def cw_ssim_value(self, target, width=30):
        """Compute the complex wavelet SSIM (CW-SSIM) value from the reference
        image to the target image.

        Args:
          target (str or PIL.Image): Input image to compare the reference image
          to. This may be a PIL Image object or, to save time, an SSIMImage
          object (e.g. the img member of another SSIM object).
          width: width for the wavelet convolution (default: 30)

        Returns:
          Computed CW-SSIM float value.
        """
        if not isinstance(target, SSIMImage):
            target = SSIMImage(target, size=self.img.size)

        # Define a width for the wavelet convolution
        widths = np.arange(1, width+1)

        # Use the image data as arrays
        sig1 = np.asarray(self.img.img_gray.getdata())
        sig2 = np.asarray(target.img_gray.getdata())

        # Convolution
        cwtmatr1 = signal.cwt(sig1, signal.ricker, widths)
        cwtmatr2 = signal.cwt(sig2, signal.ricker, widths)

        # Compute the first term
        c1c2 = np.multiply(abs(cwtmatr1), abs(cwtmatr2))
        c1_2 = np.square(abs(cwtmatr1))
        c2_2 = np.square(abs(cwtmatr2))
        num_ssim_1 = 2 * np.sum(c1c2, axis=0) + self.k
        den_ssim_1 = np.sum(c1_2, axis=0) + np.sum(c2_2, axis=0) + self.k

        # Compute the second term
        c1c2_conj = np.multiply(cwtmatr1, np.conjugate(cwtmatr2))
        num_ssim_2 = 2 * np.abs(np.sum(c1c2_conj, axis=0)) + self.k
        den_ssim_2 = 2 * np.sum(np.abs(c1c2_conj), axis=0) + self.k

        # Construct the result
        ssim_map = (num_ssim_1 / den_ssim_1) * (num_ssim_2 / den_ssim_2)

        # Average the per pixel results
        index = np.average(ssim_map)
        return index
Compute the complex wavelet SSIM (CW-SSIM) value from the reference
        image to the target image.

        Args:
          target (str or PIL.Image): Input image to compare the reference image
          to. This may be a PIL Image object or, to save time, an SSIMImage
          object (e.g. the img member of another SSIM object).
          width: width for the wavelet convolution (default: 30)

        Returns:
          Computed CW-SSIM float value.