Added support for computing 64-bit checksum of bitmap in OpenGL

Added a C++ and a GLSL implementation of a 64-bit CRC algorithm.

Changed hardcoded checksum value in ooxmlimport unit test (testN777345).

Change-Id: I16bb985a14866775efda49e21fe033ff64645896

14 files changed, 468 insertions, 60 deletions

diff --git a/vcl/Library_vcl.mk b/vcl/Library_vcl.mk
index 306178c4e794..faa8f43c2f50 100644
--- a/vcl/Library_vcl.mk
+++ b/vcl/Library_vcl.mk
@@ -318,6 +318,7 @@ $(eval $(call gb_Library_add_exception_objects,vcl,\
     vcl/source/bitmap/bitmapscalesuper \
     vcl/source/bitmap/BitmapSymmetryCheck \
     vcl/source/bitmap/BitmapFilterStackBlur \
+    vcl/source/bitmap/checksum \
     vcl/source/helper/canvasbitmap \
     vcl/source/helper/canvastools \
     vcl/source/helper/evntpost \
diff --git a/vcl/Package_opengl.mk b/vcl/Package_opengl.mk
index 2628dcd5d0bb..df3520c8483f 100644
--- a/vcl/Package_opengl.mk
+++ b/vcl/Package_opengl.mk
@@ -10,6 +10,7 @@
 $(eval $(call gb_Package_Package,vcl_opengl_shader,$(SRCDIR)/vcl/opengl))
 
