How to make a checkerboard in numpy?

Question

I\'m using numpy to initialize a pixel array to a gray checkerboard (the classic representation for \"no pixels\", or transparent). It seems like there ought to be a whizzy

Answer 1

Here's a numpy solution with some checking to make sure that the width and height are evenly divisible by the square size.

def make_checkerboard(w, h, sq, fore_color, back_color):
    """
    Creates a checkerboard pattern image
    :param w: The width of the image desired
    :param h: The height of the image desired
    :param sq: The size of the square for the checker pattern
    :param fore_color: The foreground color
    :param back_color: The background color
    :return:
    """
    w_rem = np.mod(w, sq)
    h_rem = np.mod(w, sq)
    if w_rem != 0 or h_rem != 0:
        raise ValueError('Width or height is not evenly divisible by square '
                         'size.')
    img = np.zeros((h, w, 3), dtype='uint8')
    x_divs = w // sq
    y_divs = h // sq
    fore_tile = np.ones((sq, sq, 3), dtype='uint8')
    fore_tile *= np.array([[fore_color]], dtype='uint8')
    back_tile = np.ones((sq, sq, 3), dtype='uint8')
    back_tile *= np.array([[back_color]], dtype='uint8')
    for y in np.arange(y_divs):
        if np.mod(y, 2):
            b = back_tile
            f = fore_tile
        else:
            b = fore_tile
            f = back_tile
        for x in np.arange(x_divs):
            if np.mod(x, 2) == 0:
                img[y * sq:y * sq + sq, x * sq:x * sq + sq] = f
            else:
                img[y * sq:y * sq + sq, x * sq:x * sq + sq] = b
    return img