dpt.py

import math
import types

import torch
import torch.nn as nn
import torch.nn.functional as F

import timm

class BaseModel(torch.nn.Module):
    def load(self, path):
        """Load model from file.
        Args:
            path (str): file path
        """
        parameters = torch.load(path, map_location=torch.device('cpu'))

        if "optimizer" in parameters:
            parameters = parameters["model"]

        self.load_state_dict(parameters)


def unflatten_with_named_tensor(input, dim, sizes):
    """Workaround for unflattening with named tensor."""
    # tracer acts up with unflatten. See https://github.com/pytorch/pytorch/issues/49538
    new_shape = list(input.shape)[:dim] + list(sizes) + list(input.shape)[dim+1:]
    return input.view(*new_shape)
    
class Slice(nn.Module):
    def __init__(self, start_index=1):
        super(Slice, self).__init__()
        self.start_index = start_index

    def forward(self, x):
        return x[:, self.start_index :]


class AddReadout(nn.Module):
    def __init__(self, start_index=1):
        super(AddReadout, self).__init__()
        self.start_index = start_index

    def forward(self, x):
        if self.start_index == 2:
            readout = (x[:, 0] + x[:, 1]) / 2
        else:
            readout = x[:, 0]
        return x[:, self.start_index :] + readout.unsqueeze(1)


class ProjectReadout(nn.Module):
    def __init__(self, in_features, start_index=1):
        super(ProjectReadout, self).__init__()
        self.start_index = start_index

        self.project = nn.Sequential(nn.Linear(2 * in_features, in_features), nn.GELU())

    def forward(self, x):
        readout = x[:, 0].unsqueeze(1).expand_as(x[:, self.start_index :])
        features = torch.cat((x[:, self.start_index :], readout), -1)

        return self.project(features)


class Transpose(nn.Module):
    def __init__(self, dim0, dim1):
        super(Transpose, self).__init__()
        self.dim0 = dim0
        self.dim1 = dim1

    def forward(self, x):
        x = x.transpose(self.dim0, self.dim1)
        return x


def forward_vit(pretrained, x):
    b, c, h, w = x.shape

    glob = pretrained.model.forward_flex(x)

    layer_1 = pretrained.activations["1"]
    layer_2 = pretrained.activations["2"]
    layer_3 = pretrained.activations["3"]
    layer_4 = pretrained.activations["4"]

    layer_1 = pretrained.act_postprocess1[0:2](layer_1)
    layer_2 = pretrained.act_postprocess2[0:2](layer_2)
    layer_3 = pretrained.act_postprocess3[0:2](layer_3)
    layer_4 = pretrained.act_postprocess4[0:2](layer_4)


    unflattened_dim = 2
    unflattened_size = (
        int(torch.div(h, pretrained.model.patch_size[1], rounding_mode='floor')),
        int(torch.div(w, pretrained.model.patch_size[0], rounding_mode='floor')),
    )
    unflatten = nn.Sequential(nn.Unflatten(unflattened_dim, unflattened_size))
    

    if layer_1.ndim == 3:
        layer_1 = unflatten(layer_1)
    if layer_2.ndim == 3:
        layer_2 = unflatten(layer_2)
    if layer_3.ndim == 3:
        layer_3 = unflatten_with_named_tensor(layer_3, unflattened_dim, unflattened_size)
    if layer_4.ndim == 3:
        layer_4 = unflatten_with_named_tensor(layer_4, unflattened_dim, unflattened_size)

    layer_1 = pretrained.act_postprocess1[3 : len(pretrained.act_postprocess1)](layer_1)
    layer_2 = pretrained.act_postprocess2[3 : len(pretrained.act_postprocess2)](layer_2)
    layer_3 = pretrained.act_postprocess3[3 : len(pretrained.act_postprocess3)](layer_3)
    layer_4 = pretrained.act_postprocess4[3 : len(pretrained.act_postprocess4)](layer_4)

