I only bought my Adobe suite 2 months ago; and only through curiosity have I discovered that Adobe Illustrator has the capacity to translate an image into lights and darks. I still make my lights analysis the old-fashioned way, with my eyes; but Adobe Illustrator can certainly simplify the process–especially until you understand what you are looking for.
This is how you can use Adobe Illustrator to create the image above. You may save my original leaves photograph to your pictures folder. Open the Adobe Illustrator Program. Go to Window [along the upper edge of your screen] – From the drop-down menu, select Image Trace – When the Image Trace Panel appears, Select: Low Fidelity Photo – Click Trace; and the image above magically appears.
“Ahhhhh! Technology is the Artist’s Friend.” – Jacki Kellum
I have used Adobe Illustrator Cs6. I cannot attest to how this works on earlier versions of Illustrator.