 $(eval $(call gb_Package_add_files,vcl_opengl_shader,$(LIBO_ETC_FOLDER)/opengl,\
+    areaHashCRC64TFragmentShader.glsl \
 	areaScaleFastFragmentShader.glsl \
 	areaScaleFragmentShader.glsl \
 	blendedTextureFragmentShader.glsl \
diff --git a/vcl/inc/checksum.hxx b/vcl/inc/checksum.hxx
new file mode 100644
index 000000000000..ae7c9d6f7ba4
--- /dev/null
+++ b/vcl/inc/checksum.hxx
@@ -0,0 +1,154 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+
+#ifndef INCLUDED_VCL_INC_CHECKSUM_HXX
+#define INCLUDED_VCL_INC_CHECKSUM_HXX
+
+#include <sal/config.h>
+
+#include <sal/saldllapi.h>
+#include <sal/types.h>
+
+/*========================================================================
+ *
+ * vcl_crc64Table (CRC polynomial 0x95AC9329AC4BC9B5ULL).
+ *
+ *======================================================================*/
+static const sal_uInt64 vcl_crc64Table[256] = {
+  0x0000000000000000ULL, 0x7ad870c830358979ULL, 0xf5b0e190606b12f2ULL,
+  0x8f689158505e9b8bULL, 0xc038e5739841b68fULL, 0xbae095bba8743ff6ULL,
+  0x358804e3f82aa47dULL, 0x4f50742bc81f2d04ULL, 0xab28ecb46814fe75ULL,
+  0xd1f09c7c5821770cULL, 0x5e980d24087fec87ULL, 0x24407dec384a65feULL,
+  0x6b1009c7f05548faULL, 0x11c8790fc060c183ULL, 0x9ea0e857903e5a08ULL,
+  0xe478989fa00bd371ULL, 0x7d08ff3b88be6f81ULL, 0x07d08ff3b88be6f8ULL,
+  0x88b81eabe8d57d73ULL, 0xf2606e63d8e0f40aULL, 0xbd301a4810ffd90eULL,
+  0xc7e86a8020ca5077ULL, 0x4880fbd87094cbfcULL, 0x32588b1040a14285ULL,
+  0xd620138fe0aa91f4ULL, 0xacf86347d09f188dULL, 0x2390f21f80c18306ULL,
+  0x594882d7b0f40a7fULL, 0x1618f6fc78eb277bULL, 0x6cc0863448deae02ULL,
+  0xe3a8176c18803589ULL, 0x997067a428b5bcf0ULL, 0xfa11fe77117cdf02ULL,
+  0x80c98ebf2149567bULL, 0x0fa11fe77117cdf0ULL, 0x75796f2f41224489ULL,
+  0x3a291b04893d698dULL, 0x40f16bccb908e0f4ULL, 0xcf99fa94e9567b7fULL,
+  0xb5418a5cd963f206ULL, 0x513912c379682177ULL, 0x2be1620b495da80eULL,
+  0xa489f35319033385ULL, 0xde51839b2936bafcULL, 0x9101f7b0e12997f8ULL,
+  0xebd98778d11c1e81ULL, 0x64b116208142850aULL, 0x1e6966e8b1770c73ULL,
+  0x8719014c99c2b083ULL, 0xfdc17184a9f739faULL, 0x72a9e0dcf9a9a271ULL,
+  0x08719014c99c2b08ULL, 0x4721e43f0183060cULL, 0x3df994f731b68f75ULL,
+  0xb29105af61e814feULL, 0xc849756751dd9d87ULL, 0x2c31edf8f1d64ef6ULL,
+  0x56e99d30c1e3c78fULL, 0xd9810c6891bd5c04ULL, 0xa3597ca0a188d57dULL,
+  0xec09088b6997f879ULL, 0x96d1784359a27100ULL, 0x19b9e91b09fcea8bULL,
+  0x636199d339c963f2ULL, 0xdf7adabd7a6e2d6fULL, 0xa5a2aa754a5ba416ULL,
+  0x2aca3b2d1a053f9dULL, 0x50124be52a30b6e4ULL, 0x1f423fcee22f9be0ULL,
+  0x659a4f06d21a1299ULL, 0xeaf2de5e82448912ULL, 0x902aae96b271006bULL,
+  0x74523609127ad31aULL, 0x0e8a46c1224f5a63ULL, 0x81e2d7997211c1e8ULL,
+  0xfb3aa75142244891ULL, 0xb46ad37a8a3b6595ULL, 0xceb2a3b2ba0eececULL,
+  0x41da32eaea507767ULL, 0x3b024222da65fe1eULL, 0xa2722586f2d042eeULL,
+  0xd8aa554ec2e5cb97ULL, 0x57c2c41692bb501cULL, 0x2d1ab4dea28ed965ULL,
+  0x624ac0f56a91f461ULL, 0x1892b03d5aa47d18ULL, 0x97fa21650afae693ULL,
+  0xed2251ad3acf6feaULL, 0x095ac9329ac4bc9bULL, 0x7382b9faaaf135e2ULL,
+  0xfcea28a2faafae69ULL, 0x8632586aca9a2710ULL, 0xc9622c4102850a14ULL,
+  0xb3ba5c8932b0836dULL, 0x3cd2cdd162ee18e6ULL, 0x460abd1952db919fULL,
+  0x256b24ca6b12f26dULL, 0x5fb354025b277b14ULL, 0xd0dbc55a0b79e09fULL,
+  0xaa03b5923b4c69e6ULL, 0xe553c1b9f35344e2ULL, 0x9f8bb171c366cd9bULL,
+  0x10e3202993385610ULL, 0x6a3b50e1a30ddf69ULL, 0x8e43c87e03060c18ULL,
+  0xf49bb8b633338561ULL, 0x7bf329ee636d1eeaULL, 0x012b592653589793ULL,
+  0x4e7b2d0d9b47ba97ULL, 0x34a35dc5ab7233eeULL, 0xbbcbcc9dfb2ca865ULL,
+  0xc113bc55cb19211cULL, 0x5863dbf1e3ac9decULL, 0x22bbab39d3991495ULL,
+  0xadd33a6183c78f1eULL, 0xd70b4aa9b3f20667ULL, 0x985b3e827bed2b63ULL,
+  0xe2834e4a4bd8a21aULL, 0x6debdf121b863991ULL, 0x1733afda2bb3b0e8ULL,
+  0xf34b37458bb86399ULL, 0x8993478dbb8deae0ULL, 0x06fbd6d5ebd3716bULL,
+  0x7c23a61ddbe6f812ULL, 0x3373d23613f9d516ULL, 0x49aba2fe23cc5c6fULL,
+  0xc6c333a67392c7e4ULL, 0xbc1b436e43a74e9dULL, 0x95ac9329ac4bc9b5ULL,
+  0xef74e3e19c7e40ccULL, 0x601c72b9cc20db47ULL, 0x1ac40271fc15523eULL,
