make CalcMaskShift a verifiable operation

and check it on untrusted data

Change-Id: I7c97a27d70f91b9686adf9dcb8b68c5aa25c2b4c
Reviewed-on: https://gerrit.libreoffice.org/18637
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

8 files changed, 250 insertions, 72 deletions

diff --git a/include/vcl/salbtype.hxx b/include/vcl/salbtype.hxx
index eb3b6d30e6f8..82ae03646a11 100644
--- a/include/vcl/salbtype.hxx
+++ b/include/vcl/salbtype.hxx
@@ -187,29 +187,29 @@ struct VCL_DLLPUBLIC ColorMaskElement
     int                     mnShift;
     int                     mnOrShift;
     sal_uInt8               mnOr;
-    ColorMaskElement(sal_uInt32 nMask)
+    explicit ColorMaskElement(sal_uInt32 nMask = 0)
         : mnMask(nMask)
         , mnShift(0)
         , mnOrShift(0)
         , mnOr(0)
     {
     }
-    static bool CalcMaskShift(ColorMaskElement &rElem)
+    bool CalcMaskShift()
     {
-        if (rElem.mnMask == 0)
+        if (mnMask == 0)
             return true;
 
         // from which bit starts the mask?
         int nShift = 31;
 
-        while( nShift >= 0 && !( rElem.mnMask & ( 1 << nShift ) ) )
+        while( nShift >= 0 && !( mnMask & ( 1 << nShift ) ) )
             --nShift;
 
-        rElem.mnShift = nShift - 7;
+        mnShift = nShift - 7;
         int nLen = 0;
 
         // XXX determine number of bits set => walk right until null
-        while( nShift >= 0 && ( rElem.mnMask & ( 1 << nShift ) ) )
+        while( nShift >= 0 && ( mnMask & ( 1 << nShift ) ) )
         {
             nShift--;
             nLen++;
@@ -218,8 +218,8 @@ struct VCL_DLLPUBLIC ColorMaskElement
         if (nLen > 8) // mask length must be 8 bits or less
             return false;
 
-        rElem.mnOrShift = 8 - nLen;
-        rElem.mnOr = static_cast<sal_uInt8>( ( 0xFF >> nLen ) << rElem.mnOrShift );
+        mnOrShift = 8 - nLen;
+        mnOr = static_cast<sal_uInt8>( ( 0xFF >> nLen ) << mnOrShift );
 
         return true;
     }
@@ -235,11 +235,18 @@ class VCL_DLLPUBLIC ColorMask
 
 public:
 
-    inline              ColorMask( sal_uInt32 nRedMask = 0,
-                                   sal_uInt32 nGreenMask = 0,
-                                   sal_uInt32 nBlueMask = 0,
-                                   sal_uInt32 nAlphaChannel = 0 );
-    inline              ~ColorMask() {}
+    ColorMask(const ColorMaskElement& rRedMask = ColorMaskElement(),
+              const ColorMaskElement& rGreenMask = ColorMaskElement(),
+              const ColorMaskElement& rBlueMask = ColorMaskElement(),
+              sal_uInt32 nAlphaChannel = 0)
+        : maR(rRedMask)
+        , maG(rGreenMask)
+        , maB(rBlueMask)
+        , mnAlphaChannel(nAlphaChannel)
+    {
+    }
+
+    ~ColorMask() {}
 
     inline sal_uInt32   GetRedMask() const;
     inline sal_uInt32   GetGreenMask() const;
@@ -599,20 +606,6 @@ inline sal_uInt16 BitmapPalette::GetBestIndex( const BitmapColor& rCol ) const
     return nRetIndex;
 }
 
