Coding The Soft Character Set - Digital Equipment VT520 Programming Manual

Table 7–2 (Cont.) Guidelines for Designing Soft Characters
Character Dimension
36 Lines/Screen
Cell width
Cell height
Body width
Body height
Ascender height
Descender height
Spacing before character
Spacing after character
48 Lines/Screen
Cell width
Cell height
Body width
Body height
Ascender height
Descender height
Spacing before character
Spacing after character

7.6.2 Coding the Soft Character Set

After you design your characters, you must code them for the terminal. This
section describes how to code soft characters. The next section describes how to
load the character codes into the terminal.
Each pixel of a soft character cell receives a binary value of 0 or 1. A 1 bit
indicates the pixel is on, and a 0 bit indicates the pixel is off.
The terminal receives the code for a soft character in sections, called sixels. A
sixel is a 6-bit binary code that represents a vertical column of 6 pixels on the
screen. Each bit in a sixel corresponds to a pixel on the screen. The following
example describes how to design and code a soft character.
Example
Suppose you want to design an uppercase D for a 24-line by 80-column font.
1. Draw your design on a grid.
Use the grid for an 80-column character cell to draw your design. Mark
which pixels will be on and which pixels will be off. Your design may look like
Figure 7–2.
2. Divide the character cell into columns of 6 bits each.
7.6 Soft Character Sets
80-Column Font
10 pixels
10
7
7
2
1
2
1
10 pixels
8
7
6
1
1
2
1
Character Sets
132-Column Font
6 pixels
10
5
7
1
2
1
0
6 pixels
8
4
7
1
1
1
1
Character Sets 7–9