+  0x5594765a340a7f3aULL, 0x2f4c0692043ff643ULL, 0xa02497ca54616dc8ULL,
+  0xdafce7026454e4b1ULL, 0x3e847f9dc45f37c0ULL, 0x445c0f55f46abeb9ULL,
+  0xcb349e0da4342532ULL, 0xb1eceec59401ac4bULL, 0xfebc9aee5c1e814fULL,
+  0x8464ea266c2b0836ULL, 0x0b0c7b7e3c7593bdULL, 0x71d40bb60c401ac4ULL,
+  0xe8a46c1224f5a634ULL, 0x927c1cda14c02f4dULL, 0x1d148d82449eb4c6ULL,
+  0x67ccfd4a74ab3dbfULL, 0x289c8961bcb410bbULL, 0x5244f9a98c8199c2ULL,
+  0xdd2c68f1dcdf0249ULL, 0xa7f41839ecea8b30ULL, 0x438c80a64ce15841ULL,
+  0x3954f06e7cd4d138ULL, 0xb63c61362c8a4ab3ULL, 0xcce411fe1cbfc3caULL,
+  0x83b465d5d4a0eeceULL, 0xf96c151de49567b7ULL, 0x76048445b4cbfc3cULL,
+  0x0cdcf48d84fe7545ULL, 0x6fbd6d5ebd3716b7ULL, 0x15651d968d029fceULL,
+  0x9a0d8ccedd5c0445ULL, 0xe0d5fc06ed698d3cULL, 0xaf85882d2576a038ULL,
+  0xd55df8e515432941ULL, 0x5a3569bd451db2caULL, 0x20ed197575283bb3ULL,
+  0xc49581ead523e8c2ULL, 0xbe4df122e51661bbULL, 0x3125607ab548fa30ULL,
+  0x4bfd10b2857d7349ULL, 0x04ad64994d625e4dULL, 0x7e7514517d57d734ULL,
+  0xf11d85092d094cbfULL, 0x8bc5f5c11d3cc5c6ULL, 0x12b5926535897936ULL,
+  0x686de2ad05bcf04fULL, 0xe70573f555e26bc4ULL, 0x9ddd033d65d7e2bdULL,
+  0xd28d7716adc8cfb9ULL, 0xa85507de9dfd46c0ULL, 0x273d9686cda3dd4bULL,
+  0x5de5e64efd965432ULL, 0xb99d7ed15d9d8743ULL, 0xc3450e196da80e3aULL,
+  0x4c2d9f413df695b1ULL, 0x36f5ef890dc31cc8ULL, 0x79a59ba2c5dc31ccULL,
+  0x037deb6af5e9b8b5ULL, 0x8c157a32a5b7233eULL, 0xf6cd0afa9582aa47ULL,
+  0x4ad64994d625e4daULL, 0x300e395ce6106da3ULL, 0xbf66a804b64ef628ULL,
+  0xc5bed8cc867b7f51ULL, 0x8aeeace74e645255ULL, 0xf036dc2f7e51db2cULL,
+  0x7f5e4d772e0f40a7ULL, 0x05863dbf1e3ac9deULL, 0xe1fea520be311aafULL,
+  0x9b26d5e88e0493d6ULL, 0x144e44b0de5a085dULL, 0x6e963478ee6f8124ULL,
+  0x21c640532670ac20ULL, 0x5b1e309b16452559ULL, 0xd476a1c3461bbed2ULL,
+  0xaeaed10b762e37abULL, 0x37deb6af5e9b8b5bULL, 0x4d06c6676eae0222ULL,
+  0xc26e573f3ef099a9ULL, 0xb8b627f70ec510d0ULL, 0xf7e653dcc6da3dd4ULL,
+  0x8d3e2314f6efb4adULL, 0x0256b24ca6b12f26ULL, 0x788ec2849684a65fULL,
+  0x9cf65a1b368f752eULL, 0xe62e2ad306bafc57ULL, 0x6946bb8b56e467dcULL,
+  0x139ecb4366d1eea5ULL, 0x5ccebf68aecec3a1ULL, 0x2616cfa09efb4ad8ULL,
+  0xa97e5ef8cea5d153ULL, 0xd3a62e30fe90582aULL, 0xb0c7b7e3c7593bd8ULL,
+  0xca1fc72bf76cb2a1ULL, 0x45775673a732292aULL, 0x3faf26bb9707a053ULL,
+  0x70ff52905f188d57ULL, 0x0a2722586f2d042eULL, 0x854fb3003f739fa5ULL,
+  0xff97c3c80f4616dcULL, 0x1bef5b57af4dc5adULL, 0x61372b9f9f784cd4ULL,
+  0xee5fbac7cf26d75fULL, 0x9487ca0fff135e26ULL, 0xdbd7be24370c7322ULL,
+  0xa10fceec0739fa5bULL, 0x2e675fb4576761d0ULL, 0x54bf2f7c6752e8a9ULL,
+  0xcdcf48d84fe75459ULL, 0xb71738107fd2dd20ULL, 0x387fa9482f8c46abULL,
+  0x42a7d9801fb9cfd2ULL, 0x0df7adabd7a6e2d6ULL, 0x772fdd63e7936bafULL,
+  0xf8474c3bb7cdf024ULL, 0x829f3cf387f8795dULL, 0x66e7a46c27f3aa2cULL,
+  0x1c3fd4a417c62355ULL, 0x935745fc4798b8deULL, 0xe98f353477ad31a7ULL,
+  0xa6df411fbfb21ca3ULL, 0xdc0731d78f8795daULL, 0x536fa08fdfd90e51ULL,
+  0x29b7d047efec8728ULL
+};
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*========================================================================
+ *
+ * vcl_crc64 interface.
+ *
+ *======================================================================*/
+/** Evaluate CRC64 over given data.
+
+    This function evaluates the CRC polynomial 0xEDB88320.
+
+    @param  Crc    [in] CRC64 over previous data or zero.
+    @param  Data   [in] data buffer.
+    @param  DatLen [in] data buffer length.
+    @return new CRC64 value.
+ */
+SAL_DLLPUBLIC sal_uInt64 SAL_CALL vcl_crc64 (
+    sal_uInt64  Crc,
+    const void *Data, sal_uInt32 DatLen
+)   SAL_THROW_EXTERN_C();
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif // INCLUDED_VCL_INC_CHECKSUM_HXX
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/inc/impbmp.hxx b/vcl/inc/impbmp.hxx
index 412dcecda242..9dd483a8a7f1 100644
--- a/vcl/inc/impbmp.hxx
+++ b/vcl/inc/impbmp.hxx
@@ -40,7 +40,6 @@ class ImpBitmap
 {
 private:
     sal_uLong           mnRefCount;
-    sal_uInt32          mnChecksum;
     SalBitmap*          mpSalBitmap;
 
