shape '[-1, 2, 4, 28]' is invalid for input of size 768

I’m trying to train IAM Dataset on TPSSpatialTransformerNetwork but finally I got an error: shape ‘[-1, 2, 4, 28]’ is invalid for input of size 768

Each image in the dataset has the size of (32,128). I can not figure out the shape it got in the error step. And here is the code:

class TPS_SpatialTransformerNetwork(nn.Module):
    def __init__(self):
        super(TPS_SpatialTransformerNetwork, self).__init__()
        self.conv1 = nn.Conv2d(1, 79, kernel_size=5)
        self.conv2 = nn.Conv2d(79, 256, kernel_size=5)
        self.conv2_drop = nn.Dropout2d()
        self.fc1 = nn.Linear(256, 512)
        self.fc2 = nn.Linear(512, 79)

        # Spatial transformer localization-network
        self.localization = nn.Sequential(
            nn.Conv2d(1, 8, kernel_size=7),
            nn.MaxPool2d(2, stride=2),
            nn.ReLU(True),
            nn.Conv2d(8, 79, kernel_size=5),
            nn.MaxPool2d(2, stride=2),
            nn.ReLU(True)
        )

        # Regressor for the 3 * 2 affine matrix
        self.fc_loc = nn.Sequential(
            nn.Linear(79 * 4 * 28, 32),
            nn.ReLU(True),
            nn.Linear(32, 3 * 2)
        )

        # Initialize the weights/bias with identity transformation
        self.fc_loc[2].weight.data.zero_()
        self.fc_loc[2].bias.data.copy_(torch.tensor([1, 0, 0, 0, 1, 0], dtype=torch.float))

    # Spatial transformer network forward function
    def stn(self, x):
        xs = self.localization(x)
        xs = xs.view(-1, 79 * 4 * 28)
        theta = self.fc_loc(xs)
        theta = theta.view(-1, 2, 4,28)


        grid = F.affine_grid(theta, x.size())
        x = F.grid_sample(x, grid)

        return x

    def forward(self, x):
        # transform the input
        x = self.stn(x)

        # Perform the usual forward pass
        x = F.relu(F.max_pool2d(self.conv1(x), 2))
        x = F.relu(F.max_pool2d(self.conv2_drop(self.conv2(x)), 2))
        x = x.view(-1, 320)
        x = F.relu(self.fc1(x))
        x = F.dropout(x, training=self.training)
        x = self.fc2(x)
        return F.log_softmax(x, dim=1)

4 frames
/content/drive/My Drive/OCR/transformation.py in stn(self, x)
     41         xs = xs.view(-1, 79 * 4 * 28)
     42         theta = self.fc_loc(xs)
---> 43         theta = theta.view(-1, 2, 4,28)
     44 
     45 

RuntimeError: shape '[-1, 2, 4, 28]' is invalid for input of size 768