Image methods and global methods
The Imagick class has the ability to hold and operate on multiple
images simultaneously. This is achieved through an internal stack. There
is always an internal pointer that points at the current image. Some
functions operate on all images in the Imagick class, but most operate
only on the current image in the internal stack. As a convention, method
names can contain the word Image to denote they affect only the current
image in the stack.