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model/__init__.py

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+from .u2net import U2NET
+from .u2net import U2NETP

model/u2net.py

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+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+
+class REBNCONV(nn.Module):
+    def __init__(self,in_ch=3,out_ch=3,dirate=1):
+        super(REBNCONV,self).__init__()
+
+        self.conv_s1 = nn.Conv2d(in_ch,out_ch,3,padding=1*dirate,dilation=1*dirate)
+        self.bn_s1 = nn.BatchNorm2d(out_ch)
+        self.relu_s1 = nn.ReLU(inplace=True)
+
+    def forward(self,x):
+
+        hx = x
+        xout = self.relu_s1(self.bn_s1(self.conv_s1(hx)))
+
+        return xout
+
+## upsample tensor 'src' to have the same spatial size with tensor 'tar'
+def _upsample_like(src,tar):
+
+    src = F.upsample(src,size=tar.shape[2:],mode='bilinear')
+
+    return src
+
+
+### RSU-7 ###
+class RSU7(nn.Module):#UNet07DRES(nn.Module):
+
+    def __init__(self, in_ch=3, mid_ch=12, out_ch=3):
+        super(RSU7,self).__init__()
+
+        self.rebnconvin = REBNCONV(in_ch,out_ch,dirate=1)
+
+        self.rebnconv1 = REBNCONV(out_ch,mid_ch,dirate=1)
+        self.pool1 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv2 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool2 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv3 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool3 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv4 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool4 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv5 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool5 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv6 = REBNCONV(mid_ch,mid_ch,dirate=1)
+
+        self.rebnconv7 = REBNCONV(mid_ch,mid_ch,dirate=2)
+
+        self.rebnconv6d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv5d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv4d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv3d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv2d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv1d = REBNCONV(mid_ch*2,out_ch,dirate=1)
+
+    def forward(self,x):
+
+        hx = x
+        hxin = self.rebnconvin(hx)
+
+        hx1 = self.rebnconv1(hxin)
+        hx = self.pool1(hx1)
+
+        hx2 = self.rebnconv2(hx)
+        hx = self.pool2(hx2)
+
+        hx3 = self.rebnconv3(hx)
+        hx = self.pool3(hx3)
+
+        hx4 = self.rebnconv4(hx)
+        hx = self.pool4(hx4)
+
+        hx5 = self.rebnconv5(hx)
+        hx = self.pool5(hx5)
+
+        hx6 = self.rebnconv6(hx)
+
+        hx7 = self.rebnconv7(hx6)
+
+        hx6d =  self.rebnconv6d(torch.cat((hx7,hx6),1))
+        hx6dup = _upsample_like(hx6d,hx5)
+
+        hx5d =  self.rebnconv5d(torch.cat((hx6dup,hx5),1))
+        hx5dup = _upsample_like(hx5d,hx4)
+
+        hx4d = self.rebnconv4d(torch.cat((hx5dup,hx4),1))
+        hx4dup = _upsample_like(hx4d,hx3)
+
+        hx3d = self.rebnconv3d(torch.cat((hx4dup,hx3),1))
+        hx3dup = _upsample_like(hx3d,hx2)
+
+        hx2d = self.rebnconv2d(torch.cat((hx3dup,hx2),1))
+        hx2dup = _upsample_like(hx2d,hx1)
+
+        hx1d = self.rebnconv1d(torch.cat((hx2dup,hx1),1))
+
+        return hx1d + hxin
+
+### RSU-6 ###
+class RSU6(nn.Module):#UNet06DRES(nn.Module):
+
+    def __init__(self, in_ch=3, mid_ch=12, out_ch=3):
+        super(RSU6,self).__init__()
+
+        self.rebnconvin = REBNCONV(in_ch,out_ch,dirate=1)
+
+        self.rebnconv1 = REBNCONV(out_ch,mid_ch,dirate=1)