 public:
@@ -51,6 +50,8 @@ public:
                         ImpBitmap(SalBitmap* pBitmap);
                         ~ImpBitmap();
 
+    bool                ImplIsEqual(const ImpBitmap& rBmp) const;
+
     SalBitmap*          ImplGetSalBitmap() const { return mpSalBitmap; }
 
     bool            ImplCreate( const Size& rSize, sal_uInt16 nBitCount, const BitmapPalette& rPal );
@@ -68,8 +69,8 @@ public:
     void                ImplIncRefCount() { mnRefCount++; }
     void                ImplDecRefCount() { mnRefCount--; }
 
-    inline void         ImplSetChecksum( sal_uInt32 nChecksum ) { mnChecksum = nChecksum; }
-    inline sal_uInt32   ImplGetChecksum() const { return mnChecksum; }
+    sal_uLong           ImplGetChecksum() const;
+    void                ImplInvalidateChecksum();
 
     bool                ImplScale( const double& rScaleX, const double& rScaleY, BmpScaleFlag nScaleFlag );
     bool                ImplReplace( const Color& rSearchColor, const Color& rReplaceColor, sal_uLong nTol );
diff --git a/vcl/inc/opengl/program.hxx b/vcl/inc/opengl/program.hxx
index 8289a56de4bf..7bdd43d3d51c 100644
--- a/vcl/inc/opengl/program.hxx
+++ b/vcl/inc/opengl/program.hxx
@@ -76,7 +76,7 @@ public:
 
     void ApplyMatrix(float fWidth, float fHeight, float fPixelOffset = 0.0f);
 
-    bool DrawTexture( OpenGLTexture& rTexture );
+    bool DrawTexture( const OpenGLTexture& rTexture );
 
 protected:
     void SetVertexAttrib( GLuint& rAttrib, const OString& rName, const GLvoid* pData );
diff --git a/vcl/inc/opengl/salbmp.hxx b/vcl/inc/opengl/salbmp.hxx
index 8baee941f1a4..b33d69f6e0e1 100644
--- a/vcl/inc/opengl/salbmp.hxx
+++ b/vcl/inc/opengl/salbmp.hxx
@@ -53,6 +53,9 @@ private:
     std::deque< OpenGLSalBitmapOp* >    maPendingOps;
 
     void makeCurrent();
+    virtual void updateChecksum() const;
+
+    bool calcChecksumGL(OpenGLTexture& rHashTexture, ChecksumType& rHash) const;
 
 public:
     OpenGLSalBitmap();
diff --git a/vcl/inc/salbmp.hxx b/vcl/inc/salbmp.hxx
index 91f69aeb2bdc..268e06cc384c 100644
--- a/vcl/inc/salbmp.hxx
+++ b/vcl/inc/salbmp.hxx
@@ -25,6 +25,8 @@
 #include <vcl/dllapi.h>
 #include <vcl/salbtype.hxx>
 
