Create models/modnet.py

src/models/modnet.py

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+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+
+from .backbones import SUPPORTED_BACKBONES
+
+
+#------------------------------------------------------------------------------
+#  MODNet Basic Modules
+#------------------------------------------------------------------------------
+
+class IBNorm(nn.Module):
+    """ Combine Instance Norm and Batch Norm into One Layer
+    """
+
+    def __init__(self, in_channels):
+        super(IBNorm, self).__init__()
+        in_channels = in_channels
+        self.bnorm_channels = int(in_channels / 2)
+        self.inorm_channels = in_channels - self.bnorm_channels
+
+        self.bnorm = nn.BatchNorm2d(self.bnorm_channels, affine=True)
+        self.inorm = nn.InstanceNorm2d(self.inorm_channels, affine=False)
+        
+    def forward(self, x):
+        bn_x = self.bnorm(x[:, :self.bnorm_channels, ...].contiguous())
+        in_x = self.inorm(x[:, self.bnorm_channels:, ...].contiguous())
+
+        return torch.cat((bn_x, in_x), 1)
+
+
+class Conv2dIBNormRelu(nn.Module):
+    """ Convolution + IBNorm + ReLu
+    """
+
+    def __init__(self, in_channels, out_channels, kernel_size, 
+                 stride=1, padding=0, dilation=1, groups=1, bias=True, 
+                 with_ibn=True, with_relu=True):
+        super(Conv2dIBNormRelu, self).__init__()
+
+        layers = [
+            nn.Conv2d(in_channels, out_channels, kernel_size, 
+                      stride=stride, padding=padding, dilation=dilation, 
+                      groups=groups, bias=bias)
+        ]
+
+        if with_ibn:       
+            layers.append(IBNorm(out_channels))
+        if with_relu:
+            layers.append(nn.ReLU(inplace=True))
+
+        self.layers = nn.Sequential(*layers)
+
+    def forward(self, x):
+        return self.layers(x) 
+
+
+class SEBlock(nn.Module):
+    """ SE Block Proposed in https://arxiv.org/pdf/1709.01507.pdf 
+    """
+
+    def __init__(self, in_channels, out_channels, reduction=1):
+        super(SEBlock, self).__init__()
+        self.pool = nn.AdaptiveAvgPool2d(1)
+        self.fc = nn.Sequential(
+            nn.Linear(in_channels, int(in_channels // reduction), bias=False),
+            nn.ReLU(inplace=True),
+            nn.Linear(int(in_channels // reduction), out_channels, bias=False),
+            nn.Sigmoid()
+        )
+    
+    def forward(self, x):
+        b, c, _, _ = x.size()
+        w = self.pool(x).view(b, c)
+        w = self.fc(w).view(b, c, 1, 1)
+
+        return x * w.expand_as(x)
+
+
+#------------------------------------------------------------------------------
+#  MODNet Branches
+#------------------------------------------------------------------------------
+
+class LRBranch(nn.Module):
+    """ Low Resolution Branch of MODNet
+    """
+
+    def __init__(self, backbone):
+        super(LRBranch, self).__init__()
+
+        enc_channels = backbone.enc_channels
+        
+        self.backbone = backbone
+        self.se_block = SEBlock(enc_channels[4], enc_channels[4], reduction=4)
+        self.conv_lr16x = Conv2dIBNormRelu(enc_channels[4], enc_channels[3], 5, stride=1, padding=2)
+        self.conv_lr8x = Conv2dIBNormRelu(enc_channels[3], enc_channels[2], 5, stride=1, padding=2)