+        self.pool1 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv2 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool2 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv3 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool3 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv4 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool4 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv5 = REBNCONV(mid_ch,mid_ch,dirate=1)
+
+        self.rebnconv6 = REBNCONV(mid_ch,mid_ch,dirate=2)
+
+        self.rebnconv5d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv4d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv3d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv2d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv1d = REBNCONV(mid_ch*2,out_ch,dirate=1)
+
+    def forward(self,x):
+
+        hx = x
+
+        hxin = self.rebnconvin(hx)
+
+        hx1 = self.rebnconv1(hxin)
+        hx = self.pool1(hx1)
+
+        hx2 = self.rebnconv2(hx)
+        hx = self.pool2(hx2)
+
+        hx3 = self.rebnconv3(hx)
+        hx = self.pool3(hx3)
+
+        hx4 = self.rebnconv4(hx)
+        hx = self.pool4(hx4)
+
+        hx5 = self.rebnconv5(hx)
+
+        hx6 = self.rebnconv6(hx5)
+
+
+        hx5d =  self.rebnconv5d(torch.cat((hx6,hx5),1))
+        hx5dup = _upsample_like(hx5d,hx4)
+
+        hx4d = self.rebnconv4d(torch.cat((hx5dup,hx4),1))
+        hx4dup = _upsample_like(hx4d,hx3)
+
+        hx3d = self.rebnconv3d(torch.cat((hx4dup,hx3),1))
+        hx3dup = _upsample_like(hx3d,hx2)
+
+        hx2d = self.rebnconv2d(torch.cat((hx3dup,hx2),1))
+        hx2dup = _upsample_like(hx2d,hx1)
+
+        hx1d = self.rebnconv1d(torch.cat((hx2dup,hx1),1))
+
+        return hx1d + hxin
+
+### RSU-5 ###
+class RSU5(nn.Module):#UNet05DRES(nn.Module):
+
+    def __init__(self, in_ch=3, mid_ch=12, out_ch=3):
+        super(RSU5,self).__init__()
+
+        self.rebnconvin = REBNCONV(in_ch,out_ch,dirate=1)
+
+        self.rebnconv1 = REBNCONV(out_ch,mid_ch,dirate=1)
+        self.pool1 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv2 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool2 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv3 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool3 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv4 = REBNCONV(mid_ch,mid_ch,dirate=1)
+
+        self.rebnconv5 = REBNCONV(mid_ch,mid_ch,dirate=2)
+
+        self.rebnconv4d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv3d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv2d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv1d = REBNCONV(mid_ch*2,out_ch,dirate=1)
+
+    def forward(self,x):
+
+        hx = x
+
+        hxin = self.rebnconvin(hx)
+
+        hx1 = self.rebnconv1(hxin)
+        hx = self.pool1(hx1)
+
+        hx2 = self.rebnconv2(hx)
+        hx = self.pool2(hx2)
+
+        hx3 = self.rebnconv3(hx)
+        hx = self.pool3(hx3)
+
+        hx4 = self.rebnconv4(hx)
+
+        hx5 = self.rebnconv5(hx4)
+
+        hx4d = self.rebnconv4d(torch.cat((hx5,hx4),1))
+        hx4dup = _upsample_like(hx4d,hx3)
+
+        hx3d = self.rebnconv3d(torch.cat((hx4dup,hx3),1))
+        hx3dup = _upsample_like(hx3d,hx2)
+
+        hx2d = self.rebnconv2d(torch.cat((hx3dup,hx2),1))
+        hx2dup = _upsample_like(hx2d,hx1)
+
+        hx1d = self.rebnconv1d(torch.cat((hx2dup,hx1),1))
+
+        return hx1d + hxin
+
+### RSU-4 ###
+class RSU4(nn.Module):#UNet04DRES(nn.Module):
+
+    def __init__(self, in_ch=3, mid_ch=12, out_ch=3):
+        super(RSU4,self).__init__()
+
+        self.rebnconvin = REBNCONV(in_ch,out_ch,dirate=1)
+
