draw on pinch zoom canvas android
<p>I am making an application in android in which, I want to draw on <strong>pinch zoom image</strong> on canvas and when i zoom out it should not distort. </p>

<p>I have to use both fingers in opposite and same direction for zoom <strong>in/out</strong> using pinch zoom and write on that zoom part without blurring the canvas. </p>

<p>This is my code for pinch zoom of image , now i want to draw using single finger on that view.</p>

<p><strong>I am stuck at drawing on the view. this is code</strong>:</p>

<pre><code>package com.pericent;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.FrameLayout;
import android.widget.GridView;
import android.widget.ImageView;

public class Touch extends Activity implements OnTouchListener {
private static final String TAG = "Touch";

private static final float MIN_ZOOM = 1.0f;
private static final float MAX_ZOOM = 8.0f;

// These matrices will be used to move and zoom image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();

// We can be in one of these 3 states
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;

// Remember some things for zooming
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;

ImageView view;
Canvas canvas;
Path path;
Paint paint;
private float mX, mY;
private static final float TOUCH_TOLERANCE = 4;
MotionEvent event;



@Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.main);
   view = (ImageView) findViewById(R.id.imageView);
   //view.setLayoutParams(new GridView.LayoutParams(85, 85));
   view.setScaleType(ImageView.ScaleType.FIT_CENTER);
   view.setOnTouchListener(this);   

   float width = view.getMeasuredWidth(); 
   float height = view.getMeasuredHeight();
   Log.v(TAG,"---width:"+width+"---height:"+height);  
   onDraw();   
}




public void myDrawLine(float x,float y){
    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(Color.BLUE);
    paint.setAlpha(100);

//  paint = new Paint();
    paint.setAntiAlias(true);
    paint.setDither(true);
//  paint.setColor(0xFFFF0000);
    paint.setStyle(Paint.Style.STROKE);
//  paint.setStrokeJoin(Paint.Join.ROUND);
    paint.setStrokeCap(Paint.Cap.ROUND);
    paint.setStrokeWidth(1);

    canvas.drawLine(0, 0, x, y, paint);
    Log.v(TAG,"---in myDrawLine() method---");
//  view.draw(canvas);
    //view.in
}

/**
float[] values = new float[9];
matrix.mapRadius(1);
matrix.getValues(values);
globalX = values[2];
globalY = values[5];
width = values[0]*imageWidth;
height = values[4]*imageHeight;



*/



//@Override
public void onDraw() {
    Bitmap bitmap = Bitmap.createBitmap(600,900, Bitmap.Config.ARGB_8888); 
    bitmap =  BitmapFactory.decodeResource(getResources(),R.drawable.map).copy(Bitmap.Config.ARGB_8888, true);
    canvas = new Canvas(bitmap); 
    path = new Path();
    view.setImageBitmap(bitmap);    
    paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(Color.BLUE);
    paint.setAlpha(100);
    canvas.drawBitmap(bitmap, 0, 0, paint); 
//  canvas.drawColor(Color.TRANSPARENT);
    canvas.drawBitmap(bitmap, 0, 0, paint);
    canvas.drawPath(path, paint);

    //canvas.drawRect(0, 0, 100, 100, paint); // transparent black on image
//  view.draw(canvas);
    Log.d(TAG, "---inside onDraw() method---");
}

public boolean onTouch(View v, MotionEvent event) {

    float x = event.getX();
    float y = event.getY();
    float scale;

    view = (ImageView) v;
   view.setScaleType(ImageView.ScaleType.MATRIX);

   // Dump touch event to log
   dumpEvent(event);

   // Handle touch events here...
   switch (event.getAction() &amp; MotionEvent.ACTION_MASK) {

   case MotionEvent.ACTION_DOWN: //first finger down only

       //for drawing
//     touch_start(x, y);
//       invalidate();





      savedMatrix.set(matrix);
      start.set(event.getX(), event.getY());
      Log.d(TAG, "mode=DRAG" );
      Log.v(TAG,"MotionEvent.ACTION_DOWN: //first finger down only");
      mode = DRAG;
      break;
   case MotionEvent.ACTION_UP: //first finger lifted
//     touch_up();
//       invalidate();

