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| import torch
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| import torch.nn.functional as F
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| from torch.autograd import Variable
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| from math import exp
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| def l1_loss(network_output, gt):
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| return torch.abs((network_output - gt)).mean()
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| def l2_loss(network_output, gt):
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| return ((network_output - gt) ** 2).mean()
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| def gaussian(window_size, sigma):
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| gauss = torch.Tensor([exp(-(x - window_size // 2) ** 2 / float(2 * sigma ** 2)) for x in range(window_size)])
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| return gauss / gauss.sum()
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| def create_window(window_size, channel):
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| _1D_window = gaussian(window_size, 1.5).unsqueeze(1)
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| _2D_window = _1D_window.mm(_1D_window.t()).float().unsqueeze(0).unsqueeze(0)
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| window = Variable(_2D_window.expand(channel, 1, window_size, window_size).contiguous())
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| return window
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| def ssim(img1, img2, window_size=11, size_average=True):
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| channel = img1.size(-3)
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| window = create_window(window_size, channel)
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| if img1.is_cuda:
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| window = window.cuda(img1.get_device())
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| window = window.type_as(img1)
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| return _ssim(img1, img2, window, window_size, channel, size_average)
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| def _ssim(img1, img2, window, window_size, channel, size_average=True):
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| mu1 = F.conv2d(img1, window, padding=window_size // 2, groups=channel)
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| mu2 = F.conv2d(img2, window, padding=window_size // 2, groups=channel)
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| mu1_sq = mu1.pow(2)
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| mu2_sq = mu2.pow(2)
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| mu1_mu2 = mu1 * mu2
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| sigma1_sq = F.conv2d(img1 * img1, window, padding=window_size // 2, groups=channel) - mu1_sq
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| sigma2_sq = F.conv2d(img2 * img2, window, padding=window_size // 2, groups=channel) - mu2_sq
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| sigma12 = F.conv2d(img1 * img2, window, padding=window_size // 2, groups=channel) - mu1_mu2
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| C1 = 0.01 ** 2
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| C2 = 0.03 ** 2
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| ssim_map = ((2 * mu1_mu2 + C1) * (2 * sigma12 + C2)) / ((mu1_sq + mu2_sq + C1) * (sigma1_sq + sigma2_sq + C2))
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| if size_average:
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| return ssim_map.mean()
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| else:
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| return ssim_map.mean(1).mean(1).mean(1)
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