vcl/inc/scanlinewriter.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
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   9  * This file incorporates work covered by the following license notice:
  10  *
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  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 #ifndef INCLUDED_VCL_INC_SCANLINEWRITER_HXX
  21 #define INCLUDED_VCL_INC_SCANLINEWRITER_HXX
  22
  23 #include <vcl/bitmap.hxx>
  24 #include <vcl/BitmapPalette.hxx>
  25
  26 namespace vcl
  27 {
  28 // Write color information for 1, 4 and 8 bit palette bitmap scanlines.
  29 class ScanlineWriter
  30 {
  31     BitmapPalette& maPalette;
  32     sal_uInt8 const mnColorsPerByte; // number of colors that are stored in one byte
  33     sal_uInt8 const mnColorBitSize; // number of bits a color takes
  34     sal_uInt8 const mnColorBitMask; // bit mask used to isolate the color
  35     sal_uInt8* mpCurrentScanline;
  36     tools::Long mnX;
  37
  38 public:
  39     ScanlineWriter(BitmapPalette& aPalette, sal_Int8 nColorsPerByte)
  40         : maPalette(aPalette)
  41         , mnColorsPerByte(nColorsPerByte)
  42         , mnColorBitSize(
  43               8
  44               / mnColorsPerByte) // bit size is number of bit in a byte divided by number of colors per byte (8 / 2 = 4 for 4-bit)
  45         , mnColorBitMask((1 << mnColorBitSize) - 1) // calculate the bit mask from the bit size
  46         , mpCurrentScanline(nullptr)
  47         , mnX(0)
  48     {
  49     }
  50
  51     static std::unique_ptr<ScanlineWriter> Create(sal_uInt16 nBits, BitmapPalette& aPalette)
  52     {
  53         switch (nBits)
  54         {
  55             case 1:
  56                 return std::make_unique<ScanlineWriter>(aPalette, 8);
  57             case 4:
  58                 return std::make_unique<ScanlineWriter>(aPalette, 2);
  59             case 8:
  60                 return std::make_unique<ScanlineWriter>(aPalette, 1);
  61             default:
  62                 abort();
  63         }
  64     }
  65
  66     void writeRGB(sal_uInt8 nR, sal_uInt8 nG, sal_uInt8 nB)
  67     {
  68         // calculate to which index we will write
  69         tools::Long nScanlineIndex = mnX / mnColorsPerByte;
  70
  71         // calculate the number of shifts to get the color information to the right place
  72         tools::Long nShift = (8 - mnColorBitSize) - ((mnX % mnColorsPerByte) * mnColorBitSize);
  73
  74         sal_uInt16 nColorIndex = maPalette.GetBestIndex(BitmapColor(nR, nG, nB));
  75         mpCurrentScanline[nScanlineIndex] &= ~(mnColorBitMask << nShift); // clear
  76         mpCurrentScanline[nScanlineIndex] |= (nColorIndex & mnColorBitMask) << nShift; // set
  77         mnX++;
  78     }
  79
  80     void nextLine(sal_uInt8* pScanline)
  81     {
  82         mnX = 0;
  83         mpCurrentScanline = pScanline;
  84     }
  85 };
  86
  87 } // namespace vcl
  88
  89 #endif
  90
  91 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */