title: UISlider with image on TrackImage
body: <p>I have UISLider with set setMinimumTrackImage and setMaximumTrackImage. Both images have same resolution. If I move slider... images are not showed correctly. They are moving, when I am draging slider control thumb.
  I tried to use </p>
  
  <pre><code>UIImage * sliderBarImage1 = [UIImage imageNamed:@"slider_b"];
  UIImage * sliderBarImage2 = [UIImage imageNamed:@"slider_w"];
  
  sliderBarImage1 = [sliderBarImage1 stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0];
  sliderBarImage2 = [sliderBarImage2 stretchableImageWithLeftCapWidth:10.0 topCapHeight:0.0];
  
  [self.slider setMinimumTrackImage:sliderBarImage1 forState:UIControlStateNormal];
  [self.slider setMaximumTrackImage:sliderBarImage2 forState:UIControlStateNormal];
  </code></pre>
  
  <p>With or without stretchableImageWithLeftCapWidth its not correct. And when I rotate phone, images on track are scaled incorectly, so informations in image are shifted. 
  Similar to image in this post: <a href="https://stackoverflow.com/questions/7089484/how-to-place-image-on-uislider">How to place image on UISlider?</a>. When I move slider, images are starting to move and colors are not overlapping in min and max track, resulting in ugly effect.</p>