File size: 22,326 Bytes
36d9761
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
import math
import random
import torch
from torch import nn
from torch.nn import functional as F

from basicsr.ops.fused_act import FusedLeakyReLU, fused_leaky_relu
from basicsr.utils.registry import ARCH_REGISTRY


class NormStyleCode(nn.Module):

    def forward(self, x):
        """Normalize the style codes.

        Args:
            x (Tensor): Style codes with shape (b, c).

        Returns:
            Tensor: Normalized tensor.
        """
        return x * torch.rsqrt(torch.mean(x**2, dim=1, keepdim=True) + 1e-8)


class EqualLinear(nn.Module):
    """Equalized Linear as StyleGAN2.

    Args:
        in_channels (int): Size of each sample.
        out_channels (int): Size of each output sample.
        bias (bool): If set to ``False``, the layer will not learn an additive
            bias. Default: ``True``.
        bias_init_val (float): Bias initialized value. Default: 0.
        lr_mul (float): Learning rate multiplier. Default: 1.
        activation (None | str): The activation after ``linear`` operation.
            Supported: 'fused_lrelu', None. Default: None.
    """

    def __init__(self, in_channels, out_channels, bias=True, bias_init_val=0, lr_mul=1, activation=None):
        super(EqualLinear, self).__init__()
        self.in_channels = in_channels
        self.out_channels = out_channels
        self.lr_mul = lr_mul
        self.activation = activation
        if self.activation not in ['fused_lrelu', None]:
            raise ValueError(f'Wrong activation value in EqualLinear: {activation}'
                             "Supported ones are: ['fused_lrelu', None].")
        self.scale = (1 / math.sqrt(in_channels)) * lr_mul

        self.weight = nn.Parameter(torch.randn(out_channels, in_channels).div_(lr_mul))
        if bias:
            self.bias = nn.Parameter(torch.zeros(out_channels).fill_(bias_init_val))
        else:
            self.register_parameter('bias', None)

    def forward(self, x):
        if self.bias is None:
            bias = None
        else:
            bias = self.bias * self.lr_mul
        if self.activation == 'fused_lrelu':
            out = F.linear(x, self.weight * self.scale)
            out = fused_leaky_relu(out, bias)
        else:
            out = F.linear(x, self.weight * self.scale, bias=bias)
        return out

    def __repr__(self):
        return (f'{self.__class__.__name__}(in_channels={self.in_channels}, '
                f'out_channels={self.out_channels}, bias={self.bias is not None})')


class ModulatedConv2d(nn.Module):
    """Modulated Conv2d used in StyleGAN2.

    There is no bias in ModulatedConv2d.

    Args:
        in_channels (int): Channel number of the input.
        out_channels (int): Channel number of the output.
        kernel_size (int): Size of the convolving kernel.
        num_style_feat (int): Channel number of style features.
        demodulate (bool): Whether to demodulate in the conv layer.
            Default: True.
        sample_mode (str | None): Indicating 'upsample', 'downsample' or None.
            Default: None.
        eps (float): A value added to the denominator for numerical stability.
            Default: 1e-8.
    """

    def __init__(self,
                 in_channels,
                 out_channels,
                 kernel_size,
                 num_style_feat,
                 demodulate=True,
                 sample_mode=None,
                 eps=1e-8,
                 interpolation_mode='bilinear'):
        super(ModulatedConv2d, self).__init__()
        self.in_channels = in_channels
        self.out_channels = out_channels
        self.kernel_size = kernel_size
        self.demodulate = demodulate
        self.sample_mode = sample_mode
        self.eps = eps
        self.interpolation_mode = interpolation_mode
        if self.interpolation_mode == 'nearest':
            self.align_corners = None
        else:
            self.align_corners = False

        self.scale = 1 / math.sqrt(in_channels * kernel_size**2)
        # modulation inside each modulated conv
        self.modulation = EqualLinear(
            num_style_feat, in_channels, bias=True, bias_init_val=1, lr_mul=1, activation=None)

        self.weight = nn.Parameter(torch.randn(1, out_channels, in_channels, kernel_size, kernel_size))
        self.padding = kernel_size // 2

    def forward(self, x, style):
        """Forward function.

