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+# A binary morphology add-on for the Python Imaging Library
+#
+# History:
+# 2014-06-04 Initial version.
+#
+# Copyright (c) 2014 Dov Grobgeld <dov.grobgeld@gmail.com>
+
+import re
+
+from . import Image, _imagingmorph
+
+LUT_SIZE = 1 << 9
+
+# fmt: off
+ROTATION_MATRIX = [
+ 6, 3, 0,
+ 7, 4, 1,
+ 8, 5, 2,
+]
+MIRROR_MATRIX = [
+ 2, 1, 0,
+ 5, 4, 3,
+ 8, 7, 6,
+]
+# fmt: on
+
+
+class LutBuilder:
+ """A class for building a MorphLut from a descriptive language
+
+ The input patterns is a list of a strings sequences like these::
+
+ 4:(...
+ .1.
+ 111)->1
+
+ (whitespaces including linebreaks are ignored). The option 4
+ describes a series of symmetry operations (in this case a
+ 4-rotation), the pattern is described by:
+
+ - . or X - Ignore
+ - 1 - Pixel is on
+ - 0 - Pixel is off
+
+ The result of the operation is described after "->" string.
+
+ The default is to return the current pixel value, which is
+ returned if no other match is found.
+
+ Operations:
+
+ - 4 - 4 way rotation
+ - N - Negate
+ - 1 - Dummy op for no other operation (an op must always be given)
+ - M - Mirroring
+
+ Example::
+
+ lb = LutBuilder(patterns = ["4:(... .1. 111)->1"])
+ lut = lb.build_lut()
+
+ """
+
+ def __init__(self, patterns=None, op_name=None):
+ if patterns is not None:
+ self.patterns = patterns
+ else:
+ self.patterns = []
+ self.lut = None
+ if op_name is not None:
+ known_patterns = {
+ "corner": ["1:(... ... ...)->0", "4:(00. 01. ...)->1"],
+ "dilation4": ["4:(... .0. .1.)->1"],
+ "dilation8": ["4:(... .0. .1.)->1", "4:(... .0. ..1)->1"],
+ "erosion4": ["4:(... .1. .0.)->0"],
+ "erosion8": ["4:(... .1. .0.)->0", "4:(... .1. ..0)->0"],
+ "edge": [
+ "1:(... ... ...)->0",
+ "4:(.0. .1. ...)->1",
+ "4:(01. .1. ...)->1",
+ ],
+ }
+ if op_name not in known_patterns:
+ msg = "Unknown pattern " + op_name + "!"
+ raise Exception(msg)
+
+ self.patterns = known_patterns[op_name]
+
+ def add_patterns(self, patterns):
+ self.patterns += patterns
+
+ def build_default_lut(self):
+ symbols = [0, 1]
+ m = 1 << 4 # pos of current pixel
+ self.lut = bytearray(symbols[(i & m) > 0] for i in range(LUT_SIZE))
+
+ def get_lut(self):
+ return self.lut
+
+ def _string_permute(self, pattern, permutation):
+ """string_permute takes a pattern and a permutation and returns the
+ string permuted according to the permutation list.
+ """
+ assert len(permutation) == 9
+ return "".join(pattern[p] for p in permutation)
+
+ def _pattern_permute(self, basic_pattern, options, basic_result):
+ """pattern_permute takes a basic pattern and its result and clones
+ the pattern according to the modifications described in the $options
+ parameter. It returns a list of all cloned patterns."""
+ patterns = [(basic_pattern, basic_result)]
+
+ # rotations
+ if "4" in options:
+ res = patterns[-1][1]
+ for i in range(4):
+ patterns.append(
+ (self._string_permute(patterns[-1][0], ROTATION_MATRIX), res)
+ )
+ # mirror
+ if "M" in options:
+ n = len(patterns)
+ for pattern, res in patterns[:n]:
+ patterns.append((self._string_permute(pattern, MIRROR_MATRIX), res))
+
+ # negate
+ if "N" in options:
+ n = len(patterns)
+ for pattern, res in patterns[:n]:
+ # Swap 0 and 1
+ pattern = pattern.replace("0", "Z").replace("1", "0").replace("Z", "1")
+ res = 1 - int(res)
+ patterns.append((pattern, res))
+
+ return patterns
+
+ def build_lut(self):
+ """Compile all patterns into a morphology lut.
