在图形上下文中将数据放大一倍

Question

I am trying to zoom in my canvas when the user pinches the screen In IOS.

I am translating my code from Android(which works), here's a snift:

focusX = gestureDetector.getFocusX();
focusY = gestureDetector.getFocusY();

enter code herecanvas.scale(mScaleFactor,mScaleFactor,focusX,focusY);

my translated IOS code doesn't give the same results:

- (void)onScale:(UIPinchGestureRecognizer *)gesture
{
    if (gesture.state == UIGestureRecognizerStateBegan) {
         CGPoint endPoint = [gesture locationInView:self];
         focusX = endPoint.x;
         focusY = endPoint.y;
    }
}

CGContextTranslateCTM(UIGraphicsGetCurrentContext(), focusX, focusY);
CGContextScaleCTM(UIGraphicsGetCurrentContext(), mScaleFactor, mScaleFactor)

Why?

Answer 1

I found the problem, CGContextTranslateCTM is redundant. Also I had another problem , the scale factor of the recognizer in Android is relative whereas in IOS it's absolute.