BitPlane is a Photoshop plug-in filter. It looks at each pixel in the selection and manipulates the bits in it.
When you choose BitPlane filter, you get a dialog box which invites you to set certain check boxes corresponding to the bits in a target byte. Plane 7 corresponds to the most significant (left-most) bit in the byte, plane 0 to the least significant.
So if you set plane 5, the filter creates a byte 00100000. This byte is ANDed with the components of each pixel (three components for RGB, one for greyscale). If the result is non-zero, the component is set to 11111111; if zero, it’s set to 00000000.
Copy the filter to the Photoshop Plug-ins folder to use. I’ve supplied PowerPC (PPC) and 680x0 (68K) versions.
