Chapter 6: Graphics Commands for 9-Pin Printers56
Once you've selected the density you want to use, you have to design your graphic image.
Begin by mapping out the pattern you want to print on a piece of graph paper. Here is a sample
pattern for a triangle:
Parameters L
n
and H
n
These parameters tell the printer how many columns of data you'll be sending: 8-pin modes
have one byte of data per column. To calculate the values, first determine how many columns
of dots there will be in your graphics image. Divide this number by 256 and assign the whole
number to H
n
; assign the remainder to L
n
.
In our triangle example, each triangle requires 16 columns. We'll be printing a row of 6
triangles, so the total number of columns in the image is 6 x 16, or 96. Dividing 96 by 256
gives a value of 0 for H
n
with a remainder of 96, which we'll assign to L
n
.
Next, we can write a BASIC statement that sends the command begin 8-pin graphics:
LPRINT CHR$(27);”*”;CHR$(3);CHR$(96);CHR$(0);
Note: Be sure to include the semicolon(;) at the end of this statement. That way, the printer
won't insert a carriage return and line feed before your graphics data.
The listing below is a BASIC program for the Epson emulation that will generate a row of six of
our triangles in quadruple density. To print the pattern at another density, change the value of
D in line 10 to one of the other density codes.
10 D=3 ‘Density code for quadruple density (Epson)
20 WIDTH “LPT1:”,255 ‘Set printer for maximum line width
30 LPRINT CHR$(27);”*”;CHR$(D);CHR$(96);CHR$(0);
40 REM CHR$(D) is the density; in this case D=3 for quadruple density
50 REM CHR$(96) and CHR$(0) indicate the number of columns
60 FOR I=1 TO 6 ‘Repeat triangle pattern six times
70 FOR J=1 TO 16 ‘Each triangle has 16 columns
80 READ A ‘Read the column
90 LPRINT CHR$(A); ‘Send the byte to the printer
100NEXTJ‘Nowprintthenextcolumn
110 RESTORE ‘Go back to the beginning of the DATA statements
120 NEXT I ‘Now print the next triangle
130 END
140 DATA 1,3,7,15,31,63,127,255,255,127,63,31,15,7,3,1
Your printout will look like this:
䊱䊱䊱䊱䊱䊱
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