601 lines
19 KiB
Python
601 lines
19 KiB
Python
#!/usr/bin/env python3
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# -*- coding: utf-8 -*-
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#
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# © 2013-16: jbarlow83 from Github (https://github.com/jbarlow83)
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#
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# Python FFI wrapper for Leptonica library
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import argparse
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import sys
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import os
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import logging
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from tempfile import TemporaryFile
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from ctypes.util import find_library
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from .lib._leptonica import ffi
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from functools import lru_cache
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from enum import Enum
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from .helpers import fspath
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lept = ffi.dlopen(find_library('lept'))
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logger = logging.getLogger(__name__)
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def stderr(*objs):
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"""Python 2/3 compatible print to stderr.
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"""
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print("leptonica.py:", *objs, file=sys.stderr)
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class LeptonicaErrorTrap(object):
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"""Context manager to trap errors reported by Leptonica.
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Leptonica's error return codes are unreliable to the point of being
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almost useless. It does, however, write errors to stderr provided that is
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not disabled at its compile time. Fortunately this is done using error
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macros so it is very self-consistent.
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This context manager redirects stderr to a temporary file which is then
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read and parsed for error messages. As a side benefit, debug messages
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from Leptonica are also suppressed.
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"""
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def __enter__(self):
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from io import UnsupportedOperation
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self.tmpfile = TemporaryFile()
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# Save the old stderr, and redirect stderr to temporary file
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sys.stderr.flush()
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try:
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self.copy_of_stderr = os.dup(sys.stderr.fileno())
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os.dup2(self.tmpfile.fileno(), sys.stderr.fileno(),
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inheritable=False)
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except UnsupportedOperation:
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self.copy_of_stderr = None
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return
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def __exit__(self, exc_type, exc_value, traceback):
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# Restore old stderr
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sys.stderr.flush()
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if self.copy_of_stderr is not None:
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os.dup2(self.copy_of_stderr, sys.stderr.fileno())
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os.close(self.copy_of_stderr)
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# Get data from tmpfile (in with block to ensure it is closed)
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with self.tmpfile as tmpfile:
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tmpfile.seek(0) # Cursor will be at end, so move back to beginning
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leptonica_output = tmpfile.read().decode(errors='replace')
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assert self.tmpfile.closed
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assert not sys.stderr.closed
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# If there are Python errors, let them bubble up
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if exc_type:
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logger.warning(leptonica_output)
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return False
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# If there are Leptonica errors, wrap them in Python excpetions
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if 'Error' in leptonica_output:
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if 'image file not found' in leptonica_output:
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raise FileNotFoundError()
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if 'pixWrite: stream not opened' in leptonica_output:
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raise LeptonicaIOError()
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raise LeptonicaError(leptonica_output)
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return False
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class LeptonicaError(Exception):
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pass
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class LeptonicaIOError(LeptonicaError):
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pass
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class RemoveColormap(Enum):
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to_binary = 0
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to_grayscale = 1
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to_full_color = 2
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based_on_src = 3
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class Pix:
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"""Wrapper around leptonica's PIX object.
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Leptonica uses referencing counting on PIX objects. Also, many Leptonica
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functions return the original object with an increased reference count
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if the operation had no effect (for example, image skew was found to be 0).
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This has complications for memory management in Python. Whenever Leptonica
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returns a PIX object (new or old), we wrap it in this class, which
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registers it with the FFI garbage collector. pixDestroy() decrements the
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reference count and only destroys when the last reference is removed.
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Leptonica's reference counting is not threadsafe. This class can be used
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in a threadsafe manner if a Python threading.Lock protects the data.
