diff --git a/poppler/Gfx.cc b/poppler/Gfx.cc
index 827bbed..11bd780 100644
--- a/poppler/Gfx.cc
+++ b/poppler/Gfx.cc
@@ -4580,6 +4580,68 @@ void Gfx::doImage(Object *ref, Stream *str, GBool inlineImg) {
   error(errSyntaxError, getPos(), "Bad image parameters");
 }
 
+GBool Gfx::checkTransparencyGroup(Dict *resDict) {
+  // check the effect of compositing objects as a group:
+  // look for ExtGState entries with ca != 1 or CA != 1 or BM != normal
+  Object extGStates;
+  GBool transpGroup = gFalse;
+  double opac;
+
+  if (resDict == NULL)
+    return gFalse;
+  pushResources(resDict);
+  resDict->lookup("ExtGState", &extGStates);
+  if (extGStates.isDict()) {
+    Dict *dict = extGStates.getDict();
+    for (int i = 0; i < dict->getLength() && !transpGroup; i++) {
+      Object obj1, obj2;
+      GfxBlendMode mode;
+
+      if (res->lookupGState(dict->getKey(i), &obj1)) {
+        if (!obj1.dictLookup("BM", &obj2)->isNull()) {
+          if (state->parseBlendMode(&obj2, &mode)) {
+            if (mode != gfxBlendNormal)
+              transpGroup = gTrue;
+          } else {
+            error(errSyntaxError, getPos(), "Invalid blend mode in ExtGState");
+          }
+        }
+        obj2.free();
+        if (obj1.dictLookup("ca", &obj2)->isNum()) {
+          opac = obj2.getNum();
+          opac = opac < 0 ? 0 : opac > 1 ? 1 : opac;
+          if (opac != 1)
+            transpGroup = gTrue;
+        }
+        obj2.free();
+        if (obj1.dictLookup("CA", &obj2)->isNum()) {
+          opac = obj2.getNum();
+          opac = opac < 0 ? 0 : opac > 1 ? 1 : opac;
+          if (opac != 1)
+            transpGroup = gTrue;
+        }
+        obj2.free();
+        // alpha is shape
+        if (!transpGroup && obj1.dictLookup("AIS", &obj2)->isBool()) {
+          transpGroup = obj2.getBool();
+        }
+        obj2.free();
+        // soft mask
+        if (!transpGroup && !obj1.dictLookup("SMask", &obj2)->isNull()) {
+          if (!obj2.isName("None")) {
+            transpGroup = gTrue;
+          }
+        }
+        obj2.free();
+      }
+      obj1.free();
+    }
+  }
+  extGStates.free();
+  popResources();
+  return transpGroup;
+}
+
 void Gfx::doForm(Object *str) {
   Dict *dict;
   GBool transpGroup, isolated, knockout;
@@ -4666,7 +4728,6 @@ void Gfx::doForm(Object *str) {
   blendingColorSpace = NULL;
   if (dict->lookup("Group", &obj1)->isDict()) {
     if (obj1.dictLookup("S", &obj2)->isName("Transparency")) {
-      transpGroup = gTrue;
       if (!obj1.dictLookup("CS", &obj3)->isNull()) {
 	blendingColorSpace = GfxColorSpace::parse(&obj3, this);
       }
@@ -4679,6 +4740,7 @@ void Gfx::doForm(Object *str) {
 	knockout = obj3.getBool();
       }
       obj3.free();
+      transpGroup = isolated || out->checkTransparencyGroup(state, knockout) || checkTransparencyGroup(resDict);
     }
     obj2.free();
   }
diff --git a/poppler/Gfx.h b/poppler/Gfx.h
index 689d362..23253bb 100644
--- a/poppler/Gfx.h
+++ b/poppler/Gfx.h
@@ -181,6 +181,8 @@ public:
   // Get the current graphics state object.
   GfxState *getState() { return state; }
 
+  GBool checkTransparencyGroup(Dict *resDict);
+
   void drawForm(Object *str, Dict *resDict, double *matrix, double *bbox,
 	       GBool transpGroup = gFalse, GBool softMask = gFalse,
 	       GfxColorSpace *blendingColorSpace = NULL,
diff --git a/poppler/GfxState.cc b/poppler/GfxState.cc
index 5962fcb..e274b9f 100644
--- a/poppler/GfxState.cc
+++ b/poppler/GfxState.cc
@@ -5609,6 +5609,8 @@ GfxState::GfxState(double hDPIA, double vDPIA, PDFRectangle *pageBox,
   lineCap = 0;
   miterLimit = 10;
   strokeAdjust = gFalse;
+  alphaIsShape = gFalse;
+  textKnockout = gFalse;
 
   font = NULL;
   fontSize = 0;
diff --git a/poppler/OutputDev.h b/poppler/OutputDev.h
index 803d922..5e96d72 100644
--- a/poppler/OutputDev.h
+++ b/poppler/OutputDev.h
@@ -300,6 +300,7 @@ public:
   virtual GooHash *endProfile();
 
   //----- transparency groups and soft masks
+  virtual GBool checkTransparencyGroup(GfxState * /*state*/, GBool /*knockout*/) { return gTrue; }
   virtual void beginTransparencyGroup(GfxState * /*state*/, double * /*bbox*/,
 				      GfxColorSpace * /*blendingColorSpace*/,
 				      GBool /*isolated*/, GBool /*knockout*/,
diff --git a/poppler/SplashOutputDev.cc b/poppler/SplashOutputDev.cc
index ce666b9..be35c25 100644
--- a/poppler/SplashOutputDev.cc
+++ b/poppler/SplashOutputDev.cc
@@ -3517,6 +3517,17 @@ void SplashOutputDev::drawSoftMaskedImage(GfxState *state, Object *ref,
   str->close();
 }
 
+GBool SplashOutputDev::checkTransparencyGroup(GfxState *state, GBool knockout) {
+  if (state->getFillOpacity() != 1 || 
+    state->getStrokeOpacity() != 1 ||
+    state->getAlphaIsShape() ||
+    state->getBlendMode() != gfxBlendNormal ||
+    splash->getSoftMask() != NULL ||
+    knockout) 
+    return gTrue;
+  return transpGroupStack != NULL && transpGroupStack->shape != NULL;
+}
+
 void SplashOutputDev::beginTransparencyGroup(GfxState *state, double *bbox,
 					     GfxColorSpace *blendingColorSpace,
 					     GBool isolated, GBool knockout,
diff --git a/poppler/SplashOutputDev.h b/poppler/SplashOutputDev.h
index b70ec38..f1c87ec 100644
--- a/poppler/SplashOutputDev.h
+++ b/poppler/SplashOutputDev.h
@@ -292,6 +292,7 @@ public:
 		       double llx, double lly, double urx, double ury);
 
   //----- transparency groups and soft masks
+  virtual GBool checkTransparencyGroup(GfxState *state, GBool knockout);
   virtual void beginTransparencyGroup(GfxState *state, double *bbox,
 				      GfxColorSpace *blendingColorSpace,
 				      GBool isolated, GBool knockout,