+#include <checksum.hxx>
+
 #include <com/sun/star/rendering/XBitmapCanvas.hpp>
 
 struct BitmapBuffer;
@@ -37,8 +39,11 @@ enum class BmpScaleFlag;
 class VCL_PLUGIN_PUBLIC SalBitmap
 {
 public:
-    SalBitmap() {}
-    virtual ~SalBitmap();
+
+    typedef sal_uInt64      ChecksumType;
+
+                            SalBitmap() : mbChecksumValid(false) {}
+    virtual                 ~SalBitmap();
 
     virtual bool            Create( const Size& rSize,
                                     sal_uInt16 nBitCount,
@@ -61,6 +66,48 @@ public:
 
     virtual bool            Scale( const double& rScaleX, const double& rScaleY, BmpScaleFlag nScaleFlag ) = 0;
     virtual bool            Replace( const Color& rSearchColor, const Color& rReplaceColor, sal_uLong nTol ) = 0;
+
+
+    virtual bool GetChecksum(ChecksumType& rChecksum) const
+    {
+        updateChecksum();
+        assert(mbChecksumValid);
+        rChecksum = maChecksum;
+        return mbChecksumValid;
+    }
+
+    virtual void InvalidateChecksum()
+    {
+        mbChecksumValid = false;
+    }
+
+protected:
+    ChecksumType           maChecksum;
+    bool               mbChecksumValid;
+
+protected:
+    virtual void updateChecksum() const
+    {
+        if (mbChecksumValid)
+            return;
+
+        ChecksumType nCrc = 0;
+        SalBitmap* pThis = const_cast<SalBitmap*>(this);
+        BitmapBuffer* pBuf = pThis->AcquireBuffer(BITMAP_READ_ACCESS);
+        if (pBuf)
+        {
+            pThis->ReleaseBuffer(pBuf, BITMAP_READ_ACCESS);
+            nCrc = vcl_crc64(0, pBuf->mpBits, pBuf->mnScanlineSize * pBuf->mnHeight);
+            pThis->maChecksum = nCrc;
+            pThis->mbChecksumValid = true;
+        }
+        else
+        {
+            pThis->mbChecksumValid = false;
+        }
+    }
+
+
 };
 
 #endif
diff --git a/vcl/opengl/areaHashCRC64TFragmentShader.glsl b/vcl/opengl/areaHashCRC64TFragmentShader.glsl
new file mode 100644
index 000000000000..901b481d8081
--- /dev/null
+++ b/vcl/opengl/areaHashCRC64TFragmentShader.glsl
@@ -0,0 +1,87 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+/* TODO Use textureOffset for newest version of GLSL */
+
+
+#version 130
+
+uniform sampler2D crc_table;
+uniform sampler2D sampler;
+uniform float xstep;
+uniform float ystep;
+
+varying vec2 tex_coord;
+
+const int scale = 4;
+const float ratio = 16.0;
+
+
+ivec2 crc64( ivec2 hval, int color )
+{
+    int dx = 2 * ((hval[0] ^ color) & 0xff);
+    float s = dx / 255.0;
+    vec4 table_value_lo = round(texture2D( crc_table, vec2( s, 0.0 ) ) * 255.0);
+    s = (dx+1) / 255.0;
+    vec4 table_value_hi = round(texture2D( crc_table, vec2( s, 0.0 ) ) * 255.0);
+
+    int tvalue_lo = int(table_value_lo[0]) | (int(table_value_lo[1]) << 8) | (int(table_value_lo[2]) << 16) | (int(table_value_lo[3]) << 24);
+    int tvalue_hi = int(table_value_hi[0]) | (int(table_value_hi[1]) << 8) | (int(table_value_hi[2]) << 16) | (int(table_value_hi[3]) << 24);
+
+    hval[1] = tvalue_hi ^ (hval[1] >> 8);
+    hval[0] = tvalue_lo ^ ( (hval[1] << 24) | (hval[0] >> 8) );
+
+    return hval;
+}
+
+
+void main(void)
+{
+    ivec2 Crc = ivec2( 0xffffffff, 0xffffffff );
+    vec2 offset = vec2( 0.0, 0.0 );
+    vec2 next_coord = tex_coord.st;
+    for( int y = 0; y < scale && next_coord.y <= 1.0; ++y )
+    {
+        for( int x = 0; x < scale && next_coord.x <= 1.0; ++x )
+        {
+            vec4 pixel = round(texture2D( sampler, next_coord ) * 255.0);
+
+            int r = int(pixel.r); // 0..255
+            int g = int(pixel.g); // 0..255
+            int b = int(pixel.b); // 0..255
+            int a = int(pixel.a); // 0..255
+
+            Crc = crc64( Crc, r );
+            Crc = crc64( Crc, g );
+            Crc = crc64( Crc, b );
+            Crc = crc64( Crc, a );
+
+            offset.x += xstep;
+            next_coord = tex_coord.st + offset;
+        }
+        offset.y += ystep;
+        offset.x = 0.0;
+        next_coord = tex_coord.st + offset;
+    }
+
+    Crc[0] = ~Crc[0];
+    Crc[1] = ~Crc[1];
+
+    int Hash = Crc[0] ^ Crc[1];
+
+    float fr = ( Hash        & 0xff) / 255.0;
+    float fg = ((Hash >> 8)  & 0xff) / 255.0;
+    float fb = ((Hash >> 16) & 0xff) / 255.0;
+    float fa = ((Hash >> 24) & 0xff) / 255.0;
+
+
+     gl_FragColor = vec4(fr, fg, fb, fa);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/opengl/program.cxx b/vcl/opengl/program.cxx
index b1d3cfe8291d..eec4e92bad98 100644
--- a/vcl/opengl/program.cxx
+++ b/vcl/opengl/program.cxx
@@ -276,7 +276,7 @@ void OpenGLProgram::SetBlendMode( GLenum nSFactor, GLenum nDFactor )
     mbBlending = true;
 }
 
