Xiaolin Wu's line algorithm: Difference between revisions

Revision as of 00:56, 22 March 2006

Revision as of 07:13, 7 April 2006

Line 6:

<code>

'''function''' plot(x, y, c) '''is'''

plot the pixel at (x, y) with brightness c ''// (where 0 &le; c &le; 1'')

'''function''' ipart(x)

'''returnfunction''' ipart(x) ''integer part of x'is'''

'''return''' ipart(x''integer +part 0.5)of x''

'''function''' round(x)

'''return''' ipart(x + 0.5)

'''function''' fpartround(x) '''is'''

'''return''' ''fractionalipart(x part+ of x''0.5)

'''function''' rfpart(x)

'''returnfunction''' 1 - fpart(x) '''is'''

'''return''' ''fractional part of x''

'''function''' drawLine(x1,y1,x2,y2)

''// check that x1 < x2''

'''function''' ipartrfpart(x) '''is'''

'''if x2 < x1

'''return''' 1 - fpart(x)

swap x1, x2

swap y1, y2

'''function''' drawLine(x1,y1,x2,y2) '''is'''

dx = x2 - x1

dy = y2 - y1

'''if''' x2 < x1

gradient = dy / dx

swap x1, x2

swap y1, y2

'''end if'''

dx = x2 - x1

dy = y2 - y1

gradient = dy / dx

''// handle first endpoint''

xend = round(x1)

yend = y1 + gradient * (xend - x1)

xgap = rfpart(x1 + 0.5)

xpxl1 = xend '' // this will be used in the main loop''

ypxl1 = ipart(yend)

plot(xpxl1, ypxl1, rfpart(yend) * xgap)

plot(xpxl1, ypxl1 + 1, fpart(yend) * xgap)

intery = yend + gradient ''// first y-intersection for the main loop''

''// handle second endpoint''

xend = round(x2)

yend = y2 + gradient * (xend - x2)

xgap = rfpart(x2 - 0.5)

xpxl2 = xend '' // this will be used in the main loop''

ypxl2 = ipart(yend)

plot(xpxl2, ypxl2, rfpart(yend) * xgap)

plot(xpxl2, ypxl2 + 1, fpart(yend) * xgap)

''// main loop''

'''for''' x '''from''' xpxl1 + 1 '''to''' xpxl2 - 1 {'''do'''

plot(x, ipart(intery), rfpart(intery))

plot(x, ipart(intery) + 1, fpart(intery))

intery = intery + gradient

'''repeat'''

}

'''end function''' round(x)

</code>