halftone.py 文件源码

def halftone(cmyk, size, angles, fill, sharpness):
    """
    Generates a halftone image from a cmyk image
        Args:
            cmyk (numpy array): 0.0-1.0 r x c x 4 image
            size (int): half size of the averaging kernel in pixels
            angles (list of float): 4 angles for the relative rotation of each channel
        Returns:
            numpy array: 0.0-1.0 r x c x 4 halftoned image
    """
    halftone_image = np.zeros(cmyk.shape)

    for i, (channel, angle) in enumerate(zip(np.rollaxis(cmyk, 2), angles)):

        # total width of the kernel
        s = 2 * size + 1

        # rotate the image to eliminate overlap between the channels
        rotated = rotate(channel, angle, reshape=True, prefilter=False, order=1)

        # apply a gaussian filter to average over a the region of the kernel
        averaged = gaussian_filter(rotated, size)

        # find the central value of the filtered image; this is the average intensity in the region
        halftone_weights = averaged[size::s, size::s]

        # tile the weight image with the average intensity value
        halftone_weights = np.repeat(np.repeat(halftone_weights, s, 0), s, 1)
        halftone_weights = resize(halftone_weights, rotated.shape)

        # TODO: consider using sigma to scale with magnitude
        # create a 2D gaussian kernel that will be the "dot"; normalize it to be 1.0 in the center
        kernel = gauss_kernel(size, sigma=fill*size)

        # Apply the sharpness multiplier and clip the kernel to 1.0
        kernel *= sharpness / np.max(kernel)
        kernel = np.clip(kernel, 0.0, 1.0)

        # tile the kernel across the image
        num_kernels = np.array(rotated.shape) / s + 1
        tiled_kernel = np.tile(kernel, num_kernels)
        tiled_kernel = resize(tiled_kernel, rotated.shape)

        # multiply the kernel image with the weights to generate the halftone image
        halftone = tiled_kernel * halftone_weights

        # rotate the image back to zero
        halftone = rotate(halftone, -angle, prefilter=False, order=1)

        # crop the image to the original size
        halftone = crop_center(halftone, channel.shape)

        # add this chanel to the full cmyk image
        halftone_image[:,:,i] = halftone

#        Image.fromarray(halftone*255).show()

#    Image.fromarray(cmyk_to_rgb(halftone_image)).show()

    return halftone_image