+
+ TBD :Build based on (file) morphlut:modify_lut
+ """
+ self.build_default_lut()
+ patterns = []
+
+ # Parse and create symmetries of the patterns strings
+ for p in self.patterns:
+ m = re.search(r"(\w*):?\s*\((.+?)\)\s*->\s*(\d)", p.replace("\n", ""))
+ if not m:
+ msg = 'Syntax error in pattern "' + p + '"'
+ raise Exception(msg)
+ options = m.group(1)
+ pattern = m.group(2)
+ result = int(m.group(3))
+
+ # Get rid of spaces
+ pattern = pattern.replace(" ", "").replace("\n", "")
+
+ patterns += self._pattern_permute(pattern, options, result)
+
+ # compile the patterns into regular expressions for speed
+ for i, pattern in enumerate(patterns):
+ p = pattern[0].replace(".", "X").replace("X", "[01]")
+ p = re.compile(p)
+ patterns[i] = (p, pattern[1])
+
+ # Step through table and find patterns that match.
+ # Note that all the patterns are searched. The last one
+ # caught overrides
+ for i in range(LUT_SIZE):
+ # Build the bit pattern
+ bitpattern = bin(i)[2:]
+ bitpattern = ("0" * (9 - len(bitpattern)) + bitpattern)[::-1]
+
+ for p, r in patterns:
+ if p.match(bitpattern):
+ self.lut[i] = [0, 1][r]
+
+ return self.lut
+
+
+class MorphOp:
+ """A class for binary morphological operators"""
+
+ def __init__(self, lut=None, op_name=None, patterns=None):
+ """Create a binary morphological operator"""
+ self.lut = lut
+ if op_name is not None:
+ self.lut = LutBuilder(op_name=op_name).build_lut()
+ elif patterns is not None:
+ self.lut = LutBuilder(patterns=patterns).build_lut()
+
+ def apply(self, image):
+ """Run a single morphological operation on an image
+
+ Returns a tuple of the number of changed pixels and the
+ morphed image"""
+ if self.lut is None:
+ msg = "No operator loaded"
+ raise Exception(msg)
+
+ if image.mode != "L":
+ msg = "Image mode must be L"
+ raise ValueError(msg)
+ outimage = Image.new(image.mode, image.size, None)
+ count = _imagingmorph.apply(bytes(self.lut), image.im.id, outimage.im.id)
+ return count, outimage
+
+ def match(self, image):
+ """Get a list of coordinates matching the morphological operation on
+ an image.
+
+ Returns a list of tuples of (x,y) coordinates
+ of all matching pixels. See :ref:`coordinate-system`."""
+ if self.lut is None:
+ msg = "No operator loaded"
+ raise Exception(msg)
+
+ if image.mode != "L":
+ msg = "Image mode must be L"
+ raise ValueError(msg)
+ return _imagingmorph.match(bytes(self.lut), image.im.id)
+
+ def get_on_pixels(self, image):
+ """Get a list of all turned on pixels in a binary image
+
+ Returns a list of tuples of (x,y) coordinates
+ of all matching pixels. See :ref:`coordinate-system`."""
+
+ if image.mode != "L":
+ msg = "Image mode must be L"
+ raise ValueError(msg)
+ return _imagingmorph.get_on_pixels(image.im.id)
+
+ def load_lut(self, filename):
+ """Load an operator from an mrl file"""
+ with open(filename, "rb") as f:
+ self.lut = bytearray(f.read())
+
+ if len(self.lut) != LUT_SIZE:
+ self.lut = None
+ msg = "Wrong size operator file!"
+ raise Exception(msg)
+
+ def save_lut(self, filename):
+ """Save an operator to an mrl file"""
+ if self.lut is None:
+ msg = "No operator loaded"
+ raise Exception(msg)
+ with open(filename, "wb") as f:
+ f.write(self.lut)
+
+ def set_lut(self, lut):
+ """Set the lut from an external source"""
+ self.lut = lut