    return layer_1, layer_2, layer_3, layer_4


def _resize_pos_embed(self, posemb, gs_h, gs_w):
    posemb_tok, posemb_grid = (
        posemb[:, : self.start_index],
        posemb[0, self.start_index :],
    )

    gs_old = int(math.sqrt(posemb_grid.shape[0]))

    posemb_grid = posemb_grid.reshape(1, gs_old, gs_old, -1).permute(0, 3, 1, 2)
    posemb_grid = F.interpolate(posemb_grid, size=(gs_h, gs_w), mode="bilinear")
    posemb_grid = posemb_grid.permute(0, 2, 3, 1).reshape(1, gs_h * gs_w, -1)

    posemb = torch.cat([posemb_tok, posemb_grid], dim=1)

    return posemb


def forward_flex(self, x):
    b, c, h, w = x.shape

    pos_embed = self._resize_pos_embed(
        self.pos_embed, torch.div(h, self.patch_size[1], rounding_mode='floor'), torch.div(w, self.patch_size[0], rounding_mode='floor')
    )

    B = x.shape[0]

    if hasattr(self.patch_embed, "backbone"):
        x = self.patch_embed.backbone(x)
        if isinstance(x, (list, tuple)):
            x = x[-1]  # last feature if backbone outputs list/tuple of features

    x = self.patch_embed.proj(x).flatten(2).transpose(1, 2)

    if getattr(self, "dist_token", None) is not None:
        cls_tokens = self.cls_token.expand(
            B, -1, -1
        )  # stole cls_tokens impl from Phil Wang, thanks
        dist_token = self.dist_token.expand(B, -1, -1)
        x = torch.cat((cls_tokens, dist_token, x), dim=1)
    else:
        cls_tokens = self.cls_token.expand(
            B, -1, -1
        )  # stole cls_tokens impl from Phil Wang, thanks
        x = torch.cat((cls_tokens, x), dim=1)

    x = x + pos_embed
    x = self.pos_drop(x)

    for blk in self.blocks:
        x = blk(x)

    x = self.norm(x)

    return x


activations = {}


def get_activation(name):
    def hook(model, input, output):
        activations[name] = output

    return hook


def get_readout_oper(vit_features, features, use_readout, start_index=1):
    if use_readout == "ignore":
        readout_oper = [Slice(start_index)] * len(features)
    elif use_readout == "add":
        readout_oper = [AddReadout(start_index)] * len(features)
    elif use_readout == "project":
        readout_oper = [
            ProjectReadout(vit_features, start_index) for out_feat in features
        ]
    else:
        assert (
            False
        ), "wrong operation for readout token, use_readout can be 'ignore', 'add', or 'project'"

    return readout_oper


def _make_vit_b16_backbone(
    model,
    features=[96, 192, 384, 768],
    size=[384, 384],
    hooks=[2, 5, 8, 11],
    vit_features=768,
    use_readout="ignore",
    start_index=1,
):
    pretrained = nn.Module()

    pretrained.model = model
    pretrained.model.blocks[hooks[0]].register_forward_hook(get_activation("1"))
    pretrained.model.blocks[hooks[1]].register_forward_hook(get_activation("2"))
    pretrained.model.blocks[hooks[2]].register_forward_hook(get_activation("3"))
    pretrained.model.blocks[hooks[3]].register_forward_hook(get_activation("4"))

    pretrained.activations = activations

    readout_oper = get_readout_oper(vit_features, features, use_readout, start_index)

