Xiaolin Wu's line algorithm: Difference between revisions

=={{header|Ruby}}==

<lang ruby>def ipart(n); n.truncate; end

def fpart(n); n - ipart(n); end

def rfpart(n); 1.0 - fpart(n); end

class Pixmap

def draw_line_antialised(p1, p2, colour)

x1, y1 = p1.x, p1.y

x2, y2 = p2.x, p2.y

steep = (y2 - y1).abs > (x2 - x1).abs

if steep

x1, y1 = y1, x1

x2, y2 = y2, x2

end

if x1 > x2

x1, x2 = x2, x1

y1, y2 = y2, y1

end

deltax = x2 - x1

deltay = (y2 - y1).abs

gradient = 1.0 * deltay / deltax

# handle the first endpoint

xend = x1.round

yend = y1 + gradient * (xend - x1)

xgap = rfpart(x1 + 0.5)

xpxl1 = xend

ypxl1 = ipart(yend)

put_colour(xpxl1, ypxl1, colour, steep, rfpart(yend)*xgap)

put_colour(xpxl1, ypxl1 + 1, colour, steep, fpart(yend)*xgap)

itery = yend + gradient

# handle the second endpoint

xend = x2.round

yend = y2 + gradient * (xend - x2)

xgap = rfpart(x2 + 0.5)

xpxl2 = xend

ypxl2 = ipart(yend)

put_colour(xpxl2, ypxl2, colour, steep, rfpart(yend)*xgap)

put_colour(xpxl2, ypxl2 + 1, colour, steep, fpart(yend)*xgap)

# in between

(xpxl1 + 1).upto(xpxl2 - 1).each do |x|

put_colour(x, ipart(itery), colour, steep, rfpart(itery))

put_colour(x, ipart(itery) + 1, colour, steep, fpart(itery))

itery = itery + gradient

end

end

def put_colour(x, y, colour, steep, c)

x, y = y, x if steep

self[x, y] = anti_alias(colour, self[x, y], c)

end

def anti_alias(new, old, ratio)

blended = new.values.zip(old.values).map {|n, o| (n*ratio + o*(1.0 - ratio)).round}

RGBColour.new(*blended)

end

end

bitmap = Pixmap.new(500, 500)

bitmap.fill(RGBColour::BLUE)

10.step(430, 60) do |a|

bitmap.draw_line_antialised(Pixel[10, 10], Pixel[490,a], RGBColour::YELLOW)

bitmap.draw_line_antialised(Pixel[10, 10], Pixel[a,490], RGBColour::YELLOW)

end

bitmap.draw_line_antialised(Pixel[10, 10], Pixel[490,490], RGBColour::YELLOW)</lang>