Hands-On Image Processing with Python

FC layer

After the convolutional and pooling layers, generally a couple of FC layers are added to wrap up the CNN architecture. The output of both convolutional and pooling layers are 3D volumes, but an FC layer expects a 1D vector of numbers. So, the output of the final pooling layer needs to be flattened to a vector, and that becomes the input to the FC layer. Flattening is simply arranging the 3D volume of numbers into a 1D vector.