Function GDALContourGenerateEx

alg/contour.cpp:569–966

* Create vector contours from raster DEM. * * This algorithm is an implementation of "Marching squares" [1] that will * generate contour vectors for the input raster band on the requested set * of contour levels. The vector contours are written to the passed in OGR * vector layer. Also, a NODATA value may be specified to identify pixels * that should not be considered in contour line genera

 * @return CE_None on success or CE_Failure if an error occurs.
 */
CPLErr GDALContourGenerateEx(GDALRasterBandH hBand, void *hLayer,
                             CSLConstList options, GDALProgressFunc pfnProgress,
                             void *pProgressArg)
{
    VALIDATE_POINTER1(hBand, "GDALContourGenerateEx", CE_Failure);

    if (pfnProgress == nullptr)
        pfnProgress = GDALDummyProgress;

    double contourInterval = 0.0;
    const char *opt = CSLFetchNameValue(options, "LEVEL_INTERVAL");
    if (opt)
    {
        contourInterval = CPLAtof(opt);
        // Written this way to catch NaN as well.
        if (!(contourInterval > 0))
        {
            CPLError(CE_Failure, CPLE_AppDefined,
                     "Invalid value for LEVEL_INTERVAL. Should be strictly "
                     "positive.");
            return CE_Failure;
        }
    }

    double contourBase = 0.0;
    opt = CSLFetchNameValue(options, "LEVEL_BASE");
    if (opt)
    {
        contourBase = CPLAtof(opt);
    }

    double expBase = 0.0;
    opt = CSLFetchNameValue(options, "LEVEL_EXP_BASE");
    if (opt)
    {
        expBase = CPLAtof(opt);
    }

    std::vector<double> fixedLevels;
    opt = CSLFetchNameValue(options, "FIXED_LEVELS");
    if (opt)
    {
        const CPLStringList aosLevels(
            CSLTokenizeStringComplex(opt, ",", FALSE, FALSE));
        fixedLevels.resize(aosLevels.size());
        for (size_t i = 0; i < fixedLevels.size(); i++)
        {
            // Handle min/max values
            if (EQUAL(aosLevels[i], "MIN"))
            {
                fixedLevels[i] = std::numeric_limits<double>::lowest();
            }
            else if (EQUAL(aosLevels[i], "MAX"))
            {
                fixedLevels[i] = std::numeric_limits<double>::max();
            }
            else
            {