Draw Path with zoom and darg

'm developing an application in which I'm pasting images, doing drawing and painting on canvas. This app can also Scale up/down the canvas or drag it to different location. My problem is: I can't get the correct canvas coordinates after scaling or dragging the canvas. I want to draw finger paint after the canvas is scaled or dragged but unable to retrieve the right place where i've touched...

@Override
public boolean onTouchEvent(MotionEvent event) {

    scaleListener.onTouchEvent(event);

    synchronized(thread.getSurfaceHolder()){

        switch ( event.getAction() & MotionEvent.ACTION_MASK ){

            case MotionEvent.ACTION_DOWN :
                // Remember our initial down event location.
                savedMatrix.set(m_matrix);
                start.set(event.getX() , event.getY());
                mode = DRAG;                
            break;

            case MotionEvent.ACTION_POINTER_DOWN :

                oldDist = spacing(event);
                if (oldDist > 10f) {

                    savedMatrix.set(m_matrix);
                    m_matrix.getValues(matrixValues);
                    midPoint(mid, event);
                    mode = ZOOM;
                }

             break;

            case MotionEvent.ACTION_UP :
            case MotionEvent.ACTION_POINTER_UP :
                    mode = NONE;

            break;

            case MotionEvent.ACTION_MOVE :

                if(mode==DRAG && isDragAllowd){
                        m_matrix.set(savedMatrix);
                        rebound(event.getX() , event.getY());
                }
                else if(mode==ZOOM){

                    float newDist = spacing(event);
                    if (newDist > 10f){

                            m_matrix.set(savedMatrix);

                            float scale = newDist/oldDist;
                            m_matrix.getValues(matrixValues);
                            float currentScale = matrixValues[Matrix.MSCALE_X];

                            // limit zoom
                            if (scale * currentScale > maxZoom){
                                    scale = maxZoom / currentScale;
                                    //scale = maxZoom;
                            }
                            else if (scale * currentScale < minZoom){
                                    scale = minZoom / currentScale;
                                    //scale = minZoom;
                            }

                            m_matrix.postScale(scale, scale, mid.x, mid.y);
                            m_matrix.getValues(matrixValues);

                  }

            }
       break;

    }

    return true; //done with this event so consume it


    }       

}

@Override
protected void onDraw(Canvas canvas){
    super.onDraw(canvas);

            canvas.drawColor(Color.WHITE);
        canvas.drawBitmap(currentBitmap, m_matrix, null);
        c2.drawColor(Color.BLACK); 
        commandManager.executeAll(c2); // Drawing all the Paints on Canvas c2
        // Overlay bitmap it's a transparent layour 
            canvas.drawBitmap(overlayBitmap, 0, 0, pTouch);

}

when user zoom the bitmap he is not able to draw over it , after zooming drawing doesn't happen at proper place.

use the following equation for transformed the points, after that user will not face an any difficulty painting during zoom or after scrolling.

 float f1 = (( motionEvent.getX() - m_transformedPoints[0] )/( m_transformedPoints[2] - m_transformedPoints[0] ))*currentBitmapWidth;
     float f2 = (( motionEvent.getY() - m_transformedPoints[1] )/( m_transformedPoints[3] - m_transformedPoints[1] ))*currentBitmapHeight; 

    //calculate the transformed view in onDraw Method
    this.m_transformedPoints[0] = 0.0F;
    this.m_transformedPoints[1] = 0.0F;
    this.m_transformedPoints[2] = currentBitmapWidth;
    this.m_transformedPoints[3] = currentBitmapHeight;
    this.m_matrix.mapPoints(this.m_transformedPoints);