512 lines
16 KiB
Python
512 lines
16 KiB
Python
#!/usr/bin/env python2
|
|
# -*- coding: utf-8 -*-
|
|
#
|
|
# © 2013-15: jbarlow83 from Github (https://github.com/jbarlow83)
|
|
#
|
|
#
|
|
# Use Leptonica to detect find and remove page skew. Leptonica uses the method
|
|
# of differential square sums, which its author claim is faster and more robust
|
|
# than the Hough transform used by ImageMagick.
|
|
|
|
from __future__ import print_function, absolute_import, division
|
|
import argparse
|
|
import sys
|
|
import os
|
|
import logging
|
|
from tempfile import TemporaryFile
|
|
from ctypes.util import find_library
|
|
from .lib._leptonica import ffi
|
|
from functools import lru_cache
|
|
from enum import Enum
|
|
|
|
lept = ffi.dlopen(find_library('lept'))
|
|
|
|
logger = logging.getLogger(__name__)
|
|
|
|
|
|
def stderr(*objs):
|
|
"""Python 2/3 compatible print to stderr.
|
|
"""
|
|
print("leptonica.py:", *objs, file=sys.stderr)
|
|
|
|
|
|
class LeptonicaErrorTrap(object):
|
|
"""Context manager to trap errors reported by Leptonica.
|
|
|
|
Leptonica's error return codes are unreliable to the point of being
|
|
almost useless. It does, however, write errors to stderr provided that is
|
|
not disabled at its compile time. Fortunately this is done using error
|
|
macros so it is very self-consistent.
|
|
|
|
This context manager redirects stderr to a temporary file which is then
|
|
read and parsed for error messages. As a side benefit, debug messages
|
|
from Leptonica are also suppressed.
|
|
|
|
"""
|
|
def __enter__(self):
|
|
self.tmpfile = TemporaryFile()
|
|
|
|
# Save the old stderr, and redirect stderr to temporary file
|
|
self.old_stderr_fileno = os.dup(sys.stderr.fileno())
|
|
os.dup2(self.tmpfile.fileno(), sys.stderr.fileno())
|
|
return
|
|
|
|
def __exit__(self, exc_type, exc_value, traceback):
|
|
# Restore old stderr
|
|
os.dup2(self.old_stderr_fileno, sys.stderr.fileno())
|
|
|
|
# Get data from tmpfile (in with block to ensure it is closed)
|
|
with self.tmpfile as tmpfile:
|
|
tmpfile.seek(0) # Cursor will be at end, so move back to beginning
|
|
leptonica_output = tmpfile.read().decode(errors='replace')
|
|
|
|
# If there are Python errors, let them bubble up
|
|
if exc_type:
|
|
logger.warning(leptonica_output)
|
|
return False
|
|
|
|
# If there are Leptonica errors, wrap them in Python excpetions
|
|
if 'Error' in leptonica_output:
|
|
if 'image file not found' in leptonica_output:
|
|
raise FileNotFoundError()
|
|
if 'pixWrite: stream not opened' in leptonica_output:
|
|
raise LeptonicaIOError()
|
|
raise LeptonicaError(leptonica_output)
|
|
|
|
return False
|
|
|
|
|
|
class LeptonicaError(Exception):
|
|
pass
|
|
|
|
|
|
class LeptonicaIOError(LeptonicaError):
|
|
pass
|
|
|
|
|
|
class RemoveColormap(Enum):
|
|
to_binary = 0
|
|
to_grayscale = 1
|
|
to_full_color = 2
|
|
based_on_src = 3
|
|
|
|
|
|
class Pix:
|
|
"""Wrapper around leptonica's PIX object.
|
|
|
|
Leptonica uses referencing counting on PIX objects. Also, many Leptonica
|
|
functions return the original object with an increased reference count
|
|
if the operation had no effect (for example, image skew was found to be 0).
|
|
This has complications for memory management in Python. Whenever Leptonica
|
|
returns a PIX object (new or old), we wrap it in this class, which
|
|
registers it with the FFI garbage collector. pixDestroy() decrements the
|
|
reference count and only destroys when the last reference is removed.
