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The <CTRL>-1 GQ command causes the positions of the dots to be
compared and only prints those dots which do not occur in the same
position on both pages. A dot will only be printed, therefore, if it is
unique to either hi-res page I OR hi-res page 2.
COMMANDS TO PRODUCE SPECIAL EFFECTS
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<CTRL>-IGI
Normally the page will be printed with the plotted (i.e. white) dots
of the screen printed as black dots on the printer. Using this command
causes the areas of the screen which are black to be printed instead.
A group of commands are available which allow you to affect the
shading of the printed graphics. Although the degree of shading will
depend upon the print density which is set (see <CTRL>-1
nQ
below),
two specific commands will influence large areas of black or white.
They are <CTRL>-1 GJ and <CTRL>-1 GK. The higher the print density,
the darker will be the shading effects of these two commands.
COMMANDS WHICH AFFECT THE PRINT DENSITY
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<CTRL>-1 GF
This is an overstrike mode, and has the effect of removing the pin
stripe horizontal lines which may occur during normal graphic
printing of pictures. When combined with other commands it can give
a superior graphic reproduction. For example, if <CTRL>-1 GEF is
used, extremely good positive prints of digitised photographs can be
obtained.
<CTRL>-IGE
This command affects the print density and works in the same way
as the <CTRL>-1 E command for text printing.
It
gives a darker print or
picture by using the 'emphasized' printer code. If a <CTRL>-1
nQ
instruction is used in a preceding BASIC line, this can also affect print
density.
<CTRL>-IGJ
<CTRL>-IGK
shades areas of white. This is termed post-shading.
shades areas of black. This is termed pre-shading.
<CTRL>-lnQ
The <CTRL>-1
nQ
options can be most conveniently used from
BASIC, in the form of a line preceeding the graphics commands
themselves. For example:
10 PR# 1: PRINT CHR$(9); "1Q"
20 PRINT CHR$(9); "G21"
prints a normal sized image of hi-res graphics page 2 using 1Q density,
which is 240 dots per inch.
This provides you with a means of telling the printer how close to
each other you want it to print the dots which form the images it
creates.The higher the density, the closer together the dots will be
printed and the darker the resulting picture. The progressive closing of
the gap between each dot will gradually reduce the size of a graphics
print-out; expanding the horizontal and vertical scales will compensate
for this. (See <CTRL>-1 GS to <CTRL>-1 GZ.)
The density is set by entering <CTRL>-1
nQ,
where
n
is a number
between
O and 7. The table below shows the progressive effect of the
available density settings on Epson FX series printers. Some printers
cannot use this command at all, and some, like the RX series, cannot
use all of the settings. You should look in your printer manual for the
command <ESC> •. The control command table number corresponds
10
the value of the mode number given in that manual.
It should be noted that fine detail may be lost when using the
shading option, if the vertical scale is not set to a value greater than
I.
Whether an area which would otherwise be printed as black or an
area which would be printed as white is the one that will be shaded
depends on whether or not inverse is set. The concept is best
illustrated by looking at the examples and comparing them against the
table.
combinations in examples: A
B
c
D
<CTRL>-1 G followed by:
nothing
K
J
IK
normal/inverse set to:
normal
normal
normal
inverse
shading option set to:
no shade pre-shade post-shade pre-shade
black area prints as:
black
black
shaded
white
White area prints as:
white
shaded
white
shaded
44
45
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