@KT_Wakabayashi welcome to the knime forum. You could indeed process one image at a time. You could list them and then process them in loops.
I often like to use the Table Row to variable loop start node to do things in iterations (Write multiple CSV file to a loop - #2 by mlauber71)
Maybe also interesting:
KNIME’s Flow Control Guide KNIME Flow Control Guide
@armingrudd articles about loops and flow variables How to include file CSV Writer in a loop? - #2 by armingrudd