enhance contrast levels, or use full data range
        according to value of self.panel.conf.contrast_level

def set_contrast_levels(self, contrast_level=None):
        """enhance contrast levels, or use full data range
        according to value of self.panel.conf.contrast_level
        """
        if contrast_level is None:
            clevel = self.contrast_panel.choice.GetStringSelection()
            if clevel == 'None':
                contrast_level = 0
            else:
                contrast_level = float(clevel)

        conf = self.panel.conf
        img  = self.panel.conf.data
        if contrast_level is None:
            contrast_level = 0
        conf.contrast_level = contrast_level
        clevels = [contrast_level, 100.0-contrast_level]

        if len(img.shape) == 2: # intensity map
            col = 0
            jmin = imin = img.min()
            jmax = imax = img.max()
            self.cmap_panels[col].imin_val.SetValue('%.4g' % imin)
            self.cmap_panels[col].imax_val.SetValue('%.4g' % imax)

            jmin, jmax = np.percentile(img, clevels)
            if imax == imin:
                imax = imin + 0.5
            conf.cmap_lo[col] = xlo = (jmin-imin)*conf.cmap_range/(imax-imin)
            conf.cmap_hi[col] = xhi = (jmax-imin)*conf.cmap_range/(imax-imin)


            self.cmap_panels[col].cmap_hi.SetValue(xhi)
            self.cmap_panels[col].cmap_lo.SetValue(xlo)
            self.cmap_panels[col].islider_range.SetLabel('Shown: [ %.4g :  %.4g ]' % (jmin, jmax))
            self.cmap_panels[col].redraw_cmap()

        if len(img.shape) == 3: # rgb map
            for ix in range(3):
                jmin = imin = img[:,:,ix].min()
                jmax = imax = img[:,:,ix].max()
                self.cmap_panels[ix].imin_val.SetValue('%.4g' % imin)
                self.cmap_panels[ix].imax_val.SetValue('%.4g' % imax)

                jmin, jmax = np.percentile(img[:,:,ix], clevels)
                if imax == imin:
                    imax = imin + 0.5
                conf.cmap_lo[ix] = xlo = (jmin-imin)*conf.cmap_range/(imax-imin)
                conf.cmap_hi[ix] = xhi = (jmax-imin)*conf.cmap_range/(imax-imin)
                self.cmap_panels[ix].cmap_hi.SetValue(xhi)
                self.cmap_panels[ix].cmap_lo.SetValue(xlo)

                self.cmap_panels[ix].islider_range.SetLabel('Shown: [ %.4g :  %.4g ]' % (jmin, jmax))
                self.cmap_panels[ix].redraw_cmap()
        self.panel.redraw()