class Magick::RVG::Rect

def initialize(width, height, x = 0, y = 0)

Use the RVG::ShapeConstructors#rect method to create Rect objects in a container.
If either width or height is 0, the rectangle is not rendered.
Define a width x height rectangle. The upper-left corner is at [x, y]. 
def initialize(width, height, x = 0, y = 0)
  super()
  width, height, x, y = Magick::RVG.convert_to_float(width, height, x, y)
  raise ArgumentError, "width, height must be >= 0 (#{width}, #{height} given)" if width < 0 || height < 0
  @args = [x, y, x + width, y + height]
  @primitive = :rectangle
end

def round(rx, ry = nil)

are the x- and y-axis radii. If y is omitted it defaults to x.
Specify optional rounded corners for a rectangle. The arguments 
def round(rx, ry = nil)
  rx, ry = Magick::RVG.convert_to_float(rx, ry || rx)
  raise ArgumentError, "rx, ry must be >= 0 (#{rx}, #{ry} given)" if rx < 0 || ry < 0
  @args << rx << ry
  @primitive = :roundrectangle
  self
end