Coordinates are an array containing 8 integers, in the format [x1, y1, x2, y2, x3, y3, x4, y4] Representing the coordinates of four vertices of a quadrilateral, arranged clockwise. Namely:
  • Top-left: (x1, y1)
  • Top-right: (x2, y2)
  • Bottom-right: (x3, y3)
  • Bottom-left: (x4, y4)
Coordinate values are absolute pixel values. The coordinate system is as follows: 
Image coordinate system (origin at top-left corner)
┌────────────width───────────> x
│(0,0)
│
│
│      (x1,y1) ────────── (x2,y2)
│         │                     │     
height             Text area        
│         │                     │
│      (x4,y4) ────────── (x3,y3)
│
v
y