Add new placeFormXObject that takes a matrix reference

ChangeLog

@@ -1,3 +1,10 @@
+2021-02-22  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add a new version of QPDFPageObjectHelper::placeFormXObject that
+	initializes the transformation matrix that was used so you don't
+	have to call both placeFormXObject and
+	getMatrixForFormXObjectPlacement.
+
 2021-02-21  Jay Berkenbilt  <ejb@ql.org>
 
 	* From qpdf CLI, --overlay and --underlay will copy annotations

include/qpdf/QPDFPageObjectHelper.hh

@@ -309,6 +309,17 @@ class QPDFPageObjectHelper: public QPDFObjectHelper
         bool allow_shrink = true,
         bool allow_expand = false);
 
+    // Alternative version that also fills in the transformation
+    // matrix that was used.
+    QPDF_DLL
+    std::string placeFormXObject(
+        QPDFObjectHandle fo, std::string const& name,
+        QPDFObjectHandle::Rectangle rect,
+        QPDFMatrix& cm,
+        bool invert_transformations = true,
+        bool allow_shrink = true,
+        bool allow_expand = false);
+
     // Return the transformation matrix that translates from the given
     // form XObject's coordinate system into the given rectangular
     // region on the page. The parameters have the same meaning as for

libqpdf/QPDFPageObjectHelper.cc

@@ -1070,7 +1070,22 @@ QPDFPageObjectHelper::placeFormXObject(
     bool invert_transformations,
     bool allow_shrink, bool allow_expand)
 {
-    QPDFMatrix cm = getMatrixForFormXObjectPlacement(
+    QPDFMatrix cm;
+    return placeFormXObject(
+        fo, name, rect, cm, invert_transformations,
+        allow_shrink, allow_expand);
+}
+
+std::string
+QPDFPageObjectHelper::placeFormXObject(
+    QPDFObjectHandle fo, std::string const& name,
+    QPDFObjectHandle::Rectangle rect,
+    QPDFMatrix& cm,
+    bool invert_transformations,
+    bool allow_shrink,
+    bool allow_expand)
+{
+    cm = getMatrixForFormXObjectPlacement(
         fo, rect, invert_transformations, allow_shrink, allow_expand);
     return (
         "q\n" +

qpdf/qpdf.cc

@@ -5191,20 +5191,18 @@ static void do_under_overlay_for_page(
                 pdf.copyForeignObject(
                     from_page.getFormXObjectForPage());
         }
-        auto cm = dest_page.getMatrixForFormXObjectPlacement(
-            fo[from_pageno],
-            dest_page.getTrimBox().getArrayAsRectangle());
-        dest_page.copyAnnotations(
-            from_page, cm, dest_afdh, make_afdh(from_page));
 
         // If the same page is overlaid or underlaid multiple times,
         // we'll generate multiple names for it, but that's harmless
         // and also a pretty goofy case that's not worth coding
         // around.
         std::string name = resources.getUniqueResourceName("/Fx", min_suffix);
+        QPDFMatrix cm;
         std::string new_content = dest_page.placeFormXObject(
             fo[from_pageno], name,
-            dest_page.getTrimBox().getArrayAsRectangle());
+            dest_page.getTrimBox().getArrayAsRectangle(), cm);
+        dest_page.copyAnnotations(
+            from_page, cm, dest_afdh, make_afdh(from_page));
         if (! new_content.empty())
         {
             resources.mergeResources(