
data
in
AL.
The
pixel
data
in
AL
is left
aligned
in
the
register,
bit
7
corresponds
to
the current cursor
location,
bit
6
to
the
pixel to
the
right
of
the current cursor,
etc.
3.
Set the
state
of
the affected
pixels
to
the
result of
the
togical
operation
performed
in
step
2,
147
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