Add JSON annotations function for cpdflib

cpdfannot.ml

@@ -94,6 +94,13 @@ let get_annotations encoding pdf =
         pages
         (ilist 1 (length pages))) 
 
+let get_annotations_json pdf =
+  let module J = Cpdfyojson.Safe in
+  let pages = Pdfpage.pages_of_pagetree pdf in
+  let pagenums = indx pages in
+  let json = `List (flatten (map2 (annotations_json_page pdf) pages pagenums)) in
+    Pdfio.bytes_of_string (J.to_string json)
+
 (* Equalise the page lengths of two PDFs by chopping or extending the first one.
 *)
 let equalise_lengths a b =

cpdfannot.mli

@@ -6,6 +6,9 @@ val list_annotations : json:bool -> Cpdfmetadata.encoding -> Pdf.t -> unit
 (** Return the annotations as a (pagenumber, content) list *)
 val get_annotations : Cpdfmetadata.encoding -> Pdf.t -> (int * string) list
 
+(** Get annotations as JSON *)
+val get_annotations_json : Pdf.t -> Pdfio.bytes
+
 (** Copy the annotations on a given set of pages from a to b. b is returned. *)
 val copy_annotations : int list -> Pdf.t -> Pdf.t -> Pdf.t