+        self.conv_lr = Conv2dIBNormRelu(enc_channels[2], 1, kernel_size=3, stride=2, padding=1, with_ibn=False, with_relu=False)
+
+    def forward(self, img, inference):
+        enc_features = self.backbone.forward(img)
+        enc2x, enc4x, enc32x = enc_features[0], enc_features[1], enc_features[4]
+
+        enc32x = self.se_block(enc32x)
+        lr16x = F.interpolate(enc32x, scale_factor=2, mode='bilinear', align_corners=False)
+        lr16x = self.conv_lr16x(lr16x)
+        lr8x = F.interpolate(lr16x, scale_factor=2, mode='bilinear', align_corners=False)
+        lr8x = self.conv_lr8x(lr8x)
+
+        pred_semantic = None
+        if not inference:
+            lr = self.conv_lr(lr8x)
+            pred_semantic = torch.sigmoid(lr)
+
+        return pred_semantic, lr8x, [enc2x, enc4x] 
+
+
+class HRBranch(nn.Module):
+    """ High Resolution Branch of MODNet
+    """
+
+    def __init__(self, hr_channels, enc_channels):
+        super(HRBranch, self).__init__()
+
+        self.tohr_enc2x = Conv2dIBNormRelu(enc_channels[0], hr_channels, 1, stride=1, padding=0)
+        self.conv_enc2x = Conv2dIBNormRelu(hr_channels + 3, hr_channels, 3, stride=2, padding=1)
+
+        self.tohr_enc4x = Conv2dIBNormRelu(enc_channels[1], hr_channels, 1, stride=1, padding=0)
+        self.conv_enc4x = Conv2dIBNormRelu(2 * hr_channels, 2 * hr_channels, 3, stride=1, padding=1)
+
+        self.conv_hr4x = nn.Sequential(
+            Conv2dIBNormRelu(3 * hr_channels + 3, 2 * hr_channels, 3, stride=1, padding=1),
+            Conv2dIBNormRelu(2 * hr_channels, 2 * hr_channels, 3, stride=1, padding=1),
+            Conv2dIBNormRelu(2 * hr_channels, hr_channels, 3, stride=1, padding=1),
+        )
+
+        self.conv_hr2x = nn.Sequential(
+            Conv2dIBNormRelu(2 * hr_channels, 2 * hr_channels, 3, stride=1, padding=1),
+            Conv2dIBNormRelu(2 * hr_channels, hr_channels, 3, stride=1, padding=1),
+            Conv2dIBNormRelu(hr_channels, hr_channels, 3, stride=1, padding=1),
+            Conv2dIBNormRelu(hr_channels, hr_channels, 3, stride=1, padding=1),
+        )
+
+        self.conv_hr = nn.Sequential(
+            Conv2dIBNormRelu(hr_channels + 3, hr_channels, 3, stride=1, padding=1),
+            Conv2dIBNormRelu(hr_channels, 1, kernel_size=1, stride=1, padding=0, with_ibn=False, with_relu=False),
+        )
+
+    def forward(self, img, enc2x, enc4x, lr8x, inference):
+        img2x = F.interpolate(img, scale_factor=1/2, mode='bilinear', align_corners=False)
+        img4x = F.interpolate(img, scale_factor=1/4, mode='bilinear', align_corners=False)
+
+        enc2x = self.tohr_enc2x(enc2x)
+        hr4x = self.conv_enc2x(torch.cat((img2x, enc2x), dim=1))
+
+        enc4x = self.tohr_enc4x(enc4x)
+        hr4x = self.conv_enc4x(torch.cat((hr4x, enc4x), dim=1))
+
+        lr4x = F.interpolate(lr8x, scale_factor=2, mode='bilinear', align_corners=False)
+        hr4x = self.conv_hr4x(torch.cat((hr4x, lr4x, img4x), dim=1))
+
+        hr2x = F.interpolate(hr4x, scale_factor=2, mode='bilinear', align_corners=False)
+        hr2x = self.conv_hr2x(torch.cat((hr2x, enc2x), dim=1))
+
+        pred_detail = None
+        if not inference:
+            hr = F.interpolate(hr2x, scale_factor=2, mode='bilinear', align_corners=False)
+            hr = self.conv_hr(torch.cat((hr, img), dim=1))
+            pred_detail = torch.sigmoid(hr)
+
