Preferred number of _colors in the image. The actual number of _colors in the image may be less than your request, but never more. Images with less unique _colors than specified with this option will have any duplicate or unused _colors removed.
See Implementation
Preferred number of _colors in the image. The actual number of _colors in the image may be less than your request, but never more. Images with less unique _colors than specified with this option will have any duplicate or unused _colors removed.