How to prepare different input size in CNN

Question

I'm doing a research about personality identification based on their signature using CNN method, however the learning feature for the personality traits have a different input size. I understand that in CNN we have to make the same size for the input, but can I make the input size in different size?

Here is the journal that I use for my references for the learning feature.

Answer 1

You can research "Spatial Pyramid Pooling (SPP)" Btw, as far as I know, you don't need make same size for input for convolutional layer but FCN layer