class ChunkyPNG::Canvas

def assert_size!(matrix_width, matrix_height)

Throws an exception if the matrix width and height does not match this canvas' dimensions. 
def assert_size!(matrix_width, matrix_height)
  raise ChunkyPNG::ExpectationFailed, "The width of the matrix does not match the canvas width!"   if width  != matrix_width
  raise ChunkyPNG::ExpectationFailed, "The height of the matrix does not match the canvas height!" if height != matrix_height
  return true
end