-bool OpenGLProgram::DrawTexture( OpenGLTexture& rTexture )
+bool OpenGLProgram::DrawTexture( const OpenGLTexture& rTexture )
 {
     if (!rTexture)
         return false;
diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index d6e51d9bfd72..8ab721e25f6c 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -31,6 +31,7 @@
 #include "opengl/program.hxx"
 #include "opengl/salbmp.hxx"
 
+#include "../inc/checksum.hxx"
 #include "opengl/FixedTextureAtlas.hxx"
 
 namespace
@@ -508,6 +509,94 @@ sal_uInt16 OpenGLSalBitmap::GetBitCount() const
     return mnBits;
 }
 
+bool OpenGLSalBitmap::calcChecksumGL(OpenGLTexture& rInputTexture, ChecksumType& rChecksum) const
+{
+    OUString FragShader("areaHashCRC64TFragmentShader");
+
+    static const OpenGLTexture aCRCTableTexture(512, 1, GL_RGBA, GL_UNSIGNED_BYTE,
+            (sal_uInt8*)(vcl_crc64Table));
+
+    // First Pass
+
+    int nWidth = rInputTexture.GetWidth();
+    int nHeight = rInputTexture.GetHeight();
+
+    OpenGLProgram* pProgram = mpContext->UseProgram("textureVertexShader", FragShader);
+    if (pProgram == 0)
+        return false;
+
+    int nNewWidth = ceil( nWidth / 4.0 );
+    int nNewHeight = ceil( nHeight / 4.0 );
+
+    OpenGLTexture aFirstPassTexture = OpenGLTexture(nNewWidth, nNewHeight);
+    OpenGLFramebuffer* pFramebuffer = mpContext->AcquireFramebuffer(aFirstPassTexture);
+
+    pProgram->SetUniform1f( "xstep", 1.0 / mnWidth );
+    pProgram->SetUniform1f( "ystep", 1.0 / mnHeight );
+
+    pProgram->SetTexture("crc_table", (OpenGLTexture&)(aCRCTableTexture));
+    pProgram->SetTexture("sampler", rInputTexture);
+    pProgram->DrawTexture(rInputTexture);
+    pProgram->Clean();
+
+    OpenGLContext::ReleaseFramebuffer(pFramebuffer);
+
+    CHECK_GL_ERROR();
+
+
+    // Second Pass
+
+    nWidth = aFirstPassTexture.GetWidth();
+    nHeight = aFirstPassTexture.GetHeight();
+
+    pProgram = mpContext->UseProgram("textureVertexShader", FragShader);
+    if (pProgram == 0)
+        return false;
+
+    nNewWidth = ceil( nWidth / 4.0 );
+    nNewHeight = ceil( nHeight / 4.0 );
+
+    OpenGLTexture aSecondPassTexture = OpenGLTexture(nNewWidth, nNewHeight);
+    pFramebuffer = mpContext->AcquireFramebuffer(aSecondPassTexture);
+
+    pProgram->SetUniform1f( "xstep", 1.0 / mnWidth );
+    pProgram->SetUniform1f( "ystep", 1.0 / mnHeight );
+
+    pProgram->SetTexture("crc_table", (OpenGLTexture&)(aCRCTableTexture));
+    pProgram->SetTexture("sampler", aFirstPassTexture);
+    pProgram->DrawTexture(aFirstPassTexture);
+    pProgram->Clean();
+
+    OpenGLContext::ReleaseFramebuffer(pFramebuffer);
+
+    CHECK_GL_ERROR();
+
+    // Final CRC on CPU
+    OpenGLTexture& aFinalTexture = aSecondPassTexture;
+    std::vector<sal_uInt8> aBuf( aFinalTexture.GetWidth() * aFinalTexture.GetHeight() * 4 );
+    aFinalTexture.Read(GL_RGBA, GL_UNSIGNED_BYTE, aBuf.data());
+
+    ChecksumType nCrc = vcl_crc64(0, aBuf.data(), aBuf.size());
+
+    rChecksum = nCrc;
+    return true;
+}
+
+void OpenGLSalBitmap::updateChecksum() const
+{
+    if (mbChecksumValid)
+        return;
+
+    OpenGLSalBitmap* pThis = const_cast<OpenGLSalBitmap*>(this);
+
+    if (!mpContext)
+    {
+        pThis->CreateTexture();
+    }
+
+    pThis->mbChecksumValid = calcChecksumGL(pThis->maTexture, pThis->maChecksum);
+}
+
 OpenGLContext* OpenGLSalBitmap::GetBitmapContext()
 {
     return ImplGetDefaultWindow()->GetGraphics()->GetOpenGLContext();
@@ -581,6 +670,7 @@ void OpenGLSalBitmap::ReleaseBuffer( BitmapBuffer* pBuffer, BitmapAccessMode nMo
     {
         maTexture = OpenGLTexture();
         mbDirtyTexture = true;
+        mbChecksumValid = false;
     }
     // The palette is modified on read during the BitmapWriteAccess,
     // but of course, often it is not modified; interesting.
diff --git a/vcl/source/bitmap/checksum.cxx b/vcl/source/bitmap/checksum.cxx
new file mode 100644
index 000000000000..a46db1e75265
--- /dev/null
+++ b/vcl/source/bitmap/checksum.cxx
@@ -0,0 +1,51 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#include <sal/types.h>
+#include <checksum.hxx>
+
+/*========================================================================
+ *
+ * vcl_crc64 implementation.
+ *
+ *======================================================================*/
+#define UPDCRC64(crc, octet) \
+    (vcl_crc64Table[((crc) ^ (octet)) & 0xff] ^ ((crc) >> 8))
+
+/*
+ * rtl_crc64.
+ */
+sal_uInt64 SAL_CALL vcl_crc64 (
+    sal_uInt64  Crc,
+    const void *Data, sal_uInt32 DatLen)  SAL_THROW_EXTERN_C()
+{
+    if (Data)
+    {
+        const sal_uInt8 *p = static_cast<const sal_uInt8 *>(Data);
+        const sal_uInt8 *q = p + DatLen;
+
+        Crc = ~Crc;
+        while (p < q)
+            Crc = UPDCRC64(Crc, *(p++));
+        Crc = ~Crc;
+    }
+    return Crc;
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/source/gdi/bitmap.cxx b/vcl/source/gdi/bitmap.cxx
index 9a69eb0f8af1..6f96c050685d 100644
--- a/vcl/source/gdi/bitmap.cxx
+++ b/vcl/source/gdi/bitmap.cxx
@@ -245,10 +245,8 @@ Bitmap& Bitmap::operator=( const Bitmap& rBitmap )
 