-inline ColorMask::ColorMask( sal_uInt32 nRedMask,
-                             sal_uInt32 nGreenMask,
-                             sal_uInt32 nBlueMask,
-                             sal_uInt32 nAlphaChannel )
-    : maR(nRedMask)
-    , maG(nGreenMask)
-    , maB(nBlueMask)
-    , mnAlphaChannel(nAlphaChannel)
-{
-    ColorMaskElement::CalcMaskShift(maR);
-    ColorMaskElement::CalcMaskShift(maG);
-    ColorMaskElement::CalcMaskShift(maB);
-}
-
 inline sal_uInt32 ColorMask::GetRedMask() const
 {
     return maR.mnMask;
diff --git a/vcl/headless/svpbmp.cxx b/vcl/headless/svpbmp.cxx
index 3231043a882f..30f6a56323fa 100644
--- a/vcl/headless/svpbmp.cxx
+++ b/vcl/headless/svpbmp.cxx
@@ -172,65 +172,130 @@ BitmapBuffer* SvpSalBitmap::AcquireBuffer( BitmapAccessMode )
                 pBuf->mnFormat = BMP_FORMAT_8BIT_PAL;
                 break;
             case Format::SixteenBitLsbTcMask:
+            {
                 nBitCount = 16;
                 pBuf->mnFormat = BMP_FORMAT_16BIT_TC_LSB_MASK;
-                pBuf->maColorMask = ColorMask( 0xf800, 0x07e0, 0x001f );
+                ColorMaskElement aRedMask(0xf800);
+                aRedMask.CalcMaskShift();
+                ColorMaskElement aGreenMask(0x07e0);
+                aGreenMask.CalcMaskShift();
+                ColorMaskElement aBlueMask(0x001f);
+                aBlueMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
                 break;
+            }
             case Format::SixteenBitMsbTcMask:
+            {
                 nBitCount = 16;
                 pBuf->mnFormat = BMP_FORMAT_16BIT_TC_MSB_MASK;
-                pBuf->maColorMask = ColorMask( 0xf800, 0x07e0, 0x001f );
+                ColorMaskElement aRedMask(0xf800);
+                aRedMask.CalcMaskShift();
+                ColorMaskElement aGreenMask(0x07e0);
+                aGreenMask.CalcMaskShift();
+                ColorMaskElement aBlueMask(0x001f);
+                aBlueMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
                 break;
+            }
             case Format::TwentyFourBitTcMask:
                 nBitCount = 24;
                 pBuf->mnFormat = BMP_FORMAT_24BIT_TC_BGR;
                 break;
             case Format::ThirtyTwoBitTcMaskBGRX:
+            {
                 nBitCount = 32;
                 pBuf->mnFormat = BMP_FORMAT_32BIT_TC_MASK;
 #ifdef OSL_BIGENDIAN
-                pBuf->maColorMask = ColorMask( 0x0000ff00, 0x00ff0000, 0xff000000 );
+                ColorMaskElement aRedMask(0x0000ff00);
+                ColorMaskElement aGreenMask(0x00ff0000);
+                ColorMaskElement aBlueMask(0xff000000);
 #else
-                pBuf->maColorMask = ColorMask( 0x00ff0000, 0x0000ff00, 0x000000ff );
+                ColorMaskElement aRedMask(0x00ff0000);
+                ColorMaskElement aGreenMask(0x0000ff00);
+                ColorMaskElement aBlueMask(0x000000ff);
 #endif
+                aBlueMask.CalcMaskShift();
+                aRedMask.CalcMaskShift();
+                aGreenMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
                 break;
+            }
             case Format::ThirtyTwoBitTcMaskBGRA:
+            {
                 nBitCount = 32;
                 pBuf->mnFormat = BMP_FORMAT_32BIT_TC_MASK;
 #ifdef OSL_BIGENDIAN
-                pBuf->maColorMask = ColorMask( 0x0000ff00, 0x00ff0000, 0xff000000, 0x000000ff );
+                ColorMaskElement aRedMask(0x0000ff00);
+                ColorMaskElement aGreenMask(0x00ff0000);
+                ColorMaskElement aBlueMask(0xff000000);
 #else
-                pBuf->maColorMask = ColorMask( 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000 );
+                ColorMaskElement aRedMask(0x00ff0000);
+                ColorMaskElement aGreenMask(0x0000ff00);
+                ColorMaskElement aBlueMask(0x000000ff);
 #endif
+                aBlueMask.CalcMaskShift();
+                aRedMask.CalcMaskShift();
+                aGreenMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask, 0xff000000);
                 break;
+            }
             case Format::ThirtyTwoBitTcMaskARGB:
+            {
                 nBitCount = 32;
                 pBuf->mnFormat = BMP_FORMAT_32BIT_TC_MASK;
 #ifdef OSL_BIGENDIAN
-                pBuf->maColorMask = ColorMask( 0x00ff0000, 0x0000ff00, 0x000000ff, 0xff000000 );
+                ColorMaskElement aRedMask(0x00ff0000);
+                ColorMaskElement aGreenMask(0x0000ff00);
+                ColorMaskElement aBlueMask(0x000000ff);
 #else
-                pBuf->maColorMask = ColorMask( 0x0000ff00, 0x00ff0000, 0xff000000, 0x000000ff );
+                ColorMaskElement aRedMask(0x0000ff00);
+                ColorMaskElement aGreenMask(0x00ff0000);
