Screen capture programs operate similar to the Printscreen function where a copy of the computer screen is saved to the computer's clipboard. The difference is that instead of copying to the clipboard, the image is also loaded into the capture program's image editor, and possibly automatically named and saved to file. Captures can be made by using hotkey functions or cropping an area of the screen with the mouse.
Regardless of what method is used in an attempt to capture CopySafe content, the result will be blank.