dense_motion.py

# code was heavily based on https://github.com/AliaksandrSiarohin/first-order-model
# Users should be careful about adopting these functions in any commercial matters.
# https://github.com/AliaksandrSiarohin/first-order-model/blob/master/LICENSE.md

import paddle
import paddle.nn as nn
import paddle.nn.functional as F

from .first_order import Hourglass, AntiAliasInterpolation2d, make_coordinate_grid, kp2gaussian


class DenseMotionNetwork(nn.Layer):
    """
    Module that predicting a dense motion from sparse motion representation given by kp_source and kp_driving
    """
    def __init__(self,
                 block_expansion,
                 num_blocks,
                 max_features,
                 num_kp,
                 num_channels,
                 estimate_occlusion_map=False,
                 scale_factor=1,
                 kp_variance=0.01,
                 mobile_net=False):
        super(DenseMotionNetwork, self).__init__()
        self.hourglass = Hourglass(block_expansion=block_expansion,
                                   in_features=(num_kp + 1) *
                                   (num_channels + 1),
                                   max_features=max_features,
                                   num_blocks=num_blocks,
                                   mobile_net=mobile_net)

        self.mask = nn.Conv2D(self.hourglass.out_filters,
                              num_kp + 1,
                              kernel_size=(7, 7),
                              padding=(3, 3))

        if estimate_occlusion_map:
            self.occlusion = nn.Conv2D(self.hourglass.out_filters,
                                       1,
                                       kernel_size=(7, 7),
                                       padding=(3, 3))
        else:
            self.occlusion = None

        self.num_kp = num_kp
        self.scale_factor = scale_factor
        self.kp_variance = kp_variance

        if self.scale_factor != 1:
            self.down = AntiAliasInterpolation2d(num_channels,
                                                 self.scale_factor)

    def create_heatmap_representations(self, source_image, kp_driving,
                                       kp_source):
        """
        Eq 6. in the paper H_k(z)
        """
        spatial_size = source_image.shape[2:]
        gaussian_driving = kp2gaussian(kp_driving,
                                       spatial_size=spatial_size,
                                       kp_variance=self.kp_variance)
        gaussian_source = kp2gaussian(kp_source,
                                      spatial_size=spatial_size,
                                      kp_variance=self.kp_variance)
        heatmap = gaussian_driving - gaussian_source

        #adding background feature
        zeros = paddle.zeros(
            [heatmap.shape[0], 1, spatial_size[0], spatial_size[1]],
            heatmap.dtype)  #.type(heatmap.type())
        heatmap = paddle.concat([zeros, heatmap], axis=1)
        heatmap = heatmap.unsqueeze(2)
        return heatmap

    def create_sparse_motions(self, source_image, kp_driving, kp_source):
        """
        Eq 4. in the paper T_{s<-d}(z)
        """
        bs, _, h, w = source_image.shape
        identity_grid = make_coordinate_grid((h, w),
                                             type=kp_source['value'].dtype)
        identity_grid = identity_grid.reshape([1, 1, h, w, 2])
        coordinate_grid = identity_grid - kp_driving['value'].reshape(
            [bs, self.num_kp, 1, 1, 2])
        if 'jacobian' in kp_driving:
            jacobian = paddle.matmul(kp_source['jacobian'],
                                     paddle.inverse(kp_driving['jacobian']))
            jacobian = jacobian.unsqueeze(-3).unsqueeze(-3)
            # Todo: fix bug of paddle.tile
            p_jacobian = jacobian.reshape([bs, self.num_kp, 1, 1, 4])
            paddle_jacobian = paddle.tile(p_jacobian, [1, 1, h, w, 1])
            paddle_jacobian = paddle_jacobian.reshape(
                [bs, self.num_kp, h, w, 2, 2])

            coordinate_grid = paddle.matmul(paddle_jacobian,
                                            coordinate_grid.unsqueeze(-1))

            coordinate_grid = coordinate_grid.squeeze(-1)

        driving_to_source = coordinate_grid + kp_source['value'].reshape(
            [bs, self.num_kp, 1, 1, 2])

        #adding background feature
        identity_grid = paddle.tile(identity_grid, (bs, 1, 1, 1, 1))
        sparse_motions = paddle.concat([identity_grid, driving_to_source],
                                       axis=1)
        return sparse_motions

    def create_deformed_source_image(self, source_image, sparse_motions):
        """
        Eq 7. in the paper \hat{T}_{s<-d}(z)
        """
        bs, _, h, w = source_image.shape
        source_repeat = paddle.tile(
            source_image.unsqueeze(1).unsqueeze(1),
            [1, self.num_kp + 1, 1, 1, 1, 1
             ])  #.repeat(1, self.num_kp + 1, 1, 1, 1, 1)
        source_repeat = source_repeat.reshape(
            [bs * (self.num_kp + 1), -1, h, w])
        sparse_motions = sparse_motions.reshape(
            (bs * (self.num_kp + 1), h, w, -1))
        sparse_deformed = F.grid_sample(source_repeat,
                                        sparse_motions,
                                        mode='bilinear',
                                        padding_mode='zeros',
                                        align_corners=True)
        sparse_deformed = sparse_deformed.reshape(
            (bs, self.num_kp + 1, -1, h, w))
        return sparse_deformed

    def forward(self, source_image, kp_driving, kp_source):
        if self.scale_factor != 1:
            source_image = self.down(source_image)

        bs, _, h, w = source_image.shape

        out_dict = dict()
        heatmap_representation = self.create_heatmap_representations(
            source_image, kp_driving, kp_source)
        sparse_motion = self.create_sparse_motions(source_image, kp_driving,
                                                   kp_source)
        deformed_source = self.create_deformed_source_image(
            source_image, sparse_motion)
        out_dict['sparse_deformed'] = deformed_source

        temp = paddle.concat([heatmap_representation, deformed_source], axis=2)
        temp = temp.reshape([bs, -1, h, w])

        prediction = self.hourglass(temp)

        mask = self.mask(prediction)
        mask = F.softmax(mask, axis=1)
        out_dict['mask'] = mask
        mask = mask.unsqueeze(2)
        sparse_motion = sparse_motion.transpose([0, 1, 4, 2, 3])
        deformation = (sparse_motion * mask).sum(axis=1)
        deformation = deformation.transpose([0, 2, 3, 1])

        out_dict['deformation'] = deformation

        # Sec. 3.2 in the paper
        if self.occlusion:
            occlusion_map = F.sigmoid(self.occlusion(prediction))
            out_dict['occlusion_map'] = occlusion_map

        return out_dict