slippymap.cpp Example File

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 #include <math.h>

 #include <QtWidgets>
 #include <QtNetwork>
 #include "slippymap.h"

 #ifndef M_PI
 #define M_PI 3.14159265358979323846
 #endif

 uint qHash(const QPoint& p)
 {
     return p.x() * 17 ^ p.y();
 }

 // tile size in pixels
 const int tdim = 256;

 QPointF tileForCoordinate(qreal lat, qreal lng, int zoom)
 {
     qreal zn = static_cast<qreal>(1 << zoom);
     qreal tx = (lng + 180.0) / 360.0;
     qreal ty = (1.0 - log(tan(lat * M_PI / 180.0) +
                           1.0 / cos(lat * M_PI / 180.0)) / M_PI) / 2.0;
     return QPointF(tx * zn, ty * zn);
 }

 qreal longitudeFromTile(qreal tx, int zoom)
 {
     qreal zn = static_cast<qreal>(1 << zoom);
     qreal lat = tx / zn * 360.0 - 180.0;
     return lat;
 }

 qreal latitudeFromTile(qreal ty, int zoom)
 {
     qreal zn = static_cast<qreal>(1 << zoom);
     qreal n = M_PI - 2 * M_PI * ty / zn;
     qreal lng = 180.0 / M_PI * atan(0.5 * (exp(n) - exp(-n)));
     return lng;
 }

 SlippyMap::SlippyMap(QObject *parent)
     : QObject(parent), width(400), height(300), zoom(15),
       latitude(59.9138204), longitude(10.7387413)
 {
     m_emptyTile = QPixmap(tdim, tdim);
     m_emptyTile.fill(Qt::lightGray);

     QNetworkDiskCache *cache = new QNetworkDiskCache;
     cache->setCacheDirectory(QDesktopServices::storageLocation
                                 (QDesktopServices::CacheLocation));
     m_manager.setCache(cache);
     connect(&m_manager, SIGNAL(finished(QNetworkReply*)),
             this, SLOT(handleNetworkData(QNetworkReply*)));
 }

 void SlippyMap::invalidate()
 {
     if (width <= 0 || height <= 0)
         return;

     QPointF ct = tileForCoordinate(latitude, longitude, zoom);
     qreal tx = ct.x();
     qreal ty = ct.y();

     // top-left corner of the center tile
     int xp = width / 2 - (tx - floor(tx)) * tdim;
     int yp = height / 2 - (ty - floor(ty)) * tdim;

     // first tile vertical and horizontal
     int xa = (xp + tdim - 1) / tdim;
     int ya = (yp + tdim - 1) / tdim;
     int xs = static_cast<int>(tx) - xa;
     int ys = static_cast<int>(ty) - ya;

     // offset for top-left tile
     m_offset = QPoint(xp - xa * tdim, yp - ya * tdim);

     // last tile vertical and horizontal
     int xe = static_cast<int>(tx) + (width - xp - 1) / tdim;
     int ye = static_cast<int>(ty) + (height - yp - 1) / tdim;

     // build a rect
     m_tilesRect = QRect(xs, ys, xe - xs + 1, ye - ys + 1);

     if (m_url.isEmpty())
         download();

     emit updated(QRect(0, 0, width, height));
 }

 void SlippyMap::render(QPainter *p, const QRect &rect)
 {
     for (int x = 0; x <= m_tilesRect.width(); ++x)
         for (int y = 0; y <= m_tilesRect.height(); ++y) {
             QPoint tp(x + m_tilesRect.left(), y + m_tilesRect.top());
             QRect box = tileRect(tp);
             if (rect.intersects(box)) {
                 if (m_tilePixmaps.contains(tp))
                     p->drawPixmap(box, m_tilePixmaps.value(tp));
                 else
                     p->drawPixmap(box, m_emptyTile);
             }
         }
 }

 void SlippyMap::pan(const QPoint &delta)
 {
     QPointF dx = QPointF(delta) / qreal(tdim);
     QPointF center = tileForCoordinate(latitude, longitude, zoom) - dx;
     latitude = latitudeFromTile(center.y(), zoom);
     longitude = longitudeFromTile(center.x(), zoom);
     invalidate();
 }

 void SlippyMap::handleNetworkData(QNetworkReply *reply)
 {
     QImage img;
     QPoint tp = reply->request().attribute(QNetworkRequest::User).toPoint();
     QUrl url = reply->url();
     if (!reply->error())
         if (!img.load(reply, 0))
             img = QImage();
     reply->deleteLater();
     m_tilePixmaps[tp] = QPixmap::fromImage(img);
     if (img.isNull())
         m_tilePixmaps[tp] = m_emptyTile;
     emit updated(tileRect(tp));

     // purge unused spaces
     QRect bound = m_tilesRect.adjusted(-2, -2, 2, 2);
     foreach(QPoint tp, m_tilePixmaps.keys())
     if (!bound.contains(tp))
         m_tilePixmaps.remove(tp);

     download();
 }

 void SlippyMap::download()
 {
     QPoint grab(0, 0);
     for (int x = 0; x <= m_tilesRect.width(); ++x)
         for (int y = 0; y <= m_tilesRect.height(); ++y) {
             QPoint tp = m_tilesRect.topLeft() + QPoint(x, y);
             if (!m_tilePixmaps.contains(tp)) {
                 grab = tp;
                 break;
             }
         }
     if (grab == QPoint(0, 0)) {
         m_url = QUrl();
         return;
     }

     QString path = "http://tile.openstreetmap.org/%1/%2/%3.png";
     m_url = QUrl(path.arg(zoom).arg(grab.x()).arg(grab.y()));
     QNetworkRequest request;
     request.setUrl(m_url);
     request.setRawHeader("User-Agent", "Nokia (Qt) Graphics Dojo 1.0");
     request.setAttribute(QNetworkRequest::User, QVariant(grab));
     m_manager.get(request);
 }

 QRect SlippyMap::tileRect(const QPoint &tp)
 {
     QPoint t = tp - m_tilesRect.topLeft();
     int x = t.x() * tdim + m_offset.x();
     int y = t.y() * tdim + m_offset.y();
     return QRect(x, y, tdim, tdim);
 }