+                ColorMaskElement aBlueMask(0xff000000);
 #endif
+                aBlueMask.CalcMaskShift();
+                aRedMask.CalcMaskShift();
+                aGreenMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask, 0xff000000 );
                 break;
+            }
             case Format::ThirtyTwoBitTcMaskABGR:
+            {
                 nBitCount = 32;
                 pBuf->mnFormat = BMP_FORMAT_32BIT_TC_MASK;
 #ifdef OSL_BIGENDIAN
-                pBuf->maColorMask = ColorMask( 0x000000ff, 0x0000ff00, 0x00ff0000, 0xff000000 );
+                ColorMaskElement aRedMask(0x000000ff);
+                ColorMaskElement aGreenMask(0x0000ff00);
+                ColorMaskElement aBlueMask(0x00ff0000);
 #else
-                pBuf->maColorMask = ColorMask( 0xff000000, 0x00ff0000, 0x0000ff00, 0x000000ff );
+                ColorMaskElement aRedMask(0xff000000);
+                ColorMaskElement aGreenMask(0x00ff0000);
+                ColorMaskElement aBlueMask(0x0000ff00);
 #endif
+                aBlueMask.CalcMaskShift();
+                aRedMask.CalcMaskShift();
+                aGreenMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask, 0xff000000);
                 break;
+            }
             case Format::ThirtyTwoBitTcMaskRGBA:
+            {
                 nBitCount = 32;
                 pBuf->mnFormat = BMP_FORMAT_32BIT_TC_MASK;
 #ifdef OSL_BIGENDIAN
-                pBuf->maColorMask = ColorMask( 0xff000000, 0x00ff0000, 0x0000ff00, 0x000000ff );
+                ColorMaskElement aRedMask(0xff000000);
+                ColorMaskElement aGreenMask(0x00ff0000);
+                ColorMaskElement aBlueMask(0x0000ff00);
 #else
-                pBuf->maColorMask = ColorMask( 0x000000ff, 0x0000ff00, 0x00ff0000, 0xff000000 );
+                ColorMaskElement aRedMask(0x000000ff);
+                ColorMaskElement aGreenMask(0x0000ff00);
+                ColorMaskElement aBlueMask(0x00ff0000);
 #endif
+                aBlueMask.CalcMaskShift();
+                aRedMask.CalcMaskShift();
+                aGreenMask.CalcMaskShift();
+                pBuf->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask, 0x000000ff);
                 break;
-
+            }
             default:
                 // this is an error case !!!!!
                 nBitCount = 1;
diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index 286c4632837a..6144d9a04b2e 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -709,18 +709,44 @@ BitmapBuffer* OpenGLSalBitmap::AcquireBuffer( BitmapAccessMode nMode )
     pBuffer->mnScanlineSize = mnBytesPerRow;
     pBuffer->mpBits = maUserBuffer.get();
     pBuffer->mnBitCount = mnBits;
-    switch( mnBits )
+    switch (mnBits)
     {
-    case 1:     pBuffer->mnFormat = BMP_FORMAT_1BIT_MSB_PAL; break;
-    case 4:     pBuffer->mnFormat = BMP_FORMAT_4BIT_MSN_PAL; break;
-    case 8:     pBuffer->mnFormat = BMP_FORMAT_8BIT_PAL; break;
-    case 16:    pBuffer->mnFormat = BMP_FORMAT_16BIT_TC_MSB_MASK;
-                pBuffer->maColorMask  = ColorMask( 0xf800, 0x07e0, 0x001f );
-                break;
-    case 24:    pBuffer->mnFormat = BMP_FORMAT_24BIT_TC_RGB; break;
-    case 32:    pBuffer->mnFormat = BMP_FORMAT_32BIT_TC_RGBA;
-                pBuffer->maColorMask  = ColorMask( 0xff000000, 0x00ff0000, 0x0000ff00 );
-                break;
+        case 1:
+            pBuffer->mnFormat = BMP_FORMAT_1BIT_MSB_PAL;
+            break;
+        case 4:
+            pBuffer->mnFormat = BMP_FORMAT_4BIT_MSN_PAL;
+            break;
+        case 8:
+            pBuffer->mnFormat = BMP_FORMAT_8BIT_PAL;
+            break;
+        case 16:
+        {
+            pBuffer->mnFormat = BMP_FORMAT_16BIT_TC_MSB_MASK;
+            ColorMaskElement aRedMask(0xf800);
+            aRedMask.CalcMaskShift();
+            ColorMaskElement aGreenMask(0x07e0);
+            aGreenMask.CalcMaskShift();
+            ColorMaskElement aBlueMask(0x001f);
+            aBlueMask.CalcMaskShift();
+            pBuffer->maColorMask  = ColorMask(aRedMask, aGreenMask, aBlueMask);
+            break;
+        }
+        case 24:
+            pBuffer->mnFormat = BMP_FORMAT_24BIT_TC_RGB;
+            break;
+        case 32:
+        {
+            pBuffer->mnFormat = BMP_FORMAT_32BIT_TC_RGBA;
+            ColorMaskElement aRedMask(0xff000000);
+            aRedMask.CalcMaskShift();
+            ColorMaskElement aGreenMask(0x00ff0000);
+            aGreenMask.CalcMaskShift();
+            ColorMaskElement aBlueMask(0x0000ff00);
+            aBlueMask.CalcMaskShift();
+            pBuffer->maColorMask  = ColorMask(aRedMask, aGreenMask, aBlueMask);
+            break;
+        }
     }
 
