I am desperatly searching for an app or tool or software solution to create a density plot in kinds of a heat map (see example). I want to depict frequencies of answers (better mappings) of patients in a graphical question (body scheme). These answers are provided on paper - thus there are two problems: an aquisitional (input) and a graphical (output).

My conception would be a tool which can import the picture pattern (body scheme). Thereafter for data aquisiton I want to click on (previously defined) area(s) where the patients put their cross(es) - For the output, the tool shall provide a dataset with the coordinates or areas and their frequencies depicted as color shades right over the picture pattern.