        Args:
            x (Tensor): Tensor with shape (b, c, h, w).
            style (Tensor): Tensor with shape (b, num_style_feat).

        Returns:
            Tensor: Modulated tensor after convolution.
        """
        b, c, h, w = x.shape  # c = c_in
        # weight modulation
        style = self.modulation(style).view(b, 1, c, 1, 1)
        # self.weight: (1, c_out, c_in, k, k); style: (b, 1, c, 1, 1)
        weight = self.scale * self.weight * style  # (b, c_out, c_in, k, k)

        if self.demodulate:
            demod = torch.rsqrt(weight.pow(2).sum([2, 3, 4]) + self.eps)
            weight = weight * demod.view(b, self.out_channels, 1, 1, 1)

        weight = weight.view(b * self.out_channels, c, self.kernel_size, self.kernel_size)

        if self.sample_mode == 'upsample':
            x = F.interpolate(x, scale_factor=2, mode=self.interpolation_mode, align_corners=self.align_corners)
        elif self.sample_mode == 'downsample':
            x = F.interpolate(x, scale_factor=0.5, mode=self.interpolation_mode, align_corners=self.align_corners)

        b, c, h, w = x.shape
        x = x.view(1, b * c, h, w)
        # weight: (b*c_out, c_in, k, k), groups=b
        out = F.conv2d(x, weight, padding=self.padding, groups=b)
        out = out.view(b, self.out_channels, *out.shape[2:4])

        return out

    def __repr__(self):
        return (f'{self.__class__.__name__}(in_channels={self.in_channels}, '
                f'out_channels={self.out_channels}, '
                f'kernel_size={self.kernel_size}, '
                f'demodulate={self.demodulate}, sample_mode={self.sample_mode})')


class StyleConv(nn.Module):
    """Style conv.

    Args:
        in_channels (int): Channel number of the input.
        out_channels (int): Channel number of the output.
        kernel_size (int): Size of the convolving kernel.
        num_style_feat (int): Channel number of style features.
        demodulate (bool): Whether demodulate in the conv layer. Default: True.
        sample_mode (str | None): Indicating 'upsample', 'downsample' or None.
            Default: None.
    """

    def __init__(self,
                 in_channels,
                 out_channels,
                 kernel_size,
                 num_style_feat,
                 demodulate=True,
                 sample_mode=None,
                 interpolation_mode='bilinear'):
        super(StyleConv, self).__init__()
        self.modulated_conv = ModulatedConv2d(
            in_channels,
            out_channels,
            kernel_size,
            num_style_feat,
            demodulate=demodulate,
            sample_mode=sample_mode,
            interpolation_mode=interpolation_mode)
        self.weight = nn.Parameter(torch.zeros(1))  # for noise injection
        self.activate = FusedLeakyReLU(out_channels)

    def forward(self, x, style, noise=None):
        # modulate
        out = self.modulated_conv(x, style)
        # noise injection
        if noise is None:
            b, _, h, w = out.shape
            noise = out.new_empty(b, 1, h, w).normal_()
        out = out + self.weight * noise
        # activation (with bias)
        out = self.activate(out)
        return out


class ToRGB(nn.Module):
    """To RGB from features.

    Args:
        in_channels (int): Channel number of input.
        num_style_feat (int): Channel number of style features.
        upsample (bool): Whether to upsample. Default: True.
    """

    def __init__(self, in_channels, num_style_feat, upsample=True, interpolation_mode='bilinear'):
        super(ToRGB, self).__init__()
        self.upsample = upsample
        self.interpolation_mode = interpolation_mode
        if self.interpolation_mode == 'nearest':
            self.align_corners = None
        else:
            self.align_corners = False
        self.modulated_conv = ModulatedConv2d(
            in_channels,
            3,
            kernel_size=1,
            num_style_feat=num_style_feat,
            demodulate=False,
            sample_mode=None,
            interpolation_mode=interpolation_mode)
        self.bias = nn.Parameter(torch.zeros(1, 3, 1, 1))

    def forward(self, x, style, skip=None):
        """Forward function.

