pytorch ssim损失函数
时间: 2023-07-07 19:31:46 浏览: 132
PyTorch中提供了一个SSIM(结构相似性)损失函数,通过比较两个图像之间的结构相似性来计算它们之间的差异。这个损失函数可以用于评估两个图像的相似程度,通常用于图像重建、图像去噪、图像修复等任务中。
在PyTorch中,可以使用`torchvision.transforms.functional.ssim`函数来计算SSIM损失。以下是一个简单的例子:
``` python
import torch
import torchvision.transforms.functional as TF
# 定义两个图像
img1 = torch.randn(1, 3, 256, 256)
img2 = torch.randn(1, 3, 256, 256)
# 计算SSIM损失
ssim_loss = 1 - TF.ssim(img1, img2, data_range=img2.max() - img2.min(), size_average=True)
print(ssim_loss)
```
在上面的例子中,`img1`和`img2`是两个大小为256×256的随机图像。`data_range`参数用于指定像素值的范围,通常设置为图像像素值的最大值减去最小值。`size_average`参数用于指定是否对每个像素点的SSIM值进行平均。最后,计算出来的SSIM损失值将作为一个浮点数返回。
相关问题
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!
pytorch SSIM loss
在 PyTorch 中,可以使用 PyTorch 的 SSIM 损失函数来计算图像的结构相似性指数。SSIM 损失函数是一种用于测量图像质量的指标,它考虑了图像的亮度、对比度和结构等因素。下面是一个使用 PyTorch SSIM 损失函数的示例代码:
```python
import torch
import torch.nn.functional as F
from math import exp
def gaussian(window_size, sigma):
gauss = torch.Tensor([exp(-(x - window_size//2)**2/float(2*sigma**2)) for x in range(window_size)])
return gauss/gauss.sum()
def create_window(window_size, channel):
_1D_window = gaussian(window_size, 1.5).unsqueeze(1)
_2D_window = _1D_window.mm(_1D_window.t()).float().unsqueeze(0).unsqueeze(0)
window = _2D_window.expand(channel, 1, window_size, window_size).contiguous()
return window
def ssim(img1, img2, window_size=11, window=None, size_average=True, full=False):
_, channel, _, _ = img1.size()
if window is None:
real_size = min(window_size, img1.size()[2])
window = create_window(real_size, channel).to(img1.device)
mu1 = F.conv2d(img1, window, padding=real_size//2, groups=channel)
mu2 = F.conv2d(img2, window, padding=real_size//2, groups=channel)
mu1_sq = mu1.pow(2)
mu2_sq = mu2.pow(2)
mu1_mu2 = mu1 * mu2
sigma1_sq = F.conv2d(img1 * img1, window, padding=real_size//2, groups=channel) - mu1_sq
sigma2_sq = F.conv2d(img2 * img2, window, padding=real_size//2, groups=channel) - mu2_sq
sigma12 = F.conv2d(img1 * img2, window, padding=real_size//2, groups=channel) - mu1_mu2
C1 = (0.01) ** 2
C2 = (0.03) ** 2
ssim_map = ((2 * mu1_mu2 + C1) * (2 * sigma12 + C2)) / ((mu1_sq + mu2_sq + C1) * (sigma1_sq + sigma2_sq + C2))
if size_average:
ret = ssim_map.mean()
else:
ret = ssim_map.mean(1).mean(1).mean(1)
if full:
return ret, ssim_map
return ret
```
在上面的代码中,`ssim()` 函数接受两个输入图像 `img1` 和 `img2`,并返回它们的 SSIM 相似度。函数中使用了高斯滤波器来计算图像的均值和方差,以及结构相似性指数。如果需要返回 SSIM 相似度图,则可以将 `full` 参数设置为 `True`。