qgstiles.cpp

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/***************************************************************************
  qgstiles.cpp
  --------------------------------------
  Date                 : March 2020
  Copyright            : (C) 2020 by Martin Dobias
  Email                : wonder dot sk at gmail dot com
 ***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
 
#include "qgstiles.h"
 
#include "qgslogger.h"
 
QgsTileMatrix QgsTileMatrix::fromWebMercator( int zoomLevel )
{
  int numTiles = static_cast<int>( pow( 2, zoomLevel ) ); // assuming we won't ever go over 30 zoom levels
  double z0xMin = -20037508.3427892, z0yMin = -20037508.3427892;
  double z0xMax =  20037508.3427892, z0yMax =  20037508.3427892;
  double s0 = 559082264.0287178;   // scale denominator at zoom level 0 of GoogleCRS84Quad
 
  QgsTileMatrix tm;
  tm.mZoomLevel = zoomLevel;
  tm.mMatrixWidth = numTiles;
  tm.mMatrixHeight = numTiles;
  tm.mTileXSpan = ( z0xMax - z0xMin ) / tm.mMatrixWidth;
  tm.mTileYSpan = ( z0yMax - z0yMin ) / tm.mMatrixHeight;
  tm.mExtent = QgsRectangle( z0xMin, z0yMin, z0xMax, z0yMax );
  tm.mScaleDenom = s0 / pow( 2, zoomLevel );
  return tm;
}
 
QgsRectangle QgsTileMatrix::tileExtent( QgsTileXYZ id ) const
{
  double xMin = mExtent.xMinimum() + mTileXSpan * id.column();
  double xMax = xMin + mTileXSpan;
  double yMax = mExtent.yMaximum() - mTileYSpan * id.row();
  double yMin = yMax - mTileYSpan;
  return QgsRectangle( xMin, yMin, xMax, yMax );
}
 
QgsPointXY QgsTileMatrix::tileCenter( QgsTileXYZ id ) const
{
  double x = mExtent.xMinimum() + mTileXSpan / 2 * id.column();
  double y = mExtent.yMaximum() - mTileYSpan / 2 * id.row();
  return QgsPointXY( x, y );
}
 
QgsTileRange QgsTileMatrix::tileRangeFromExtent( const QgsRectangle &r )
{
  double x0 = std::clamp( r.xMinimum(), mExtent.xMinimum(), mExtent.xMaximum() );
  double y0 = std::clamp( r.yMinimum(), mExtent.yMinimum(), mExtent.yMaximum() );
  double x1 = std::clamp( r.xMaximum(), mExtent.xMinimum(), mExtent.xMaximum() );
  double y1 = std::clamp( r.yMaximum(), mExtent.yMinimum(), mExtent.yMaximum() );
  if ( x0 >= x1 || y0 >= y1 )
    return QgsTileRange();   // nothing to display
 
  double tileX1 = ( x0 - mExtent.xMinimum() ) / mTileXSpan;
  double tileX2 = ( x1 - mExtent.xMinimum() ) / mTileXSpan;
  double tileY1 = ( mExtent.yMaximum() - y1 ) / mTileYSpan;
  double tileY2 = ( mExtent.yMaximum() - y0 ) / mTileYSpan;
 
  QgsDebugMsgLevel( QStringLiteral( "Tile range of edges [%1,%2] - [%3,%4]" ).arg( tileX1 ).arg( tileY1 ).arg( tileX2 ).arg( tileY2 ), 2 );
 
  // figure out tile range from zoom
  int startColumn = std::clamp( static_cast<int>( floor( tileX1 ) ), 0, mMatrixWidth - 1 );
  int endColumn = std::clamp( static_cast<int>( floor( tileX2 ) ), 0, mMatrixWidth - 1 );
  int startRow = std::clamp( static_cast<int>( floor( tileY1 ) ), 0, mMatrixHeight - 1 );
  int endRow = std::clamp( static_cast<int>( floor( tileY2 ) ), 0, mMatrixHeight - 1 );
  return QgsTileRange( startColumn, endColumn, startRow, endRow );
}
 
QPointF QgsTileMatrix::mapToTileCoordinates( const QgsPointXY &mapPoint ) const
{
  double dx = mapPoint.x() - mExtent.xMinimum();
  double dy = mExtent.yMaximum() - mapPoint.y();
  return QPointF( dx / mTileXSpan, dy / mTileYSpan );
}