        Args:
            x (Tensor): Feature tensor with shape (b, c, h, w).
            style (Tensor): Tensor with shape (b, num_style_feat).
            skip (Tensor): Base/skip tensor. Default: None.

        Returns:
            Tensor: RGB images.
        """
        out = self.modulated_conv(x, style)
        out = out + self.bias
        if skip is not None:
            if self.upsample:
                skip = F.interpolate(
                    skip, scale_factor=2, mode=self.interpolation_mode, align_corners=self.align_corners)
            out = out + skip
        return out


class ConstantInput(nn.Module):
    """Constant input.

    Args:
        num_channel (int): Channel number of constant input.
        size (int): Spatial size of constant input.
    """

    def __init__(self, num_channel, size):
        super(ConstantInput, self).__init__()
        self.weight = nn.Parameter(torch.randn(1, num_channel, size, size))

    def forward(self, batch):
        out = self.weight.repeat(batch, 1, 1, 1)
        return out


@ARCH_REGISTRY.register(suffix='basicsr')
class StyleGAN2GeneratorBilinear(nn.Module):
    """StyleGAN2 Generator.

    Args:
        out_size (int): The spatial size of outputs.
        num_style_feat (int): Channel number of style features. Default: 512.
        num_mlp (int): Layer number of MLP style layers. Default: 8.
        channel_multiplier (int): Channel multiplier for large networks of
            StyleGAN2. Default: 2.
        lr_mlp (float): Learning rate multiplier for mlp layers. Default: 0.01.
        narrow (float): Narrow ratio for channels. Default: 1.0.
    """

    def __init__(self,
                 out_size,
                 num_style_feat=512,
                 num_mlp=8,
                 channel_multiplier=2,
                 lr_mlp=0.01,
                 narrow=1,
                 interpolation_mode='bilinear'):
        super(StyleGAN2GeneratorBilinear, self).__init__()
        # Style MLP layers
        self.num_style_feat = num_style_feat
        style_mlp_layers = [NormStyleCode()]
        for i in range(num_mlp):
            style_mlp_layers.append(
                EqualLinear(
                    num_style_feat, num_style_feat, bias=True, bias_init_val=0, lr_mul=lr_mlp,
                    activation='fused_lrelu'))
        self.style_mlp = nn.Sequential(*style_mlp_layers)

        channels = {
            '4': int(512 * narrow),
            '8': int(512 * narrow),
            '16': int(512 * narrow),
            '32': int(512 * narrow),
            '64': int(256 * channel_multiplier * narrow),
            '128': int(128 * channel_multiplier * narrow),
            '256': int(64 * channel_multiplier * narrow),
            '512': int(32 * channel_multiplier * narrow),
            '1024': int(16 * channel_multiplier * narrow)
        }
        self.channels = channels

        self.constant_input = ConstantInput(channels['4'], size=4)
        self.style_conv1 = StyleConv(
            channels['4'],
            channels['4'],
            kernel_size=3,
            num_style_feat=num_style_feat,
            demodulate=True,
            sample_mode=None,
            interpolation_mode=interpolation_mode)
        self.to_rgb1 = ToRGB(channels['4'], num_style_feat, upsample=False, interpolation_mode=interpolation_mode)

        self.log_size = int(math.log(out_size, 2))
        self.num_layers = (self.log_size - 2) * 2 + 1
        self.num_latent = self.log_size * 2 - 2

        self.style_convs = nn.ModuleList()
        self.to_rgbs = nn.ModuleList()
        self.noises = nn.Module()

        in_channels = channels['4']
        # noise
        for layer_idx in range(self.num_layers):
            resolution = 2**((layer_idx + 5) // 2)
            shape = [1, 1, resolution, resolution]
            self.noises.register_buffer(f'noise{layer_idx}', torch.randn(*shape))
        # style convs and to_rgbs
        for i in range(3, self.log_size + 1):
            out_channels = channels[f'{2**i}']
            self.style_convs.append(
                StyleConv(
                    in_channels,
                    out_channels,
                    kernel_size=3,
                    num_style_feat=num_style_feat,
                    demodulate=True,
                    sample_mode='upsample',
                    interpolation_mode=interpolation_mode))
            self.style_convs.append(
                StyleConv(
                    out_channels,
                    out_channels,
                    kernel_size=3,
                    num_style_feat=num_style_feat,
                    demodulate=True,
                    sample_mode=None,
                    interpolation_mode=interpolation_mode))
            self.to_rgbs.append(
                ToRGB(out_channels, num_style_feat, upsample=True, interpolation_mode=interpolation_mode))
            in_channels = out_channels