     return pBuffer;
diff --git a/vcl/qa/cppunit/graphicfilter/data/bmp/pass/crash-1.bmp b/vcl/qa/cppunit/graphicfilter/data/bmp/pass/crash-1.bmp
new file mode 100644
index 000000000000..84b6c35c87e6
--- /dev/null
+++ b/vcl/qa/cppunit/graphicfilter/data/bmp/pass/crash-1.bmp
diff --git a/vcl/quartz/salbmp.cxx b/vcl/quartz/salbmp.cxx
index 8463d06b0bf5..6699e8038308 100644
--- a/vcl/quartz/salbmp.cxx
+++ b/vcl/quartz/salbmp.cxx
@@ -759,16 +759,42 @@ BitmapBuffer* QuartzSalBitmap::AcquireBuffer( BitmapAccessMode /*nMode*/ )
     pBuffer->mnBitCount = mnBits;
     switch( mnBits )
     {
-    case 1:     pBuffer->mnFormat = BMP_FORMAT_1BIT_MSB_PAL; break;
-    case 4:     pBuffer->mnFormat = BMP_FORMAT_4BIT_MSN_PAL; break;
-    case 8:     pBuffer->mnFormat = BMP_FORMAT_8BIT_PAL; break;
-    case 16:    pBuffer->mnFormat = BMP_FORMAT_16BIT_TC_MSB_MASK;
-                pBuffer->maColorMask  = ColorMask( k16BitRedColorMask, k16BitGreenColorMask, k16BitBlueColorMask );
-                break;
-    case 24:    pBuffer->mnFormat = BMP_FORMAT_24BIT_TC_BGR; break;
-    case 32:    pBuffer->mnFormat = BMP_FORMAT_32BIT_TC_ARGB;
-                pBuffer->maColorMask  = ColorMask( k32BitRedColorMask, k32BitGreenColorMask, k32BitBlueColorMask );
-                break;
+        case 1:
+            pBuffer->mnFormat = BMP_FORMAT_1BIT_MSB_PAL;
+            break;
+        case 4:
+            pBuffer->mnFormat = BMP_FORMAT_4BIT_MSN_PAL;
+            break;
+        case 8:
+            pBuffer->mnFormat = BMP_FORMAT_8BIT_PAL;
+            break;
+        case 16:
+        {
+            pBuffer->mnFormat = BMP_FORMAT_16BIT_TC_MSB_MASK;
+            ColorMaskElement aRedMask(k16BitRedColorMask);
+            aRedMask.CalcMaskShift();
+            ColorMaskElement aGreenMask(k16BitGreenColorMask);
+            aGreenMask.CalcMaskShift();
+            ColorMaskElement aBlueMask(k16BitBlueColorMask);
+            aBlueMask.CalcMaskShift();
+            pBuffer->maColorMask  = ColorMask(aRedMask, aGreenMask, aBlueMask);
+            break;
+        }
+        case 24:
+            pBuffer->mnFormat = BMP_FORMAT_24BIT_TC_BGR;
+            break;
+        case 32:
+        {
+            pBuffer->mnFormat = BMP_FORMAT_32BIT_TC_ARGB;
+            ColorMaskElement aRedMask(k32BitRedColorMask);
+            aRedMask.CalcMaskShift();
+            ColorMaskElement aGreenMask(k32BitGreenColorMask);
+            aGreenMask.CalcMaskShift();
+            ColorMaskElement aBlueMask(k32BitBlueColorMask);
+            aBlueMask.CalcMaskShift();
+            pBuffer->maColorMask  = ColorMask(aRedMask, aGreenMask, aBlueMask);
+            break;
+        }
     }
     pBuffer->mnFormat |= BMP_FORMAT_BOTTOM_UP;
 