|
|
|
|
Leptonica's reference counting is not threadsafe. This class can be used
|
|
in a threadsafe manner if a Python threading.Lock protects the data.
|
|
"""
|
|
|
|
def __init__(self, pix):
|
|
self._pix = ffi.gc(pix, Pix._pix_destroy)
|
|
|
|
def __repr__(self):
|
|
if self._pix:
|
|
s = "<leptonica.Pix image size={0}x{1} depth={2} at 0x{3:x}>"
|
|
return s.format(self._pix.w, self._pix.h, self._pix.d,
|
|
int(ffi.cast("intptr_t", self._pix)))
|
|
else:
|
|
return "<leptonica.Pix image NULL>"
|
|
|
|
def __getstate__(self):
|
|
data = ffi.new('l_uint32 **')
|
|
size = ffi.new('size_t *')
|
|
|
|
err = lept.pixSerializeToMemory(self._pix, data, size)
|
|
if err != 0:
|
|
raise LeptonicaIOError("pixSerializeToMemory")
|
|
|
|
char_data = ffi.cast('char *', data[0])
|
|
|
|
# Copy from C bytes to python bytes()
|
|
data_bytes = ffi.buffer(char_data, size[0])[:]
|
|
|
|
# Can now free C bytes
|
|
lept.lept_free(char_data)
|
|
return dict(data=data_bytes)
|
|
|
|
def __setstate__(self, state):
|
|
cdata_bytes = ffi.new('char[]', state['data'])
|
|
cdata_uint32 = ffi.cast('l_uint32 *', cdata_bytes)
|
|
|
|
pix = lept.pixDeserializeFromMemory(
|
|
cdata_uint32, len(state['data']))
|
|
Pix.__init__(self, pix)
|
|
|
|
@property
|
|
def width(self):
|
|
return self._pix.w
|
|
|
|
@property
|
|
def height(self):
|
|
return self._pix.h
|
|
|
|
@property
|
|
def depth(self):
|
|
return self._pix.d
|
|
|
|
@property
|
|
def size(self):
|
|
return (self._pix.w, self._pix.h)
|
|
|
|
@property
|
|
def info(self):
|
|
return {'dpi': (self._pix.xres, self._pix.yres)}
|
|
|
|
@property
|
|
def mode(self):
|
|
"Return mode like PIL.Image"
|
|
if self.depth == 1:
|
|
return '1'
|
|
elif self.depth >= 16:
|
|
return 'RGB'
|
|
elif not self._pix.colormap:
|
|
return 'L'
|
|
else:
|
|
return 'P'
|
|
|
|
@classmethod
|
|
def read(cls, filename):
|
|
"""Load an image file into a PIX object.
|
|
|
|
Leptonica can load TIFF, PNM (PBM, PGM, PPM), PNG, and JPEG. If
|
|
loading fails then the object will wrap a C null pointer.
|
|
"""
|
|
with LeptonicaErrorTrap():
|
|
return cls(lept.pixRead(
|
|
filename.encode(sys.getfilesystemencoding())))
|
|
|
|
def write_implied_format(
|
|
self, filename, jpeg_quality=0, jpeg_progressive=0):
|
|
"""Write pix to the filename, with the extension indicating format.
|
|
|
|
jpeg_quality -- quality (iff JPEG; 1 - 100, 0 for default)
|
|
jpeg_progressive -- (iff JPEG; 0 for baseline seq., 1 for progressive)
|
|
"""
|
|
with LeptonicaErrorTrap():
|
|
lept.pixWriteImpliedFormat(
|
|
filename.encode(sys.getfilesystemencoding()),
|
|
self._pix, jpeg_quality, jpeg_progressive)
|
|
|
|
def topil(self):
|
|
"Returns a PIL.Image version of this Pix"
|
|
from PIL import Image
|
|
|
|
with LeptonicaErrorTrap():
|
|
pix_swapped = Pix(lept.pixEndianByteSwapNew(self._pix))
|
|
|
|
size = (pix_swapped._pix.wpl * 4, pix_swapped._pix.h)
|
|
buf = ffi.buffer(pix_swapped._pix.data, size[0] * size[1])
|
|
|
|
im_raw = Image.frombytes(self.mode, size, buf, 'raw')
|
|
|
|
# Leptonica stores images in 32-bit words
|
|
# Need to crop the any trailing amount
|
|
box = (0, 0, self.width, self.height)
|
|
im = im_raw.crop(box)
|
|
|
|
return im
|
|
|
|
def show(self):
|
|
return self.topil().show()
|
|
|
|
def deskew(self, reduction_factor=0):
|
|
"""Returns the deskewed pix object.
