For contrast enhancement with input argument of type uint8, why imsharpen can't be used?

For contrast enhancement with input argument of type uint8, why imsharpen can't be used?

[Image Analyst]

It can. Why do you say it can't? See this.

Answer 1

[Walter Roberson]

imsharpen() lists uint8 as being permitted for its inputs

If it is saying that it cannot find imsharpen() for uint8 arguments then it means that you do not have installed the Image Processing Toolkit for release R2013a or later. For older releases you can use fspecial() with the 'unsharp' option.