tdf#97666 -opengl: convert the bitmap to 8bit grays using GL shader

Change-Id: I4d48d29ab752814f71c697a201e70a26ae937775
Reviewed-on: https://gerrit.libreoffice.org/22223
Reviewed-by: Tor Lillqvist <tml@collabora.com>
Tested-by: Tor Lillqvist <tml@collabora.com>

9 files changed, 101 insertions, 0 deletions

diff --git a/vcl/Package_opengl.mk b/vcl/Package_opengl.mk
index 9d4250279bd9..b8851df57625 100644
--- a/vcl/Package_opengl.mk
+++ b/vcl/Package_opengl.mk
@@ -17,6 +17,7 @@ $(eval $(call gb_Package_add_files,vcl_opengl_shader,$(LIBO_ETC_FOLDER)/opengl,\
 	blendedTextureVertexShader.glsl \
 	dumbVertexShader.glsl \
 	diffTextureFragmentShader.glsl \
+	greyscaleFragmentShader.glsl \
     invert50FragmentShader.glsl \
 	convolutionFragmentShader.glsl \
 	linearGradientFragmentShader.glsl \
diff --git a/vcl/inc/impbmp.hxx b/vcl/inc/impbmp.hxx
index feb94a8d6fd3..5787b3f0f755 100644
--- a/vcl/inc/impbmp.hxx
+++ b/vcl/inc/impbmp.hxx
@@ -72,6 +72,7 @@ public:
 
     bool                ImplScale( const double& rScaleX, const double& rScaleY, BmpScaleFlag nScaleFlag );
     bool                ImplReplace( const Color& rSearchColor, const Color& rReplaceColor, sal_uLong nTol );
+    bool                ImplConvert( BmpConversion eConversion );
 };
 
 #endif // INCLUDED_VCL_INC_IMPBMP_HXX
diff --git a/vcl/inc/opengl/salbmp.hxx b/vcl/inc/opengl/salbmp.hxx
index 98e09b3c16eb..7577f9f2c3c8 100644
--- a/vcl/inc/opengl/salbmp.hxx
+++ b/vcl/inc/opengl/salbmp.hxx
@@ -80,6 +80,7 @@ public:
 
     bool            Scale( const double& rScaleX, const double& rScaleY, BmpScaleFlag nScaleFlag ) override;
     bool            Replace( const Color& rSearchColor, const Color& rReplaceColor, sal_uLong nTol ) override;
+    bool            ConvertToGreyscale() override;
 
 public:
 
diff --git a/vcl/inc/salbmp.hxx b/vcl/inc/salbmp.hxx
index 574b11c79f1a..305f8a63f74d 100644
--- a/vcl/inc/salbmp.hxx
+++ b/vcl/inc/salbmp.hxx
@@ -69,6 +69,10 @@ 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            ConvertToGreyscale()
+    {
+        return false;
+    }
 
     void GetChecksum(ChecksumType& rChecksum) const
     {
diff --git a/vcl/opengl/greyscaleFragmentShader.glsl b/vcl/opengl/greyscaleFragmentShader.glsl
new file mode 100644
index 000000000000..758109e98678
--- /dev/null
+++ b/vcl/opengl/greyscaleFragmentShader.glsl
@@ -0,0 +1,18 @@
+/* -*- 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/.
+ */
+
+varying vec2 tex_coord;
+uniform sampler2D sampler;
+
+void main() {
+    vec4 texel = texture2D(sampler, tex_coord);
+    gl_FragColor = vec4(vec3(dot(texel.rgb, vec3(0.301, 0.591, 0.108))), 1.0);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/opengl/salbmp.cxx b/vcl/opengl/salbmp.cxx
index 703aedc10b98..683ca5fe5ac0 100644
--- a/vcl/opengl/salbmp.cxx
+++ b/vcl/opengl/salbmp.cxx
@@ -902,4 +902,40 @@ bool OpenGLSalBitmap::Replace( const Color& rSearchColor, const Color& rReplaceC
     return true;
 }
 
