# Copyright (c) 2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import Union, Sequence
try:
from typing import override
except ImportError:
from typing_extensions import override
import nvidia.dali.fn as fn
from ..pipeline.sample_data_group import SampleDataGroup
from .pipeline_step_base import PipelineStepBase
[docs]
class AxesLayoutSetter(PipelineStepBase):
'''Set the DALI axes layout string (e.g., "HWC", "CHW") for selected fields.'''
def __init__(self, names_fields_to_set: Union[str, int, Sequence[Union[str, int]]], layout_to_set: str):
'''
Args:
names_fields_to_set: Name or list of names of fields for which the layout should be set.
All matching fields are processed.
layout_to_set: DALI axes layout string (e.g., "HWC", "CHW")
'''
if isinstance(names_fields_to_set, str) or isinstance(names_fields_to_set, int):
names_fields_to_set = [names_fields_to_set]
self._names_fields_to_set = names_fields_to_set
self._layout_to_set = layout_to_set
@override
def _process(self, data: SampleDataGroup) -> SampleDataGroup:
# Note that only the actual image normalization becomes part of the DALI graph, the search for images as well as resolvong the paths obtained in order to access the image,
# and the change of the data type, happen at graph construction time and do not influence the run time.
for field_name in self._names_fields_to_set:
# Find all fields
field_paths = data.find_all_occurrences(field_name)
for fp in field_paths:
# Get the field
field = data.get_item_in_path(fp)
# Adjust layout (use reshape to set layout metadata without changing data)
field = fn.reshape(field, layout=self._layout_to_set)
# Set the updated field
data.set_item_in_path(fp, field)
return data
@override
def _check_and_adjust_data_format_input_to_output(self, data_empty: SampleDataGroup) -> SampleDataGroup:
for field_name in self._names_fields_to_set:
field_paths = data_empty.find_all_occurrences(field_name)
# Make sure at least 1 field is available
if len(field_paths) == 0:
raise KeyError(f"No occurrences of field '{field_name}' found.")
return data_empty