Graphic Objects (Grobs) - HP 48gII User Manual

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 (binary digits
= 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@) P ICT @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
Press @CANCL to return to normal calculator
calculator's graphics display.
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@) G ROB @ 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.
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