How to analyze the colors of a photo taken with a photographic camera of an iron-deficient plant leaf? Is there a program to upload photos for analysis?
There's open-source software made to analyze photos. And will work well for your question.. - Named Image-J and available from the NIH in US at this link : https://imagej.nih.gov/ij/download.html
As open source, many people have added tools for analysis in a variety of fields. Be sure to look at the contents of the above link for those and some documentation and other filters and scripts.