|
|
|
|
A clone of the original is returned when the algorithm cannot find a
|
|
skew angle with sufficient confidence.
|
|
|
|
reduction_factor -- amount to downsample (0 for default) when searching
|
|
for skew angle
|
|
"""
|
|
with LeptonicaErrorTrap():
|
|
return Pix(lept.pixDeskew(self._pix, reduction_factor))
|
|
|
|
def scale(self, scalex, scaley):
|
|
"Returns the pix object rescaled according to the proportions given."
|
|
with LeptonicaErrorTrap():
|
|
return Pix(lept.pixScale(self._pix, scalex, scaley))
|
|
|
|
def rotate180(self):
|
|
with LeptonicaErrorTrap():
|
|
return Pix(lept.pixRotate180(ffi.NULL, self._pix))
|
|
|
|
def rotate_orth(self, quads):
|
|
"Orthographic rotation, quads: 0-3, number of clockwise rotations"
|
|
with LeptonicaErrorTrap():
|
|
return Pix(lept.pixRotateOrth(self._pix, quads))
|
|
|
|
def find_skew(self):
|
|
"""Returns a tuple (deskew angle in degrees, confidence value).
|
|
|
|
Returns (None, None) if no angle is available.
|
|
"""
|
|
with LeptonicaErrorTrap():
|
|
angle = ffi.new('float *', 0.0)
|
|
confidence = ffi.new('float *', 0.0)
|
|
result = lept.pixFindSkew(self._pix, angle, confidence)
|
|
if result == 0:
|
|
return (angle[0], confidence[0])
|
|
else:
|
|
return (None, None)
|
|
|
|
def convert_rgb_to_luminance(self):
|
|
with LeptonicaErrorTrap():
|
|
gray_pix = lept.pixConvertRGBToLuminance(self._pix)
|
|
if gray_pix:
|
|
return Pix(gray_pix)
|
|
return None
|
|
|
|
def remove_colormap(self, removal_type):
|
|
"""Remove a palette
|
|
|
|
removal_type - RemovalColormap()
|
|
"""
|
|
|
|
with LeptonicaErrorTrap():
|
|
return Pix(lept.pixRemoveColormap(self._pix, removal_type))
|
|
|
|
def otsu_adaptive_threshold(
|
|
self, tile_size=(300, 300), kernel_size=(4, 4), scorefract=0.1):
|
|
with LeptonicaErrorTrap():
|
|
sx, sy = tile_size
|
|
smoothx, smoothy = kernel_size
|
|
p_pix = ffi.new('PIX **')
|
|
|
|
result = lept.pixOtsuAdaptiveThreshold(
|
|
self._pix,
|
|
sx, sy,
|
|
smoothx, smoothy,
|
|
scorefract,
|
|
ffi.NULL,
|
|
p_pix)
|
|
if result == 0:
|
|
return Pix(p_pix[0])
|
|
else:
|
|
return None
|
|
|
|
def otsu_threshold_on_background_norm(
|
|
self, mask=None, tile_size=(10, 15), thresh=100, mincount=50,
|
|
bgval=255, kernel_size=(2, 2), scorefract=0.1):
|
|
with LeptonicaErrorTrap():
|
|
sx, sy = tile_size
|
|
smoothx, smoothy = kernel_size
|
|
if mask is None:
|
|
mask = ffi.NULL
|
|
if isinstance(mask, Pix):
|
|
mask = mask._pix
|
|
|
|
thresh_pix = lept.pixOtsuThreshOnBackgroundNorm(
|
|
self._pix,
|
|
mask,
|
