Seven colors in Gr.15

[atariksi]

Hi folks,

 

since a lot of graphics capabilities of the Ataris have been discussed lately, here's another simple method how to create more colors by mixing; this method works definitely on PAL

due to the way how the TV system works - namely by taking chroma averages between adjacent horizontal lines. I'm unclear whether it works on NTSC (maybe not), would anyone like to give this a try on a real (non-emulated) NTSC machine and post the results here?

 

10 GRAPHICS 15+16

20 SETCOLOR 0,3,6

30 SETCOLOR 1,12,6

40 SETCOLOR 2,7,6

50 C1=1:C2=1

60 FOR B=0 TO 5

70 X1=B*26:X2=B*26+25

80 FOR Y=0 TO 191 STEP 2

90 COLOR C1:PLOT X1,Y:DRAWTO X2,Y:COLOR C2:PLOT X1,Y+1:DRAWTO X2,Y+1

100 NEXT Y

120 C1=C1+1:IF C1=4 THEN C2=C2+1:C1=C2

130 NEXT B

140 GOTO 140

 

As simple as this is, you get red,brown,magenta,green,turquoise, blue and black - at least on my TV. The drawback is that this requires that the colors have the same luminance, otherwise stripes become visible. An alternating (checkerboard) pattern as offered by several graphic programs (e.g. Atari Artist) is very less efficient and creates a visible pattern on the screen.

 

Probably, something similar works on the C64 by combining the "right" colors from the palette.

 

So long,

 

Thomas

Tried this on a UK CRT TV but only showed brown/green/grey/green/grey/grey - probably due to it being a 100hz set will have to hook up the portable set

 

Didn't think there were different TV standards within UK itself.

[Rybags]

Modern Digital TVs don't have all the same restrictions of the older sets.

 

It would theoretically be fairly easy to build a PAL receiver that did away with the colour mixing altogether. *

 

 

_{* Easy = easy for a manufacturer, not individual}