How to assign to each layer used for be randomnly assembled, game stats that will be used for calculate final image stats in json?

as a beginner I look for a way to assign game stats to png layers that I use for randomly generate final character. I know how to generate image , I know how to assign to the final image extra attributes, but those values are randomly return and it is not what I would like. I would like on each layer randomly assembled in .png I assign specific game stats and skills and when the final image will be generated, be able to return a json file of the character with the final stats and skills with calculation of each stats build done.I have look for on net and not find yet relevant answer.Thks