import torch
import torch.nn as nn

class RotationInvariantNet(nn.Module):
    """轻量级旋转不变特征提取网络"""
    def __init__(self, input_channels=1, num_features=64):
        super().__init__()
        self.cnn = nn.Sequential(
            # 基础卷积层
            nn.Conv2d(input_channels, 32, kernel_size=3, padding=1),
            nn.ReLU(),
            nn.MaxPool2d(2),                     # 下采样
            nn.Conv2d(32, 64, kernel_size=3, padding=1),
            nn.ReLU(),
            nn.AdaptiveAvgPool2d((1,1))          # 全局池化获取全局特征
        )
        
    def forward(self, x):
        features = self.cnn(x)
        return torch.flatten(features, 1)         # 展平为特征向量
    
def get_rotational_features(model, input_image):
    """计算输入图像所有旋转角度的特征平均值"""
    rotations = [0, 90, 180, 270]
    features_list = []
    for angle in rotations:
        rotated_img = torch.rot90(input_image, k=angle//90, dims=[2,3])
        feat = model(rotated_img.unsqueeze(0))
        features_list.append(feat)
    return torch.mean(torch.stack(features_list), dim=0).detach().numpy()