From a139d2b36da39fbfb018ef6973e9316a64a4ca6c Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Fri, 1 Jan 2021 07:31:54 -0500
Subject: Add several methods for working with form XObjects (fixes #436)

Make some more methods in QPDFPageObjectHelper work with form
XObjects, provide forEach methods to walk through nested form
XObjects, possibly recursively. This should make it easier to work
with form XObjects from user code.
---
 libqpdf/QPDFPageObjectHelper.cc | 108 ++++++++++++++++++++++++++++++----------
 1 file changed, 83 insertions(+), 25 deletions(-)

(limited to 'libqpdf/QPDFPageObjectHelper.cc')

diff --git a/libqpdf/QPDFPageObjectHelper.cc b/libqpdf/QPDFPageObjectHelper.cc
index ce244253..ef563dc2 100644
--- a/libqpdf/QPDFPageObjectHelper.cc
+++ b/libqpdf/QPDFPageObjectHelper.cc
@@ -386,6 +386,73 @@ QPDFPageObjectHelper::getMediaBox(bool copy_if_shared)
     return getAttribute("/MediaBox", copy_if_shared);
 }
 
+void
+QPDFPageObjectHelper::forEachXObject(
+    bool recursive,
+    std::function<void(QPDFObjectHandle& obj,
+                       QPDFObjectHandle& xobj_dict,
+                       std::string const& key)> action,
+    std::function<bool(QPDFObjectHandle)> selector)
+{
+    QTC::TC("qpdf", "QPDFPageObjectHelper::forEachXObject",
+            recursive
+            ? (this->oh.isFormXObject() ? 0 : 1)
+            : (this->oh.isFormXObject() ? 2 : 3));
+    std::set<QPDFObjGen> seen;
+    std::list<QPDFPageObjectHelper> queue;
+    queue.push_back(*this);
+    while (! queue.empty())
+    {
+        QPDFPageObjectHelper ph = queue.front();
+        queue.pop_front();
+        QPDFObjGen og = ph.oh.getObjGen();
+        if (seen.count(og))
+        {
+            continue;
+        }
+        seen.insert(og);
+        QPDFObjectHandle resources = ph.getAttribute("/Resources", false);
+        if (resources.isDictionary() && resources.hasKey("/XObject"))
+        {
+            QPDFObjectHandle xobj_dict = resources.getKey("/XObject");
+            for (auto const& key: xobj_dict.getKeys())
+            {
+                QPDFObjectHandle obj = xobj_dict.getKey(key);
+                if ((! selector) || selector(obj))
+                {
+                    action(obj, xobj_dict, key);
+                }
+                if (recursive && obj.isFormXObject())
+                {
+                    queue.push_back(QPDFPageObjectHelper(obj));
+                }
+            }
+	}
+    }
+}
+
+void
+QPDFPageObjectHelper::forEachImage(
+    bool recursive,
+    std::function<void(QPDFObjectHandle& obj,
+                       QPDFObjectHandle& xobj_dict,
+                       std::string const& key)> action)
+{
+    forEachXObject(recursive, action,
+                   [](QPDFObjectHandle obj) { return obj.isImage(); });
+}
+
+void
+QPDFPageObjectHelper::forEachFormXObject(
+    bool recursive,
+    std::function<void(QPDFObjectHandle& obj,
+                       QPDFObjectHandle& xobj_dict,
+                       std::string const& key)> action)
+{
+    forEachXObject(recursive, action,
+                   [](QPDFObjectHandle obj) { return obj.isFormXObject(); });
+}
+
 std::map<std::string, QPDFObjectHandle>
 QPDFPageObjectHelper::getPageImages()
 {
@@ -396,32 +463,23 @@ std::map<std::string, QPDFObjectHandle>
 QPDFPageObjectHelper::getImages()
 {
     std::map<std::string, QPDFObjectHandle> result;
-    QPDFObjectHandle resources = getAttribute("/Resources", false);
-    if (resources.isDictionary())
-    {
-	if (resources.hasKey("/XObject"))
-	{
-	    QPDFObjectHandle xobject = resources.getKey("/XObject");
-	    std::set<std::string> keys = xobject.getKeys();
-	    for (std::set<std::string>::iterator iter = keys.begin();
-		 iter != keys.end(); ++iter)
-	    {
-		std::string key = (*iter);
-		QPDFObjectHandle value = xobject.getKey(key);
-		if (value.isStream())
-		{
-		    QPDFObjectHandle dict = value.getDict();
-		    if (dict.hasKey("/Subtype") &&
-			(dict.getKey("/Subtype").getName() == "/Image") &&
-			(! dict.hasKey("/ImageMask")))
-		    {
-			result[key] = value;
-		    }
-		}
-	    }
-	}
-    }
+    forEachImage(false, [&result](QPDFObjectHandle& obj,
+                                  QPDFObjectHandle&,
+                                  std::string const& key) {
+        result[key] = obj;
+    });
+    return result;
+}
 
+std::map<std::string, QPDFObjectHandle>
+QPDFPageObjectHelper::getFormXObjects()
+{
+    std::map<std::string, QPDFObjectHandle> result;
+    forEachFormXObject(false, [&result](QPDFObjectHandle& obj,
+                                        QPDFObjectHandle&,
+                                        std::string const& key) {
+        result[key] = obj;
+    });
     return result;
 }
 
-- 
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