+        return pred_detail, hr2x
+
+
+class FusionBranch(nn.Module):
+    """ Fusion Branch of MODNet
+    """
+
+    def __init__(self, hr_channels, enc_channels):
+        super(FusionBranch, self).__init__()
+        self.conv_lr4x = Conv2dIBNormRelu(enc_channels[2], hr_channels, 5, stride=1, padding=2)
+        
+        self.conv_f2x = Conv2dIBNormRelu(2 * hr_channels, hr_channels, 3, stride=1, padding=1)
+        self.conv_f = nn.Sequential(
+            Conv2dIBNormRelu(hr_channels + 3, int(hr_channels / 2), 3, stride=1, padding=1),
+            Conv2dIBNormRelu(int(hr_channels / 2), 1, 1, stride=1, padding=0, with_ibn=False, with_relu=False),
+        )
+
+    def forward(self, img, lr8x, hr2x):
+        lr4x = F.interpolate(lr8x, scale_factor=2, mode='bilinear', align_corners=False)
+        lr4x = self.conv_lr4x(lr4x)
+        lr2x = F.interpolate(lr4x, scale_factor=2, mode='bilinear', align_corners=False)
+
+        f2x = self.conv_f2x(torch.cat((lr2x, hr2x), dim=1))
+        f = F.interpolate(f2x, scale_factor=2, mode='bilinear', align_corners=False)
+        f = self.conv_f(torch.cat((f, img), dim=1))
+        pred_matte = torch.sigmoid(f)
+
+        return pred_matte
+
+
+#------------------------------------------------------------------------------
+#  MODNet
+#------------------------------------------------------------------------------
+
+class MODNet(nn.Module):
+    """ Architecture of MODNet
+    """
+
+    def __init__(self, in_channels=3, hr_channels=32, backbone_arch='mobilenetv2', backbone_pretrained=True):
+        super(MODNet, self).__init__()
+
+        self.in_channels = in_channels
+        self.hr_channels = hr_channels
+        self.backbone_arch = backbone_arch
+        self.backbone_pretrained = backbone_pretrained
+
+        self.backbone = SUPPORTED_BACKBONES[self.backbone_arch](self.in_channels)
+
+        self.lr_branch = LRBranch(self.backbone)
+        self.hr_branch = HRBranch(self.hr_channels, self.backbone.enc_channels)
+        self.f_branch = FusionBranch(self.hr_channels, self.backbone.enc_channels)
+
+        for m in self.modules():
+            if isinstance(m, nn.Conv2d):
+                self._init_conv(m)
+            elif isinstance(m, nn.BatchNorm2d) or isinstance(m, nn.InstanceNorm2d):
+                self._init_norm(m)
+
+        if self.backbone_pretrained:
+            self.backbone.load_pretrained_ckpt()                
+
+    def forward(self, img, inference):
+        pred_semantic, lr8x, [enc2x, enc4x] = self.lr_branch(img, inference)
+        pred_detail, hr2x = self.hr_branch(img, enc2x, enc4x, lr8x, inference)
+        pred_matte = self.f_branch(img, lr8x, hr2x)
+
+        return pred_semantic, pred_detail, pred_matte
+    
+    def freeze_norm(self):
+        norm_types = [nn.BatchNorm2d, nn.InstanceNorm2d]
+        for m in self.modules():
+            for n in norm_types:
+                if isinstance(m, n):
+                    m.eval()
+                    continue
+
+    def _init_conv(self, conv):
+        nn.init.kaiming_uniform_(
+            conv.weight, a=0, mode='fan_in', nonlinearity='relu')
+        if conv.bias is not None:
+            nn.init.constant_(conv.bias, 0)
+
+    def _init_norm(self, norm):
+        if norm.weight is not None:
+            nn.init.constant_(norm.weight, 1)
+            nn.init.constant_(norm.bias, 0)