From 5f8c53eb149547e4fbeba3da381be4ea9c0b6907 Mon Sep 17 00:00:00 2001
From: John Whitington <john@coherentgraphics.co.uk>
Date: Fri, 22 Mar 2024 15:24:48 +0000
Subject: [PATCH] JPEG2000 embedding

---
 cpdfcommand.ml  |  1 +
 cpdfjpeg2000.ml | 39 +++++++++++++++++++++++++++++++++++++--
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/cpdfcommand.ml b/cpdfcommand.ml
index 76da0c8..fbe2665 100644
--- a/cpdfcommand.ml
+++ b/cpdfcommand.ml
@@ -1063,6 +1063,7 @@ let anon_fun s =
         | a::b::c::'.'::r when implode (map Char.uppercase_ascii [c; b; a]) = "JPG" -> set_input_jpeg s
         | a::b::c::'.'::r when implode (map Char.uppercase_ascii [c; b; a]) = "JP2" -> set_input_jpeg2000 s
         | a::b::c::'.'::r when implode (map Char.uppercase_ascii [c; b; a]) = "JPX" -> set_input_jpeg2000 s
+        | a::b::c::'.'::r when implode (map Char.uppercase_ascii [c; b; a]) = "JPF" -> set_input_jpeg2000 s
         | a::b::c::'.'::r when implode (map Char.uppercase_ascii [c; b; a]) = "PNG" -> set_input_png s
         | _ -> args.inputs <- (InFile s, "all", "", "", ref false, None)::args.inputs
         end;
diff --git a/cpdfjpeg2000.ml b/cpdfjpeg2000.ml
index a27acd1..ac058ed 100644
--- a/cpdfjpeg2000.ml
+++ b/cpdfjpeg2000.ml
@@ -1,5 +1,40 @@
 open Pdfutil
 open Pdfio
+open Cpdferror
 
-(* Return the width and height of a JPEG2000 image. *)
-let jpeg2000_dimensions bs = (28, 30)
+let read_word i =
+  let a = i32ofi (i.input_byte ()) in
+  let b = i32ofi (i.input_byte ()) in
+  let c = i32ofi (i.input_byte ()) in
+  let d = i32ofi (i.input_byte ()) in
+    lor32 (lor32 (lor32 (lsl32 a 24) (lsl32 b 16)) (lsl32 c 8)) d
+
+exception Answer of int * int
+
+let id_IMAGE_HEADER_BOX = 0x69686472l (* ihdr *)
+
+(* Return the width and height of a JPEG2000 (.jp2 or .jpx) image. *)
+let jpeg2000_dimensions_inner bs =
+  let i = Pdfio.input_of_bytes bs in
+  let a = read_word i in
+  let b = read_word i in
+  let c = read_word i in
+    if a <> 0x0000000cl || b <> 0x6a502020l || c <> 0x0d0a870al then
+      Cpdferror.error "bad JPEG2000 header"
+    else
+    while true do
+      let box = read_word i in
+      if box = id_IMAGE_HEADER_BOX then
+        begin
+          let h = read_word i in
+          let w = read_word i in
+          raise (Answer (i32toi w, i32toi h))
+        end;
+      (* Read words starting at each byte until we find ihdr. *)
+      i.seek_in (i.pos_in () - 3)
+    done
+
+let jpeg2000_dimensions bs =
+  try jpeg2000_dimensions_inner bs; (0, 0) with
+  | Answer (w, h) -> (w, h)
+  | Exit -> error "could not determine JPEG2000 dimensions"