could you tell me how to rotate the text to any angle I like ?

See the documentation for  $image->stringFT( fgcolor, fontname, ptsize, angle, x, y, string ) ...

The arguments are as follows:
  fgcolor    Color index to draw the string in
  fontname   A path to the TrueType (.ttf) font file or a font pattern
+.
  ptsize     The desired point size (may be fractional)
  angle      The rotation angle, in radians (positive values rotate co
+unter clockwise)
  x,y        X and Y coordinates to start drawing the string
  string     The string itself

If successful, the method returns an eight-element list giving the bou
+ndaries of the rendered string:
 @bounds[0,1]  Lower left corner (x,y)
 @bounds[2,3]  Lower right corner (x,y)
 @bounds[4,5]  Upper right corner (x,y)
 @bounds[6,7]  Upper left corner (x,y)
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