+        self.rebnconv1 = REBNCONV(out_ch,mid_ch,dirate=1)
+        self.pool1 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv2 = REBNCONV(mid_ch,mid_ch,dirate=1)
+        self.pool2 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.rebnconv3 = REBNCONV(mid_ch,mid_ch,dirate=1)
+
+        self.rebnconv4 = REBNCONV(mid_ch,mid_ch,dirate=2)
+
+        self.rebnconv3d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv2d = REBNCONV(mid_ch*2,mid_ch,dirate=1)
+        self.rebnconv1d = REBNCONV(mid_ch*2,out_ch,dirate=1)
+
+    def forward(self,x):
+
+        hx = x
+
+        hxin = self.rebnconvin(hx)
+
+        hx1 = self.rebnconv1(hxin)
+        hx = self.pool1(hx1)
+
+        hx2 = self.rebnconv2(hx)
+        hx = self.pool2(hx2)
+
+        hx3 = self.rebnconv3(hx)
+
+        hx4 = self.rebnconv4(hx3)
+
+        hx3d = self.rebnconv3d(torch.cat((hx4,hx3),1))
+        hx3dup = _upsample_like(hx3d,hx2)
+
+        hx2d = self.rebnconv2d(torch.cat((hx3dup,hx2),1))
+        hx2dup = _upsample_like(hx2d,hx1)
+
+        hx1d = self.rebnconv1d(torch.cat((hx2dup,hx1),1))
+
+        return hx1d + hxin
+
+### RSU-4F ###
+class RSU4F(nn.Module):#UNet04FRES(nn.Module):
+
+    def __init__(self, in_ch=3, mid_ch=12, out_ch=3):
+        super(RSU4F,self).__init__()
+
+        self.rebnconvin = REBNCONV(in_ch,out_ch,dirate=1)
+
+        self.rebnconv1 = REBNCONV(out_ch,mid_ch,dirate=1)
+        self.rebnconv2 = REBNCONV(mid_ch,mid_ch,dirate=2)
+        self.rebnconv3 = REBNCONV(mid_ch,mid_ch,dirate=4)
+
+        self.rebnconv4 = REBNCONV(mid_ch,mid_ch,dirate=8)
+
+        self.rebnconv3d = REBNCONV(mid_ch*2,mid_ch,dirate=4)
+        self.rebnconv2d = REBNCONV(mid_ch*2,mid_ch,dirate=2)
+        self.rebnconv1d = REBNCONV(mid_ch*2,out_ch,dirate=1)
+
+    def forward(self,x):
+
+        hx = x
+
+        hxin = self.rebnconvin(hx)
+
+        hx1 = self.rebnconv1(hxin)
+        hx2 = self.rebnconv2(hx1)
+        hx3 = self.rebnconv3(hx2)
+
+        hx4 = self.rebnconv4(hx3)
+
+        hx3d = self.rebnconv3d(torch.cat((hx4,hx3),1))
+        hx2d = self.rebnconv2d(torch.cat((hx3d,hx2),1))
+        hx1d = self.rebnconv1d(torch.cat((hx2d,hx1),1))
+
+        return hx1d + hxin
+
+
+##### U^2-Net ####
+class U2NET(nn.Module):
+
+    def __init__(self,in_ch=3,out_ch=1):
+        super(U2NET,self).__init__()
+
+        self.stage1 = RSU7(in_ch,32,64)
+        self.pool12 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage2 = RSU6(64,32,128)
+        self.pool23 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage3 = RSU5(128,64,256)
+        self.pool34 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage4 = RSU4(256,128,512)
+        self.pool45 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage5 = RSU4F(512,256,512)
+        self.pool56 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage6 = RSU4F(512,256,512)
+
+        # decoder
+        self.stage5d = RSU4F(1024,256,512)
+        self.stage4d = RSU4(1024,128,256)
+        self.stage3d = RSU5(512,64,128)
+        self.stage2d = RSU6(256,32,64)
+        self.stage1d = RSU7(128,16,64)
+
+        self.side1 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side2 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side3 = nn.Conv2d(128,out_ch,3,padding=1)
+        self.side4 = nn.Conv2d(256,out_ch,3,padding=1)
+        self.side5 = nn.Conv2d(512,out_ch,3,padding=1)
+        self.side6 = nn.Conv2d(512,out_ch,3,padding=1)
+
+        self.outconv = nn.Conv2d(6*out_ch,out_ch,1)
+
+    def forward(self,x):
+
+        hx = x
+
+        #stage 1
+        hx1 = self.stage1(hx)
