gdal/alg/gdalrasterpolygonenumerator.cpp

/******************************************************************************
 *
 * Project:  GDAL
 * Purpose:  Raster Polygon Enumerator
 * Author:   Frank Warmerdam, warmerdam@pobox.com
 *
 ******************************************************************************
 * Copyright (c) 2008, Frank Warmerdam
 * Copyright (c) 2015, Even Rouault <even.rouault at spatialys.com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "cpl_port.h"
#include "gdal_alg_priv.h"

#include <cstddef>
#include <limits>

#include "cpl_conv.h"
#include "cpl_error.h"

/*! @cond Doxygen_Suppress */

/************************************************************************/
/*                    GDALRasterPolygonEnumeratorT()                    */
/************************************************************************/

template <class DataType, class EqualityTest>
GDALRasterPolygonEnumeratorT<
    DataType, EqualityTest>::GDALRasterPolygonEnumeratorT(int nConnectednessIn)
    : nConnectedness(nConnectednessIn)

{
    CPLAssert(nConnectedness == 4 || nConnectedness == 8);
}

/************************************************************************/
/*                    ~GDALRasterPolygonEnumeratorT()                    */
/************************************************************************/

template <class DataType, class EqualityTest>
GDALRasterPolygonEnumeratorT<DataType,
                             EqualityTest>::~GDALRasterPolygonEnumeratorT()

{
    Clear();
}

/************************************************************************/
/*                               Clear()                                */
/************************************************************************/

template <class DataType, class EqualityTest>
void GDALRasterPolygonEnumeratorT<DataType, EqualityTest>::Clear()

{
    CPLFree(panPolyIdMap);
    CPLFree(panPolyValue);

    panPolyIdMap = nullptr;
    panPolyValue = nullptr;

    nNextPolygonId = 0;
    nPolyAlloc = 0;
}

/************************************************************************/
/*                            MergePolygon()                            */
/*                                                                      */
/*      Update the polygon map to indicate the merger of two polygons.  */
/************************************************************************/

template <class DataType, class EqualityTest>
void GDALRasterPolygonEnumeratorT<DataType, EqualityTest>::MergePolygon(
    int nSrcId, int nDstIdInit)

{
    // Figure out the final dest id.
    int nDstIdFinal = nDstIdInit;
    while (panPolyIdMap[nDstIdFinal] != nDstIdFinal)
        nDstIdFinal = panPolyIdMap[nDstIdFinal];

    // Map the whole intermediate chain to it.
    int nDstIdCur = nDstIdInit;
    while (panPolyIdMap[nDstIdCur] != nDstIdCur)
    {
        int nNextDstId = panPolyIdMap[nDstIdCur];
        panPolyIdMap[nDstIdCur] = nDstIdFinal;
        nDstIdCur = nNextDstId;
    }

    // And map the whole source chain to it too (can be done in one pass).
    while (panPolyIdMap[nSrcId] != nSrcId)
    {
        int nNextSrcId = panPolyIdMap[nSrcId];
        panPolyIdMap[nSrcId] = nDstIdFinal;
        nSrcId = nNextSrcId;
    }
    panPolyIdMap[nSrcId] = nDstIdFinal;
}

/************************************************************************/
/*                             NewPolygon()                             */
/*                                                                      */
/*      Allocate a new polygon id, and reallocate the polygon maps      */
/*      if needed.                                                      */
/************************************************************************/

template <class DataType, class EqualityTest>
int GDALRasterPolygonEnumeratorT<DataType, EqualityTest>::NewPolygon(
    DataType nValue)

{
    if (nNextPolygonId == std::numeric_limits<int>::max())
    {
        CPLError(CE_Failure, CPLE_AppDefined,
                 "GDALRasterPolygonEnumeratorT::NewPolygon(): maximum number "
                 "of polygons reached");
        return -1;
    }
    if (nNextPolygonId >= nPolyAlloc)
    {
        int nPolyAllocNew;
        if (nPolyAlloc < (std::numeric_limits<int>::max() - 20) / 2)
            nPolyAllocNew = nPolyAlloc * 2 + 20;
        else
            nPolyAllocNew = std::numeric_limits<int>::max();
#if SIZEOF_VOIDP == 4
        if (nPolyAllocNew >
                static_cast<int>(std::numeric_limits<size_t>::max() /
                                 sizeof(GInt32)) ||
            nPolyAllocNew >
                static_cast<int>(std::numeric_limits<size_t>::max() /
                                 sizeof(DataType)))
        {
            CPLError(CE_Failure, CPLE_OutOfMemory,
                     "GDALRasterPolygonEnumeratorT::NewPolygon(): too many "
                     "polygons");
            return -1;
        }
#endif
        auto panPolyIdMapNew = static_cast<GInt32 *>(
            VSI_REALLOC_VERBOSE(panPolyIdMap, nPolyAllocNew * sizeof(GInt32)));
        auto panPolyValueNew = static_cast<DataType *>(VSI_REALLOC_VERBOSE(
            panPolyValue, nPolyAllocNew * sizeof(DataType)));
        if (panPolyIdMapNew == nullptr || panPolyValueNew == nullptr)
        {
            VSIFree(panPolyIdMapNew);
            VSIFree(panPolyValueNew);
            return -1;
        }
        panPolyIdMap = panPolyIdMapNew;
        panPolyValue = panPolyValueNew;
        nPolyAlloc = nPolyAllocNew;
    }

    const int nPolyId = nNextPolygonId;
    panPolyIdMap[nPolyId] = nPolyId;
    panPolyValue[nPolyId] = nValue;
    nNextPolygonId++;

    return nPolyId;
}

/************************************************************************/
/*                           CompleteMerges()                           */
/*                                                                      */
/*      Make a pass through the maps, ensuring every polygon id         */
/*      points to the final id it should use, not an intermediate       */
/*      value.                                                          */
/************************************************************************/

template <class DataType, class EqualityTest>
void GDALRasterPolygonEnumeratorT<DataType, EqualityTest>::CompleteMerges()

