contour-creator/src/main.cpp

#include "contour_creator.hh"
#include <gdal/ogr_api.h>
#include "ogrsf_frmts.h"
#include <gdal/ogr_core.h>
#include <gdal/ogr_feature.h>
#include <gdal/ogr_geometry.h>
#include <iostream>
#include <ostream>
#include <vector>
#include <cstdint>
#include <gdal/gdal.h>
#include "gdal/gdal_priv.h"
#include <gdal/gdal_frmts.h>
#include <omp.h>

CellMap produce_cellmap(HeightMap* heightmap, float z)
{
    int length = (heightmap->width-1)*(heightmap->height-1);
    uint8_t *cells = (uint8_t *) CPLMalloc(sizeof(uint8_t)*length);
    for (int i = 0; i<length; i++) {
        int y = i/(heightmap->width-1);
        int x = i%(heightmap->width-1);
        uint8_t result = (heightmap->get_pixel(x,y)>z) + 
        (heightmap->get_pixel(x+1,y)>z)*2 +
        (heightmap->get_pixel(x+1,y+1)>z)*4 +
        (heightmap->get_pixel(x,y+1)>z)*8;
        *(cells + i) = result;
    }
    
    return CellMap(heightmap->width-1, heightmap->height-1, cells, heightmap->reference_system, heightmap->geotransform);


}

std::vector<CellMap> vector_cellmap(HeightMap* heightmap, int interval)
{
    int num_contours = (heightmap->max - heightmap->min)/interval;
    std::vector<CellMap> vector_contours;
    omp_set_num_threads(12);

    #pragma omp parallel
    {
        std::vector<CellMap> vec_private;
        #pragma omp for
        for (int i = 1; i <= num_contours; i++) 
        {
            vec_private.push_back(produce_cellmap(heightmap, heightmap->min + interval*i));
        }
        #pragma omp critical
        vector_contours.insert(vector_contours.end(), vec_private.begin(), vec_private.end());

    }
        return vector_contours;
}

std::tuple<double, double> local_to_projected(double* geotransform, int x, int y)
{
    return {
        geotransform[1] * x + geotransform[2] * y +
        geotransform[1] * 0.5 + geotransform[2] * 0.5 + geotransform[0],
        geotransform[4] * x + geotransform[5] * y +
        geotransform[4] * 0.5 + geotransform[5] * 0.5 + geotransform[3]
        };
}

constexpr std::tuple<double, double, double, double> marching_squares_lookup(int mcase)
{
    switch (mcase) {
        case 1: return {0, 0.5, 0.5, 0};
        case 2: return {1, 0.5, 0.5, 0};
        case 3: return {0, 0.5, 1, 0};
        case 4: return {0.5, 1, 1, 0.5};
        case 5: return {0, 0, 0, 0}; //FIXME
        case 6: return {0.5, 1, 0.5, 0};
        case 7: return {0, 0.5, 0.5, 1};
        case 8: return {0, 0.5, 0.5, 1};
        case 9: return {0.5, 1, 0.5, 0};
        case 10: return {0, 0, 0, 0}; //FIXME
        case 11: return {0.5, 1, 1, 0.5};
        case 12: return {0, 0.5, 1, 0.5};
        case 13: return {0.5, 0, 1, 0.5};
        case 14: return {0, 0.5, 0.5, 0};
    };
}
void write_output_file(std::vector<CellMap> cellmaps, const char *filepath)
{

    const char *pszDriverName = "GeoJSON";
    GDALDriver *poDriver;

    GDALAllRegister();

    poDriver = GetGDALDriverManager()->GetDriverByName(pszDriverName );
    if( poDriver == NULL )
    {
        printf( "%s driver not available.\n", pszDriverName );
        exit( 1 );
    }

    GDALDataset *poDS;

    poDS = poDriver->Create( filepath, 0, 0, 0, GDT_Unknown, NULL );
    if( poDS == NULL )
    {
        printf( "Creation of output file failed.\n" );
        exit( 1 );
    }

    OGRLayer *poLayer;

    poLayer = poDS->CreateLayer( "contours", &(cellmaps[0]).reference_system, wkbLineString, NULL );
    if( poLayer == NULL )
    {
        printf( "Layer creation failed.\n" );
        exit( 1 );
    }

    OGRFieldDefn oField( "Name", OFTString );

    oField.SetWidth(32);

    if( poLayer->CreateField( &oField ) != OGRERR_NONE )
    {
        printf( "Creating Name field failed.\n" );
        exit( 1 );
    }
    for (int j = 0; j < cellmaps.size(); j++)
    {
        CellMap* cellmap = &cellmaps[j];

        for (int i = 0; i < cellmap->height*cellmap->width; i++) 
        {
            if (*(cellmap->cells + i) != 0 && *(cellmap->cells + i) != 15)
            {
                OGRFeature *feature;
                OGRLineString *geometry = new OGRLineString();
                feature = OGRFeature::CreateFeature( poLayer->GetLayerDefn() );
                feature->SetField( "Name", j );
                int x_raw = i%cellmap->width;
                int y_raw = i/cellmap->width;
                auto [x, y] = local_to_projected(cellmap->geotransform, x_raw, y_raw);
                auto [x_bl, y_bl, x_tr, y_tr] = marching_squares_lookup(*(cellmap->cells + i) );
                //std::cout << x << ", " << y << "  ";
                geometry->setPoint( geometry->getNumPoints(), x+x_tr*0.25, y+y_tr*0.25 ); 
                geometry->setPoint( geometry->getNumPoints(), x+x_bl*0.25, y+y_bl*0.25 ); 
                

                if ( feature->SetGeometry(geometry) != OGRERR_NONE)
                {
                    printf( "Failed to set geometry.\n" );
                    exit( 1 );
                }
                OGRGeometryFactory::destroyGeometry(geometry);
                if( poLayer->CreateFeature( feature ) != OGRERR_NONE )
                {
                    printf( "Failed to create feature in shapefile.\n" );
                    exit( 1 );
                }
                OGRFeature::DestroyFeature( feature );  
                    }
            
        }
        

    }

    GDALClose( poDS );
}

int main(int argc, const char* argv[])
{
    const char* filepath = argv[1];
    HeightMap map(filepath); 
    
    std::cout << "x: " << map.width << "    y: " << map.height << "\n";
    std::cout << "max: " << map.max << "    min: " << map.min << "\n";

    map.blur(0.8);
    
    auto cellmap = produce_cellmap(&map, 40);
    
    auto cellmaps = vector_cellmap(&map, 5);
    write_output_file(cellmaps, "out.geojson");
}