+        hx = self.pool12(hx1)
+
+        #stage 2
+        hx2 = self.stage2(hx)
+        hx = self.pool23(hx2)
+
+        #stage 3
+        hx3 = self.stage3(hx)
+        hx = self.pool34(hx3)
+
+        #stage 4
+        hx4 = self.stage4(hx)
+        hx = self.pool45(hx4)
+
+        #stage 5
+        hx5 = self.stage5(hx)
+        hx = self.pool56(hx5)
+
+        #stage 6
+        hx6 = self.stage6(hx)
+        hx6up = _upsample_like(hx6,hx5)
+
+        #-------------------- decoder --------------------
+        hx5d = self.stage5d(torch.cat((hx6up,hx5),1))
+        hx5dup = _upsample_like(hx5d,hx4)
+
+        hx4d = self.stage4d(torch.cat((hx5dup,hx4),1))
+        hx4dup = _upsample_like(hx4d,hx3)
+
+        hx3d = self.stage3d(torch.cat((hx4dup,hx3),1))
+        hx3dup = _upsample_like(hx3d,hx2)
+
+        hx2d = self.stage2d(torch.cat((hx3dup,hx2),1))
+        hx2dup = _upsample_like(hx2d,hx1)
+
+        hx1d = self.stage1d(torch.cat((hx2dup,hx1),1))
+
+
+        #side output
+        d1 = self.side1(hx1d)
+
+        d2 = self.side2(hx2d)
+        d2 = _upsample_like(d2,d1)
+
+        d3 = self.side3(hx3d)
+        d3 = _upsample_like(d3,d1)
+
+        d4 = self.side4(hx4d)
+        d4 = _upsample_like(d4,d1)
+
+        d5 = self.side5(hx5d)
+        d5 = _upsample_like(d5,d1)
+
+        d6 = self.side6(hx6)
+        d6 = _upsample_like(d6,d1)
+
+        d0 = self.outconv(torch.cat((d1,d2,d3,d4,d5,d6),1))
+
+        return F.sigmoid(d0), F.sigmoid(d1), F.sigmoid(d2), F.sigmoid(d3), F.sigmoid(d4), F.sigmoid(d5), F.sigmoid(d6)
+
+### U^2-Net small ###
+class U2NETP(nn.Module):
+
+    def __init__(self,in_ch=3,out_ch=1):
+        super(U2NETP,self).__init__()
+
+        self.stage1 = RSU7(in_ch,16,64)
+        self.pool12 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage2 = RSU6(64,16,64)
+        self.pool23 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage3 = RSU5(64,16,64)
+        self.pool34 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage4 = RSU4(64,16,64)
+        self.pool45 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage5 = RSU4F(64,16,64)
+        self.pool56 = nn.MaxPool2d(2,stride=2,ceil_mode=True)
+
+        self.stage6 = RSU4F(64,16,64)
+
+        # decoder
+        self.stage5d = RSU4F(128,16,64)
+        self.stage4d = RSU4(128,16,64)
+        self.stage3d = RSU5(128,16,64)
+        self.stage2d = RSU6(128,16,64)
+        self.stage1d = RSU7(128,16,64)
+
+        self.side1 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side2 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side3 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side4 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side5 = nn.Conv2d(64,out_ch,3,padding=1)
+        self.side6 = nn.Conv2d(64,out_ch,3,padding=1)
+
+        self.outconv = nn.Conv2d(6*out_ch,out_ch,1)
+
+    def forward(self,x):
+
+        hx = x
+
+        #stage 1
+        hx1 = self.stage1(hx)
+        hx = self.pool12(hx1)
+
+        #stage 2
+        hx2 = self.stage2(hx)
+        hx = self.pool23(hx2)
+
+        #stage 3
+        hx3 = self.stage3(hx)
+        hx = self.pool34(hx3)
+
+        #stage 4
+        hx4 = self.stage4(hx)
+        hx = self.pool45(hx4)
+
+        #stage 5
+        hx5 = self.stage5(hx)
+        hx = self.pool56(hx5)
+
+        #stage 6
+        hx6 = self.stage6(hx)
+        hx6up = _upsample_like(hx6,hx5)
+
+        #decoder
+        hx5d = self.stage5d(torch.cat((hx6up,hx5),1))
+        hx5dup = _upsample_like(hx5d,hx4)
+
+        hx4d = self.stage4d(torch.cat((hx5dup,hx4),1))
