BitmapSobelGreyFilter.cxx

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/* -*- 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 <sal/config.h>

#include <vcl/bitmap.hxx>
#include <vcl/bitmapex.hxx>
#include <vcl/BitmapSobelGreyFilter.hxx>

#include <bitmap/BitmapWriteAccess.hxx>

#include <algorithm>

BitmapEx BitmapSobelGreyFilter::execute(BitmapEx const& rBitmapEx) const
{
    Bitmap aBitmap(rBitmapEx.GetBitmap());

    bool bRet = aBitmap.ImplMakeGreyscales();

    if (bRet)
    {
        bRet = false;

        Bitmap::ScopedReadAccess pReadAcc(aBitmap);

        if (pReadAcc)
        {
            Bitmap aNewBmp(aBitmap.GetSizePixel(), vcl::PixelFormat::N8_BPP,
                           &pReadAcc->GetPalette());
            BitmapScopedWriteAccess pWriteAcc(aNewBmp);

            if (pWriteAcc)
            {
                BitmapColor aGrey(sal_uInt8(0));
                const tools::Long nWidth = pWriteAcc->Width();
                const tools::Long nHeight = pWriteAcc->Height();
                const tools::Long nMask111 = -1, nMask121 = 0, nMask131 = 1;
                const tools::Long nMask211 = -2, nMask221 = 0, nMask231 = 2;
                const tools::Long nMask311 = -1, nMask321 = 0, nMask331 = 1;
                const tools::Long nMask112 = 1, nMask122 = 2, nMask132 = 1;
                const tools::Long nMask212 = 0, nMask222 = 0, nMask232 = 0;
                const tools::Long nMask312 = -1, nMask322 = -2, nMask332 = -1;
                tools::Long nGrey11, nGrey12, nGrey13;
                tools::Long nGrey21, nGrey22, nGrey23;
                tools::Long nGrey31, nGrey32, nGrey33;
                std::unique_ptr<long[]> pHMap(new long[nWidth + 2]);
                std::unique_ptr<long[]> pVMap(new long[nHeight + 2]);
                tools::Long nX, nY, nSum1, nSum2;

                // fill mapping tables
                pHMap[0] = 0;

                for (nX = 1; nX <= nWidth; nX++)
                {
                    pHMap[nX] = nX - 1;
                }

                pHMap[nWidth + 1] = nWidth - 1;

                pVMap[0] = 0;

                for (nY = 1; nY <= nHeight; nY++)
                {
                    pVMap[nY] = nY - 1;
                }

                pVMap[nHeight + 1] = nHeight - 1;

                for (nY = 0; nY < nHeight; nY++)
                {
                    nGrey11 = pReadAcc->GetPixel(pVMap[nY], pHMap[0]).GetIndex();
                    nGrey12 = pReadAcc->GetPixel(pVMap[nY], pHMap[1]).GetIndex();
                    nGrey13 = pReadAcc->GetPixel(pVMap[nY], pHMap[2]).GetIndex();
                    nGrey21 = pReadAcc->GetPixel(pVMap[nY + 1], pHMap[0]).GetIndex();
                    nGrey22 = pReadAcc->GetPixel(pVMap[nY + 1], pHMap[1]).GetIndex();
                    nGrey23 = pReadAcc->GetPixel(pVMap[nY + 1], pHMap[2]).GetIndex();
                    nGrey31 = pReadAcc->GetPixel(pVMap[nY + 2], pHMap[0]).GetIndex();
                    nGrey32 = pReadAcc->GetPixel(pVMap[nY + 2], pHMap[1]).GetIndex();
                    nGrey33 = pReadAcc->GetPixel(pVMap[nY + 2], pHMap[2]).GetIndex();

                    Scanline pScanline = pWriteAcc->GetScanline(nY);
                    for (nX = 0; nX < nWidth; nX++)
                    {
                        nSum1 = nSum2 = 0;

                        nSum1 += nMask111 * nGrey11;
                        nSum2 += nMask112 * nGrey11;

                        nSum1 += nMask121 * nGrey12;
                        nSum2 += nMask122 * nGrey12;

                        nSum1 += nMask131 * nGrey13;
                        nSum2 += nMask132 * nGrey13;

                        nSum1 += nMask211 * nGrey21;
                        nSum2 += nMask212 * nGrey21;

                        nSum1 += nMask221 * nGrey22;
                        nSum2 += nMask222 * nGrey22;

                        nSum1 += nMask231 * nGrey23;
                        nSum2 += nMask232 * nGrey23;

                        nSum1 += nMask311 * nGrey31;
                        nSum2 += nMask312 * nGrey31;

                        nSum1 += nMask321 * nGrey32;
                        nSum2 += nMask322 * nGrey32;

                        nSum1 += nMask331 * nGrey33;
                        nSum2 += nMask332 * nGrey33;

                        nSum1 = static_cast<tools::Long>(
                            sqrt(static_cast<double>(nSum1 * nSum1 + nSum2 * nSum2)));

                        aGrey.SetIndex(~static_cast<sal_uInt8>(
                            std::clamp(nSum1, tools::Long(0), tools::Long(255))));
                        pWriteAcc->SetPixelOnData(pScanline, nX, aGrey);

                        if (nX < (nWidth - 1))
                        {
                            const tools::Long nNextX = pHMap[nX + 3];

                            nGrey11 = nGrey12;
                            nGrey12 = nGrey13;
                            nGrey13 = pReadAcc->GetPixel(pVMap[nY], nNextX).GetIndex();
                            nGrey21 = nGrey22;
                            nGrey22 = nGrey23;
                            nGrey23 = pReadAcc->GetPixel(pVMap[nY + 1], nNextX).GetIndex();
                            nGrey31 = nGrey32;
                            nGrey32 = nGrey33;
                            nGrey33 = pReadAcc->GetPixel(pVMap[nY + 2], nNextX).GetIndex();
                        }
                    }
                }

                pHMap.reset();
                pVMap.reset();
                pWriteAcc.reset();
                bRet = true;
            }

            pReadAcc.reset();

            if (bRet)
            {
                const MapMode aMap(aBitmap.GetPrefMapMode());
                const Size aPrefSize(aBitmap.GetPrefSize());

                aBitmap = aNewBmp;

                aBitmap.SetPrefMapMode(aMap);
                aBitmap.SetPrefSize(aPrefSize);
            }
        }
    }

    if (bRet)
        return BitmapEx(aBitmap);

    return BitmapEx();
}

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