Pytorch上下采样函数--interpolate
可以指定分辨率了，解决了奇数采样对齐的问题
import torch
import torch.nn.functional as funtion
x = torch.randn([1, 3, 63, 63])
y0 = funtion.interpolate(x, scale_factor=0.5)
y1 = funtion.interpolate(x, size=[32, 32])
y2 = funtion.interpolate(x, size=[128, 128], mode="bilinear")
print(y0.shape)
print(y1.shape)
print(y2.shape)torch.Size([1, 3, 31, 31])
torch.Size([1, 3, 32, 32])
torch.Size([1, 3, 128, 128])
最近用到了上采样下采样操作，pytorch中使用interpolate可以很轻松的完成
def interpolate(input, size=None, scale_factor=None, mode='nearest', align_corners=None):
r"""
根据给定 size 或 scale_factor，上采样或下采样输入数据input.
当前支持 temporal, spatial 和 volumetric 输入数据的上采样，其shape 分别为：3-D, 4-D 和 5-D.
输入数据的形式为：mini-batch x channels x [optional depth] x [optional height] x width.
上采样算法有：nearest, linear(3D-only), bilinear(4D-only), trilinear(5D-only).
参数:
- input (Tensor): input tensor
- size (int or Tuple[int] or Tuple[int, int] or Tuple[int, int, int]):输出的 spatial 尺寸.
- scale_factor (float or Tuple[float]): spatial 尺寸的缩放因子.
- mode (string): 上采样算法:nearest, linear, bilinear, trilinear, area. 默认为 nearest.
- align_corners (bool, optional): 如果 align_corners=True，则对齐 input 和 output 的角点像素(corner pixels)，保持在角点像素的值. 只会对 mode=linear, bilinear 和 trilinear 有作用. 默认是 False.
"""
from numbers import Integral
from .modules.utils import _ntuple
def _check_size_scale_factor(dim):
if size is None and scale_factor is None:
raise ValueError('either size or scale_factor should be defined')
if size is not None and scale_factor is not None:
raise ValueError('only one of size or scale_factor should be defined')
if scale_factor is not None and isinstance(scale_factor, tuple)\
and len(scale_factor) != dim:
raise ValueError('scale_factor shape must match input shape. '
'Input is {}D, scale_factor size is {}'.format(dim, len(scale_factor)))
def _output_size(dim):
_check_size_scale_factor(dim)
if size is not None:
return size
scale_factors = _ntuple(dim)(scale_factor)
# math.floor might return float in py2.7
return [int(math.floor(input.size(i + 2) * scale_factors[i])) for i in range(dim)]
if mode in ('nearest', 'area'):
if align_corners is not None:
raise ValueError("align_corners option can only be set with the "
"interpolating modes: linear | bilinear | trilinear")
else:
if align_corners is None:
warnings.warn("Default upsampling behavior when mode={} is changed "
"to align_corners=False since 0.4.0. Please specify "
"align_corners=True if the old behavior is desired. "
"See the documentation of nn.Upsample for details.".format(mode))
align_corners = False
if input.dim() == 3 and mode == 'nearest':
return torch._C._nn.upsample_nearest1d(input, _output_size(1))
elif input.dim() == 4 and mode == 'nearest':
return torch._C._nn.upsample_nearest2d(input, _output_size(2))
elif input.dim() == 5 and mode == 'nearest':
return torch._C._nn.upsample_nearest3d(input, _output_size(3))
elif input.dim() == 3 and mode == 'area':
return adaptive_avg_pool1d(input, _output_size(1))
elif input.dim() == 4 and mode == 'area':
return adaptive_avg_pool2d(input, _output_size(2))
elif input.dim() == 5 and mode == 'area':
return adaptive_avg_pool3d(input, _output_size(3))
elif input.dim() == 3 and mode == 'linear':
return torch._C._nn.upsample_linear1d(input, _output_size(1), align_corners)
elif input.dim() == 3 and mode == 'bilinear':
raise NotImplementedError("Got 3D input, but bilinear mode needs 4D input")
elif input.dim() == 3 and mode == 'trilinear':
raise NotImplementedError("Got 3D input, but trilinear mode needs 5D input")
elif input.dim() == 4 and mode == 'linear':
raise NotImplementedError("Got 4D input, but linear mode needs 3D input")
elif input.dim() == 4 and mode == 'bilinear':
return torch._C._nn.upsample_bilinear2d(input, _output_size(2), align_corners)
elif input.dim() == 4 and mode == 'trilinear':
raise NotImplementedError("Got 4D input, but trilinear mode needs 5D input")
elif input.dim() == 5 and mode == 'linear':
raise NotImplementedError("Got 5D input, but linear mode needs 3D input")
elif input.dim() == 5 and mode == 'bilinear':
raise NotImplementedError("Got 5D input, but bilinear mode needs 4D input")
elif input.dim() == 5 and mode == 'trilinear':
return torch._C._nn.upsample_trilinear3d(input, _output_size(3), align_corners)
else:
raise NotImplementedError("Input Error: Only 3D, 4D and 5D input Tensors supported"
" (got {}D) for the modes: nearest | linear | bilinear | trilinear"
" (got {})".format(input.dim(), mode))
这里注意上采样的时候mode默认是“nearest”，这里指定双线性插值“bilinear”
得到结果
torch.Size([1, 3, 32, 32])
torch.Size([1, 3, 32, 32])
torch.Size([1, 3, 128, 128])