diff --git a/vcl/source/gdi/dibtools.cxx b/vcl/source/gdi/dibtools.cxx
index d597ee15d1b9..bbd2658059fd 100644
--- a/vcl/source/gdi/dibtools.cxx
+++ b/vcl/source/gdi/dibtools.cxx
@@ -596,7 +596,17 @@ bool ImplReadDIBBits(SvStream& rIStm, DIBV5Header& rHeader, BitmapWriteAccess& r
 
                 case( 16 ):
                 {
-                    ColorMask   aMask( nRMask, nGMask, nBMask );
+                    ColorMaskElement aRedMask(nRMask);
+                    if (!aRedMask.CalcMaskShift())
+                        return false;
+                    ColorMaskElement aGreenMask(nGMask);
+                    if (!aGreenMask.CalcMaskShift())
+                        return false;
+                    ColorMaskElement aBlueMask(nBMask);
+                    if (!aBlueMask.CalcMaskShift())
+                        return false;
+
+                    ColorMask   aMask(aRedMask, aGreenMask, aBlueMask);
                     BitmapColor aColor;
                     sal_uInt16*     pTmp16;
 
@@ -643,7 +653,17 @@ bool ImplReadDIBBits(SvStream& rIStm, DIBV5Header& rHeader, BitmapWriteAccess& r
 
                 case( 32 ):
                 {
-                    ColorMask aMask(nRMask, nGMask, nBMask);
+                    ColorMaskElement aRedMask(nRMask);
+                    if (!aRedMask.CalcMaskShift())
+                        return false;
+                    ColorMaskElement aGreenMask(nGMask);
+                    if (!aGreenMask.CalcMaskShift())
+                        return false;
+                    ColorMaskElement aBlueMask(nBMask);
+                    if (!aBlueMask.CalcMaskShift())
+                        return false;
+                    ColorMask aMask(aRedMask, aGreenMask, aBlueMask);
+
                     BitmapColor aColor;
                     sal_uInt32* pTmp32;
 
diff --git a/vcl/unx/generic/gdi/salbmp.cxx b/vcl/unx/generic/gdi/salbmp.cxx
index c6c156b2c29b..82044492904f 100644
--- a/vcl/unx/generic/gdi/salbmp.cxx
+++ b/vcl/unx/generic/gdi/salbmp.cxx
@@ -154,14 +154,30 @@ BitmapBuffer* X11SalBitmap::ImplCreateDIB(
                 case( 8 ): pDIB->mnFormat |= BMP_FORMAT_8BIT_PAL; break;
 #ifdef OSL_BIGENDIAN
                 case(16 ):
+                {
                     pDIB->mnFormat|= BMP_FORMAT_16BIT_TC_MSB_MASK;
-                    pDIB->maColorMask = ColorMask( 0xf800, 0x07e0, 0x001f );
+                    ColorMaskElement aRedMask(0xf800);
+                    aRedMask.CalcMaskShift();
+                    ColorMaskElement aGreenMask(0x07e0);
+                    aGreenMask.CalcMaskShift();
+                    ColorMaskElement aBlueMask(0x001f);
+                    aBlueMask.CalcMaskShift();
+                    pDIB->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
                     break;
+                }
 #else
                 case(16 ):
+                {
                     pDIB->mnFormat|= BMP_FORMAT_16BIT_TC_LSB_MASK;
-                    pDIB->maColorMask = ColorMask( 0xf800, 0x07e0, 0x001f );
+                    ColorMaskElement aRedMask(0xf800);
+                    aRedMask.CalcMaskShift();
+                    ColorMaskElement aGreenMask(0x07e0);
+                    aGreenMask.CalcMaskShift();
+                    ColorMaskElement aBlueMask(0x001f);
+                    aBlueMask.CalcMaskShift();
+                    pDIB->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
                     break;
+                }
 #endif
                 default:
                     nBitCount = 24;
@@ -274,7 +290,13 @@ BitmapBuffer* X11SalBitmap::ImplCreateDIB(
 
