【581】PyTorch 实现上采样 —— nn.Upsampling

参考：pytorch torch.nn 实现上采样——nn.Upsample

参考：PyTorch Upsample() 函数实现上采样

参考：Official - Docs >  torch.nn > Upsample 

　　举例

>>> input = torch.arange(1, 5, dtype=torch.float32).view(1, 1, 2, 2)
>>> input
tensor([[[[ 1.,  2.],
          [ 3.,  4.]]]])

>>> m = nn.Upsample(scale_factor=2, mode='nearest')
>>> m(input)
tensor([[[[ 1.,  1.,  2.,  2.],
          [ 1.,  1.,  2.,  2.],
          [ 3.,  3.,  4.,  4.],
          [ 3.,  3.,  4.,  4.]]]])

>>> m = nn.Upsample(scale_factor=2, mode='bilinear')  # align_corners=False
>>> m(input)
tensor([[[[ 1.0000,  1.2500,  1.7500,  2.0000],
          [ 1.5000,  1.7500,  2.2500,  2.5000],
          [ 2.5000,  2.7500,  3.2500,  3.5000],
          [ 3.0000,  3.2500,  3.7500,  4.0000]]]])

>>> m = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
>>> m(input)
tensor([[[[ 1.0000,  1.3333,  1.6667,  2.0000],
          [ 1.6667,  2.0000,  2.3333,  2.6667],
          [ 2.3333,  2.6667,  3.0000,  3.3333],
          [ 3.0000,  3.3333,  3.6667,  4.0000]]]])

>>> # Try scaling the same data in a larger tensor
>>>
>>> input_3x3 = torch.zeros(3, 3).view(1, 1, 3, 3)
>>> input_3x3[:, :, :2, :2].copy_(input)
tensor([[[[ 1.,  2.],
          [ 3.,  4.]]]])
>>> input_3x3
tensor([[[[ 1.,  2.,  0.],
          [ 3.,  4.,  0.],
          [ 0.,  0.,  0.]]]])

>>> m = nn.Upsample(scale_factor=2, mode='bilinear')  # align_corners=False
>>> # Notice that values in top left corner are the same with the small input (except at boundary)
>>> m(input_3x3)
tensor([[[[ 1.0000,  1.2500,  1.7500,  1.5000,  0.5000,  0.0000],
          [ 1.5000,  1.7500,  2.2500,  1.8750,  0.6250,  0.0000],
          [ 2.5000,  2.7500,  3.2500,  2.6250,  0.8750,  0.0000],
          [ 2.2500,  2.4375,  2.8125,  2.2500,  0.7500,  0.0000],
          [ 0.7500,  0.8125,  0.9375,  0.7500,  0.2500,  0.0000],
          [ 0.0000,  0.0000,  0.0000,  0.0000,  0.0000,  0.0000]]]])

>>> m = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
>>> # Notice that values in top left corner are now changed
>>> m(input_3x3)
tensor([[[[ 1.0000,  1.4000,  1.8000,  1.6000,  0.8000,  0.0000],
          [ 1.8000,  2.2000,  2.6000,  2.2400,  1.1200,  0.0000],
          [ 2.6000,  3.0000,  3.4000,  2.8800,  1.4400,  0.0000],
          [ 2.4000,  2.7200,  3.0400,  2.5600,  1.2800,  0.0000],
          [ 1.2000,  1.3600,  1.5200,  1.2800,  0.6400,  0.0000],
          [ 0.0000,  0.0000,  0.0000,  0.0000,  0.0000,  0.0000]]]])