See figure 2.6.
These functions may be split into three broad groups: functions which convert
between the VIPS numeric formats (im_clip2fmt(), for example, converts
an image of any type to the specified IM_BANDFMT), functions
supporting complex arithmetic (im_c2amph(), for example, converts
a complex image from rectangular to polar co ordinates) and functions
which perform some simple geometric conversion (im_extract() forms
a sub-image).
gbandjoin and the C function im_gbandjoin() will do a bandwise
join of many images at the same time. See the manual pages.