title: How to Cut a ImageView to a subimage in the range of four specified points
body: <p>I know we can cat a imageView by useing system action "com.android.camera.action.CROP"</p>
  
  <p>But  some times i want to cut the image by myself like:</p>
  
  <p>bitmap of imageView A is 300dip*300dip ;</p>
  
  <p>sub-image should be the range in the four point lefttop(0,0) leftbottom(0,100) rightbottom(100,100),righttop(100,0).</p>
  
  <p>How to create the sub-image(bitmap)?</p>