LM2467 datasheet(20/43 Pages) NSC

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OSD Generator Operation (Continued)

FOUR COLOR FONT AS TWO 2-COLOR

Using a 4 color character as two 2 color characters is

achieved by careful assignment of the four colors. When two

2 color characters are combined, there will be four pixel

colors:

Color 0: Those

that

are

background

pixels

for

both

characters,

Color 1: Those that are foreground pixels in character one

and background pixels in character two,

Color 2: Those that are foreground pixels in character two

and background pixels in character one,

Color 3: Those

that

are

foreground

pixels

for

both

characters.

In order to identify which pixels are which, both characters

should be drawn in one character cell using the same back-

ground color, and different background colors. In Figure 17,

both “A” and a “B” are drawn separately, then superimposed,

with the final 4 color character on the right. Comparing it to

the list of colors, it is seen that white is color 0, black is color

1, blue is color 2 and red is color 3. (These particular four

colors were chosen for clarity).

Figure 18 shows the composite four color character in the

center and the palette choices on the left and the right which

result in the display of the two original characters.

To display character 1, which has a foreground color 1,

character 2 must be hidden by setting its foreground color

(color 2) to equal the background. Color 3 (common pixels)

must be set to the desired foreground (color 1). In this case,

color 0 and color 2 are black and color 1 and color 3 are

white.

To display character 2, set color 1 = color 0 (to hide charac-

ter 1) and color 3 = color 2. Other than this, there is no

restriction on the choice of the actual colors used.

20075731

FIGURE 16. Four-Color Character

20075732

FIGURE 17. Four Color Character asa2x2 Color

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