can we zoom in zoom out the drawing we draw on the Canvas android

Question

I am trying to make an application in which i can zoom in and draw some thing on the image i have used following link to make a zoomable image view which is working fine zoom functionality for images

now the problem is that i dont know how to scale and translate whatever i am drawing on my canvas to the image size when it is zoomed out. following is the onDraw() function. i have recorded the touch points added them into a list and in this onDraw() function of my view i am retrieving those points but these points are relative to screen . i have to translate and scale it according to the image operation(in case of zoom in/out of the image) .

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

if(mMarkers!=null)
{
for(Marker m : mMarkers) {
    // draw the marker
     Log.v("IP","position"+ m.x+"    "+ m.y);
    Paint paint=new Paint();
    paint.setARGB(255, 2, 255, 2);
    canvas.drawText("O", m.x, m.y, paint);

    if(x!=-1){
         Log.v("IP","LINE"+x+"   " + y+ "  "+ m.x+"    "+ m.y);
    canvas.drawLine(x, y,m.x, m.y, paint);
    }
    x=m.x;
    y=m.y;
}
x=y=-1;

}

Hey take a look at the following SO question of mine.. this will help you. http://stackoverflow.com/questions/7524843/get-canvas-coordinates-after-scaling-up-down-or-dragging-in-android — Awais Tariq, Oct 17 '12 at 07:19

score 1 · Answer 1 · answered Jul 15 '13 at 12:48

1

Please try this code

public boolean onTouchEvent(MotionEvent env) {
float x = env.getX() / mScaleFactor + rect.left;
float y = env.getY() / mScaleFactor + rect.top;
}

answered Jul 15 '13 at 12:48

user2583537

13
3

score 1 · Accepted Answer · answered Jul 15 '13 at 13:43

1

Use this code

public boolean onTouchEvent(MotionEvent env) {
float x = env.getX() / mScaleFactor + rect.left;
float y = env.getY() / mScaleFactor + rect.top;
}

answered Jul 15 '13 at 13:43

vinmnit48

26
2

score 0 · Answer 3 · edited Oct 29 '12 at 08:28

0

you can get 9 point array from the matrix which contain the relative x,y and scale factor in x and y use this to convert you current x,y (which is with respect to screen) to x,y on original image and reconvert it before drawing again on different zoom levels.

edited Oct 29 '12 at 08:28

Mehul Mistri

15,037
14
70
94

answered Oct 29 '12 at 08:08

vinmnit48

26
2

can we zoom in zoom out the drawing we draw on the Canvas android

3 Answers3