Definition:Image/Also denoted as

Definition
The notation $\Img f$ to denote the image of a mapping $f$ is specific to.

The usual notation is $\map {\mathrm {Im} } f$ or a variant, but this is too easily confused with $\map \Im z$, the imaginary part of a complex number.

Hence the non-standard usage $\Img f$.

Some sources use $f \sqbrk S$, where $S$ is the domain of $f$.

Others just use $\map f S$, but that notation is deprecated on so as not to confuse it with the notation for the image of an element.