source/PIL/ImageMorph.py

# 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>
from __future__ import annotations

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: list[str] | None = None, op_name: str | None = None
    ) -> None:
        """
        :param patterns: A list of input patterns, or None.
        :param op_name: The name of a known pattern. One of "corner", "dilation4",
           "dilation8", "erosion4", "erosion8" or "edge".
        :exception Exception: If the op_name is not recognized.
        """
        self.lut: bytearray | None = 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 = f"Unknown pattern {op_name}!"
                raise Exception(msg)

            self.patterns = known_patterns[op_name]
        elif patterns is not None:
            self.patterns = patterns
        else:
            self.patterns = []

    def add_patterns(self, patterns: list[str]) -> None:
        """
        Append to list of patterns.

        :param patterns: Additional patterns.
        """
        self.patterns += patterns

    def build_default_lut(self) -> bytearray:
        """
        Set the current LUT, and return it.

        This is the default LUT that patterns will be applied against when building.
        """
        symbols = [0, 1]
        m = 1 << 4  # pos of current pixel
        self.lut = bytearray(symbols[(i & m) > 0] for i in range(LUT_SIZE))
        return self.lut

    def get_lut(self) -> bytearray | None:
        """
        Returns the current LUT
        """
        return self.lut

    def _string_permute(self, pattern: str, permutation: list[int]) -> str:
        """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: str, options: str, basic_result: int
    ) -> list[tuple[str, int]]:
        """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) -> bytearray:
        """Compile all patterns into a morphology LUT, and return it.

        This is the data to be passed into MorphOp."""
        self.build_default_lut()
        assert self.lut is not None
        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
        compiled_patterns = []
        for pattern in patterns:
            p = pattern[0].replace(".", "X").replace("X", "[01]")
            compiled_patterns.append((re.compile(p), pattern[1]))

        # Step through table and find patterns that match.
        # Note that all the patterns are searched. The last one found takes priority
        for i in range(LUT_SIZE):
            # Build the bit pattern
            bitpattern = bin(i)[2:]
            bitpattern = ("0" * (9 - len(bitpattern)) + bitpattern)[::-1]

            for pattern, r in compiled_patterns:
                if pattern.match(bitpattern):
                    self.lut[i] = [0, 1][r]

        return self.lut


class MorphOp:
    """A class for binary morphological operators"""

    def __init__(
        self,
        lut: bytearray | None = None,
        op_name: str | None = None,
        patterns: list[str] | None = None,
    ) -> None:
        """Create a binary morphological operator.

        If the LUT is not provided, then it is built using LutBuilder from the op_name
        or the patterns.

        :param lut: The LUT data.
        :param patterns: A list of input patterns, or None.
        :param op_name: The name of a known pattern. One of "corner", "dilation4",
        "dilation8", "erosion4", "erosion8", "edge".
        :exception Exception: If the op_name is not recognized.
        """
        if patterns is None and op_name is None:
            self.lut = lut
        else:
            self.lut = LutBuilder(patterns, op_name).build_lut()

    def apply(self, image: Image.Image) -> tuple[int, Image.Image]:
        """Run a single morphological operation on an image.

        Returns a tuple of the number of changed pixels and the
        morphed image.

        :param image: A 1-mode or L-mode image.
        :exception Exception: If the current operator is None.
        :exception ValueError: If the image is not 1 or L mode."""
        if self.lut is None:
            msg = "No operator loaded"
            raise Exception(msg)

        if image.mode not in ("1", "L"):
            msg = "Image mode must be 1 or L"
            raise ValueError(msg)
        outimage = Image.new(image.mode, image.size)
        count = _imagingmorph.apply(bytes(self.lut), image.getim(), outimage.getim())
        return count, outimage

    def match(self, image: Image.Image) -> list[tuple[int, int]]:
        """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`.

        :param image: A 1-mode or L-mode image.
        :exception Exception: If the current operator is None.
        :exception ValueError: If the image is not 1 or L mode."""
        if self.lut is None:
            msg = "No operator loaded"
            raise Exception(msg)

        if image.mode not in ("1", "L"):
            msg = "Image mode must be 1 or L"
            raise ValueError(msg)
        return _imagingmorph.match(bytes(self.lut), image.getim())

    def get_on_pixels(self, image: Image.Image) -> list[tuple[int, int]]:
        """Get a list of all turned on pixels in a 1 or L mode image.

        Returns a list of tuples of (x,y) coordinates of all non-empty pixels. See
        :ref:`coordinate-system`.

        :param image: A 1-mode or L-mode image.
        :exception ValueError: If the image is not 1 or L mode."""

        if image.mode not in ("1", "L"):
            msg = "Image mode must be 1 or L"
            raise ValueError(msg)
        return _imagingmorph.get_on_pixels(image.getim())

    def load_lut(self, filename: str) -> None:
        """
        Load an operator from an mrl file

        :param filename: The file to read from.
        :exception Exception: If the length of the file data is not 512.
        """
        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: str) -> None:
        """
        Save an operator to an mrl file.

        :param filename: The destination file.
        :exception Exception: If the current operator is None.
        """
        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: bytearray | None) -> None:
        """
        Set the LUT from an external source

        :param lut: A new LUT.
        """
        self.lut = lut