Bit count? I'm not quite sure what you mean. If you mean the file size, the -s operator returns the size of the file.

If you want to know the number of pixels, you could use Image::Size, then multiply the x and y dimension.

I couldn't find a module called "perlmagick", but I did find Image::Magick which is the Perl interface to Imagemagick, and which can return various kinds of information about the image if you use the Get method.