numbers between 0 and 14 define the luminance. If you type an odd
number, the computer uses the color of the previous even number.
Change the 7 to an 8 and watch the color get lighter yet. The following
program shows all 128 colors and luminances:
NEW
10 REM ** 128 ATARI COLORS
20 REM ** 16 COLORS
30 FOR COLOR =0 TO 15
40 REM ** 8 LUMINANCES
50 FOR LUMINANCE=0 TO 14 STEP 2
60 SETCOLOR 2,COLOR,LUMINANCE
65 PRINT "COLOR=";COLOR;" LUMINANCE=";LUMINANCE
70 REM ** PAUSE TO SEE COLOR
80 FOR PAUSE=1 TO 600:NEXT PAUSE
90 NEXT LUMINANCE
100 NEXT COLOR
RUN
When the luminance reaches number 10, the text disappears because
the default luminance of the text is also 10. (The default luminance is
the luminance that the computer automatically uses unless it is
instructed to do otherwise.) Whenever the background luminance is
the same as the text luminance, the text seems to disappear. Pay
attention to background and text luminances as you work more with
color and luminance in graphics mode 0. Type GR.0 (which is an
abbreviation for graphics mode 0) to restore the normal screen colors.
Change SETCOLOR 2 to SETCOLOR 4 in line 60 and run the program
again. Because register 4 governs the border, the border changes
color this time instead of the background area. Type GR.0 to restore
the normal screen colors.
Graphics Modes 1 and 2
Graphics modes 1 and 2 provide large-size text and color options.
Graphics mode 2 is identical to graphics mode 1 except that each
character is twice as tall. Mode 1 has 24 horizontal screen lines, and
mode 2 has 12. To enter graphics mode 1, type
NEW
10 GRAPHICS 1
20 PRINT #6;"GRAPHICS MODE ONE"
Run the program. Graphics mode 1 is in orange text at the top of the
screen. At the bottom is a blue strip containing the word READY. The
blue strip is the text window and displays text in graphics mode 0.
Type GR.0 to return to the text mode.
70
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