HOW can i get the coordinate data from an airfoil graphics?
You can obtain all the geometric data from the name itself.
The airofoil name 63-621 was given. .The NACA 63621 profile describes an airfoil with design lift coefficient of 0.9 (0.15*6), the point of maximum camber located at 15% chord (5*3), reflex camber, and maximum thickness of 21% of chord length (21).
Other details are irrelevant
visit http://airfoiltools.com/airfoil/naca5digit for more information.
According to 5 digit nomenclature
The first digit, when multiplied by 0.15, gives lift coefficient.
The second digit, when multiplied by 5, gives the relative position, as a percentage, of the point of maximum camber along the chord from the leading edge.
The third digit indicates whether the camber is simple or reflex.
The fourth and fifth digits give the maximum thickness of the airfoil (as a percentage of the chord), the same as 4-digit NACA profiles.