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# Copyright (c) Facebook, Inc. and its affiliates.
import random
from typing import Optional, Tuple
import torch
from densepose.converters import ToChartResultConverterWithConfidences
from .densepose_base import DensePoseBaseSampler
class DensePoseConfidenceBasedSampler(DensePoseBaseSampler):
"""
Samples DensePose data from DensePose predictions.
Samples for each class are drawn using confidence value estimates.
"""
def __init__(
self,
confidence_channel: str,
count_per_class: int = 8,
search_count_multiplier: Optional[float] = None,
search_proportion: Optional[float] = None,
):
"""
Constructor
Args:
confidence_channel (str): confidence channel to use for sampling;
possible values:
"sigma_2": confidences for UV values
"fine_segm_confidence": confidences for fine segmentation
"coarse_segm_confidence": confidences for coarse segmentation
(default: "sigma_2")
count_per_class (int): the sampler produces at most `count_per_class`
samples for each category (default: 8)
search_count_multiplier (float or None): if not None, the total number
of the most confident estimates of a given class to consider is
defined as `min(search_count_multiplier * count_per_class, N)`,
where `N` is the total number of estimates of the class; cannot be
specified together with `search_proportion` (default: None)
search_proportion (float or None): if not None, the total number of the
of the most confident estimates of a given class to consider is
defined as `min(max(search_proportion * N, count_per_class), N)`,
where `N` is the total number of estimates of the class; cannot be
specified together with `search_count_multiplier` (default: None)
"""
super().__init__(count_per_class)
self.confidence_channel = confidence_channel
self.search_count_multiplier = search_count_multiplier
self.search_proportion = search_proportion
assert (search_count_multiplier is None) or (search_proportion is None), (
f"Cannot specify both search_count_multiplier (={search_count_multiplier})"
f"and search_proportion (={search_proportion})"
)
def _produce_index_sample(self, values: torch.Tensor, count: int):
"""
Produce a sample of indices to select data based on confidences
Args:
values (torch.Tensor): an array of size [n, k] that contains
estimated values (U, V, confidences);
n: number of channels (U, V, confidences)
k: number of points labeled with part_id
count (int): number of samples to produce, should be positive and <= k
Return:
list(int): indices of values (along axis 1) selected as a sample
"""
k = values.shape[1]
if k == count:
index_sample = list(range(k))
else:
# take the best count * search_count_multiplier pixels,
# sample from them uniformly
# (here best = smallest variance)
_, sorted_confidence_indices = torch.sort(values[2])
if self.search_count_multiplier is not None:
search_count = min(int(count * self.search_count_multiplier), k)
elif self.search_proportion is not None:
search_count = min(max(int(k * self.search_proportion), count), k)
else:
search_count = min(count, k)
sample_from_top = random.sample(range(search_count), count)
index_sample = sorted_confidence_indices[:search_count][sample_from_top]
return index_sample
def _produce_labels_and_results(self, instance) -> Tuple[torch.Tensor, torch.Tensor]:
"""
Method to get labels and DensePose results from an instance, with confidences
Args:
instance (Instances): an instance of `DensePoseChartPredictorOutputWithConfidences`
Return:
labels (torch.Tensor): shape [H, W], DensePose segmentation labels
dp_result (torch.Tensor): shape [3, H, W], DensePose results u and v
stacked with the confidence channel
"""
converter = ToChartResultConverterWithConfidences
chart_result = converter.convert(instance.pred_densepose, instance.pred_boxes)
labels, dp_result = chart_result.labels.cpu(), chart_result.uv.cpu()
dp_result = torch.cat(
(dp_result, getattr(chart_result, self.confidence_channel)[None].cpu())
)
return labels, dp_result
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