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Graphic objects (GROBs)
The word GROB stands for GRaphics OBjects and is used in the calculator’s
environment to represent a pixel-by-pixel description of an image that has
been produced in the calculator’s screen. Therefore, when an image is
converted into a GROB, it becomes a sequence of binary digits (
b
inary dig
its
=
bits
), i.e., 0’s and 1’s. To illustrate GROBs and conversion of images to
GROBS consider the following exercise.
When we produce a graph in the calculator, the graph become the contents
of a special variable called PICT. Thus, to see the last contents of PICT, you
could use: PICT RCL
(
„°L
@)PICT @PICT
„©
).
The display shows in stack level 1 the
line Graphic 131
×
64
(if using the
standard screen size) followed by a sketch of the top part of the graph. For
example,
If you press
˜
then the graph contained in level 1 is shown in the
calculator’s graphics display. Press
@CANCL
to return to normal calculator
display.
The graph in level 1 is still not in GROB format, although it is, by definition, a
graphics object. To convert a graph in the stack into a GROB, use:
3`
„°L
@)GROB @
GROB
. Now we have the following information in level 1:
The first part of the description is similar to what we had originally, namely,
Graphic 131
×
64
, but now it is expressed as
Graphic 13128
×
8
.
However, the graphic display is now replaced by a sequence of zeroes and
ones representing the pixels of the original graph. Thus, the original graph as
now been converted to its equivalent representation in bits.