|
sx, sy,
|
|
thresh, mincount, bgval,
|
|
smoothx, smoothy,
|
|
scorefract,
|
|
ffi.NULL
|
|
)
|
|
if thresh_pix == ffi.NULL:
|
|
return None
|
|
return Pix(thresh_pix)
|
|
|
|
def crop_to_foreground(
|
|
self, threshold=128, mindist=70, erasedist=30, pagenum=0,
|
|
showmorph=0, display=0, pdfdir=ffi.NULL):
|
|
with LeptonicaErrorTrap():
|
|
cropbox = Box(lept.pixFindPageForeground(
|
|
self._pix,
|
|
threshold,
|
|
mindist,
|
|
erasedist,
|
|
pagenum,
|
|
showmorph,
|
|
display,
|
|
pdfdir))
|
|
|
|
print(repr(cropbox))
|
|
|
|
cropped_pix = lept.pixClipRectangle(
|
|
self._pix,
|
|
cropbox._box,
|
|
ffi.NULL)
|
|
|
|
return Pix(cropped_pix)
|
|
|
|
def clean_background_to_white(
|
|
self, mask=None, grayscale=None, gamma=1.0, black=0, white=255):
|
|
with LeptonicaErrorTrap():
|
|
return Pix(lept.pixCleanBackgroundToWhite(
|
|
self._pix,
|
|
mask or ffi.NULL,
|
|
grayscale or ffi.NULL,
|
|
gamma,
|
|
black,
|
|
white))
|
|
|
|
@staticmethod
|
|
@lru_cache(maxsize=1)
|
|
def make_pixel_sum_tab8():
|
|
return lept.makePixelSumTab8()
|
|
|
|
@staticmethod
|
|
def correlation_binary(pix1, pix2):
|
|
if get_leptonica_version() < 'leptonica-1.72':
|
|
# Older versions of Leptonica (pre-1.72) have a buggy
|
|
# implementation of pixCorrelationBinary that overflows on larger
|
|
# images. Ubuntu trusty has 1.70. Ubuntu PPA
|
|
# ppa:rebuntu16/avidemux+unofficial has "leptonlib" 1.73.
|
|
pix1_count = ffi.new('l_int32 *')
|
|
pix2_count = ffi.new('l_int32 *')
|
|
pixn_count = ffi.new('l_int32 *')
|
|
tab8 = Pix.make_pixel_sum_tab8()
|
|
|
|
lept.pixCountPixels(pix1._pix, pix1_count, tab8)
|
|
lept.pixCountPixels(pix2._pix, pix2_count, tab8)
|
|
pixn = Pix(lept.pixAnd(ffi.NULL, pix1._pix, pix2._pix))
|
|
lept.pixCountPixels(pixn._pix, pixn_count, tab8)
|
|
|
|
# Python converts these int32s to larger units as needed
|
|
# to avoid overflow. Overflow happens easily here.
|
|
correlation = (
|
|
(pixn_count[0] * pixn_count[0]) /
|
|
(pix1_count[0] * pix2_count[0])
|
|
)
|
|
return correlation
|
|
else:
|
|
correlation = ffi.new('float *', 0.0)
|
|
result = lept.pixCorrelationBinary(pix1._pix, pix2._pix,
|
|
correlation)
|
|
if result != 0:
|
|
raise LeptonicaError("Correlation failed")
|
|
return correlation[0]
|
|
|
|
@staticmethod
|
|
def _pix_destroy(pix):
|
|
p_pix = ffi.new('PIX **', pix)
|
|
lept.pixDestroy(p_pix)
|
|
# print('pix destroy ' + repr(pix))
|
|
|
|
|
|
class Box:
|
|
"""Wrapper around Leptonica's BOX objects.
|
|
|
|
See class Pix for notes about reference counting.
