From c520bf9ff5d55220b2c4d3ef6142775ddf838fa1 Mon Sep 17 00:00:00 2001
From: John Whitington <john@coherentgraphics.co.uk>
Date: Mon, 20 Nov 2023 16:12:33 +0200
Subject: [PATCH] -chop coming along

---
 cpdfchop.ml | 33 +++++++++++++++++++++------------
 1 file changed, 21 insertions(+), 12 deletions(-)

diff --git a/cpdfchop.ml b/cpdfchop.ml
index f73b21d..0611d0f 100644
--- a/cpdfchop.ml
+++ b/cpdfchop.ml
@@ -6,24 +6,33 @@ open Cpdferror
 
 (* Chop a single page into pieces. We prefer the cropbox when available. We set
    mediabox only, and delete any other boxes. *)
-(* FIXME check non-zero based boxes *)
-(* FIXME erase boxes *)
-(* FIXME Get mediabox / cropbox properly *)
-(* FIXME Check rotated pages just work *)
 (* FIXME btt / rtl *)
-let chop_boxes x y p =
+let get_box pdf page =
+  match Pdf.lookup_direct pdf "/CropBox" page.Pdfpage.rest with
+  | Some r -> Pdf.parse_rectangle pdf r
+  | None -> Pdf.parse_rectangle pdf page.Pdfpage.mediabox
+
+let erase_boxes d =
+  let f = Pdf.remove_dict_entry in
+    f (f (f (f d "/CropBox") "/BleedBox") "/TrimBox") "/ArtBox"
+
+let chop_boxes pdf x y p =
   if x < 1 || y < 1 then Cpdferror.error "chop_boxes bad specification" else
-    let move_page p w h dx dy =
-      (*Printf.printf "move_page %f %f\n" dx dy;*)
-      let nminx, nminy, nmaxx, nmaxy = (0. +. dx, 0. +. dy, w +. dx, h +. dy) in
-        {p with Pdfpage.mediabox = Pdf.Array [Pdf.Real nminx; Pdf.Real nminy; Pdf.Real nmaxx; Pdf.Real nmaxy]}
+    let move_page mx my p w h dx dy =
+      (*Printf.printf "move_page by %f %f\n" dx dy;*)
+      let nminx, nminy, nmaxx, nmaxy = (mx +. dx, my +. dy, mx +. w +. dx, my +. h +. dy) in
+        (*Printf.printf "new box: %f, %f, %f, %f\n" nminx nminy nmaxx nmaxy;*)
+        {p with
+          Pdfpage.mediabox = Pdf.Array [Pdf.Real nminx; Pdf.Real nminy; Pdf.Real nmaxx; Pdf.Real nmaxy];
+          Pdfpage.rest = erase_boxes p.Pdfpage.rest}
     in
-    let minx, miny, maxx, maxy = 0., 0., 540., 666. in
+    let minx, miny, maxx, maxy = get_box pdf p in
+    (*Printf.printf "minx, miny, maxx, maxy = %f, %f, %f, %f\n" minx miny maxx maxy;*)
     let w, h = (maxx -. minx) /. float_of_int x, (maxy -. miny) /. float_of_int y in
     let ps = ref [] in
       for ty = y - 1 downto 0 do
         for tx = 0 to x - 1 do
-          ps =| move_page p w h (w *. float_of_int tx) (h *. float_of_int ty)
+          ps =| move_page minx miny p w h (w *. float_of_int tx) (h *. float_of_int ty)
         done
       done;
       rev !ps
@@ -34,7 +43,7 @@ let chop ~x ~y pdf range =
   let pages =
     flatten
       (map2
-        (fun n p -> if mem n range then (chop_boxes x y p) else [p])
+        (fun n p -> if mem n range then (chop_boxes pdf x y p) else [p])
         (ilist 1 (Pdfpage.endpage pdf))
         pages)
   in