+        hx4dup = _upsample_like(hx4d,hx3)
+
+        hx3d = self.stage3d(torch.cat((hx4dup,hx3),1))
+        hx3dup = _upsample_like(hx3d,hx2)
+
+        hx2d = self.stage2d(torch.cat((hx3dup,hx2),1))
+        hx2dup = _upsample_like(hx2d,hx1)
+
+        hx1d = self.stage1d(torch.cat((hx2dup,hx1),1))
+
+
+        #side output
+        d1 = self.side1(hx1d)
+
+        d2 = self.side2(hx2d)
+        d2 = _upsample_like(d2,d1)
+
+        d3 = self.side3(hx3d)
+        d3 = _upsample_like(d3,d1)
+
+        d4 = self.side4(hx4d)
+        d4 = _upsample_like(d4,d1)
+
+        d5 = self.side5(hx5d)
+        d5 = _upsample_like(d5,d1)
+
+        d6 = self.side6(hx6)
+        d6 = _upsample_like(d6,d1)
+
+        d0 = self.outconv(torch.cat((d1,d2,d3,d4,d5,d6),1))
+
+        return F.sigmoid(d0), F.sigmoid(d1), F.sigmoid(d2), F.sigmoid(d3), F.sigmoid(d4), F.sigmoid(d5), F.sigmoid(d6)

model/u2net_refactor.py

@@ -0,0 +1,168 @@
+import torch
+import torch.nn as nn
+
+import math
+
+__all__ = ['U2NET_full', 'U2NET_lite']
+
+
+def _upsample_like(x, size):
+    return nn.Upsample(size=size, mode='bilinear', align_corners=False)(x)
+
+
+def _size_map(x, height):
+    # {height: size} for Upsample
+    size = list(x.shape[-2:])
+    sizes = {}
+    for h in range(1, height):
+        sizes[h] = size
+        size = [math.ceil(w / 2) for w in size]
+    return sizes
+
+
+class REBNCONV(nn.Module):
+    def __init__(self, in_ch=3, out_ch=3, dilate=1):
+        super(REBNCONV, self).__init__()
+
+        self.conv_s1 = nn.Conv2d(in_ch, out_ch, 3, padding=1 * dilate, dilation=1 * dilate)
+        self.bn_s1 = nn.BatchNorm2d(out_ch)
+        self.relu_s1 = nn.ReLU(inplace=True)
+
+    def forward(self, x):
+        return self.relu_s1(self.bn_s1(self.conv_s1(x)))
+
+
+class RSU(nn.Module):
+    def __init__(self, name, height, in_ch, mid_ch, out_ch, dilated=False):
+        super(RSU, self).__init__()
+        self.name = name
+        self.height = height
+        self.dilated = dilated
+        self._make_layers(height, in_ch, mid_ch, out_ch, dilated)
+
+    def forward(self, x):
+        sizes = _size_map(x, self.height)
+        x = self.rebnconvin(x)
+
+        # U-Net like symmetric encoder-decoder structure
+        def unet(x, height=1):
+            if height < self.height:
+                x1 = getattr(self, f'rebnconv{height}')(x)
+                if not self.dilated and height < self.height - 1:
+                    x2 = unet(getattr(self, 'downsample')(x1), height + 1)
+                else:
+                    x2 = unet(x1, height + 1)
+
+                x = getattr(self, f'rebnconv{height}d')(torch.cat((x2, x1), 1))
+                return _upsample_like(x, sizes[height - 1]) if not self.dilated and height > 1 else x
+            else:
+                return getattr(self, f'rebnconv{height}')(x)
+
+        return x + unet(x)
+
+    def _make_layers(self, height, in_ch, mid_ch, out_ch, dilated=False):
+        self.add_module('rebnconvin', REBNCONV(in_ch, out_ch))
+        self.add_module('downsample', nn.MaxPool2d(2, stride=2, ceil_mode=True))
+
+        self.add_module(f'rebnconv1', REBNCONV(out_ch, mid_ch))
+        self.add_module(f'rebnconv1d', REBNCONV(mid_ch * 2, out_ch))
+
+        for i in range(2, height):
+            dilate = 1 if not dilated else 2 ** (i - 1)
+            self.add_module(f'rebnconv{i}', REBNCONV(mid_ch, mid_ch, dilate=dilate))
+            self.add_module(f'rebnconv{i}d', REBNCONV(mid_ch * 2, mid_ch, dilate=dilate))
+
+        dilate = 2 if not dilated else 2 ** (height - 1)
