module ChunkyPNG::Canvas::Drawing

def line_xiaolin_wu(x0, y0, x1, y1, stroke_color, inclusive = true)

Returns:
  • (ChunkyPNG::Canvas) - Itself, with the line drawn.

Parameters:
  • inclusive (true, false) -- Whether to draw the last pixel. Set to
  • stroke_color (Integer) -- The color to use for this line.
  • y1 (Integer) -- The y-coordinate of the second control point.
  • x1 (Integer) -- The x-coordinate of the second control point.
  • y0 (Integer) -- The y-coordinate of the first control point.
  • x0 (Integer) -- The x-coordinate of the first control point. 
def line_xiaolin_wu(x0, y0, x1, y1, stroke_color, inclusive = true)
  stroke_color = ChunkyPNG::Color.parse(stroke_color)
  dx = x1 - x0
  sx = dx < 0 ? -1 : 1
  dx *= sx
  dy = y1 - y0
  sy = dy < 0 ? -1 : 1
  dy *= sy
  if dy == 0 # vertical line
    x0.step(inclusive ? x1 : x1 - sx, sx) do |x|
      compose_pixel(x, y0, stroke_color)
    end
  elsif dx == 0 # horizontal line
    y0.step(inclusive ? y1 : y1 - sy, sy) do |y|
      compose_pixel(x0, y, stroke_color)
    end
  elsif dx == dy # diagonal
    x0.step(inclusive ? x1 : x1 - sx, sx) do |x|
      compose_pixel(x, y0, stroke_color)
      y0 += sy
    end
  elsif dy > dx  # vertical displacement
    compose_pixel(x0, y0, stroke_color)
    e_acc = 0
    e = ((dx << 16) / dy.to_f).round
    (dy - 1).downto(0) do |i|
      e_acc_temp, e_acc = e_acc, (e_acc + e) & 0xffff
      x0 += sx if e_acc <= e_acc_temp
      w = 0xff - (e_acc >> 8)
      compose_pixel(x0, y0, ChunkyPNG::Color.fade(stroke_color, w))
      if inclusive || i > 0
        compose_pixel(x0 + sx,
                      y0 + sy,
                      ChunkyPNG::Color.fade(stroke_color, 0xff - w))
      end
      y0 += sy
    end
    compose_pixel(x1, y1, stroke_color) if inclusive
  else # horizontal displacement
    compose_pixel(x0, y0, stroke_color)
    e_acc = 0
    e = ((dy << 16) / dx.to_f).round
    (dx - 1).downto(0) do |i|
      e_acc_temp, e_acc = e_acc, (e_acc + e) & 0xffff
      y0 += sy if e_acc <= e_acc_temp
      w = 0xff - (e_acc >> 8)
      compose_pixel(x0, y0, ChunkyPNG::Color.fade(stroke_color, w))
      if inclusive || i > 0
        compose_pixel(x0 + sx,
                      y0 + sy,
                      ChunkyPNG::Color.fade(stroke_color, 0xff - w))
      end
      x0 += sx
    end
    compose_pixel(x1, y1, stroke_color) if inclusive
  end
  self
end