 bool Bitmap::IsEqual( const Bitmap& rBmp ) const
 {
-    return( IsSameInstance( rBmp ) ||
-            ( rBmp.GetSizePixel() == GetSizePixel() &&
-              rBmp.GetBitCount() == GetBitCount() &&
-              rBmp.GetChecksum() == GetChecksum() ) );
+    return(IsSameInstance(rBmp) || // Includes both are nullptr
+        (rBmp.mpImpBmp && mpImpBmp && mpImpBmp->ImplIsEqual(*rBmp.mpImpBmp)));
 }
 
 void Bitmap::SetEmpty()
@@ -293,49 +291,6 @@ sal_uInt32 Bitmap::GetChecksum() const
     if( mpImpBmp )
     {
         nRet = mpImpBmp->ImplGetChecksum();
-
-        if( !nRet )
-        {
-            BitmapReadAccess* pRAcc = const_cast<Bitmap*>(this)->AcquireReadAccess();
-
-            if( pRAcc && pRAcc->Width() && pRAcc->Height() )
-            {
-                sal_uInt32  nCrc = 0;
-                SVBT32      aBT32;
-
-                pRAcc->ImplZeroInitUnusedBits();
-
-                UInt32ToSVBT32( pRAcc->Width(), aBT32 );
-                nCrc = rtl_crc32( nCrc, aBT32, 4 );
-
-                UInt32ToSVBT32( pRAcc->Height(), aBT32 );
-                nCrc = rtl_crc32( nCrc, aBT32, 4 );
-
-                UInt32ToSVBT32( pRAcc->GetBitCount(), aBT32 );
-                nCrc = rtl_crc32( nCrc, aBT32, 4 );
-
-                UInt32ToSVBT32( pRAcc->GetColorMask().GetRedMask(), aBT32 );
-                nCrc = rtl_crc32( nCrc, aBT32, 4 );
-
-                UInt32ToSVBT32( pRAcc->GetColorMask().GetGreenMask(), aBT32 );
-                nCrc = rtl_crc32( nCrc, aBT32, 4 );
-
-                UInt32ToSVBT32( pRAcc->GetColorMask().GetBlueMask(), aBT32 );
-                nCrc = rtl_crc32( nCrc, aBT32, 4 );
-
-                if( pRAcc->HasPalette() )
-                {
-                    nCrc = rtl_crc32( nCrc, pRAcc->GetPalette().ImplGetColorBuffer(),
-                                      pRAcc->GetPaletteEntryCount() * sizeof( BitmapColor ) );
-                }
-
-                nRet = rtl_crc32( nCrc, pRAcc->GetBuffer(), pRAcc->GetScanlineSize() * pRAcc->Height() );
-
-                mpImpBmp->ImplSetChecksum( nRet );
-            }
-
-            if (pRAcc) ReleaseAccess( pRAcc );
-        }
     }
 