    # 32, 48, 136, 384
    pretrained.act_postprocess1 = nn.Sequential(
        readout_oper[0],
        Transpose(1, 2),
        nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
        nn.Conv2d(
            in_channels=vit_features,
            out_channels=features[0],
            kernel_size=1,
            stride=1,
            padding=0,
        ),
        nn.ConvTranspose2d(
            in_channels=features[0],
            out_channels=features[0],
            kernel_size=4,
            stride=4,
            padding=0,
            bias=True,
            dilation=1,
            groups=1,
        ),
    )

    pretrained.act_postprocess2 = nn.Sequential(
        readout_oper[1],
        Transpose(1, 2),
        nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
        nn.Conv2d(
            in_channels=vit_features,
            out_channels=features[1],
            kernel_size=1,
            stride=1,
            padding=0,
        ),
        nn.ConvTranspose2d(
            in_channels=features[1],
            out_channels=features[1],
            kernel_size=2,
            stride=2,
            padding=0,
            bias=True,
            dilation=1,
            groups=1,
        ),
    )

    pretrained.act_postprocess3 = nn.Sequential(
        readout_oper[2],
        Transpose(1, 2),
        nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
        nn.Conv2d(
            in_channels=vit_features,
            out_channels=features[2],
            kernel_size=1,
            stride=1,
            padding=0,
        ),
    )

    pretrained.act_postprocess4 = nn.Sequential(
        readout_oper[3],
        Transpose(1, 2),
        nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
        nn.Conv2d(
            in_channels=vit_features,
            out_channels=features[3],
            kernel_size=1,
            stride=1,
            padding=0,
        ),
        nn.Conv2d(
            in_channels=features[3],
            out_channels=features[3],
            kernel_size=3,
            stride=2,
            padding=1,
        ),
    )

    pretrained.model.start_index = start_index
    pretrained.model.patch_size = [16, 16]

    # We inject this function into the VisionTransformer instances so that
    # we can use it with interpolated position embeddings without modifying the library source.
    pretrained.model.forward_flex = types.MethodType(forward_flex, pretrained.model)
    pretrained.model._resize_pos_embed = types.MethodType(
        _resize_pos_embed, pretrained.model
    )

    return pretrained


def _make_pretrained_vitl16_384(pretrained, use_readout="ignore", hooks=None):
    model = timm.create_model("vit_large_patch16_384", pretrained=pretrained)

    hooks = [5, 11, 17, 23] if hooks == None else hooks
    return _make_vit_b16_backbone(
        model,
        features=[256, 512, 1024, 1024],
        hooks=hooks,
        vit_features=1024,
        use_readout=use_readout,
    )


def _make_pretrained_vitb16_384(pretrained, use_readout="ignore", hooks=None):
    model = timm.create_model("vit_base_patch16_384", pretrained=pretrained)

    hooks = [2, 5, 8, 11] if hooks == None else hooks
    return _make_vit_b16_backbone(
        model, features=[96, 192, 384, 768], hooks=hooks, use_readout=use_readout
    )


def _make_pretrained_deitb16_384(pretrained, use_readout="ignore", hooks=None):
    model = timm.create_model("vit_deit_base_patch16_384", pretrained=pretrained)

    hooks = [2, 5, 8, 11] if hooks == None else hooks
    return _make_vit_b16_backbone(
        model, features=[96, 192, 384, 768], hooks=hooks, use_readout=use_readout
    )


def _make_pretrained_deitb16_distil_384(pretrained, use_readout="ignore", hooks=None):
    model = timm.create_model(
        "vit_deit_base_distilled_patch16_384", pretrained=pretrained
    )

    hooks = [2, 5, 8, 11] if hooks == None else hooks
    return _make_vit_b16_backbone(
        model,
        features=[96, 192, 384, 768],
        hooks=hooks,
        use_readout=use_readout,
        start_index=2,
    )


def _make_vit_b_rn50_backbone(
    model,
    features=[256, 512, 768, 768],
    size=[384, 384],
    hooks=[0, 1, 8, 11],
    vit_features=768,
    use_vit_only=False,
    use_readout="ignore",
    start_index=1,
):
    pretrained = nn.Module()

    pretrained.model = model

    if use_vit_only == True:
        pretrained.model.blocks[hooks[0]].register_forward_hook(get_activation("1"))
        pretrained.model.blocks[hooks[1]].register_forward_hook(get_activation("2"))
    else:
        pretrained.model.patch_embed.backbone.stages[0].register_forward_hook(
            get_activation("1")
        )
        pretrained.model.patch_embed.backbone.stages[1].register_forward_hook(
            get_activation("2")
        )

