ssim损失函数pytorch实现

好的，关于ssim损失函数的PyTorch实现，可以参考以下代码：

import torch
import torch.nn.functional as F

def ssim_loss(img1, img2, window_size=11, size_average=True, sigma=1.5):
    # Set the window size
    window = create_window(window_size, img1.size(1), sigma=sigma)

    # Compute the mean of the images
    mu1 = F.conv2d(img1, window, padding=window_size//2, groups=img1.size(1))
    mu2 = F.conv2d(img2, window, padding=window_size//2, groups=img1.size(1))

    # Compute the variances and the covariances
    sigma1_sq = F.conv2d(img1*img1, window, padding=window_size//2, groups=img1.size(1)) - mu1*mu1
    sigma2_sq = F.conv2d(img2*img2, window, padding=window_size//2, groups=img1.size(1)) - mu2*mu2
    sigma12 = F.conv2d(img1*img2, window, padding=window_size//2, groups=img1.size(1)) - mu1*mu2

    # Compute the SSIM index
    C1 = (0.01)**2
    C2 = (0.03)**2
    ssim_map = ((2*mu1*mu2 + C1)*(2*sigma12 + C2))/((mu1**2 + mu2**2 + C1)*(sigma1_sq + sigma2_sq + C2))
    ssim_index = torch.mean(ssim_map)

    # Compute the loss
    return 1 - ssim_index

def create_window(window_size, channel, sigma=1.5):
    # Create a 2D Gaussian window
    gauss = torch.Tensor([math.exp(-(x - window_size//2)**2/float(2*sigma**2)) for x in range(window_size)])
    gauss_2d = torch.mm(gauss.unsqueeze(1), gauss.unsqueeze(0))
    window = torch.Tensor(gauss_2d.expand(channel, 1, window_size, window_size).contiguous())

    # Normalize the window
    window = window / window.sum()

    return window

希望对你有帮助！