identity.reflectY()

identity.reflectY([reflect])

If reflect is specified, sets whether or not the y-dimension is reflected (negated) in the output. If reflect is not specified, returns true if y-reflection is enabled, which defaults to false. This is especially useful for transforming from standard spatial reference systems, which treat positive y as pointing up, to display coordinate systems such as Canvas and SVG, which treat positive y as pointing down.