    pretrained.model.blocks[hooks[2]].register_forward_hook(get_activation("3"))
    pretrained.model.blocks[hooks[3]].register_forward_hook(get_activation("4"))

    pretrained.activations = activations

    readout_oper = get_readout_oper(vit_features, features, use_readout, start_index)

    if use_vit_only == True:
        pretrained.act_postprocess1 = nn.Sequential(
            readout_oper[0],
            Transpose(1, 2),
            nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
            nn.Conv2d(
                in_channels=vit_features,
                out_channels=features[0],
                kernel_size=1,
                stride=1,
                padding=0,
            ),
            nn.ConvTranspose2d(
                in_channels=features[0],
                out_channels=features[0],
                kernel_size=4,
                stride=4,
                padding=0,
                bias=True,
                dilation=1,
                groups=1,
            ),
        )

        pretrained.act_postprocess2 = nn.Sequential(
            readout_oper[1],
            Transpose(1, 2),
            nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
            nn.Conv2d(
                in_channels=vit_features,
                out_channels=features[1],
                kernel_size=1,
                stride=1,
                padding=0,
            ),
            nn.ConvTranspose2d(
                in_channels=features[1],
                out_channels=features[1],
                kernel_size=2,
                stride=2,
                padding=0,
                bias=True,
                dilation=1,
                groups=1,
            ),
        )
    else:
        pretrained.act_postprocess1 = nn.Sequential(
            nn.Identity(), nn.Identity(), nn.Identity()
        )
        pretrained.act_postprocess2 = nn.Sequential(
            nn.Identity(), nn.Identity(), nn.Identity()
        )

    pretrained.act_postprocess3 = nn.Sequential(
        readout_oper[2],
        Transpose(1, 2),
        nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
        nn.Conv2d(
            in_channels=vit_features,
            out_channels=features[2],
            kernel_size=1,
            stride=1,
            padding=0,
        ),
    )

    pretrained.act_postprocess4 = nn.Sequential(
        readout_oper[3],
        Transpose(1, 2),
        nn.Unflatten(2, torch.Size([size[0] // 16, size[1] // 16])),
        nn.Conv2d(
            in_channels=vit_features,
            out_channels=features[3],
            kernel_size=1,
            stride=1,
            padding=0,
        ),
        nn.Conv2d(
            in_channels=features[3],
            out_channels=features[3],
            kernel_size=3,
            stride=2,
            padding=1,
        ),
    )

    pretrained.model.start_index = start_index
    pretrained.model.patch_size = [16, 16]

    # We inject this function into the VisionTransformer instances so that
    # we can use it with interpolated position embeddings without modifying the library source.
    pretrained.model.forward_flex = types.MethodType(forward_flex, pretrained.model)

    # We inject this function into the VisionTransformer instances so that
    # we can use it with interpolated position embeddings without modifying the library source.
    pretrained.model._resize_pos_embed = types.MethodType(
        _resize_pos_embed, pretrained.model
    )

    return pretrained


def _make_pretrained_vitb_rn50_384(
    pretrained, use_readout="ignore", hooks=None, use_vit_only=False
):
    model = timm.create_model("vit_base_resnet50_384", pretrained=pretrained)

    hooks = [0, 1, 8, 11] if hooks == None else hooks
    return _make_vit_b_rn50_backbone(
        model,
        features=[256, 512, 768, 768],
        size=[384, 384],
        hooks=hooks,
        use_vit_only=use_vit_only,
        use_readout=use_readout,
    )