     return nRet;
@@ -549,6 +504,7 @@ bool Bitmap::Invert()
                     pAcc->SetPixel( nY, nX, pAcc->GetPixel( nY, nX ).Invert() );
         }
 
+        mpImpBmp->ImplInvalidateChecksum();
         ReleaseAccess( pAcc );
         bRet = true;
     }
diff --git a/vcl/source/gdi/impbmp.cxx b/vcl/source/gdi/impbmp.cxx
index 298bfaa1cd0f..f70012202b07 100644
--- a/vcl/source/gdi/impbmp.cxx
+++ b/vcl/source/gdi/impbmp.cxx
@@ -26,14 +26,12 @@
 
 ImpBitmap::ImpBitmap() :
             mnRefCount  ( 1 ),
-            mnChecksum  ( 0 ),
             mpSalBitmap ( ImplGetSVData()->mpDefInst->CreateSalBitmap() )
 {
 }
 
 ImpBitmap::ImpBitmap(SalBitmap* pBitmap) :
             mnRefCount  ( 1 ),
-            mnChecksum  ( 0 ),
             mpSalBitmap ( pBitmap )
 {
 }
@@ -43,14 +41,20 @@ ImpBitmap::~ImpBitmap()
     delete mpSalBitmap;
 }
 
-bool ImpBitmap::ImplCreate( const Size& rSize, sal_uInt16 nBitCount, const BitmapPalette& rPal )
+bool ImpBitmap::ImplIsEqual(const ImpBitmap& rBmp) const
+{
+    return (rBmp.ImplGetSize() == ImplGetSize() &&
+        rBmp.ImplGetBitCount() == ImplGetBitCount() &&
+        rBmp.ImplGetChecksum() == ImplGetChecksum());
+}
+
+bool ImpBitmap::ImplCreate(const Size& rSize, sal_uInt16 nBitCount, const BitmapPalette& rPal)
 {
     return mpSalBitmap->Create( rSize, nBitCount, rPal );
 }
 
 bool ImpBitmap::ImplCreate( const ImpBitmap& rImpBitmap )
 {
-    mnChecksum = rImpBitmap.mnChecksum;
     return mpSalBitmap->Create( *rImpBitmap.mpSalBitmap );
 }
 
@@ -85,7 +89,20 @@ void ImpBitmap::ImplReleaseBuffer( BitmapBuffer* pBuffer, BitmapAccessMode nMode
     mpSalBitmap->ReleaseBuffer( pBuffer, nMode );
 
     if( nMode == BITMAP_WRITE_ACCESS )
-        mnChecksum = 0;
+        ImplInvalidateChecksum();
+}
+
+sal_uLong ImpBitmap::ImplGetChecksum() const
+{
+    SalBitmap::ChecksumType aChecksum;
+    mpSalBitmap->GetChecksum(aChecksum);
+    sal_uLong a32BitChecksum = aChecksum;
+    return a32BitChecksum;
+}
+
+void ImpBitmap::ImplInvalidateChecksum()
+{
+    mpSalBitmap->InvalidateChecksum();
 }
 
 bool ImpBitmap::ImplScale( const double& rScaleX, const double& rScaleY, BmpScaleFlag nScaleFlag )
diff --git a/vcl/unx/gtk/app/gtkinst.cxx b/vcl/unx/gtk/app/gtkinst.cxx
index 53582c7e5b02..cbdbc6ece609 100644
--- a/vcl/unx/gtk/app/gtkinst.cxx
+++ b/vcl/unx/gtk/app/gtkinst.cxx
@@ -338,7 +338,7 @@ SalBitmap* GtkInstance::CreateSalBitmap()
 {
     EnsureInit();
 #if GTK_CHECK_VERSION(3,0,0)
-    return new SvpSalBitmap();
+    return SvpSalInstance::CreateSalBitmap();//new SvpSalBitmap();
 #else
     return X11SalInstance::CreateSalBitmap();
 #endif