What are the recommended ways to change shape of feature maps channel wise other than using Convolutional neural networks?

Question

Suppose I have a feature map with size $C_1 \times H \times W$. And I need to convert it into a feature map of size $C_2 \times H \times W$.

One way to do this is to use convolutional neural networks as Conv2d($C_1, C_2$)

I want to know whether there are any other ways in Literature to perform the desired operation?