def _make_encoder(backbone, features, use_pretrained, groups=1, expand=False, exportable=True, hooks=None, use_vit_only=False, use_readout="ignore",):
    if backbone == "vitl16_384":
        pretrained = _make_pretrained_vitl16_384(
            use_pretrained, hooks=hooks, use_readout=use_readout
        )
        scratch = _make_scratch(
            [256, 512, 1024, 1024], features, groups=groups, expand=expand
        )  # ViT-L/16 - 85.0% Top1 (backbone)
    elif backbone == "vitb_rn50_384":
        pretrained = _make_pretrained_vitb_rn50_384(
            use_pretrained,
            hooks=hooks,
            use_vit_only=use_vit_only,
            use_readout=use_readout,
        )
        scratch = _make_scratch(
            [256, 512, 768, 768], features, groups=groups, expand=expand
        )  # ViT-H/16 - 85.0% Top1 (backbone)
    elif backbone == "vitb16_384":
        pretrained = _make_pretrained_vitb16_384(
            use_pretrained, hooks=hooks, use_readout=use_readout
        )
        scratch = _make_scratch(
            [96, 192, 384, 768], features, groups=groups, expand=expand
        )  # ViT-B/16 - 84.6% Top1 (backbone)
    elif backbone == "resnext101_wsl":
        pretrained = _make_pretrained_resnext101_wsl(use_pretrained)
        scratch = _make_scratch([256, 512, 1024, 2048], features, groups=groups, expand=expand)     # efficientnet_lite3  
    elif backbone == "efficientnet_lite3":
        pretrained = _make_pretrained_efficientnet_lite3(use_pretrained, exportable=exportable)
        scratch = _make_scratch([32, 48, 136, 384], features, groups=groups, expand=expand)  # efficientnet_lite3     
    else:
        print(f"Backbone '{backbone}' not implemented")
        assert False
        
    return pretrained, scratch


def _make_scratch(in_shape, out_shape, groups=1, expand=False):
    scratch = nn.Module()

    out_shape1 = out_shape
    out_shape2 = out_shape
    out_shape3 = out_shape
    out_shape4 = out_shape
    if expand==True:
        out_shape1 = out_shape
        out_shape2 = out_shape*2
        out_shape3 = out_shape*4
        out_shape4 = out_shape*8

    scratch.layer1_rn = nn.Conv2d(
        in_shape[0], out_shape1, kernel_size=3, stride=1, padding=1, bias=False, groups=groups
    )
    scratch.layer2_rn = nn.Conv2d(
        in_shape[1], out_shape2, kernel_size=3, stride=1, padding=1, bias=False, groups=groups
    )
    scratch.layer3_rn = nn.Conv2d(
        in_shape[2], out_shape3, kernel_size=3, stride=1, padding=1, bias=False, groups=groups
    )
    scratch.layer4_rn = nn.Conv2d(
        in_shape[3], out_shape4, kernel_size=3, stride=1, padding=1, bias=False, groups=groups
    )

    return scratch


def _make_pretrained_efficientnet_lite3(use_pretrained, exportable=False):
    efficientnet = torch.hub.load(
        "rwightman/gen-efficientnet-pytorch",
        "tf_efficientnet_lite3",
        pretrained=use_pretrained,
        exportable=exportable
    )
    return _make_efficientnet_backbone(efficientnet)


def _make_efficientnet_backbone(effnet):
    pretrained = nn.Module()

    pretrained.layer1 = nn.Sequential(
        effnet.conv_stem, effnet.bn1, effnet.act1, *effnet.blocks[0:2]
    )
    pretrained.layer2 = nn.Sequential(*effnet.blocks[2:3])
    pretrained.layer3 = nn.Sequential(*effnet.blocks[3:5])
    pretrained.layer4 = nn.Sequential(*effnet.blocks[5:9])

    return pretrained
    

def _make_resnet_backbone(resnet):
    pretrained = nn.Module()
    pretrained.layer1 = nn.Sequential(
        resnet.conv1, resnet.bn1, resnet.relu, resnet.maxpool, resnet.layer1
    )

    pretrained.layer2 = resnet.layer2
    pretrained.layer3 = resnet.layer3
    pretrained.layer4 = resnet.layer4