+        self.add_module(f'rebnconv{height}', REBNCONV(mid_ch, mid_ch, dilate=dilate))
+
+
+class U2NET(nn.Module):
+    def __init__(self, cfgs, out_ch):
+        super(U2NET, self).__init__()
+        self.out_ch = out_ch
+        self._make_layers(cfgs)
+
+    def forward(self, x):
+        sizes = _size_map(x, self.height)
+        maps = []  # storage for maps
+
+        # side saliency map
+        def unet(x, height=1):
+            if height < 6:
+                x1 = getattr(self, f'stage{height}')(x)
+                x2 = unet(getattr(self, 'downsample')(x1), height + 1)
+                x = getattr(self, f'stage{height}d')(torch.cat((x2, x1), 1))
+                side(x, height)
+                return _upsample_like(x, sizes[height - 1]) if height > 1 else x
+            else:
+                x = getattr(self, f'stage{height}')(x)
+                side(x, height)
+                return _upsample_like(x, sizes[height - 1])
+
+        def side(x, h):
+            # side output saliency map (before sigmoid)
+            x = getattr(self, f'side{h}')(x)
+            x = _upsample_like(x, sizes[1])
+            maps.append(x)
+
+        def fuse():
+            # fuse saliency probability maps
+            maps.reverse()
+            x = torch.cat(maps, 1)
+            x = getattr(self, 'outconv')(x)
+            maps.insert(0, x)
+            return [torch.sigmoid(x) for x in maps]
+
+        unet(x)
+        maps = fuse()
+        return maps
+
+    def _make_layers(self, cfgs):
+        self.height = int((len(cfgs) + 1) / 2)
+        self.add_module('downsample', nn.MaxPool2d(2, stride=2, ceil_mode=True))
+        for k, v in cfgs.items():
+            # build rsu block
+            self.add_module(k, RSU(v[0], *v[1]))
+            if v[2] > 0:
+                # build side layer
+                self.add_module(f'side{v[0][-1]}', nn.Conv2d(v[2], self.out_ch, 3, padding=1))
+        # build fuse layer
+        self.add_module('outconv', nn.Conv2d(int(self.height * self.out_ch), self.out_ch, 1))
+
+
+def U2NET_full():
+    full = {
+        # cfgs for building RSUs and sides
+        # {stage : [name, (height(L), in_ch, mid_ch, out_ch, dilated), side]}
+        'stage1': ['En_1', (7, 3, 32, 64), -1],
+        'stage2': ['En_2', (6, 64, 32, 128), -1],
+        'stage3': ['En_3', (5, 128, 64, 256), -1],
+        'stage4': ['En_4', (4, 256, 128, 512), -1],
+        'stage5': ['En_5', (4, 512, 256, 512, True), -1],
+        'stage6': ['En_6', (4, 512, 256, 512, True), 512],
+        'stage5d': ['De_5', (4, 1024, 256, 512, True), 512],
+        'stage4d': ['De_4', (4, 1024, 128, 256), 256],
+        'stage3d': ['De_3', (5, 512, 64, 128), 128],
+        'stage2d': ['De_2', (6, 256, 32, 64), 64],
+        'stage1d': ['De_1', (7, 128, 16, 64), 64],
+    }
+    return U2NET(cfgs=full, out_ch=1)
+
+
+def U2NET_lite():
+    lite = {
+        # cfgs for building RSUs and sides
+        # {stage : [name, (height(L), in_ch, mid_ch, out_ch, dilated), side]}
+        'stage1': ['En_1', (7, 3, 16, 64), -1],
+        'stage2': ['En_2', (6, 64, 16, 64), -1],
+        'stage3': ['En_3', (5, 64, 16, 64), -1],
+        'stage4': ['En_4', (4, 64, 16, 64), -1],
+        'stage5': ['En_5', (4, 64, 16, 64, True), -1],
+        'stage6': ['En_6', (4, 64, 16, 64, True), 64],
+        'stage5d': ['De_5', (4, 128, 16, 64, True), 64],
+        'stage4d': ['De_4', (4, 128, 16, 64), 64],
+        'stage3d': ['De_3', (5, 128, 16, 64), 64],
+        'stage2d': ['De_2', (6, 128, 16, 64), 64],
+        'stage1d': ['De_1', (7, 128, 16, 64), 64],
+    }
+    return U2NET(cfgs=lite, out_ch=1)