   case MotionEvent.ACTION_POINTER_UP: //second finger lifted
      mode = NONE;
      Log.d(TAG, "mode=NONE" );
      Log.v(TAG,"MotionEvent.ACTION_POINTER_UP: //second finger lifted");
      break;
   case MotionEvent.ACTION_POINTER_DOWN: //second finger down
      oldDist = spacing(event);
      Log.d(TAG, "oldDist=" + oldDist);
      Log.v(TAG,"MotionEvent.ACTION_POINTER_DOWN: //second finger down");
      if (oldDist &gt; 5f) {
         savedMatrix.set(matrix);
         midPoint(mid, event);
         mode = ZOOM;
         Log.d(TAG, "mode=ZOOM" );
      }
      break;

   case MotionEvent.ACTION_MOVE: 
//     touch_move(x, y);
//       invalidate();
      if (mode == DRAG) { //movement of first finger
         matrix.set(savedMatrix);
       //  if (view.getLeft() &gt;= -392){
             Log.v("in DrG", "DRAWING POINT AT X="+event.getX()+" Y="+event.getY());
             myDrawLine(event.getX(),event.getY());
            //matrix.postTranslate(event.getX() - start.x, event.getY() - start.y);
     //    }
      }
      else if (mode == ZOOM) { //pinch zooming
         float newDist = spacing(event);
         Log.d(TAG, "newDist=" + newDist);
         if (newDist &gt; 5f) {
            matrix.set(savedMatrix);
            scale = newDist / oldDist; //thinking i need to play around with this value to limit it**
            matrix.postScale(scale, scale, mid.x, mid.y);
         }
      }
      break;
   }

   // Perform the transformation
   view.setImageMatrix(matrix);

   return true; // indicate event was handled
}

private void touch_start(float x, float y) {
  //  path.reset();
    path.moveTo(x, y);
    mX = x;
    mY = y;
}
private void touch_move(float x, float y) {
    float dx = Math.abs(x - mX);
    float dy = Math.abs(y - mY);
    if (dx &gt;= TOUCH_TOLERANCE || dy &gt;= TOUCH_TOLERANCE) {
        path.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
        mX = x;
        mY = y;
    }
}
private void touch_up() {
    path.lineTo(mX, mY);
    // commit the path to our offscreen
    canvas.drawPath(path, paint);
    // kill this so we don't double draw
    path.reset();
}






private float spacing(MotionEvent event) {
   float x = event.getX(0) - event.getX(1);
   float y = event.getY(0) - event.getY(1);
   return FloatMath.sqrt(x * x + y * y);
}

private void midPoint(PointF point, MotionEvent event) {
   float x = event.getX(0) + event.getX(1);
   float y = event.getY(0) + event.getY(1);
   point.set(x / 2, y / 2);
}

/** Show an event in the LogCat view, for debugging */
private void dumpEvent(MotionEvent event) {
   String names[] = { "DOWN" , "UP" , "MOVE" , "CANCEL" , "OUTSIDE" ,
      "POINTER_DOWN" , "POINTER_UP" , "7?" , "8?" , "9?" };
   StringBuilder sb = new StringBuilder();
   int action = event.getAction();
   int actionCode = action &amp; MotionEvent.ACTION_MASK;
   sb.append("event ACTION_" ).append(names[actionCode]);
   if (actionCode == MotionEvent.ACTION_POINTER_DOWN
         || actionCode == MotionEvent.ACTION_POINTER_UP) {
      sb.append("(pid " ).append(
      action &gt;&gt; MotionEvent.ACTION_POINTER_ID_SHIFT);
      sb.append(")" );
   }
   sb.append("[" );
   for (int i = 0; i &lt; event.getPointerCount(); i++) {
      sb.append("#" ).append(i);
      sb.append("(pid " ).append(event.getPointerId(i));
      sb.append(")=" ).append((int) event.getX(i));
      sb.append("," ).append((int) event.getY(i));
      if (i + 1 &lt; event.getPointerCount())
         sb.append(";" );
   }
   sb.append("]" );
   Log.d(TAG, sb.toString());
}

}
</code></pre>

<p><strong>This is my xml code</strong>:
    
    </p>

<pre><code>&lt;ImageView android:id="@+id/imageView"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:src="@drawable/map"
     android:scaleType="matrix" &gt;

&lt;/ImageView&gt;


&lt;/FrameLayout&gt;
</code></pre>

<p>Please help me for this as soon as possible.
Thank you in advance.</p>
