title: detect when mouse cursor is over an irregular shape picture in Qt5 and QML
body: <p>I'm developing a little application with Qt5 and QML (QtCreator and C++).</p>
  
  <p>I would like to display a map with countries and when user passes the mouse over a country I would like to change the color of the country, thought it would be easy, and it is if all countries were rectangles.</p>
  
  <pre><code>    Image {
      id: mycountry
      width: 250
      height: 250
      source: "images/myCountry_gray.png"
  
      MouseArea {
          anchors.fill: parent
          hoverEnabled : true
          onEntered: {
              region.source = "images/myCountry_red.png"
          }
          onExited: {
              region.source = "images/myCountry_gray.png"
          }
      }
  }
  </code></pre>
  
  <p>Unfortunately, countries have irregular shapes, and I would like only highlight the country when mouse cursor is inside its frontier</p>
  
  <p>Have you some idea how to develop that? I think it won't be possible using QML alone.</p>