iOS 手势放大缩小 算法

1.声明变量

CGFloat deviceZoom;
CGFloat lastZoome;

2.在视图上 添加缩放手势

UIPinchGestureRecognizer *pinchGestureRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handlePinch:)];
    
[self.videoView addGestureRecognizer:pinchGestureRecognizer];

3.实现方法

- (void) handlePinch:(UIPinchGestureRecognizer*) recognizer {

     CGFloat zoomSize = recognizer.scale;
     if ( zoomSize > 1 ) { // 放大
        if (zoomSize > lastZoome) {
            deviceZoom = zoomSize - lastZoome + deviceZoom;
            if (deviceZoom >5) {
                deviceZoom = 5;
            }
        }
    } else { // 缩小
        if (zoomSize < lastZoome) {
            deviceZoom = deviceZoom - (1 - zoomSize);
            if (deviceZoom < 1) {
                deviceZoom = 1;
            }
        }
    }
   lastZoome = zoomSize;
}

deviceZoom 就是最后得到的比例