LUT converter into Darktable base curve

basecurve.py

"""lut to darkatable basecurve converter
usage: python basecurve.py <NAME> <LUT>
"""


import struct
import sys


def hexify(blob):
    def convert(byte):
        hex_value = hex(byte)[2:]
        return "0" * (2 - len(hex_value)) + hex_value
    return "".join(map(convert, blob))


class Anchor:

    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __lt__(self, other):
        return self.x < other.x

    def get_bytes(self):
        return struct.pack("f", self.x) + struct.pack("f", self.y)


class BaseCurve(list):

    MAX_NODES = 20
    CURVE_TYPE = 2

    def __init__(self):
        super(BaseCurve, self).__init__()

    def load_lut(self, path):
        lut = list()
        with open(path, "r") as file:
            for i, line in enumerate(file.readlines()):
                lut.append(Anchor(float(line.strip()) / 255, i / 255))
        step = 256 // BaseCurve.MAX_NODES
        for i in range(BaseCurve.MAX_NODES // 2):
            self.append(lut[i * step])
            self.append(lut[-1 - i * step])
        self.sort()

    def get_blob(self):
        blob = b""
        for anchor in self:
            blob += anchor.get_bytes()
        while len(blob) < 480:
            blob += struct.pack("f", 0)
        for i in [len(self), 0, 0, BaseCurve.CURVE_TYPE, 0, 0]:
            blob += struct.pack("i", i)
        return blob

    def print_command(self, name, dbpath="~/.config/darktable/data.db"):
        template = """echo \"INSERT INTO presets (name,description,operation,op_version,op_params,enabled,blendop_params,blendop_version,multi_priority,multi_name,model,maker,lens,iso_min,iso_max,exposure_min,exposure_max,aperture_min,aperture_max,focal_length_min,focal_length_max,writeprotect,autoapply,filter,def,format) VALUES('{name}','','basecurve',4,X'{blob}',1,X'00000000180000000000C842000000000000000000000000000000000000000000000000000000000000000000000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F00000000000000000000803F0000803F',7,0,'','%','%','%',0.0,340282346638528859812000000000000000000,0.0,10000000.0,0.0,100000000.0,0.0,1000.0,0,0,0,0,2);\" | sqlite3 {dbpath}\n"""
        print(template.format(
            name=name,
            blob=hexify(self.get_blob()).upper(),
            dbpath=dbpath
        ))


if __name__ == "__main__":
    if len(sys.argv) != 3:
        print(__doc__)
    else:
        script, name, lut = sys.argv
        curve = BaseCurve()
        curve.load_lut(lut)
        curve.print_command(name)