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This class treats Pix objects as immutable. All methods return new
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modified objects. This allows convenient chaining:
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>>> Pix.read('filename.jpg').scale((0.5, 0.5)).deskew().show()
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"""
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def __init__(self, pix):
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self._pix = ffi.gc(pix, Pix._pix_destroy)
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def __repr__(self):
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if self._pix:
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s = "<leptonica.Pix image size={0}x{1} depth={2} at 0x{3:x}>"
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return s.format(self._pix.w, self._pix.h, self._pix.d,
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int(ffi.cast("intptr_t", self._pix)))
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else:
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return "<leptonica.Pix image NULL>"
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def _repr_png_(self):
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"""iPython display hook
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returns png version of image
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"""
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data = ffi.new('l_uint8 **')
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size = ffi.new('size_t *')
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err = lept.pixWriteMemPng(data, size, self._pix, 0)
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if err != 0:
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raise LeptonicaIOError("pixWriteMemPng")
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char_data = ffi.cast('char *', data[0])
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return ffi.buffer(char_data, size[0])[:]
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def __getstate__(self):
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data = ffi.new('l_uint32 **')
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size = ffi.new('size_t *')
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err = lept.pixSerializeToMemory(self._pix, data, size)
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if err != 0:
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raise LeptonicaIOError("pixSerializeToMemory")
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char_data = ffi.cast('char *', data[0])
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# Copy from C bytes to python bytes()
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data_bytes = ffi.buffer(char_data, size[0])[:]
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# Can now free C bytes
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lept.lept_free(char_data)
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return dict(data=data_bytes)
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def __setstate__(self, state):
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cdata_bytes = ffi.new('char[]', state['data'])
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cdata_uint32 = ffi.cast('l_uint32 *', cdata_bytes)
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pix = lept.pixDeserializeFromMemory(
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cdata_uint32, len(state['data']))
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Pix.__init__(self, pix)
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def __eq__(self, other):
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return self.__getstate__() == other.__getstate__()
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@property
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def width(self):
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return self._pix.w
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@property
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def height(self):
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return self._pix.h
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@property
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def depth(self):
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return self._pix.d
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@property
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def size(self):
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return (self._pix.w, self._pix.h)
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@property
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def info(self):
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return {'dpi': (self._pix.xres, self._pix.yres)}
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@property
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def mode(self):
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"Return mode like PIL.Image"
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if self.depth == 1:
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return '1'
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elif self.depth >= 16:
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return 'RGB'
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elif not self._pix.colormap:
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return 'L'
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else:
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return 'P'
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@classmethod
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def read(cls, path):
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"""Load an image file into a PIX object.
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Leptonica can load TIFF, PNM (PBM, PGM, PPM), PNG, and JPEG. If
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loading fails then the object will wrap a C null pointer.
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"""
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filename = fspath(path)
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with LeptonicaErrorTrap():
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return cls(lept.pixRead(os.fsencode(filename)))
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def write_implied_format(
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self, path, jpeg_quality=0, jpeg_progressive=0):
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"""Write pix to the filename, with the extension indicating format.
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jpeg_quality -- quality (iff JPEG; 1 - 100, 0 for default)
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jpeg_progressive -- (iff JPEG; 0 for baseline seq., 1 for progressive)
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"""
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filename = fspath(path)
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with LeptonicaErrorTrap():
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lept.pixWriteImpliedFormat(
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os.fsencode(filename),
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self._pix, jpeg_quality, jpeg_progressive)
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def topil(self):
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"Returns a PIL.Image version of this Pix"
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from PIL import Image
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# Leptonica manages data in words, so it implicitly does an endian
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# swap. Tell Pillow about this when it reads the data.
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pix = self
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if sys.byteorder == 'little':
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if self.mode == 'RGB':
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raw_mode = 'XBGR'
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elif self.mode == 'RGBA':
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raw_mode = 'ABGR'
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elif self.mode == '1':
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raw_mode = '1;I'
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pix = Pix(lept.pixEndianByteSwapNew(pix._pix))
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else:
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raw_mode = self.mode
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pix = Pix(lept.pixEndianByteSwapNew(pix._pix))
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else:
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raw_mode = self.mode # no endian swap needed
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size = (pix._pix.w, pix._pix.h)
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bytecount = pix._pix.wpl * 4 * pix._pix.h
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buf = ffi.buffer(pix._pix.data, bytecount)
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stride = pix._pix.wpl * 4
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im = Image.frombytes(self.mode, size, buf, 'raw', raw_mode, stride)
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return im
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def show(self):
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return self.topil().show()
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def deskew(self, reduction_factor=0):
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"""Returns the deskewed pix object.
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A clone of the original is returned when the algorithm cannot find a
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skew angle with sufficient confidence.
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reduction_factor -- amount to downsample (0 for default) when searching
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for skew angle
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"""
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with LeptonicaErrorTrap():
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return Pix(lept.pixDeskew(self._pix, reduction_factor))
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def scale(self, scale_xy):
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"Returns the pix object rescaled according to the proportions given."
