fix: Fix get_ranges for empty channels in Image (#1136)

fix PARTSEG-TZ

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Enhanced class initialization with list comprehension for better range
adjustments.
  - Introduced new methods for internal adjustments and mask fitting.

- **Improvements**
- Updated method signatures to use modern type hinting for improved code
clarity and maintainability.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

package/PartSegImage/image.py

@@ -1,9 +1,10 @@
+from __future__ import annotations
+
 import re
 import typing
 import warnings
 from collections.abc import Iterable
 from contextlib import suppress
-from typing import Union
 
 import numpy as np
 
@@ -33,8 +34,8 @@ def minimal_dtype(val: int):
 
 def reduce_array(
     array: np.ndarray,
-    components: typing.Optional[typing.Collection[int]] = None,
-    max_val: typing.Optional[int] = None,
+    components: typing.Collection[int] | None = None,
+    max_val: int | None = None,
     dtype=None,
 ) -> np.ndarray:
     """
@@ -102,12 +103,12 @@ def __init__(
         data: _IMAGE_DATA,
         image_spacing: Spacing,
         file_path=None,
-        mask: typing.Union[None, np.ndarray] = None,
+        mask: None | np.ndarray = None,
         default_coloring=None,
         ranges=None,
         channel_names=None,
-        axes_order: typing.Optional[str] = None,
-        shift: typing.Optional[Spacing] = None,
+        axes_order: str | None = None,
+        shift: Spacing | None = None,
         name: str = "",
     ):
         # TODO add time distance to image spacing
@@ -144,18 +145,26 @@ def __init__(
             self.default_coloring = [np.array(x) for x in default_coloring]
 
         self._channel_names = self._prepare_channel_names(channel_names, self.channels)
+
+        self.ranges = self._adjust_ranges(ranges, self._channel_arrays)
+        self._mask_array = self._fit_mask(mask, data, axes_order)
+
+    @staticmethod
+    def _adjust_ranges(
+        ranges: list[tuple[float, float]] | None, channel_arrays: list[np.ndarray]
+    ) -> list[tuple[float, float]]:
         if ranges is None:
-            self.ranges = list(
-                zip((np.min(c) for c in self._channel_arrays), (np.max(c) for c in self._channel_arrays))
-            )
-        else:
-            self.ranges = ranges
-        self._mask_array = self._prepare_mask(mask, data, axes_order)
-        if self._mask_array is not None:
-            self._mask_array = self.fit_mask_to_image(self._mask_array)
+            ranges = list(zip((np.min(c) for c in channel_arrays), (np.max(c) for c in channel_arrays)))
+        return [(min_val, max_val) if (min_val != max_val) else (min_val, min_val + 1) for (min_val, max_val) in ranges]
+
+    def _fit_mask(self, mask, data, axes_order):
+        mask_array = self._prepare_mask(mask, data, axes_order)
+        if mask_array is not None:
+            mask_array = self.fit_mask_to_image(mask_array)
+        return mask_array
 
     @classmethod
-    def _prepare_mask(cls, mask, data, axes_order) -> typing.Optional[np.ndarray]:
+    def _prepare_mask(cls, mask, data, axes_order) -> np.ndarray | None:
         if mask is None:
             return None
 
@@ -170,7 +179,7 @@ def _prepare_mask(cls, mask, data, axes_order) -> typing.Optional[np.ndarray]:
         return cls.reorder_axes(mask, axes_order.replace("C", ""))
 
     @staticmethod
-    def _prepare_channel_names(channel_names, channels_num) -> typing.List[str]:
+    def _prepare_channel_names(channel_names, channels_num) -> list[str]:
         default_channel_names = [f"channel {i + 1}" for i in range(channels_num)]
         if isinstance(channel_names, str):
             channel_names = [channel_names]
@@ -182,9 +191,7 @@ def _prepare_channel_names(channel_names, channels_num) -> typing.List[str]:
         return channel_names_list[:channels_num]
 
     @classmethod
-    def _split_data_on_channels(
-        cls, data: typing.Union[np.ndarray, typing.List[np.ndarray]], axes_order: str
-    ) -> typing.List[np.ndarray]:
+    def _split_data_on_channels(cls, data: np.ndarray | list[np.ndarray], axes_order: str) -> list[np.ndarray]:
         if isinstance(data, list) and not axes_order.startswith("C"):  # pragma: no cover
             raise ValueError("When passing data as list of numpy arrays then Channel must be first axis.")
         if "C" not in axes_order:
@@ -199,7 +206,7 @@ def _split_data_on_channels(
 
         if not isinstance(data, np.ndarray):
             raise TypeError("If `data` is list of arrays then `axes_order` must start with `C`")  # pragma: no cover
-        pos: typing.List[typing.Union[slice, int]] = [slice(None) for _ in range(data.ndim)]
+        pos: list[slice | int] = [slice(None) for _ in range(data.ndim)]
         c_pos = axes_order.index("C")
         res = []
         for i in range(data.shape[c_pos]):
@@ -208,9 +215,7 @@ def _split_data_on_channels(
         return res
 
