XProfan

WindowTitle "Antialiased Line (Xiaolin Wu-Algorithmus)"
'Q: https://en.wikipedia.org/wiki/Xiaolin_Wu%27s_line_algorithm
'S: https://rosettacode.org/wiki/Xiaolin_Wu%27s_line_algorithm#BBC_BASIC
WindowStyle 24
Window 0,0-%maxx,%maxy
screen width(%hwnd)\5,height(%hwnd)\5
set("Truecolor",0)
cls rgb(255,255,180)
drawAntiAliasedLine(20,20, 50,100,   255,0,0)
screen width(%hwnd),height(%hwnd)
Waitinput
END

Proc drawAntiAliasedLine

    parameters x1!,y1& , x2&,y2&, r%,g%,b%
    declare tmp&, dx&,dy&, xend&,yend!, grad!,yf!,xgap!, ix1%,iy1%, ix2%,iy2%, x%
    dx& = x2& - x1!
    dy& = y2& - y1&

    IF ABS(dx&) < ABS(dy&)

        tmp&=x1!:x1!=y1&:y1&=tmp&
        tmp&=x2&:x2&=y2&:y2&=tmp&
        tmp&=dx&:dx&=dy&:dy&=tmp&

    ENDIF

    IF x2& < x1!

        tmp&=x1!:x1!=x2&:x2&=tmp&
        tmp&=y1&:y1&=y2&:y2&=tmp&

    ENDIF

    grad! = dy& / dx&
    xend& = INT(x1! + 0.5)
    yend! = y1& + grad! * (xend& - x1!)
    xgap! = xend& + 0.5 - x1!
    ix1% = xend&
    iy1% = INT(yend!)
    plot(ix1%, iy1%, r%,g%,b%, (INT(yend!) + 1 - yend!) * xgap!)
    plot(ix1%, iy1% + 1, r%,g%,b%, (yend! - INT(yend!)) * xgap!)
    yf! = yend! + grad!
    xend& = INT(x2& + 0.5)
    yend! = y2& + grad! * (xend& - x2&)
    xgap! = x2& + 0.5 - xend&
    ix2% = xend&
    iy2% = INT(yend!)
    plot(ix2%,iy2%,   r%,g%,b%,(INT(yend!) + 1 - yend!) * xgap!)
    plot(ix2%,iy2%+1, r%,g%,b%,(yend! - INT(yend!)) * xgap!)

    Whileloop ix1%+1,ix2%-1 : x%=&Loop

        plot(x%, INT(yf!),   r%,g%,b%, INT(yf!) + 1 - yf!)'RGBA-Format
        plot(x%, INT(yf!)+1, r%,g%,b%, yf!-INT(yf!))
        yf!=yf!+grad!

    Endwhile

ENDPROC

Proc plot : parameters X%,Y%, R%,G%,B%, A!

    var C% = GetPixel(X%*2,Y%*2)
    'print int(1000*A!);
    USEPEN 0,2, R%*(1-a!) + ( C% AND 255)*a!, \
    G%*(1-a!) + ((C%>>8) AND 255)*a!, \
    B%*(1-a!) + ((C%>>16) AND 255)*a!
    'MODE "OR" wäre nachzubauen
    LINE X%*2,Y%*2 - X%*2,Y%*2

ENDPROC