    return pretrained


def _make_pretrained_resnext101_wsl(use_pretrained):
    resnet = torch.hub.load("facebookresearch/WSL-Images", "resnext101_32x8d_wsl")
    return _make_resnet_backbone(resnet)



class Interpolate(nn.Module):
    """Interpolation module.
    """

    def __init__(self, scale_factor, mode, align_corners=False):
        """Init.
        Args:
            scale_factor (float): scaling
            mode (str): interpolation mode
        """
        super(Interpolate, self).__init__()

        self.interp = nn.functional.interpolate
        self.scale_factor = scale_factor
        self.mode = mode
        self.align_corners = align_corners

    def forward(self, x):
        """Forward pass.
        Args:
            x (tensor): input
        Returns:
            tensor: interpolated data
        """

        x = self.interp(
            x, scale_factor=self.scale_factor, mode=self.mode, align_corners=self.align_corners
        )

        return x


class ResidualConvUnit(nn.Module):
    """Residual convolution module.
    """

    def __init__(self, features):
        """Init.
        Args:
            features (int): number of features
        """
        super().__init__()

        self.conv1 = nn.Conv2d(
            features, features, kernel_size=3, stride=1, padding=1, bias=True
        )

        self.conv2 = nn.Conv2d(
            features, features, kernel_size=3, stride=1, padding=1, bias=True
        )

        self.relu = nn.ReLU(inplace=True)

    def forward(self, x):
        """Forward pass.
        Args:
            x (tensor): input
        Returns:
            tensor: output
        """
        out = self.relu(x)
        out = self.conv1(out)
        out = self.relu(out)
        out = self.conv2(out)

        return out + x


class FeatureFusionBlock(nn.Module):
    """Feature fusion block.
    """

    def __init__(self, features):
        """Init.
        Args:
            features (int): number of features
        """
        super(FeatureFusionBlock, self).__init__()

        self.resConfUnit1 = ResidualConvUnit(features)
        self.resConfUnit2 = ResidualConvUnit(features)

    def forward(self, *xs):
        """Forward pass.
        Returns:
            tensor: output
        """
        output = xs[0]

        if len(xs) == 2:
            output += self.resConfUnit1(xs[1])

        output = self.resConfUnit2(output)

        output = nn.functional.interpolate(
            output, scale_factor=2, mode="bilinear", align_corners=True
        )

        return output




class ResidualConvUnit_custom(nn.Module):
    """Residual convolution module.
    """

    def __init__(self, features, activation, bn):
        """Init.
        Args:
            features (int): number of features
        """
        super().__init__()

        self.bn = bn

        self.groups=1

        self.conv1 = nn.Conv2d(
            features, features, kernel_size=3, stride=1, padding=1, bias=True, groups=self.groups
        )
        
        self.conv2 = nn.Conv2d(
            features, features, kernel_size=3, stride=1, padding=1, bias=True, groups=self.groups
        )

        if self.bn==True:
            self.bn1 = nn.BatchNorm2d(features)
            self.bn2 = nn.BatchNorm2d(features)

        self.activation = activation

        self.skip_add = nn.quantized.FloatFunctional()

    def forward(self, x):
        """Forward pass.
        Args:
            x (tensor): input
        Returns:
            tensor: output
        """
        
        out = self.activation(x)
        out = self.conv1(out)
        if self.bn==True:
            out = self.bn1(out)
       
        out = self.activation(out)
        out = self.conv2(out)
        if self.bn==True:
            out = self.bn2(out)

        if self.groups > 1:
            out = self.conv_merge(out)

        return self.skip_add.add(out, x)