{
    int nFinalPolyCount = 0;

    for (int iPoly = 0; iPoly < nNextPolygonId; iPoly++)
    {
        // Figure out the final id.
        int nId = panPolyIdMap[iPoly];
        while (nId != panPolyIdMap[nId])
        {
            nId = panPolyIdMap[nId];
        }

        // Then map the whole intermediate chain to it.
        int nIdCur = panPolyIdMap[iPoly];
        panPolyIdMap[iPoly] = nId;
        while (nIdCur != panPolyIdMap[nIdCur])
        {
            int nNextId = panPolyIdMap[nIdCur];
            panPolyIdMap[nIdCur] = nId;
            nIdCur = nNextId;
        }

        if (panPolyIdMap[iPoly] == iPoly)
            nFinalPolyCount++;
    }

    CPLDebug("GDALRasterPolygonEnumerator",
             "Counted %d polygon fragments forming %d final polygons.",
             nNextPolygonId, nFinalPolyCount);
}

/************************************************************************/
/*                            ProcessLine()                             */
/*                                                                      */
/*      Assign ids to polygons, one line at a time.                     */
/************************************************************************/

template <class DataType, class EqualityTest>
bool GDALRasterPolygonEnumeratorT<DataType, EqualityTest>::ProcessLine(
    DataType *panLastLineVal, DataType *panThisLineVal, GInt32 *panLastLineId,
    GInt32 *panThisLineId, int nXSize)

{
    EqualityTest eq;

    /* -------------------------------------------------------------------- */
    /*      Special case for the first line.                                */
    /* -------------------------------------------------------------------- */
    if (panLastLineVal == nullptr)
    {
        for (int i = 0; i < nXSize; i++)
        {
            if (panThisLineVal[i] == GP_NODATA_MARKER)
            {
                panThisLineId[i] = -1;
            }
            else if (i == 0 ||
                     !(eq.operator()(panThisLineVal[i], panThisLineVal[i - 1])))
            {
                panThisLineId[i] = NewPolygon(panThisLineVal[i]);
                if (panThisLineId[i] < 0)
                    return false;
            }
            else
            {
                panThisLineId[i] = panThisLineId[i - 1];
            }
        }

        return true;
    }

    /* -------------------------------------------------------------------- */
    /*      Process each pixel comparing to the previous pixel, and to      */
    /*      the last line.                                                  */
    /* -------------------------------------------------------------------- */
    for (int i = 0; i < nXSize; i++)
    {
        if (panThisLineVal[i] == GP_NODATA_MARKER)
        {
            panThisLineId[i] = -1;
        }
        else if (i > 0 &&
                 eq.operator()(panThisLineVal[i], panThisLineVal[i - 1]))
        {
            panThisLineId[i] = panThisLineId[i - 1];

            if (eq.operator()(panLastLineVal[i], panThisLineVal[i]) &&
                (panPolyIdMap[panLastLineId[i]] !=
                 panPolyIdMap[panThisLineId[i]]))
            {
                MergePolygon(panLastLineId[i], panThisLineId[i]);
            }

            if (nConnectedness == 8 &&
                eq.operator()(panLastLineVal[i - 1], panThisLineVal[i]) &&
                (panPolyIdMap[panLastLineId[i - 1]] !=
                 panPolyIdMap[panThisLineId[i]]))
            {
                MergePolygon(panLastLineId[i - 1], panThisLineId[i]);
            }

            if (nConnectedness == 8 && i < nXSize - 1 &&
                eq.operator()(panLastLineVal[i + 1], panThisLineVal[i]) &&
                (panPolyIdMap[panLastLineId[i + 1]] !=
                 panPolyIdMap[panThisLineId[i]]))
            {
                MergePolygon(panLastLineId[i + 1], panThisLineId[i]);
            }
        }
        else if (eq.operator()(panLastLineVal[i], panThisLineVal[i]))
        {
            panThisLineId[i] = panLastLineId[i];
        }
        else if (i > 0 && nConnectedness == 8 &&
                 eq.operator()(panLastLineVal[i - 1], panThisLineVal[i]))
        {
            panThisLineId[i] = panLastLineId[i - 1];

            if (i < nXSize - 1 &&
                eq.operator()(panLastLineVal[i + 1], panThisLineVal[i]) &&
                (panPolyIdMap[panLastLineId[i + 1]] !=
                 panPolyIdMap[panThisLineId[i]]))
            {
                MergePolygon(panLastLineId[i + 1], panThisLineId[i]);
            }
        }
        else if (i < nXSize - 1 && nConnectedness == 8 &&
                 eq.operator()(panLastLineVal[i + 1], panThisLineVal[i]))
        {
            panThisLineId[i] = panLastLineId[i + 1];
        }
        else
        {
            panThisLineId[i] = NewPolygon(panThisLineVal[i]);
            if (panThisLineId[i] < 0)
                return false;
        }
    }
    return true;
}

template class GDALRasterPolygonEnumeratorT<std::int64_t, IntEqualityTest>;

template class GDALRasterPolygonEnumeratorT<float, FloatEqualityTest>;

/*! @endcond */