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with LeptonicaErrorTrap():
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return Pix(lept.pixScale(self._pix, scale_xy[0], scale_xy[1]))
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def rotate180(self):
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with LeptonicaErrorTrap():
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return Pix(lept.pixRotate180(ffi.NULL, self._pix))
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def rotate_orth(self, quads):
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"Orthographic rotation, quads: 0-3, number of clockwise rotations"
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with LeptonicaErrorTrap():
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return Pix(lept.pixRotateOrth(self._pix, quads))
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def find_skew(self):
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"""Returns a tuple (deskew angle in degrees, confidence value).
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Returns (None, None) if no angle is available.
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"""
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with LeptonicaErrorTrap():
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angle = ffi.new('float *', 0.0)
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confidence = ffi.new('float *', 0.0)
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result = lept.pixFindSkew(self._pix, angle, confidence)
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if result == 0:
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return (angle[0], confidence[0])
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else:
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return (None, None)
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def convert_rgb_to_luminance(self):
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with LeptonicaErrorTrap():
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gray_pix = lept.pixConvertRGBToLuminance(self._pix)
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if gray_pix:
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return Pix(gray_pix)
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return None
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def remove_colormap(self, removal_type):
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"""Remove a palette
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removal_type - RemovalColormap()
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"""
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with LeptonicaErrorTrap():
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return Pix(lept.pixRemoveColormap(self._pix, removal_type))
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def otsu_adaptive_threshold(
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self, tile_size=(300, 300), kernel_size=(4, 4), scorefract=0.1):
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with LeptonicaErrorTrap():
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sx, sy = tile_size
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smoothx, smoothy = kernel_size
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p_pix = ffi.new('PIX **')
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result = lept.pixOtsuAdaptiveThreshold(
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self._pix,
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sx, sy,
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smoothx, smoothy,
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scorefract,
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ffi.NULL,
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p_pix)
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if result == 0:
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return Pix(p_pix[0])
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else:
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return None
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def otsu_threshold_on_background_norm(
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self, mask=None, tile_size=(10, 15), thresh=100, mincount=50,
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bgval=255, kernel_size=(2, 2), scorefract=0.1):
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with LeptonicaErrorTrap():
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sx, sy = tile_size
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smoothx, smoothy = kernel_size
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if mask is None:
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mask = ffi.NULL
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if isinstance(mask, Pix):
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mask = mask._pix
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thresh_pix = lept.pixOtsuThreshOnBackgroundNorm(
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self._pix,
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mask,
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sx, sy,
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thresh, mincount, bgval,
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smoothx, smoothy,
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scorefract,
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ffi.NULL
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)
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if thresh_pix == ffi.NULL:
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return None
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return Pix(thresh_pix)
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def crop_to_foreground(
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self, threshold=128, mindist=70, erasedist=30, pagenum=0,
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showmorph=0, display=0, pdfdir=ffi.NULL):
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with LeptonicaErrorTrap():
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cropbox = Box(lept.pixFindPageForeground(
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self._pix,
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threshold,
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mindist,
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erasedist,
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pagenum,
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showmorph,
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display,
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pdfdir))
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print(repr(cropbox))
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cropped_pix = lept.pixClipRectangle(
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self._pix,
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cropbox._box,
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ffi.NULL)
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return Pix(cropped_pix)
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def clean_background_to_white(
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self, mask=None, grayscale=None, gamma=1.0, black=0, white=255):
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with LeptonicaErrorTrap():
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return Pix(lept.pixCleanBackgroundToWhite(
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self._pix,
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mask or ffi.NULL,
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grayscale or ffi.NULL,
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gamma,
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black,
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white))
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def gamma_trc(self, gamma=1.0, minval=0, maxval=255):
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with LeptonicaErrorTrap():
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return Pix(lept.pixGammaTRC(
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ffi.NULL,
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self._pix,
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gamma,
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minval,
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maxval
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))
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def background_norm(
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self, mask=None, grayscale=None, tile_size=(10, 15), fg_threshold=60,
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min_count=40, bg_val=200, smooth_kernel=(2, 1)):
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with LeptonicaErrorTrap():
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return Pix(lept.pixBackgroundNorm(
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self._pix,
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mask or ffi.NULL,
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grayscale or ffi.NULL,
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tile_size[0],
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tile_size[1],
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fg_threshold,
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min_count,
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bg_val,
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smooth_kernel[0],
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smooth_kernel[1]
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))
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@staticmethod
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@lru_cache(maxsize=1)
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def make_pixel_sum_tab8():
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return lept.makePixelSumTab8()
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@staticmethod
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def correlation_binary(pix1, pix2):
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if get_leptonica_version() < 'leptonica-1.72':
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# Older versions of Leptonica (pre-1.72) have a buggy
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# implementation of pixCorrelationBinary that overflows on larger
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# images. Ubuntu trusty has 1.70. Ubuntu PPA
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# ppa:rebuntu16/avidemux+unofficial has "leptonlib" 1.73.