        # return out + x


class FeatureFusionBlock_custom(nn.Module):
    """Feature fusion block.
    """

    def __init__(self, features, activation, deconv=False, bn=False, expand=False, align_corners=True):
        """Init.
        Args:
            features (int): number of features
        """
        super(FeatureFusionBlock_custom, self).__init__()

        self.deconv = deconv
        self.align_corners = align_corners

        self.groups=1

        self.expand = expand
        out_features = features
        if self.expand==True:
            out_features = features//2
        
        self.out_conv = nn.Conv2d(features, out_features, kernel_size=1, stride=1, padding=0, bias=True, groups=1)

        self.resConfUnit1 = ResidualConvUnit_custom(features, activation, bn)
        self.resConfUnit2 = ResidualConvUnit_custom(features, activation, bn)
        
        self.skip_add = nn.quantized.FloatFunctional()

    def forward(self, *xs):
        """Forward pass.
        Returns:
            tensor: output
        """
        output = xs[0]

        if len(xs) == 2:
            res = self.resConfUnit1(xs[1])
            output = self.skip_add.add(output, res)
            # output += res

        output = self.resConfUnit2(output)

        output = nn.functional.interpolate(
            output, scale_factor=2, mode="bilinear", align_corners=self.align_corners
        )

        output = self.out_conv(output)

        return output        



def _make_fusion_block(features, use_bn):
    return FeatureFusionBlock_custom(
        features,
        nn.ReLU(False),
        deconv=False,
        bn=use_bn,
        expand=False,
        align_corners=True,
    )


class DPT(BaseModel):
    def __init__(
        self,
        head,
        features=256,
        backbone="vitb_rn50_384",
        readout="project",
        channels_last=False,
        use_bn=False,
    ):

        super(DPT, self).__init__()

        self.channels_last = channels_last

        hooks = {
            "vitb_rn50_384": [0, 1, 8, 11],
            "vitb16_384": [2, 5, 8, 11],
            "vitl16_384": [5, 11, 17, 23],
        }

        # Instantiate backbone and reassemble blocks
        self.pretrained, self.scratch = _make_encoder(
            backbone,
            features,
            True, # Set to true of you want to train from scratch, uses ImageNet weights
            groups=1,
            expand=False,
            exportable=False,
            hooks=hooks[backbone],
            use_readout=readout,
        )

        self.scratch.refinenet1 = _make_fusion_block(features, use_bn)
        self.scratch.refinenet2 = _make_fusion_block(features, use_bn)
        self.scratch.refinenet3 = _make_fusion_block(features, use_bn)
        self.scratch.refinenet4 = _make_fusion_block(features, use_bn)

        self.scratch.output_conv = head


    def forward(self, x):
        if self.channels_last == True:
            x.contiguous(memory_format=torch.channels_last)

        layer_1, layer_2, layer_3, layer_4 = forward_vit(self.pretrained, x)

        layer_1_rn = self.scratch.layer1_rn(layer_1)
        layer_2_rn = self.scratch.layer2_rn(layer_2)
        layer_3_rn = self.scratch.layer3_rn(layer_3)
        layer_4_rn = self.scratch.layer4_rn(layer_4)

        path_4 = self.scratch.refinenet4(layer_4_rn)
        path_3 = self.scratch.refinenet3(path_4, layer_3_rn)
        path_2 = self.scratch.refinenet2(path_3, layer_2_rn)
        path_1 = self.scratch.refinenet1(path_2, layer_1_rn)

        out = self.scratch.output_conv(path_1)

        return out

class DPTDepthModel(DPT):
    def __init__(self, path=None, non_negative=True, num_channels=1, **kwargs):
        features = kwargs["features"] if "features" in kwargs else 256

        head = nn.Sequential(
            nn.Conv2d(features, features // 2, kernel_size=3, stride=1, padding=1),
            Interpolate(scale_factor=2, mode="bilinear", align_corners=True),
            nn.Conv2d(features // 2, 32, kernel_size=3, stride=1, padding=1),
            nn.ReLU(True),
            nn.Conv2d(32, num_channels, kernel_size=1, stride=1, padding=0),
            nn.ReLU(True) if non_negative else nn.Identity(),
            nn.Identity(),
        )

        super().__init__(head, **kwargs)

        if path is not None:
           self.load(path)

    def forward(self, x):
        return super().forward(x).squeeze(dim=1)