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(* This file is part of the tutorial
http://cairo.forge.ocamlcore.org/tutorial/
*)
open Cairo
let () =
let text = "joy" in
let surface = Cairo.Image.create Cairo.Image.ARGB32 ~w:600 ~h:600 in
let cr = Cairo.create surface in
(* Examples are in 1.0 x 1.0 coordinate space *)
Cairo.scale cr 600. 600.;
Cairo.set_font_size cr 0.5;
(* Drawing code goes here *)
Cairo.set_source_rgb cr 0.0 0.0 0.0;
Cairo.select_font_face cr "Georgia" ~weight:Bold;
let ux, uy = Cairo.device_to_user_distance cr 1. 1. in
let px = max ux uy in
let fe = Cairo.font_extents cr in
let te = Cairo.text_extents cr text in
(* The position of the text will be (x, y) *)
let x = 0.5 -. te.x_bearing -. te.width /. 2.
and y = 0.5 -. fe.descent +. fe.baseline /. 2. in
(* baseline, descent, ascent, height (in dashed green) *)
Cairo.set_line_width cr (4. *. px);
Cairo.set_dash cr [| 9. *. px |];
Cairo.set_source_rgba cr 0. 0.6 0. 0.5;
let horizontal_line y =
Cairo.move_to cr (x +. te.x_bearing) y;
Cairo.rel_line_to cr te.width 0. in
horizontal_line y;
horizontal_line (y +. fe.descent);
horizontal_line (y -. fe.ascent);
horizontal_line (y -. fe.baseline);
Cairo.stroke cr;
(* extents: width & height (in dashed blue) *)
Cairo.set_source_rgba cr 0. 0. 0.75 0.5;
Cairo.set_line_width cr px;
Cairo.set_dash cr [| 3. *. px |];
Cairo.rectangle cr (x +. te.x_bearing) (y +. te.y_bearing)
~w:te.width ~h:te.height;
Cairo.stroke cr;
(* text *)
Cairo.move_to cr x y;
Cairo.set_source_rgb cr 0. 0. 0.;
Cairo.show_text cr text;
(* bearing (solid blue line) *)
Cairo.set_dash cr [| |];
Cairo.set_line_width cr (2. *. px);
Cairo.set_source_rgba cr 0. 0. 0.75 0.5;
Cairo.move_to cr x y;
Cairo.rel_line_to cr te.x_bearing te.y_bearing;
Cairo.stroke cr;
(* text's advance (blue dot) *)
Cairo.set_source_rgba cr 0. 0. 0.75 0.5;
let two_pi = 8. *. atan 1. in
Cairo.arc cr (x +. te.x_advance) (y +. te.y_advance) ~r:(6. *. px)
~a1:0. ~a2:two_pi;
Cairo.fill cr;
(* reference point (x,y) (red dot) *)
Cairo.arc cr x y ~r:(6. *. px) ~a1:0. ~a2:two_pi;
Cairo.set_source_rgba cr 0.75 0. 0. 0.5;
Cairo.fill cr;
(* Write output *)
Cairo.PNG.write surface "textextents.png"
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