def lu2010(im):
im_h, im_w = im.shape
# im_bg_row = polynomial_background_easy(im) # TODO: implement full
# im_bg = polynomial_background_easy(im_bg_row.T).T
# im_bg = im_bg.clip(0.1, 255)
IM = cv2.erode(niblack(im, window_size=61, k=0.2), rect33)
inpainted, modified = inpaint.inpaint_ng14(im, -IM)
im_bg = (inpainted & ~IM) | (modified & IM)
im_bg = im_bg.astype(np.float32).clip(0.1, 255)
debug_imwrite('bg.png', im_bg)
C = np.percentile(im, 30)
I_bar = clip_u8(C / im_bg * im)
debug_imwrite('ibar.png', I_bar)
I_bar_padded = np.pad(I_bar, (1, 1), 'edge')
V_h = cv2.absdiff(I_bar_padded[2:, 1:-1], I_bar_padded[:-2, 1:-1])
V_v = cv2.absdiff(I_bar_padded[1:-1, 2:], I_bar_padded[1:-1, :-2])
V = V_h + V_v
V[V < V_h] = 255 # clip overflow
_, stroke_edges = cv2.threshold(V, 0, 255,
cv2.THRESH_BINARY | cv2.THRESH_OTSU)
# 1 if high contrast, 0 otherwise.
E_inv = stroke_edges & 1
E_inv_255 = E_inv * 255
debug_imwrite('e_inv.png', E_inv_255)
im_high = im & E_inv_255
debug_imwrite('im_high.png', im_high)
# calculate stroke width
H, _ = np.histogram(nonzero_distances_row(E_inv), np.arange(im_h / 100))
H[1] = 0 # don't use adjacent pix
W = H.argmax()
print('stroke width:', W)
size = 2 * W
N_min = W
if size >= 16:
E_inv = E_inv.astype(np.uint16)
window = (size | 1, size | 1)
N_e = cv2.boxFilter(E_inv, -1, window, normalize=False)
debug_imwrite('n_e.png', bool_to_u8(N_e >= N_min))
E_mean = cv2.boxFilter(im_high, cv2.CV_32S, window,
normalize=False) / (N_e.astype(np.float64) + 0.1)
debug_imwrite('i_bar_e_mean.png', bool_to_u8(I_bar <= E_mean))
out = ~bool_to_u8((N_e >= N_min) & (I_bar <= E_mean))
debug_imwrite('lu2010.png', out)
return out
def ng2014_normalize(im):
IM = niblack(im, window_size=61, k=-0.2)
debug_imwrite('niblack.png', IM)
IM = cv2.erode(IM, rect33)
debug_imwrite('dilated.png', IM)
inpainted_min, inpainted_avg, modified = inpaint.inpaint_ng14(im, -IM)
debug_imwrite('inpainted_min.png', inpainted_min)
debug_imwrite('inpainted_avg.png', inpainted_avg)
bg = (inpainted_min & ~IM) | (modified & IM)
debug_imwrite('bg.png', bg)
bgp = (inpainted_avg & ~IM) | (modified & IM)
debug_imwrite('bgp.png', bg)
im_f = im.astype(float) + 1
bg_f = bg.astype(float) + 1
F = im_f / bg_f
N = clip_u8(255 * (F - F.min()))
debug_imwrite('N.png', N)
return N, bgp