     @staticmethod
-    def _merge_channel_names(
-        base_channel_names: typing.List[str], new_channel_names: typing.List[str]
-    ) -> typing.List[str]:
+    def _merge_channel_names(base_channel_names: list[str], new_channel_names: list[str]) -> list[str]:
         base_channel_names = base_channel_names[:]
         reg = re.compile(r"channel \d+")
         for name in new_channel_names:
@@ -228,7 +233,7 @@ def _merge_channel_names(
             base_channel_names.append(new_name)
         return base_channel_names
 
-    def merge(self, image: "Image", axis: str) -> "Image":
+    def merge(self, image: Image, axis: str) -> Image:
         """
         Produce new image merging image data along given axis. All metadata
         are obtained from self.
@@ -256,7 +261,7 @@ def merge(self, image: "Image", axis: str) -> "Image":
         return self.substitute(data=data, ranges=self.ranges + image.ranges, channel_names=channel_names)
 
     @property
-    def channel_names(self) -> typing.List[str]:
+    def channel_names(self) -> list[str]:
         return self._channel_names[:]
 
     @property
@@ -333,7 +338,7 @@ def substitute(
         default_coloring=None,
         ranges=None,
         channel_names=None,
-    ) -> "Image":
+    ) -> Image:
         """Create copy of image with substitution of not None elements"""
         data = self._channel_arrays if data is None else data
         image_spacing = self._image_spacing if image_spacing is None else image_spacing
@@ -353,7 +358,7 @@ def substitute(
             axes_order=self.axis_order,
         )
 
-    def set_mask(self, mask: typing.Optional[np.ndarray], axes: typing.Optional[str] = None):
+    def set_mask(self, mask: np.ndarray | None, axes: str | None = None):
         """
         Set mask for image, check if it has proper shape.
 
@@ -374,7 +379,7 @@ def get_data(self) -> np.ndarray:
         return self._channel_arrays[0]
 
     @property
-    def mask(self) -> typing.Optional[np.ndarray]:
+    def mask(self) -> np.ndarray | None:
         return self._mask_array[:] if self._mask_array is not None else None
 
     @staticmethod
@@ -430,7 +435,7 @@ def get_image_for_save(self) -> np.ndarray:
             )
         return self._reorder_axes(self._channel_arrays[0], self.axis_order, "TZCYX")
 
-    def get_mask_for_save(self) -> typing.Optional[np.ndarray]:
+    def get_mask_for_save(self) -> np.ndarray | None:
         """
         :return: if image has mask then return mask with axes in proper order
         """
@@ -469,7 +474,7 @@ def times(self) -> int:
         return self._channel_arrays[0].shape[self.time_pos]
 
     @property
-    def plane_shape(self) -> typing.Tuple[int, int]:
+    def plane_shape(self) -> tuple[int, int]:
         """y,x size of image"""
         return self._channel_arrays[0].shape[self.y_pos], self._channel_arrays[0].shape[self.x_pos]
 
@@ -487,15 +492,15 @@ def swap_time_and_stack(self):
         return self.substitute(data=self._image_data_normalize(image_array_list))
 
     @classmethod
-    def get_axis_positions(cls) -> typing.Dict[str, int]:
+    def get_axis_positions(cls) -> dict[str, int]:
         """
         :return: dict with mapping axis to its position
         :rtype: dict
         """
         return {letter: i for i, letter in enumerate(cls.axis_order)}
 
     @classmethod
-    def get_array_axis_positions(cls) -> typing.Dict[str, int]:
+    def get_array_axis_positions(cls) -> dict[str, int]:
         """
         :return: dict with mapping axis to its position for array fitted to image
         :rtype: dict
@@ -510,7 +515,7 @@ def get_data_by_axis(self, **kwargs) -> np.ndarray:
         :return:
         :rtype:
         """
-        slices: typing.List[typing.Union[int, slice]] = [slice(None) for _ in range(len(self.array_axis_order))]
+        slices: list[int | slice] = [slice(None) for _ in range(len(self.array_axis_order))]
         axis_pos = self.get_array_axis_positions()
         if "c" in kwargs:
             kwargs["C"] = kwargs.pop("c")
@@ -533,7 +538,7 @@ def get_data_by_axis(self, **kwargs) -> np.ndarray:
             return self._channel_arrays[channel][slices_t]
         return np.stack([x[slices_t] for x in self._channel_arrays[channel]], axis=axis_order.index("C"))
 
