col601.txt

REM MODE MODE   :REM Reset Screen display. but leave in current mode.
ON ERROR PRINTREPORT$;" at line ";ERL:END

CLG
OFF         : REM Turn off text cursor
:
REM The following four line read the current screen size co-ords.
SYS "OS_ReadModeVariable",-1,4 TO ,,XEigFactor%
SYS "OS_ReadModeVariable",-1,5 TO ,,YEigFactor%
SYS "OS_ReadModeVariable",-1,11 TO ,,XSize%:XSize%+=1
SYS "OS_ReadModeVariable",-1,12 TO ,,YSize%:YSize%+=1
:

XStep%=1<<XEigFactor%
YStep%=1<<YEigFactor%
MaxX%=XSize%<<XEigFactor%
MaxY%=YSize%<<YEigFactor%
CentreX%=MaxX% DIV 2
CentreY%=MaxY% DIV 2

DIM conv601(2,2)
conv601() = 1,0,1.403 ,1,-.344,-0.714,1,1.773,0


DIM rgb(2)
DIM in(2)

LUMA =0

FOR X%= 0 TO MaxX% STEP XStep%
    FOR Y%= 0 TO MaxY% STEP YStep%
            u= (X%-CentreX%)/(2*CentreX%)
            v =(Y%-CentreY%)/(2*CentreY%)
            PROCyuv2rgb601(LUMA ,u,v)
            REM PRINT  u,v
            REM PRINT rgb(0),rgb(1),rgb(2)
            GCOL INT(rgb(0)*255),INT(rgb(1)*255),INT(rgb(2)*255 )
            PLOT 69, X%,Y%
        NEXT
NEXT


END


DEF PROCyuv2rgb601(y,u,v):
    REM LOCAL DIM in(2)
    in(0)=y
    in(1)=u
    in(2)=v

    rgb() = conv601().in()
    FOR c% = 0 TO 2

     IF rgb(c%) < 0 THEN rgb(c%)=0
     IF rgb(c%) > 1 THEN rgb(c%)=1


 NEXT
ENDPROC