Add QPDFObjectHandle::isFormXObject

ChangeLog

@@ -1,3 +1,8 @@
+2020-12-31  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add QPDFObjectHandle::isFormXObject to test whether an object is
+	a form XObject.
+
 2020-12-30  Jay Berkenbilt  <ejb@ql.org>
 
 	* Add QPDFPageObjectHelper::flattenRotation and --flatten-rotation

include/qpdf/QPDFObjectHandle.hh

@@ -1147,6 +1147,9 @@ class QPDFObjectHandle
     QPDF_DLL
     void assertPageObject();
 
+    QPDF_DLL
+    bool isFormXObject();
+
   private:
     QPDFObjectHandle(QPDF*, int objid, int generation);
     QPDFObjectHandle(QPDFObject*);

libqpdf/QPDFObjectHandle.cc

@@ -2962,6 +2962,20 @@ QPDFObjectHandle::isPagesObject()
     return (this->isDictionary() && this->hasKey("/Kids"));
 }
 
+bool
+QPDFObjectHandle::isFormXObject()
+{
+    if (! this->isStream())
+    {
+        return false;
+    }
+    QPDFObjectHandle dict = this->getDict();
+    return (dict.getKey("/Type").isName() &&
+            ("/XObject" == dict.getKey("/Type").getName()) &&
+            dict.getKey("/Subtype").isName() &&
+            ("/Form" == dict.getKey("/Subtype").getName()));
+}
+
 void
 QPDFObjectHandle::assertPageObject()
 {

libqpdf/QPDFPageObjectHelper.cc

@@ -565,11 +565,7 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper(
                 dict.removeKey(*k_iter);
             }
             QPDFObjectHandle resource = dict.getKey(*k_iter);
-            if (resource.isStream() &&
-                resource.getDict().getKey("/Type").isName() &&
-                ("/XObject" == resource.getDict().getKey("/Type").getName()) &&
-                resource.getDict().getKey("/Subtype").isName() &&
-                ("/Form" == resource.getDict().getKey("/Subtype").getName()))
+            if (resource.isFormXObject())
             {
                 QTC::TC("qpdf", "QPDFPageObjectHelper filter form xobject");
                 removeUnreferencedResourcesHelper(