imageview - Poor Image Quality on scaling image in android -

i working on android application development...when click on thumbnail image, enlarges give extreme poor quality...please me how resolve it

imageview ivpreview = (imageview)nagdialog.findviewbyid(r.id.image1);  int h =200 ; // height in pixels int w = 200; // width in pixels     bitmap scaled = bitmap.createscaledbitmap(bm, h, w, true);  ivpreview.setimagebitmap(scaled); 

if understand correctly want enlarge thumbnail. bad idea because thumbnails' size small image , enhancing makes worse. bitmap.createscaledbitmap() method stretches bitmap resulting in quality loss. should use bigger original image, create thubmnail image , load original image when click on it. here's code going:

  bitmap original = //get original image   bitmap thumbnail = bitmap.createscaledbitmap(original, 50, 50, true);    //when user clicks on imageview:   imgview.setimagebitmap(original);