Python 为什么unet有课程?
当我阅读UNet架构时,我发现它有Python 为什么unet有课程?,python,pytorch,image-segmentation,unity3d-unet,Python,Pytorch,Image Segmentation,Unity3d Unet,当我阅读UNet架构时,我发现它有n_类作为输出 import torch import torch.nn as nn import torch.nn.functional as F class double_conv(nn.Module): '''(conv => BN => ReLU) * 2''' def __init__(self, in_ch, out_ch): super(double_conv, self).__init__()
n_类
作为输出
import torch
import torch.nn as nn
import torch.nn.functional as F
class double_conv(nn.Module):
'''(conv => BN => ReLU) * 2'''
def __init__(self, in_ch, out_ch):
super(double_conv, self).__init__()
self.conv = nn.Sequential(
nn.Conv2d(in_ch, out_ch, 3, padding=1),
nn.BatchNorm2d(out_ch),
nn.ReLU(inplace=True),
nn.Conv2d(out_ch, out_ch, 3, padding=1),
nn.BatchNorm2d(out_ch),
nn.ReLU(inplace=True)
)
def forward(self, x):
x = self.conv(x)
return x
class inconv(nn.Module):
def __init__(self, in_ch, out_ch):
super(inconv, self).__init__()
self.conv = double_conv(in_ch, out_ch)
def forward(self, x):
x = self.conv(x)
return x
class down(nn.Module):
def __init__(self, in_ch, out_ch):
super(down, self).__init__()
self.mpconv = nn.Sequential(
nn.MaxPool2d(2),
double_conv(in_ch, out_ch)
)
def forward(self, x):
x = self.mpconv(x)
return x
class up(nn.Module):
def __init__(self, in_ch, out_ch, bilinear=True):
super(up, self).__init__()
# would be a nice idea if the upsampling could be learned too,
# but my machine do not have enough memory to handle all those weights
if bilinear:
self.up = nn.Upsample(scale_factor=2, mode='bilinear', align_corners=True)
else:
self.up = nn.ConvTranspose2d(in_ch//2, in_ch//2, 2, stride=2)
self.conv = double_conv(in_ch, out_ch)
def forward(self, x1, x2):
x1 = self.up(x1)
diffX = x1.size()[2] - x2.size()[2]
diffY = x1.size()[3] - x2.size()[3]
x2 = F.pad(x2, (diffX // 2, int(diffX / 2),
diffY // 2, int(diffY / 2)))
x = torch.cat([x2, x1], dim=1)
x = self.conv(x)
return x
class outconv(nn.Module):
def __init__(self, in_ch, out_ch):
super(outconv, self).__init__()
self.conv = nn.Conv2d(in_ch, out_ch, 1)
def forward(self, x):
x = self.conv(x)
return x
class UNet(nn.Module):
def __init__(self, n_channels, n_classes):
super(UNet, self).__init__()
self.inc = inconv(n_channels, 64)
self.down1 = down(64, 128)
self.down2 = down(128, 256)
self.down3 = down(256, 512)
self.down4 = down(512, 512)
self.up1 = up(1024, 256)
self.up2 = up(512, 128)
self.up3 = up(256, 64)
self.up4 = up(128, 64)
self.outc = outconv(64, n_classes)
def forward(self, x):
self.x1 = self.inc(x)
self.x2 = self.down1(self.x1)
self.x3 = self.down2(self.x2)
self.x4 = self.down3(self.x3)
self.x5 = self.down4(self.x4)
self.x6 = self.up1(self.x5, self.x4)
self.x7 = self.up2(self.x6, self.x3)
self.x8 = self.up3(self.x7, self.x2)
self.x9 = self.up4(self.x8, self.x1)
self.y = self.outc(self.x9)
return self.y
但是为什么它有n_类
,因为它用于图像分割
我正在尝试使用此代码进行图像去噪,但我无法确定n_classes
参数应该是什么,因为我没有任何类
n_类
是否表示多类分割?如果是,二进制UNet分段的输出是什么?答案
n_类是否表示多类分割
是的,如果指定n_classes=4
,它将输出(批次、4、宽度、高度)
形状的张量,其中每个像素可以分割为4
类中的一个。此外,还应将其用于培训
如果是,二进制UNet分段的输出是什么
如果要使用二进制分段,请指定n_classes=1
(黑色为0
,白色为1
)并使用
我正在尝试使用这段代码进行图像去噪,但我不知道n_classes参数应该是什么
它应该等于n_通道
,对于RGB通常等于3
,对于灰度通常等于1
。如果你想教这个模型去噪图像,你应该:
- 向图像添加一些噪波(例如使用)
- 在末尾使用
激活,因为像素的值介于sigmoid
和0
之间(除非标准化)1
- 用于培训
[0255]
像素范围表示为[0,1]
像素值(至少不进行标准化)sigmoid
正是这样做的-将值压缩到[0,1]
范围内,因此线性
输出(logits)的范围可以从-inf
到+inf
为什么不是线性输出和钳位
为了使线性层在钳位后处于[0,1]
范围内,线性层的可能输出值必须大于0
(符合目标的logits范围:[0,+inf]
)
为什么不使用无钳位的线性输出
输出的登录必须在[0,1]
范围内
为什么不采取其他方法呢
您可以这样做,但是sigmoid
的思想是:
- 帮助神经网络(可以输出任何logit值)
的一阶导数是高斯标准正态分布,因此它模拟了许多现实生活中发生现象的概率(更多信息,请参见)sigmoid
class UNet(nn.Module):
def __init__(self, n_channels, n_classes):