    def make_noise(self):
        """Make noise for noise injection."""
        device = self.constant_input.weight.device
        noises = [torch.randn(1, 1, 4, 4, device=device)]

        for i in range(3, self.log_size + 1):
            for _ in range(2):
                noises.append(torch.randn(1, 1, 2**i, 2**i, device=device))

        return noises

    def get_latent(self, x):
        return self.style_mlp(x)

    def mean_latent(self, num_latent):
        latent_in = torch.randn(num_latent, self.num_style_feat, device=self.constant_input.weight.device)
        latent = self.style_mlp(latent_in).mean(0, keepdim=True)
        return latent

    def forward(self,
                styles,
                input_is_latent=False,
                noise=None,
                randomize_noise=True,
                truncation=1,
                truncation_latent=None,
                inject_index=None,
                return_latents=False):
        """Forward function for StyleGAN2Generator.

        Args:
            styles (list[Tensor]): Sample codes of styles.
            input_is_latent (bool): Whether input is latent style.
                Default: False.
            noise (Tensor | None): Input noise or None. Default: None.
            randomize_noise (bool): Randomize noise, used when 'noise' is
                False. Default: True.
            truncation (float): TODO. Default: 1.
            truncation_latent (Tensor | None): TODO. Default: None.
            inject_index (int | None): The injection index for mixing noise.
                Default: None.
            return_latents (bool): Whether to return style latents.
                Default: False.
        """
        # style codes -> latents with Style MLP layer
        if not input_is_latent:
            styles = [self.style_mlp(s) for s in styles]
        # noises
        if noise is None:
            if randomize_noise:
                noise = [None] * self.num_layers  # for each style conv layer
            else:  # use the stored noise
                noise = [getattr(self.noises, f'noise{i}') for i in range(self.num_layers)]
        # style truncation
        if truncation < 1:
            style_truncation = []
            for style in styles:
                style_truncation.append(truncation_latent + truncation * (style - truncation_latent))
            styles = style_truncation
        # get style latent with injection
        if len(styles) == 1:
            inject_index = self.num_latent

            if styles[0].ndim < 3:
                # repeat latent code for all the layers
                latent = styles[0].unsqueeze(1).repeat(1, inject_index, 1)
            else:  # used for encoder with different latent code for each layer
                latent = styles[0]
        elif len(styles) == 2:  # mixing noises
            if inject_index is None:
                inject_index = random.randint(1, self.num_latent - 1)
            latent1 = styles[0].unsqueeze(1).repeat(1, inject_index, 1)
            latent2 = styles[1].unsqueeze(1).repeat(1, self.num_latent - inject_index, 1)
            latent = torch.cat([latent1, latent2], 1)

        # main generation
        out = self.constant_input(latent.shape[0])
        out = self.style_conv1(out, latent[:, 0], noise=noise[0])
        skip = self.to_rgb1(out, latent[:, 1])

        i = 1
        for conv1, conv2, noise1, noise2, to_rgb in zip(self.style_convs[::2], self.style_convs[1::2], noise[1::2],
                                                        noise[2::2], self.to_rgbs):
            out = conv1(out, latent[:, i], noise=noise1)
            out = conv2(out, latent[:, i + 1], noise=noise2)
            skip = to_rgb(out, latent[:, i + 2], skip)
            i += 2

        image = skip

        if return_latents:
            return image, latent
        else:
            return image, None


class ScaledLeakyReLU(nn.Module):
    """Scaled LeakyReLU.

    Args:
        negative_slope (float): Negative slope. Default: 0.2.
    """

    def __init__(self, negative_slope=0.2):
        super(ScaledLeakyReLU, self).__init__()
        self.negative_slope = negative_slope

    def forward(self, x):
        out = F.leaky_relu(x, negative_slope=self.negative_slope)
        return out * math.sqrt(2)


class EqualConv2d(nn.Module):
    """Equalized Linear as StyleGAN2.

