image Phi
image(Phi,d)
This computation is done through the kernel of a ring map representing the rational map. See kernel(RingMap) and kernel(RingMap,ZZ) for more details.
The source of this document is in /build/reproducible-path/macaulay2-1.25.05+ds/M2/Macaulay2/packages/Cremona/documentation.m2:672:0.