+// Convert texture to greyscale and adjust bitmap metadata
+bool OpenGLSalBitmap::ConvertToGreyscale()
+{
+    VCL_GL_INFO("::ConvertToGreyscale");
+
+    // avoid re-converting to 8bits.
+    if ( mnBits == 8 && maPalette == Bitmap::GetGreyPalette(256) )
+        return false;
+
+    OpenGLZone aZone;
+    rtl::Reference<OpenGLContext> xContext = OpenGLContext::getVCLContext();
+
+    OpenGLFramebuffer* pFramebuffer;
+    OpenGLProgram* pProgram;
+
+    GetTexture();
+    pProgram = xContext->UseProgram("textureVertexShader", "greyscaleFragmentShader");
+
+    if (!pProgram)
+        return false;
+
+    OpenGLTexture aNewTex(mnWidth, mnHeight);
+    pFramebuffer = xContext->AcquireFramebuffer(aNewTex);
+    pProgram->SetTexture("sampler", maTexture);
+    pProgram->DrawTexture(maTexture);
+    pProgram->Clean();
+
+    OpenGLContext::ReleaseFramebuffer( pFramebuffer );
+    maTexture = aNewTex;
+    mnBits = 8;
+    maPalette = Bitmap::GetGreyPalette(256);
+
+    CHECK_GL_ERROR();
+    return true;
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/source/gdi/bitmap3.cxx b/vcl/source/gdi/bitmap3.cxx
index 9251af18a766..53dd598de1c2 100644
--- a/vcl/source/gdi/bitmap3.cxx
+++ b/vcl/source/gdi/bitmap3.cxx
@@ -244,6 +244,23 @@ void ImplCreateDitherMatrix( sal_uInt8 (*pDitherMatrix)[16][16] )
 
 bool Bitmap::Convert( BmpConversion eConversion )
 {
+    // try to convert in backend
+    if (mpImpBmp)
+    {
+        ImpBitmap* pImpBmp = new ImpBitmap;
+
+        if (pImpBmp->ImplCreate(*mpImpBmp) && pImpBmp->ImplConvert(eConversion))
+        {
+            ImplSetImpBitmap(pImpBmp);
+            SAL_INFO( "vcl.opengl", "Ref count: " << mpImpBmp->ImplGetRefCount() );
+            return true;
+        }
+        else
+        {
+            delete pImpBmp;
+        }
+    }
+
     const sal_uInt16 nBitCount = GetBitCount ();
     bool bRet = false;
 
diff --git a/vcl/source/gdi/impbmp.cxx b/vcl/source/gdi/impbmp.cxx
index ad1eca9515be..416fa29a3df0 100644
--- a/vcl/source/gdi/impbmp.cxx
+++ b/vcl/source/gdi/impbmp.cxx
@@ -115,4 +115,14 @@ bool ImpBitmap::ImplReplace( const Color& rSearchColor, const Color& rReplaceCol
     return mpSalBitmap->Replace( rSearchColor, rReplaceColor, nTol );
 }
 
+bool ImpBitmap::ImplConvert( BmpConversion eConversion )
+{
+    // avoid large chunk of obsolete and hopefully rarely used conversions.
+    if (eConversion != BMP_CONVERSION_8BIT_GREYS)
+        return false;
+
+    // frequently used conversion for creating alpha masks
+    return mpSalBitmap->ConvertToGreyscale();
+}
+
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/vcl/workben/vcldemo.cxx b/vcl/workben/vcldemo.cxx
index 889db52d08a9..3726e00b7dd1 100644
--- a/vcl/workben/vcldemo.cxx
+++ b/vcl/workben/vcldemo.cxx
@@ -1215,6 +1215,19 @@ public:
                     aBelow.Move(0,aResult.GetSizePixel().Height());
                     rDev.DrawBitmapEx(aBelow, aResult);
 
+                    // mini convert test.
+                    aBelow.Move(aResult.GetSizePixel().Width()+4,0);
+                    rDev.DrawBitmapEx(aBelow, aResult);
+
+                    Bitmap aGrey = aSrc.GetBitmap();
+                    aGrey.Convert(BMP_CONVERSION_8BIT_GREYS);
+                    rDev.DrawBitmap(aBelow, aGrey);
+
+                    aBelow.Move(aGrey.GetSizePixel().Width(),0);
+                    BitmapEx aGreyMask(aSrc.GetBitmap(),
+                                       AlphaMask(aSrc.GetMask()));
+                    rDev.DrawBitmapEx(aBelow, aGreyMask);
+
                     aLocation.Move(aSrc.GetSizePixel().Width()*6,0);
                     if (aLocation.X() > r.Right())
                         aLocation = Point(0,aLocation.Y()+aSrc.GetSizePixel().Height()*3+4);