matrix.postScale(scale,scale,缩放中心,缩放中心); 
image.setImageMatrix(matrix);

package com.test.administrator.imageviewscale;

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.renderscript.Float2;
import android.renderscript.Float4;
import android.util.AttributeSet;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.widget.ImageView;
/**
 * Created by Administrator on 2016/3/21.
 */
public class MyImageView extends ImageView {
private PointF centerPoint;
private float firstdistance;
private Matrix matrix;
public MyImageView(Context context) {
super(context);
initParams();
}
private void initParams() {
matrix = new Matrix();
setImageMatrix(matrix);
}
public MyImageView(Context context, AttributeSet attrs) {
super(context, attrs);
initParams();
}
public MyImageView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
initParams();
}
@Override
public boolean onTouchEvent(MotionEvent event) {
int count = event.getPointerCount();
if(count == 1){
switch (event.getAction()){
case MotionEvent.ACTION_DOWN:
System.out.println("actiondown 1----");
break;
case MotionEvent.ACTION_MOVE:
System.out.println("actionmove 1----");
break;
case MotionEvent.ACTION_UP:
System.out.println("actionup 1----");
break;
default:
break;
}
}else if(count == 2){
switch (event.getAction()&MotionEvent.ACTION_MASK){
case MotionEvent.ACTION_POINTER_DOWN:
 firstdistance = getDistance(event);
centerPoint = getCenterPoint(event);
System.out.println("actiondown 2===");
break;
case MotionEvent.ACTION_MOVE:
float distance = getDistance(event);
float scale = distance / firstdistance;
matrix.postScale(scale,scale,centerPoint.x,centerPoint.y);
setImageMatrix(matrix);
System.out.println(scale + "====");
firstdistance = distance;
System.out.println("actionmove 2===");
break;
case MotionEvent.ACTION_UP:
break;
default:
break;
}
}
return true;
}
/**
 * 获取两个点的中心点坐标
 * @param event
 */
private PointF getCenterPoint(MotionEvent event) {
PointF point = new PointF();
point.x = (event.getX()+event.getX(1))/2;
point.y = (event.getY()+event.getY(1))/2;
return point;
}
/**
 * 两根手指时手指间的距离
 * @param event
 */
private float getDistance(MotionEvent event) {
float x1 = event.getX();
float y1 = event.getY();
float x2 = event.getX(1);
float y2 = event.getY(1);
float distance = (float) Math.sqrt((x1 - x2)*(x1 - x2)+(y1 - y2)*(y1- y2));
return distance;
}
}

<com.test.administrator.imageviewscale.MyImageView
android:id="@+id/iv"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:focusable="true"
android:clickable="true"
android:scaleType="matrix"
  android:src="@drawable/qq" />