why did you make /drawpic's Nth icon and Mth frames 0 based index ?
Ah, grasshopper, you are asking a "why" question, about a feature implemented long ago. There is no way to know. To find the answer, we would need to time-travel through 30 years of development history and take note of the different times that $pic()/drawpic/etc. were added/updated/extended. I am going to take a punt and say it probably seemed like a jolly good idea at the time :-)
