TileCoordinate p1_t = GeoCoordToTileCoord(p1_lat, p1_long, zoom);
TileCoordinate p2_t = GeoCoordToTileCoord(p2_lat, p2_long, zoom);

CPoint p1;
p1.x = 256*p1_t.intpartX + p1_t.fractpartX;
p1.y = 256*p1_t.intpartY + p1_t.fractpartY;

CPoint p2;
p2.x = 256*p2_t.intpartX + p2_t.fractpartX;
p2.y = 256*p2_t.intpartY + p2_t.fractpartY;

CPoint pIntersect;

for(double i  = p1.x; i < p2.x ; ++i)
{
    if(i%256 == 0)
    {
        double dy = p2.y-p1.y;
        double p = i/(p2.x-p1.x);
        pIntersect.y = dy*p;
    }
}
for(double i  = p1.y; i < p2.y ; ++i)
{
    if(i%256 == 0)
    {
        double dx = p2.x-p1.x;
        double p = i/(p2.y-p1.y);
        pIntersect.x = dx*p;
    }
}

//retransform px part to tile coord and add pIntersect