'Calculate thumb dimensions based on device DPI.
Using the specified output profile, calculate thumb_width
in pixels, then set height to width * 1.33. Special-case for
Kindle/MOBI, as rendering off by 2.
*** dead code? ***
Inputs:
opts.thumb_width (str|float): specified thumb_width
opts.output_profile.dpi (int): device DPI
Outputs:
thumb_width (float): calculated thumb_width
thumb_height (float): calculated thumb_height'

def calculate_thumbnail_dimensions(self):

    for x in output_profiles():
        if (x.short_name == self.opts.output_profile):
            self.thumb_width = (x.dpi * float(self.opts.thumb_width))
            self.thumb_height = (self.thumb_width * 1.33)
            if (('kindle' in x.short_name) and (self.opts.fmt == 'mobi')):
                self.thumb_width = (self.thumb_width / 2)
                self.thumb_height = (self.thumb_height / 2)
            break
    if self.opts.verbose:
        self.opts.log('    Thumbnails:')
        self.opts.log(('        DPI    =    %d;    thumbnail    dimensions:    %d    x    %d' % (x.dpi, self.thumb_width, self.thumb_height)))
