I need to convert Rs/Ro ratios of my MQ-4 sensor to PPM. For that I found the sensitivity plot in the datasheet (https://www.sparkfun.com/datasheets/Sensors/Biometric/MQ-4.pdf). However that is a pdf and an image in it. How can I get the raw values out to get a precise fit function? Is there any standard way of doing that, or do I simply need to use a look&feel approach or fiddle around by counting pixels?
Thanks!