A Simple Method for Obtaining Original Data from Published Graphs and Plots

Was thinking of how to extract data points for infant age and weight distribution from a printed graph and I landed at this old paper http://www.ajronline.org/content/174/5/1241.full . it pointed me to NIH Image which reminds me of an old software i used to use for lab practicals as an undergrad .. and upon reaching the NIH Image site, Indeed! imageJ is an 'update' of sorts to the NIH Image software .. 

Experimentation continues...