# Can you use fully convolutional networks for binary classification?

I know that fully convolutional networks can be used for image segmentation and similar but I wondered if you could also apply them to simple image classification tasks. And if so, what is the proper way to do it (in pytorch)?

Imagine that we have RGB images of cats and dogs of size 30x30 and the following (demo) networks.

class NormalNetwork(nn.Module):
def __init__(self):
super().__init__()
self.first_layer = nn.Conv2d(3, 1, (3, 3))
self.fc = nn.Linear(784, 2)

def forward(self, x):
x = self.first_layer(x)
x = x.reshape(-1, 784)
return self.fc(x)

class FullyConvolutionalNetwork(nn.Module):
def __init__(self):
super().__init__()
self.layer = nn.Conv2d(3, 2, (30, 30))

def forward(self, x):
x = self.layer(x)
return x.reshape(-1, 2)


Then you could use:

sample_image = torch.rand((10, 3, 30, 30))
normal_network = NormalNetwork()
fully_convolutional_network = FullyConvolutionalNetwork()
ret1 = normal_network(sample_image)
ret2 = fully_convolutional_network(sample_image)


and both of these networks would return a tensor of dimension torch.Size([10, 2]) which can then be fed into a BCELoss or similar. Is this a proper way to do it or is this bad for some reason?