-    def clip_array(self, array: np.ndarray, **kwargs: typing.Union[int, slice]) -> np.ndarray:
+    def clip_array(self, array: np.ndarray, **kwargs: int | slice) -> np.ndarray:
         """
         Clip array by axis. Axis is selected by single letter from :py:attr:`axis_order`
 
@@ -542,14 +547,14 @@ def clip_array(self, array: np.ndarray, **kwargs: typing.Union[int, slice]) -> n
         :return: clipped array
         """
         array = self.fit_array_to_image(array)
-        slices: typing.List[typing.Union[int, slice]] = [slice(None) for _ in range(len(self.array_axis_order))]
+        slices: list[int | slice] = [slice(None) for _ in range(len(self.array_axis_order))]
         axis_pos = self.get_array_axis_positions()
         for name in kwargs:
             if (n := name.upper()) in axis_pos:
                 slices[axis_pos[n]] = kwargs[name]
         return array[tuple(slices)]
 
-    def get_channel(self, num: Union[int, str, Channel]) -> np.ndarray:
+    def get_channel(self, num: int | str | Channel) -> np.ndarray:
         """
         Alias for :py:func:`get_sub_data` with argument ``c=num``
 
@@ -611,7 +616,7 @@ def set_spacing(self, value: Spacing):
         self._image_spacing = tuple(value)
 
     @staticmethod
-    def _frame_array(array: typing.Optional[np.ndarray], index_to_add: typing.List[int], frame=FRAME_THICKNESS):
+    def _frame_array(array: np.ndarray | None, index_to_add: list[int], frame=FRAME_THICKNESS):
         if array is None:  # pragma: no cover
             return array
         result_shape = list(array.shape)
@@ -626,7 +631,7 @@ def _frame_array(array: typing.Optional[np.ndarray], index_to_add: typing.List[i
         return data
 
     @staticmethod
-    def calc_index_to_frame(array_axis: str, important_axis: str) -> typing.List[int]:
+    def calc_index_to_frame(array_axis: str, important_axis: str) -> list[int]:
         """
         calculate in which axis frame should be added
 
@@ -650,15 +655,15 @@ def _frame_cut_area(self, cut_area: typing.Iterable[slice], frame: int):
 
     def _cut_image_slices(
         self, cut_area: typing.Iterable[slice], frame: int
-    ) -> typing.Tuple[typing.List[np.ndarray], typing.Optional[np.ndarray]]:
+    ) -> tuple[list[np.ndarray], np.ndarray | None]:
         new_mask = None
         cut_area = self._frame_cut_area(cut_area, frame)
         new_image = [x[tuple(cut_area)] for x in self._channel_arrays]
         if self._mask_array is not None:
             new_mask = self._mask_array[tuple(cut_area)]
         return new_image, new_mask
 
-    def _roi_to_slices(self, roi: np.ndarray) -> typing.List[slice]:
+    def _roi_to_slices(self, roi: np.ndarray) -> list[slice]:
         cut_area = self.fit_array_to_image(roi)
         points = np.nonzero(cut_area)
         lower_bound = np.min(points, axis=1)
@@ -689,11 +694,11 @@ def _cut_with_roi(self, cut_area: np.ndarray, replace_mask: bool, frame: int):
 
     def cut_image(
         self,
-        cut_area: typing.Union[np.ndarray, typing.Iterable[slice]],
+        cut_area: np.ndarray | typing.Iterable[slice],
         replace_mask=False,
         frame: int = FRAME_THICKNESS,
         zero_out_cut_area: bool = True,
-    ) -> "Image":
+    ) -> Image:
         """
         Create new image base on mask or list of slices
         :param bool replace_mask: if cut area is represented by mask array,
@@ -771,7 +776,7 @@ def get_um_shift(self) -> Spacing:
         """image spacing in micrometers"""
         return tuple(float(x * 10**6) for x in self.shift)
 
-    def get_ranges(self) -> typing.List[typing.Tuple[float, float]]:
+    def get_ranges(self) -> list[tuple[float, float]]:
         """image brightness ranges for each channel"""
         return self.ranges[:]