tdf#48062: Add support for arithmetic in feComposite

Took https://github.com/w3c/csswg-drafts/issues/3831
as a reference

Change-Id: I42039c481ec114c3faeae51526a5f29b86960146
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/165828
Tested-by: Jenkins
Reviewed-by: Xisco Fauli <xiscofauli@libreoffice.org>

1 files changed, 105 insertions, 0 deletions

diff --git a/vcl/source/bitmap/BitmapArithmeticBlendFilter.cxx b/vcl/source/bitmap/BitmapArithmeticBlendFilter.cxx
new file mode 100644
index 000000000000..da52a436b6f6
--- /dev/null
+++ b/vcl/source/bitmap/BitmapArithmeticBlendFilter.cxx
@@ -0,0 +1,105 @@
+/* -*- 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/.
+ *
+ */
+
+#include <comphelper/diagnose_ex.hxx>
+#include <vcl/BitmapArithmeticBlendFilter.hxx>
+#include <vcl/BitmapWriteAccess.hxx>
+#include <vcl/BitmapTools.hxx>
+
+BitmapArithmeticBlendFilter::BitmapArithmeticBlendFilter(BitmapEx const& rBitmapEx,
+                                                         BitmapEx const& rBitmapEx2)
+    : maBitmapEx(rBitmapEx)
+    , maBitmapEx2(rBitmapEx2)
+{
+}
+
+BitmapArithmeticBlendFilter::~BitmapArithmeticBlendFilter() {}
+
+static sal_uInt8 lcl_calculate(sal_uInt8 aColor, sal_uInt8 aColor2, double aK1, double aK2,
+                               double aK3, double aK4)
+{
+    const double i1 = aColor / 255.0;
+    const double i2 = aColor2 / 255.0;
+    const double result = aK1 * i1 * i2 + aK2 * i1 + aK3 * i2 + aK4;
+
+    return std::clamp(result, 0.0, 1.0) * 255.0;
+}
+
+static BitmapColor premultiply(const BitmapColor c)
+{
+    return BitmapColor(ColorAlpha, vcl::bitmap::premultiply(c.GetRed(), c.GetAlpha()),
+                       vcl::bitmap::premultiply(c.GetGreen(), c.GetAlpha()),
+                       vcl::bitmap::premultiply(c.GetBlue(), c.GetAlpha()), c.GetAlpha());
+}
+
+static BitmapColor unpremultiply(const BitmapColor c)
+{
+    return BitmapColor(ColorAlpha, vcl::bitmap::unpremultiply(c.GetRed(), c.GetAlpha()),
+                       vcl::bitmap::unpremultiply(c.GetGreen(), c.GetAlpha()),
+                       vcl::bitmap::unpremultiply(c.GetBlue(), c.GetAlpha()), c.GetAlpha());
+}
+
+BitmapEx BitmapArithmeticBlendFilter::execute(double aK1, double aK2, double aK3, double aK4)
+{
+    if (maBitmapEx.IsEmpty() || maBitmapEx2.IsEmpty())
+        return BitmapEx();
+
+    Size aSize = maBitmapEx.GetBitmap().GetSizePixel();
+    Size aSize2 = maBitmapEx2.GetBitmap().GetSizePixel();
+    sal_Int32 nHeight = std::min(aSize.getHeight(), aSize2.getHeight());
+    sal_Int32 nWidth = std::min(aSize.getWidth(), aSize2.getWidth());
+
+    BitmapScopedReadAccess pReadAccess(maBitmapEx.GetBitmap());
+    Bitmap aDstBitmap(Size(nWidth, nHeight), maBitmapEx.GetBitmap().getPixelFormat(),
+                      &pReadAccess->GetPalette());
+    Bitmap aDstAlpha(AlphaMask(Size(nWidth, nHeight)).GetBitmap());
+
+    {
+        // just to be on the safe side: let the
+        // ScopedAccessors get destructed before
+        // copy-constructing the resulting bitmap. This will
+        // rule out the possibility that cached accessor data
+        // is not yet written back.
+
+        BitmapScopedWriteAccess pWriteAccess(aDstBitmap);
+        BitmapScopedWriteAccess pAlphaWriteAccess(aDstAlpha);
+
+        if (pWriteAccess.get() != nullptr && pAlphaWriteAccess.get() != nullptr)
+        {
+            for (tools::Long y(0); y < nHeight; ++y)
+            {
+                Scanline pScanline = pWriteAccess->GetScanline(y);
+                Scanline pScanAlpha = pAlphaWriteAccess->GetScanline(y);
+                for (tools::Long x(0); x < nWidth; ++x)
+                {
+                    BitmapColor i1 = premultiply(maBitmapEx.GetPixelColor(x, y));
+                    BitmapColor i2 = premultiply(maBitmapEx2.GetPixelColor(x, y));
+                    sal_uInt8 r(lcl_calculate(i1.GetRed(), i2.GetRed(), aK1, aK2, aK3, aK4));
+                    sal_uInt8 g(lcl_calculate(i1.GetGreen(), i2.GetGreen(), aK1, aK2, aK3, aK4));
+                    sal_uInt8 b(lcl_calculate(i1.GetBlue(), i2.GetBlue(), aK1, aK2, aK3, aK4));
+                    sal_uInt8 a(lcl_calculate(i1.GetAlpha(), i2.GetAlpha(), aK1, aK2, aK3, aK4));
+
+                    pWriteAccess->SetPixelOnData(
+                        pScanline, x, unpremultiply(BitmapColor(ColorAlpha, r, g, b, a)));
+                    pAlphaWriteAccess->SetPixelOnData(pScanAlpha, x, BitmapColor(a));
+                }
+            }
+        }
+        else
+        {
+            // TODO(E2): Error handling!
+            ENSURE_OR_THROW(false, "BitmapScreenBlendFilter: could not access bitmap");
+        }
+    }
+
+    return BitmapEx(aDstBitmap, AlphaMask(aDstAlpha));
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */