title: Scaling image of ImageView while maintaining center point in same place
body: <p>I have set a prescaled Bitmap as ImageView's source. Then I've read Matrix of an <code>ImageView</code> and shift Bitmap of an ImageView via <code>matrix.postTranslate(shiftX, shiftY)</code>.</p>
  
  <p>Now I want to zoom in / out and image while maintaining center of <code>ImageView</code> at the same point of Bitmap that was before scale.</p>
  
  <p>If I try to zoom in an image with <code>matrix.postScale(zoom, zoom)</code>, point that I want to maintain (blue dot) shifts to other place (purple dot). </p>
  
  <p>I have tried several different ways to shift Bitmap back, but I cant get it to work correctly. I know initial Bitmap size, ImageView size, distances marked by doted line. Tried to calculate needed shift and use <code>matrix.postTranslate(-zoomshiftX, -zoomshiftY)</code> afterwards, but it doesn't shift correctly.</p>
  
  <p>Even found out, that underlying Bitmap's pixel count doesnt change after  matrix.postScale() function and tried matrix.postTranslate(-zoomshiftX/zoom, -zoomshiftY/zoom) - but still no luck.</p>
  
  <p>How do I achieve such zoom?</p>
  
  <p><img src="https://i.stack.imgur.com/qjkC9.jpg" alt="scalling issue"></p>