download map with tracks in C++

Hello,

i trying to write some application in C++.

at this time I can handle download a map with correct center coordinate, using a url requests.

 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);
 ...

I need: a) Download a clear map and be able to paint to it in right scale. (in this situation i have download a picture - i know a center coordinate, but draw some tracks in pixels of picture is bad solution with horrible accuracy)

b) Download a map with drawed gps tracks, which i send.

please can someone push me to the right direction? Thanks much.