diff --git a/poppler/SplashOutputDev.cc b/poppler/SplashOutputDev.cc
index 0e956c7..e80bcd2 100644
--- a/poppler/SplashOutputDev.cc
+++ b/poppler/SplashOutputDev.cc
@@ -1145,6 +1145,10 @@ struct SplashTransparencyGroup {
   GfxColorSpace *blendingColorSpace;
   GBool isolated;
 
+  //----- for knockout
+  GBool knockedout;
+  SplashBitmap *shape;
+
   //----- saved state
   SplashBitmap *origBitmap;
   Splash *origSplash;
@@ -3585,6 +3589,8 @@ void SplashOutputDev::beginTransparencyGroup(GfxState *state, double *bbox,
   transpGroup->ty = ty;
   transpGroup->blendingColorSpace = blendingColorSpace;
   transpGroup->isolated = isolated;
+  transpGroup->shape = (knockout) ? SplashBitmap::copy(bitmap) : NULL;
+  transpGroup->knockedout = gFalse; 
   transpGroup->next = transpGroupStack;
   transpGroupStack = transpGroup;
 
@@ -3637,8 +3643,10 @@ void SplashOutputDev::beginTransparencyGroup(GfxState *state, double *bbox,
     if (colorMode == splashModeXBGR8) color[3] = 255;
     splash->clear(color, 0);
   } else {
+    SplashBitmap *shape = (knockout) ? transpGroup->shape : (transpGroup->next != NULL && transpGroup->next->shape != NULL) ?
+      transpGroup->next->shape : transpGroup->origBitmap;
     splash->blitTransparent(transpGroup->origBitmap, tx, ty, 0, 0, w, h);
-    splash->setInNonIsolatedGroup(transpGroup->origBitmap, tx, ty);
+    splash->setInNonIsolatedGroup(shape, tx, ty);
   }
   transpGroup->tBitmap = bitmap;
   state->shiftCTM(-tx, -ty);
@@ -3672,14 +3680,22 @@ void SplashOutputDev::paintTransparencyGroup(GfxState *state, double *bbox) {
   // - the clip path was set in the parent's state)
   if (tx < bitmap->getWidth() && ty < bitmap->getHeight()) {
     splash->setOverprintMask(0xffffffff, gFalse);
-    splash->composite(tBitmap, 0, 0, tx, ty,
+    if (transpGroupStack->next != NULL && transpGroupStack->next->knockedout) {
+      splash->blitTransparent(tBitmap, 0, 0, tx, ty,
+		      tBitmap->getWidth(), tBitmap->getHeight(), gFalse);
+    } else {
+      if (transpGroupStack->next != NULL && transpGroupStack->next->shape != NULL)
+        transpGroupStack->next->knockedout = gTrue;
+      splash->composite(tBitmap, 0, 0, tx, ty,
 		      tBitmap->getWidth(), tBitmap->getHeight(),
 		      gFalse, !isolated);
+    }
   }
-
   // pop the stack
   transpGroup = transpGroupStack;
   transpGroupStack = transpGroup->next;
+  if (transpGroup->shape)
+    delete transpGroup->shape;
   delete transpGroup;
 
   delete tBitmap;
diff --git a/splash/Splash.cc b/splash/Splash.cc
index 0e2058c..396e595 100644
--- a/splash/Splash.cc
+++ b/splash/Splash.cc
@@ -5189,9 +5189,9 @@ GBool Splash::gouraudTriangleShadedFill(SplashGouraudColor *shading)
 }
 
 SplashError Splash::blitTransparent(SplashBitmap *src, int xSrc, int ySrc,
-				    int xDest, int yDest, int w, int h) {
+				    int xDest, int yDest, int w, int h, GBool fClearAlpha) {
   SplashColorPtr p, sp;
-  Guchar *q;
+  Guchar *q, *sq;
   int x, y, mask, srcMask;
 
   if (src->mode != bitmap->mode) {
@@ -5275,7 +5275,16 @@ SplashError Splash::blitTransparent(SplashBitmap *src, int xSrc, int ySrc,
   if (bitmap->alpha) {
     for (y = 0; y < h; ++y) {
       q = &bitmap->alpha[(yDest + y) * bitmap->width + xDest];
-      memset(q, 0x00, w);
+      if (fClearAlpha)
+        memset(q, 0x00, w);
+      else {
+        sq = &src->alpha[(ySrc + y) * src->width + xSrc];
+        for (x = 0; x < w; x++) {
+          if (*sq != 0)
+            *q = *sq;
+          q++; sq++;
+        }
+      }
     }
   }
 
diff --git a/splash/Splash.h b/splash/Splash.h
index 53bfa81..3e418cf 100644
--- a/splash/Splash.h
+++ b/splash/Splash.h
@@ -225,7 +225,7 @@ public:
   // this Splash object.  The destination alpha values are all set to
   // zero.
   SplashError blitTransparent(SplashBitmap *src, int xSrc, int ySrc,
-			      int xDest, int yDest, int w, int h);
+			      int xDest, int yDest, int w, int h, GBool fClearAlpha = gTrue);
 
   //----- misc
 
diff --git a/splash/SplashBitmap.cc b/splash/SplashBitmap.cc
index ab5176e..db86d9d 100644
--- a/splash/SplashBitmap.cc
+++ b/splash/SplashBitmap.cc
@@ -111,6 +111,25 @@ SplashBitmap::SplashBitmap(int widthA, int heightA, int rowPadA,
   }
 }
 
+SplashBitmap *SplashBitmap::copy(SplashBitmap *src) {
+  SplashBitmap *result = new SplashBitmap(src->getWidth(), src->getHeight(), src->getRowPad(), 
+    src->getMode(), src->getAlphaPtr() != NULL, src->getRowSize() >= 0);
+  Guchar *dataSource = src->getDataPtr();
+  Guchar *dataDest = result->getDataPtr();
+  int amount = src->getRowSize();
+  if (amount < 0) {
+    dataSource = dataSource + (src->getHeight() - 1) * amount;
+    dataDest = dataDest + (src->getHeight() - 1) * amount;
+    amount *= -src->getHeight();
+  } else {
+    amount *= src->getHeight();
+  }
+  memcpy(dataDest, dataSource, amount);
+  if (src->getAlphaPtr() != NULL)
+    memcpy(result->getAlphaPtr(), src->getAlphaPtr(), src->getWidth() * src->getHeight());
+  return result;
+}
+
 SplashBitmap::~SplashBitmap() {
   if (data) {
     if (rowSize < 0) {
diff --git a/splash/SplashBitmap.h b/splash/SplashBitmap.h
index 8bcc941..7fd31a4 100644
--- a/splash/SplashBitmap.h
+++ b/splash/SplashBitmap.h
@@ -51,6 +51,7 @@ public:
   SplashBitmap(int widthA, int heightA, int rowPad,
 	       SplashColorMode modeA, GBool alphaA,
 	       GBool topDown = gTrue);
+  static SplashBitmap *copy(SplashBitmap *src);
 
   ~SplashBitmap();