|
|
"""
|
|
|
|
def __init__(self, box):
|
|
self._box = ffi.gc(box, Box._box_destroy)
|
|
|
|
def __repr__(self):
|
|
if self._box:
|
|
return '<leptonica.Box x={0} y={1} w={2} h={3}>'.format(
|
|
self.x, self.y, self.w, self.h)
|
|
return '<leptonica.Box NULL>'
|
|
|
|
@property
|
|
def x(self):
|
|
return self._box.x
|
|
|
|
@property
|
|
def y(self):
|
|
return self._box.y
|
|
|
|
@property
|
|
def w(self):
|
|
return self._box.w
|
|
|
|
@property
|
|
def h(self):
|
|
return self._box.h
|
|
|
|
@staticmethod
|
|
def _box_destroy(box):
|
|
p_box = ffi.new('BOX **', box)
|
|
lept.boxDestroy(p_box)
|
|
|
|
|
|
@lru_cache(maxsize=1)
|
|
def get_leptonica_version():
|
|
"""Get Leptonica version string.
|
|
|
|
Caveat: Leptonica expects the caller to free this memory. We don't,
|
|
since that would involve binding to libc to access libc.free(),
|
|
a pointless effort to reclaim 100 bytes of memory.
|
|
"""
|
|
return ffi.string(lept.getLeptonicaVersion()).decode()
|
|
|
|
|
|
def deskew(infile, outfile, dpi):
|
|
try:
|
|
pix_source = Pix.read(infile)
|
|
except LeptonicaIOError:
|
|
raise LeptonicaIOError("Failed to open file: %s" % infile)
|
|
|
|
if dpi < 150:
|
|
reduction_factor = 1 # Don't downsample too much if DPI is already low
|
|
else:
|
|
reduction_factor = 0 # Use default
|
|
pix_deskewed = pix_source.deskew(reduction_factor)
|
|
|
|
try:
|
|
pix_deskewed.write_implied_format(outfile)
|
|
except LeptonicaIOError:
|
|
raise LeptonicaIOError("Failed to open destination file: %s" % outfile)
|
|
|
|
|
|
if __name__ == '__main__':
|
|
parser = argparse.ArgumentParser(
|
|
description="Python wrapper to access Leptonica")
|
|
|
|
subparsers = parser.add_subparsers(title='commands',
|
|
description='supported operations')
|
|
|
|
parser_deskew = subparsers.add_parser('deskew')
|
|
parser_deskew.add_argument('-r', '--dpi', dest='dpi', action='store',
|
|
type=int, default=300, help='input resolution')
|
|
parser_deskew.add_argument('infile', help='image to deskew')
|
|
parser_deskew.add_argument('outfile', help='deskewed output image')
|
|
parser_deskew.set_defaults(func=deskew)
|
|
|
|
args = parser.parse_args()
|
|
|
|
if get_leptonica_version() != u'leptonica-1.69':
|
|
print("Unexpected leptonica version: %s" % getLeptonicaVersion())
|
|
|
|
args.func(args)
|
|
|
|
|
|
def test_skew_angle():
|
|
from PIL import Image, ImageDraw
|
|
from tempfile import NamedTemporaryFile
|
|
|
|
im = Image.new(mode='1', size=(1000, 1000), color=1)
|
|
|
|
draw = ImageDraw.Draw(im)
|
|
for n in range(20):
|
|
draw.line([(50, 25 + 50*n), (950, 25 + 50*n)], width=1)
|
|
del draw
|
|
|
|
test_angles = [0.1 * ang for ang in range(1, 10)] + \
|
|
[float(ang) for ang in range(1, 7)]
|
|
test_angles += [-ang for ang in test_angles]
|
|
test_angles = sorted(test_angles)
|
|
|
|
for rotate_angle in test_angles:
|
|
rotated_im = im.rotate(rotate_angle)
|
|
with NamedTemporaryFile(prefix='lept-skew', suffix='.png', delete=True) as tmpfile:
|
|
rotated_im.save(tmpfile)
|
|
pix = pixRead(tmpfile.name)
|
|
angle, confidence = pixFindSkew(pix)
|
|
print('{0} {1} {2}'.format(rotate_angle, angle, confidence), file=sys.stderr)
|
|
|
|
|