Envelope constructor
Creates an Envelope
for a region defined by maximum and minimum values.
@param x1 the first x-value @param x2 the second x-value @param y1 the first y-value @param y2 the second y-value
Implementation
Envelope(double x1, double x2, double y1, double y2) {
init(x1, x2, y1, y2);
}