redraw image, applying the following:
        rotation, flips, log scale
        max/min values from sliders or explicit intensity ranges
        color map
        interpolation

def redraw(self, col=0):
        """redraw image, applying the following:
        rotation, flips, log scale
        max/min values from sliders or explicit intensity ranges
        color map
        interpolation
        """
        conf = self.conf
        # note: rotation re-calls display(), to reset the image
        # other transformations will just do .set_data() on image
        if conf.rot:
            if self.xdata is not None:
                self.xdata = self.xdata[::-1]
            if self.ydata is not None:
                self.ydata = self.ydata[:]

            self.display(np.rot90(conf.data),
                         x=self.ydata, xlabel=self.ylab,
                         y=self.xdata, ylabel=self.xlab)
        # flips, log scales
        img = conf.data
        if img is None: return
        if len(img.shape) == 2:
            col = 0
        if self.conf.style == 'image':
            if conf.flip_ud:   img = np.flipud(img)
            if conf.flip_lr:   img = np.fliplr(img)
            if conf.log_scale:
                img = np.log10(1 + 9.0*img)

        # apply intensity scale for current limited (zoomed) image
        if len(img.shape) == 2:
            # apply clipped color scale, as from sliders

            imin = float(conf.int_lo[col])
            imax = float(conf.int_hi[col])
            if conf.log_scale:
                imin = np.log10(1 + 9.0*imin)
                imax = np.log10(1 + 9.0*imax)

            (xmin, xmax, ymin, ymax) = self.conf.datalimits
            if xmin is None:  xmin = 0
            if xmax is None:  xmax = img.shape[1]
            if ymin is None:  ymin = 0
            if ymax is None:  ymax = img.shape[0]


            img = (img - imin)/(imax - imin + 1.e-8)
            mlo = conf.cmap_lo[0]/(1.0*conf.cmap_range)
            mhi = conf.cmap_hi[0]/(1.0*conf.cmap_range)
            if self.conf.style == 'image':
                conf.image.set_data(np.clip((img - mlo)/(mhi - mlo + 1.e-8), 0, 1))
                conf.image.set_interpolation(conf.interp)
        else:
            r, g, b = img[:,:,0], img[:,:,1], img[:,:,2]

            rmin = float(conf.int_lo[0])
            rmax = float(conf.int_hi[0])
            gmin = float(conf.int_lo[1])
            gmax = float(conf.int_hi[1])
            bmin = float(conf.int_lo[2])
            bmax = float(conf.int_hi[2])
            if conf.log_scale:
                rmin = np.log10(1 + 9.0*rmin)
                rmax = np.log10(1 + 9.0*rmax)
                gmin = np.log10(1 + 9.0*gmin)
                gmax = np.log10(1 + 9.0*gmax)
                bmin = np.log10(1 + 9.0*bmin)
                bmax = np.log10(1 + 9.0*bmax)

            rlo = conf.cmap_lo[0]/(1.0*conf.cmap_range)
            rhi = conf.cmap_hi[0]/(1.0*conf.cmap_range)
            glo = conf.cmap_lo[1]/(1.0*conf.cmap_range)
            ghi = conf.cmap_hi[1]/(1.0*conf.cmap_range)
            blo = conf.cmap_lo[2]/(1.0*conf.cmap_range)
            bhi = conf.cmap_hi[2]/(1.0*conf.cmap_range)
            r = (r - rmin)/(rmax - rmin + 1.e-8)
            g = (g - gmin)/(gmax - gmin + 1.e-8)
            b = (b - bmin)/(bmax - bmin + 1.e-8)

            inew = img*1.0
            inew[:,:,0] = np.clip((r - rlo)/(rhi - rlo + 1.e-8), 0, 1)
            inew[:,:,1] = np.clip((g - glo)/(ghi - glo + 1.e-8), 0, 1)
            inew[:,:,2] = np.clip((b - blo)/(bhi - blo + 1.e-8), 0, 1)

            whitebg = conf.tricolor_bg.startswith('wh')

            if whitebg:
                inew = conf.tricolor_white_bg(inew)

            if self.conf.style == 'image':
                conf.image.set_data(inew)
                conf.image.set_interpolation(conf.interp)
        self.canvas.draw()
        if callable(self.redraw_callback):
            self.redraw_callback(wid=self.GetId())