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| 1 | +'''SSIM in PyTorch. |
| 2 | +
|
| 3 | +The source code is adopted from: |
| 4 | +https://github.com/Po-Hsun-Su/pytorch-ssim |
| 5 | +
|
| 6 | +
|
| 7 | +Reference: |
| 8 | +[1] Wang Z, Bovik A C, Sheikh H R, et al. |
| 9 | + Image quality assessment: from error visibility to structural similarity. IEEE transactions on image processing |
| 10 | +''' |
| 11 | + |
| 12 | +import torch |
| 13 | +import torch.nn.functional as F |
| 14 | +from torch.autograd import Variable |
| 15 | +import numpy as np |
| 16 | +from math import exp |
| 17 | +import math |
| 18 | + |
| 19 | + |
| 20 | +# def gaussian(window_size, sigma): |
| 21 | +# gauss = torch.Tensor([exp(-(x - window_size//2)**2/float(2*sigma**2)) for x in range(window_size)]) |
| 22 | +# return gauss/gauss.sum() |
| 23 | + |
| 24 | +def uniform(window_size,sigma): |
| 25 | + uniform_tensor = torch.ones(window_size) |
| 26 | + return uniform_tensor / uniform_tensor.sum() |
| 27 | + |
| 28 | + |
| 29 | +def create_window(window_size, channel, sigma=1.5): |
| 30 | + _1D_window = uniform(window_size, sigma).unsqueeze(1) |
| 31 | + _2D_window = _1D_window.mm(_1D_window.t()).float().unsqueeze(0).unsqueeze(0) |
| 32 | + window = Variable(_2D_window.expand(channel, 1, window_size, window_size).contiguous()) |
| 33 | + return window |
| 34 | + |
| 35 | +def _ssim(img1, img2, window, window_size, channel, size_average = True, stride=None, drop=None): |
| 36 | + mu1 = F.conv2d(img1, window, padding = (window_size-1)//2, groups = channel, stride=stride) |
| 37 | + mu2 = F.conv2d(img2, window, padding = (window_size-1)//2, groups = channel, stride=stride) |
| 38 | + |
| 39 | + mu1_sq = mu1.pow(2) |
| 40 | + mu2_sq = mu2.pow(2) |
| 41 | + mu1_mu2 = mu1*mu2 |
| 42 | + |
| 43 | + sigma1_sq = F.conv2d(img1*img1, window, padding = (window_size-1)//2, groups = channel, stride=stride) - mu1_sq |
| 44 | + sigma2_sq = F.conv2d(img2*img2, window, padding = (window_size-1)//2, groups = channel, stride=stride) - mu2_sq |
| 45 | + sigma12 = F.conv2d(img1*img2, window, padding = (window_size-1)//2, groups = channel, stride=stride) - mu1_mu2 |
| 46 | + |
| 47 | + C1 = 0.01**2 |
| 48 | + C2 = 0.03**2 |
| 49 | + C3 = C2/2 |
| 50 | + |
| 51 | + L = (2*mu1_mu2 + C1) / (mu1_sq + mu2_sq + C1) |
| 52 | + C = (2*torch.sqrt(sigma1_sq)*torch.sqrt(sigma2_sq) + C2) / (sigma1_sq + sigma2_sq + C2) |
| 53 | + S = (sigma12 + C3) / (torch.sqrt(sigma1_sq)*torch.sqrt(sigma2_sq) + C3) |
| 54 | + |
| 55 | + if drop == "L": |
| 56 | + ssim_map = C*S |
| 57 | + elif drop == "C": |
| 58 | + ssim_map = L*S |
| 59 | + elif drop == "S": |
| 60 | + ssim_map = L*C |
| 61 | + elif drop == "LC": |
| 62 | + ssim_map = S |
| 63 | + else: |
| 64 | + ssim_map = ((2*mu1_mu2 + C1)*(2*sigma12 + C2))/((mu1_sq + mu2_sq + C1)*(sigma1_sq + sigma2_sq + C2)) |
| 65 | + |
| 66 | + if size_average: |
| 67 | + return ssim_map.mean() |
| 68 | + else: |
| 69 | + return ssim_map.mean(1).mean(1).mean(1) |
| 70 | + |
| 71 | +class LocalGlance(torch.nn.Module): |
| 72 | + def __init__(self, window_size = 3, size_average = True, stride=3, drop=None, sigma=1.5, channel=1): |
| 73 | + super(LocalGlance, self).__init__() |
| 74 | + self.window_size = window_size |
| 75 | + self.size_average = size_average |
| 76 | + self.channel = channel |
| 77 | + self.stride = stride |
| 78 | + self.window = create_window(window_size, self.channel, sigma) |
| 79 | + self.drop = drop |
| 80 | + self.sigma = sigma |
| 81 | + |
| 82 | + |
| 83 | + def forward(self, img1, img2): |
| 84 | + """ |
| 85 | + img1, img2: torch.Tensor([b,2,h,w]) - 2表示复数的实部和虚部 |
| 86 | + """ |
| 87 | + # 计算幅值 |
| 88 | + (_, channel, _, _) = img1.size() |
| 89 | + |
| 90 | + if channel == self.channel and self.window.data.type() == img1.data.type(): |
| 91 | + window = self.window |
| 92 | + else: |
| 93 | + window = create_window(self.window_size, channel, self.sigma) |
| 94 | + |
| 95 | + if img1.is_cuda: |
| 96 | + window = window.cuda(img1.get_device()) |
| 97 | + window = window.type_as(img1) |
| 98 | + |
| 99 | + self.window = window |
| 100 | + self.channel = channel |
| 101 | + |
| 102 | + return _ssim(img1, img2, window, self.window_size, channel, self.size_average, stride=self.stride, drop=self.drop) |
| 103 | + |
| 104 | + |
| 105 | +def ssim(img1, img2, window_size = 11, size_average = True, sigma=1.5): |
| 106 | + (_, channel, _, _) = img1.size() |
| 107 | + window = create_window(window_size, channel, sigma) |
| 108 | + |
| 109 | + if img1.is_cuda: |
| 110 | + window = window.cuda(img1.get_device()) |
| 111 | + window = window.type_as(img1) |
| 112 | + |
| 113 | + return _ssim(img1, img2, window, window_size, channel, size_average) |
| 114 | + |
| 115 | + |
| 116 | + |
| 117 | + |
| 118 | + |
| 119 | + |
| 120 | + |
| 121 | + |
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