    Args:
        in_channels (int): Channel number of the input.
        out_channels (int): Channel number of the output.
        kernel_size (int): Size of the convolving kernel.
        stride (int): Stride of the convolution. Default: 1
        padding (int): Zero-padding added to both sides of the input.
            Default: 0.
        bias (bool): If ``True``, adds a learnable bias to the output.
            Default: ``True``.
        bias_init_val (float): Bias initialized value. Default: 0.
    """

    def __init__(self, in_channels, out_channels, kernel_size, stride=1, padding=0, bias=True, bias_init_val=0):
        super(EqualConv2d, self).__init__()
        self.in_channels = in_channels
        self.out_channels = out_channels
        self.kernel_size = kernel_size
        self.stride = stride
        self.padding = padding
        self.scale = 1 / math.sqrt(in_channels * kernel_size**2)

        self.weight = nn.Parameter(torch.randn(out_channels, in_channels, kernel_size, kernel_size))
        if bias:
            self.bias = nn.Parameter(torch.zeros(out_channels).fill_(bias_init_val))
        else:
            self.register_parameter('bias', None)

    def forward(self, x):
        out = F.conv2d(
            x,
            self.weight * self.scale,
            bias=self.bias,
            stride=self.stride,
            padding=self.padding,
        )

        return out

    def __repr__(self):
        return (f'{self.__class__.__name__}(in_channels={self.in_channels}, '
                f'out_channels={self.out_channels}, '
                f'kernel_size={self.kernel_size},'
                f' stride={self.stride}, padding={self.padding}, '
                f'bias={self.bias is not None})')


class ConvLayer(nn.Sequential):
    """Conv Layer used in StyleGAN2 Discriminator.

    Args:
        in_channels (int): Channel number of the input.
        out_channels (int): Channel number of the output.
        kernel_size (int): Kernel size.
        downsample (bool): Whether downsample by a factor of 2.
            Default: False.
        bias (bool): Whether with bias. Default: True.
        activate (bool): Whether use activateion. Default: True.
    """

    def __init__(self,
                 in_channels,
                 out_channels,
                 kernel_size,
                 downsample=False,
                 bias=True,
                 activate=True,
                 interpolation_mode='bilinear'):
        layers = []
        self.interpolation_mode = interpolation_mode
        # downsample
        if downsample:
            if self.interpolation_mode == 'nearest':
                self.align_corners = None
            else:
                self.align_corners = False

            layers.append(
                torch.nn.Upsample(scale_factor=0.5, mode=interpolation_mode, align_corners=self.align_corners))
        stride = 1
        self.padding = kernel_size // 2
        # conv
        layers.append(
            EqualConv2d(
                in_channels, out_channels, kernel_size, stride=stride, padding=self.padding, bias=bias
                and not activate))
        # activation
        if activate:
            if bias:
                layers.append(FusedLeakyReLU(out_channels))
            else:
                layers.append(ScaledLeakyReLU(0.2))

        super(ConvLayer, self).__init__(*layers)


class ResBlock(nn.Module):
    """Residual block used in StyleGAN2 Discriminator.

    Args:
        in_channels (int): Channel number of the input.
        out_channels (int): Channel number of the output.
    """

    def __init__(self, in_channels, out_channels, interpolation_mode='bilinear'):
        super(ResBlock, self).__init__()

        self.conv1 = ConvLayer(in_channels, in_channels, 3, bias=True, activate=True)
        self.conv2 = ConvLayer(
            in_channels,
            out_channels,
            3,
            downsample=True,
            interpolation_mode=interpolation_mode,
            bias=True,
            activate=True)
        self.skip = ConvLayer(
            in_channels,
            out_channels,
            1,
            downsample=True,
            interpolation_mode=interpolation_mode,
            bias=False,
            activate=False)

    def forward(self, x):
        out = self.conv1(x)
        out = self.conv2(out)
        skip = self.skip(x)
        out = (out + skip) / math.sqrt(2)
        return out