private void ExtractTiles(PolygonShape polygonShape, string targetFilePath)
{
RectangleShape bbox = polygonShape.GetBoundingBox();
List <VectorTileRange> tileRanges = new List <VectorTileRange>();
for (int zoomLevel = 0; zoomLevel <= maxZoom; zoomLevel++)
{
VectorTileRange tileRange = GetTileRange(zoomLevel, bbox);
tileRanges.Add(tileRange);
}
ThinkGeoMBTilesLayer.CreateDatabase(targetFilePath);
var targetDBConnection = new SqliteConnection($"Data Source={targetFilePath}");
targetDBConnection.Open();
var targetMap = new TilesTable(targetDBConnection);
var targetMetadata = new MetadataTable(targetDBConnection);
var sourceDBConnection = new SqliteConnection($"Data Source={mbtilesPathFilename}");
sourceDBConnection.Open();
var sourceMap = new TilesTable(sourceDBConnection);
var sourceMetadata = new MetadataTable(sourceDBConnection);
sourceMetadata.ReadAllEntries();
ProjectionConverter projection = new ProjectionConverter(3857, 4326);
projection.Open();
var wgs84BBox = projection.ConvertToExternalProjection(bbox);
foreach (MetadataEntry entry in sourceMetadata.Entries)
{
if (entry.Name.Equals("center"))
{
PointShape centerPoint = wgs84BBox.GetCenterPoint();
entry.Value = $"{centerPoint.X},{centerPoint.Y},{maxZoom}";
}
else if (entry.Name.Equals("bounds"))
{
entry.Value = $"{wgs84BBox.UpperLeftPoint.X},{wgs84BBox.UpperLeftPoint.Y},{wgs84BBox.LowerRightPoint.X},{wgs84BBox.LowerRightPoint.Y}";
}
}
targetMetadata.Insert(sourceMetadata.Entries);
int recordLimit = 1000;
foreach (var tileRange in tileRanges)
{
long offset = 0;
bool isEnd = false;
while (!isEnd)
{
string querySql = $"SELECT * FROM {sourceMap.TableName} WHERE " + ConvetToSqlString(tileRange) + $" LIMIT {offset},{recordLimit}";
var entries = sourceMap.Query(querySql);
for (int i = entries.Count - 1; i >= 0; i--)
{
RectangleShape pbfExtent = GetPbfTileExent((int)entries[i].ZoomLevel, entries[i].TileColumn, entries[i].TileRow);
if (polygonShape.IsDisjointed(pbfExtent))
{
entries.RemoveAt(i);
}
}
targetMap.Insert(entries);
if (entries.Count < recordLimit)
{
isEnd = true;
}
offset = offset + recordLimit;
}
}
}