module ChunkyPNG::Canvas::Drawing

def circle(x0, y0, radius,

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

Parameters:
  • fill_color (Integer) -- The color to use that fills the circle.
  • stroke_color (Integer) -- The color to use for the line.
  • radius (Integer) -- The radius of the circle from the center point.
  • y0 (Integer) -- The y-coordinate of the center of the circle.
  • x0 (Integer) -- The x-coordinate of the center of the circle. 
def circle(x0, y0, radius,
           stroke_color = ChunkyPNG::Color::BLACK,
           fill_color   = ChunkyPNG::Color::TRANSPARENT)
  stroke_color = ChunkyPNG::Color.parse(stroke_color)
  fill_color   = ChunkyPNG::Color.parse(fill_color)
  f = 1 - radius
  ddF_x = 1
  ddF_y = -2 * radius
  x = 0
  y = radius
  compose_pixel(x0, y0 + radius, stroke_color)
  compose_pixel(x0, y0 - radius, stroke_color)
  compose_pixel(x0 + radius, y0, stroke_color)
  compose_pixel(x0 - radius, y0, stroke_color)
  lines = [radius - 1] unless fill_color == ChunkyPNG::Color::TRANSPARENT
  while x < y
    if f >= 0
      y -= 1
      ddF_y += 2
      f += ddF_y
    end
    x += 1
    ddF_x += 2
    f += ddF_x
    unless fill_color == ChunkyPNG::Color::TRANSPARENT
      lines[y] = lines[y] ? [lines[y], x - 1].min : x - 1
      lines[x] = lines[x] ? [lines[x], y - 1].min : y - 1
    end
    compose_pixel(x0 + x, y0 + y, stroke_color)
    compose_pixel(x0 - x, y0 + y, stroke_color)
    compose_pixel(x0 + x, y0 - y, stroke_color)
    compose_pixel(x0 - x, y0 - y, stroke_color)
    unless x == y
      compose_pixel(x0 + y, y0 + x, stroke_color)
      compose_pixel(x0 - y, y0 + x, stroke_color)
      compose_pixel(x0 + y, y0 - x, stroke_color)
      compose_pixel(x0 - y, y0 - x, stroke_color)
    end
  end
  unless fill_color == ChunkyPNG::Color::TRANSPARENT
    lines.each_with_index do |length, y_offset|
      if length > 0
        line(x0 - length, y0 - y_offset, x0 + length, y0 - y_offset, fill_color)
      end
      if length > 0 && y_offset > 0
        line(x0 - length, y0 + y_offset, x0 + length, y0 + y_offset, fill_color)
      end
    end
  end
  self
end