Applying LUTs with PIL

apply_lut.py

from PIL import Image, ImageFile
ImageFile.LOAD_TRUNCATED_IMAGES = True

img_path = "image.jpg"
lut_path = "lut.cube"

img = Image.open(img_path)  # .convert("RGB")
lut = read_lut(lut_path)

# This returns a PIL Image with the LUT applied
img.filter(lut)

lut_class_interface.py

import os
from PIL import Image, ImageFilter
from typing import List, Union
from pathlib import Path
import random

# lut = LUT(lut_path)
# img = PIL.Image.open(img_path)
# lut(img)  |  lut.apply(img)

class LUT:
    """
    Load in a LUT from, say, a `.cube` file. The header of files
    that contain metadata are ignored. After initialising with
    the path like so:
        lut = LUT("lut_file.cube")

    You can call the object or use `.apply` to pass in a PIL Image
    to apply the lut to.
        lut.apply(img <PIL.Image>)
        lut(img)  # also valid
    """

    def __init__(self, path: os.PathLike, num_channels: int = 3):
        self.path = path
        self.num_channels = num_channels
        self.lut = self.read(self.path)

    def apply(self, img: Image.Image):
        return self(img)

    def __call__(self, img: Image.Image):
        return img.filter(self.lut)

    def __repr__(self):
        return "\n".join([f"{self.lut}", f"Path: {self.path}"])

    def read(self, path_lut: Union[str, Path]):  # , num_channels: int = 3):
        "Read LUT from raw file. Filters out rows that aren't recognised as valid values"
        with open(path_lut) as f:
            lut_raw = f.read().splitlines()

        # some luts we need to read from line 11
        # some from line 7
        lut_raw = lut_raw[6:]  # 11

        size = round(len(lut_raw) ** (1 / 3))
        row2val = lambda row: tuple([float(val) for val in row.split(" ")])
        lut_table = [row2val(row) for row in lut_raw if self._is_3dlut_row(row)]

        return ImageFilter.Color3DLUT(size, lut_table, self.num_channels)

    @staticmethod
    def _is_3dlut_row(row: str) -> bool:
        "Check if one line in the file has exactly 3 values"
        row_values = []
        for val in row.split(" "):
            try:
                row_values.append(float(val))
            except:
                return False
        if len(row_values) == 3:
            return True
        return False

read_lut.py

from PIL import ImageFilter
from typing import List
import os

def is_3dlut_row(row: List) -> bool:
    "Check if one line in the file has exactly 3 values"
    row_values = []
    for val in row:
        try:
            row_values.append(float(val))
        except:
            return False
    if len(row_values) == 3:
        return True
    return False


def read_lut(path_lut: Union[str, os.PathLike], num_channels: int = 3):
    "Read LUT from raw file. Assumes each line in a file is part of the lut table"
    with open(path_lut) as f:
        lut_raw = f.read().splitlines()

    size = round(len(lut_raw) ** (1 / 3))
    row2val = lambda row: tuple([float(val) for val in row])
    lut_table = [
        row2val(row.split(" ")) for row in lut_raw if is_3dlut_row(row.split(" "))
    ]

    return ImageFilter.Color3DLUT(size, lut_table, num_channels)