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pix1_count = ffi.new('l_int32 *')
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pix2_count = ffi.new('l_int32 *')
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pixn_count = ffi.new('l_int32 *')
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tab8 = Pix.make_pixel_sum_tab8()
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lept.pixCountPixels(pix1._pix, pix1_count, tab8)
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lept.pixCountPixels(pix2._pix, pix2_count, tab8)
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pixn = Pix(lept.pixAnd(ffi.NULL, pix1._pix, pix2._pix))
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lept.pixCountPixels(pixn._pix, pixn_count, tab8)
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# Python converts these int32s to larger units as needed
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# to avoid overflow. Overflow happens easily here.
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correlation = (
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(pixn_count[0] * pixn_count[0]) /
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(pix1_count[0] * pix2_count[0])
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)
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return correlation
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else:
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correlation = ffi.new('float *', 0.0)
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result = lept.pixCorrelationBinary(pix1._pix, pix2._pix,
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correlation)
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if result != 0:
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raise LeptonicaError("Correlation failed")
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return correlation[0]
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@staticmethod
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def _pix_destroy(pix):
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p_pix = ffi.new('PIX **', pix)
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lept.pixDestroy(p_pix)
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# print('pix destroy ' + repr(pix))
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class Box:
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"""Wrapper around Leptonica's BOX objects.
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See class Pix for notes about reference counting.
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"""
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def __init__(self, box):
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self._box = ffi.gc(box, Box._box_destroy)
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def __repr__(self):
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if self._box:
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return '<leptonica.Box x={0} y={1} w={2} h={3}>'.format(
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self.x, self.y, self.w, self.h)
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return '<leptonica.Box NULL>'
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@property
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def x(self):
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return self._box.x
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@property
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def y(self):
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return self._box.y
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@property
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def w(self):
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return self._box.w
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@property
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def h(self):
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return self._box.h
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@staticmethod
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def _box_destroy(box):
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p_box = ffi.new('BOX **', box)
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lept.boxDestroy(p_box)
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@lru_cache(maxsize=1)
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def get_leptonica_version():
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"""Get Leptonica version string.
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Caveat: Leptonica expects the caller to free this memory. We don't,
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since that would involve binding to libc to access libc.free(),
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a pointless effort to reclaim 100 bytes of memory.
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"""
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return ffi.string(lept.getLeptonicaVersion()).decode()
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def deskew(infile, outfile, dpi):
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try:
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pix_source = Pix.read(infile)
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except LeptonicaIOError:
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raise LeptonicaIOError("Failed to open file: %s" % infile)
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if dpi < 150:
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reduction_factor = 1 # Don't downsample too much if DPI is already low
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else:
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reduction_factor = 0 # Use default
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pix_deskewed = pix_source.deskew(reduction_factor)
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try:
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pix_deskewed.write_implied_format(outfile)
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except LeptonicaIOError:
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raise LeptonicaIOError("Failed to open destination file: %s" % outfile)
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def remove_background(infile, outfile, tile_size=(40, 60), gamma=1.0,
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|
black_threshold=70, white_threshold=190):
|
|
try:
|
|
pix = Pix.read(infile)
|
|
except LeptonicaIOError:
|
|
raise LeptonicaIOError("Failed to open file: %s" % infile)
|
|
|
|
pix = pix.background_norm(tile_size=tile_size).gamma_trc(
|
|
gamma, black_threshold, white_threshold)
|
|
|
|
try:
|
|
pix.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)
|
|
|
|
|