                 case( 16 ):
                 {
-                    aSrcBuf.maColorMask = ColorMask( pImage->red_mask, pImage->green_mask, pImage->blue_mask );
+                    ColorMaskElement aRedMask(pImage->red_mask);
+                    aRedMask.CalcMaskShift();
+                    ColorMaskElement aGreenMask(pImage->green_mask);
+                    aGreenMask.CalcMaskShift();
+                    ColorMaskElement aBlueMask(pImage->blue_mask);
+                    aBlueMask.CalcMaskShift();
+                    aSrcBuf.maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
 
                     if( LSBFirst == pImage->byte_order )
                     {
@@ -444,7 +466,13 @@ XImage* X11SalBitmap::ImplCreateXImage(
 
                     #endif
 
-                    xMask.reset(new ColorMask( pImage->red_mask, pImage->green_mask, pImage->blue_mask ));
+                    ColorMaskElement aRedMask(pImage->red_mask);
+                    aRedMask.CalcMaskShift();
+                    ColorMaskElement aGreenMask(pImage->green_mask);
+                    aGreenMask.CalcMaskShift();
+                    ColorMaskElement aBlueMask(pImage->blue_mask);
+                    aBlueMask.CalcMaskShift();
+                    xMask.reset(new ColorMask(aRedMask, aGreenMask, aBlueMask));
                 }
                 break;
 
diff --git a/vcl/win/source/gdi/salbmp.cxx b/vcl/win/source/gdi/salbmp.cxx
index 014700570d45..eeaa1cd49aec 100644
--- a/vcl/win/source/gdi/salbmp.cxx
+++ b/vcl/win/source/gdi/salbmp.cxx
@@ -906,14 +906,34 @@ BitmapBuffer* WinSalBitmap::AcquireBuffer( BitmapAccessMode /*nMode*/ )
                     if( pBIH->biCompression == BI_BITFIELDS )
                     {
                         nOffset = 3 * sizeof( RGBQUAD );
-                        pBuffer->maColorMask = ColorMask( *(UINT32*) &pBI->bmiColors[ 0 ],
-                                                          *(UINT32*) &pBI->bmiColors[ 1 ],
-                                                          *(UINT32*) &pBI->bmiColors[ 2 ] );
+                        ColorMaskElement aRedMask(*(UINT32*) &pBI->bmiColors[ 0 ]);
+                        aRedMask.CalcMaskShift();
+                        ColorMaskElement aGreenMask(*(UINT32*) &pBI->bmiColors[ 1 ]);
+                        aGreenMask.CalcMaskShift();
+                        ColorMaskElement aBlueMask(*(UINT32*) &pBI->bmiColors[ 2 ]);
+                        aBlueMask.CalcMaskShift();
+                        pBuffer->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
                     }
                     else if( pBIH->biBitCount == 16 )
-                        pBuffer->maColorMask = ColorMask( 0x00007c00UL, 0x000003e0UL, 0x0000001fUL );
+                    {
+                        ColorMaskElement aRedMask(0x00007c00UL);
+                        aRedMask.CalcMaskShift();
+                        ColorMaskElement aGreenMask(0x000003e0UL);
+                        aGreenMask.CalcMaskShift();
+                        ColorMaskElement aBlueMask(0x0000001fUL);
+                        aBlueMask.CalcMaskShift();
+                        pBuffer->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
+                    }
                     else
-                        pBuffer->maColorMask = ColorMask( 0x00ff0000UL, 0x0000ff00UL, 0x000000ffUL );
+                    {
+                        ColorMaskElement aRedMask(0x00ff0000UL);
+                        aRedMask.CalcMaskShift();
+                        ColorMaskElement aGreenMask(0x0000ff00UL);
+                        aGreenMask.CalcMaskShift();
+                        ColorMaskElement aBlueMask(0x000000ffUL);
+                        aBlueMask.CalcMaskShift();
+                        pBuffer->maColorMask = ColorMask(aRedMask, aGreenMask, aBlueMask);
+                    }
 
                     pBuffer->mpBits = (PBYTE) pBI + *(DWORD*) pBI + nOffset;
                 }