getTextSize calculates the size of a box that contains
 the specified text string, the tight box surrounding it, and the baseline.
Arguments
- text
 A character string representing the text to be drawn.
- font_face
 A character string representing the font type of the text (default: "simplex"). See notes for a list of available font types.
- font_scale
 A numeric value representing the scale factor by which the font-specific base size is multiplied (default: 1).
- italic
 A logical specifying whether the text should italicized (default: FALSE).
- thickness
 A numeric value representing the thickness in pixels of the line (default: 1).
Author
Simon Garnier, garnier@njit.edu