1 files changed, 91 insertions, 0 deletions
diff --git a/vcl/inc/scanlinewriter.hxx b/vcl/inc/scanlinewriter.hxx
new file mode 100644
index 0000000000..87a7827b7a
--- /dev/null
+++ b/vcl/inc/scanlinewriter.hxx
@@ -0,0 +1,91 @@
+/* -*- 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_SCANLINEWRITER_HXX
+#define INCLUDED_VCL_INC_SCANLINEWRITER_HXX
+
+#include <tools/long.hxx>
+#include <vcl/BitmapPalette.hxx>
+
+namespace vcl
+{
+// Write color information for 1, 4 and 8 bit palette bitmap scanlines.
+class ScanlineWriter
+{
+    BitmapPalette& maPalette;
+    sal_uInt8 const mnColorsPerByte; // number of colors that are stored in one byte
+    sal_uInt8 const mnColorBitSize; // number of bits a color takes
+    sal_uInt8 const mnColorBitMask; // bit mask used to isolate the color
+    sal_uInt8* mpCurrentScanline;
+    tools::Long mnX;
+
+public:
+    ScanlineWriter(BitmapPalette& aPalette, sal_Int8 nColorsPerByte)
+        : maPalette(aPalette)
+        , mnColorsPerByte(nColorsPerByte)
+        , mnColorBitSize(
+              8
+              / mnColorsPerByte) // bit size is number of bit in a byte divided by number of colors per byte (8 / 2 = 4 for 4-bit)
+        , mnColorBitMask((1 << mnColorBitSize) - 1) // calculate the bit mask from the bit size
+        , mpCurrentScanline(nullptr)
+        , mnX(0)
+    {
+    }
+
+    static std::unique_ptr<ScanlineWriter> Create(sal_uInt16 nBits, BitmapPalette& aPalette)
+    {
+        switch (nBits)
+        {
+            case 1:
+                return std::make_unique<ScanlineWriter>(aPalette, 8);
+            case 4:
+                return std::make_unique<ScanlineWriter>(aPalette, 2);
+            case 8:
+                return std::make_unique<ScanlineWriter>(aPalette, 1);
+            default:
+                abort();
+        }
+    }
+
+    void writeRGB(sal_uInt8 nR, sal_uInt8 nG, sal_uInt8 nB)
+    {
+        // calculate to which index we will write
+        tools::Long nScanlineIndex = mnX / mnColorsPerByte;
+
+        // calculate the number of shifts to get the color information to the right place
+        tools::Long nShift = (8 - mnColorBitSize) - ((mnX % mnColorsPerByte) * mnColorBitSize);
+
+        sal_uInt16 nColorIndex = maPalette.GetBestIndex(BitmapColor(nR, nG, nB));
+        mpCurrentScanline[nScanlineIndex] &= ~(mnColorBitMask << nShift); // clear
+        mpCurrentScanline[nScanlineIndex] |= (nColorIndex & mnColorBitMask) << nShift; // set
+        mnX++;
+    }
+
+    void nextLine(sal_uInt8* pScanline)
+    {
+        mnX = 0;
+        mpCurrentScanline = pScanline;
+    }
+};
+
+} // namespace vcl
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */