iOS扫描二维码实现手势拉近拉远镜头

在做扫码需求，往往会有放大镜头需求。

苹果提供了avcaptureconnection中，videoscaleandcropfactor：缩放裁剪系数,使用该属性，可以实现拉近拉远镜头。再结合手势uipinchgesturerecognizer，就很简单实现手势拉近拉远镜头。

手势代码

///记录开始的缩放比例
@property(nonatomic,assign)cgfloat begingesturescale;

///最后的缩放比例
@property(nonatomic,assign)cgfloat effectivescale;

- (void)camerainitover
{
 if (self.isvideozoom) {
  uipinchgesturerecognizer *pinch = [[uipinchgesturerecognizer alloc] initwithtarget:self action:@selector(pinchdetected:)];
  pinch.delegate = self;
  [self.view addgesturerecognizer:pinch];
 }
}

- (void)pinchdetected:(uipinchgesturerecognizer*)recogniser
{
 self.effectivescale = self.begingesturescale * recogniser.scale;
 if (self.effectivescale < 1.0){
  self.effectivescale = 1.0;
 }
 [self.scanobj setvideoscale:self.effectivescale];

}

- (bool)gesturerecognizershouldbegin:(uigesturerecognizer *)gesturerecognizer
{
 if ( [gesturerecognizer iskindofclass:[uipinchgesturerecognizer class]] ) {
  _begingesturescale = _effectivescale;
 }
 return yes;
}

拉近拉远镜头代码

- (void)setvideoscale:(cgfloat)scale
{
 [_input.device lockforconfiguration:nil];

 avcaptureconnection *videoconnection = [self connectionwithmediatype:avmediatypevideo fromconnections:[[self stillimageoutput] connections]];
 cgfloat maxscaleandcropfactor = ([[self.stillimageoutput connectionwithmediatype:avmediatypevideo] videomaxscaleandcropfactor])/16;

 if (scale > maxscaleandcropfactor)
  scale = maxscaleandcropfactor;

 cgfloat zoom = scale / videoconnection.videoscaleandcropfactor;

 videoconnection.videoscaleandcropfactor = scale;

 [_input.device unlockforconfiguration];

 cgaffinetransform transform = _videopreview.transform;
 [catransaction begin];
 [catransaction setanimationduration:.025];

  _videopreview.transform = cgaffinetransformscale(transform, zoom, zoom);

 [catransaction commit];

}

有一点需要注意：the videoscaleandcropfactor property may be set to a value in the range of 1.0 to videomaxscaleandcropfactor，videoscaleandcropfactor这个属性取值范围是1.0-videomaxscaleandcropfactor，如果你设置超出范围会崩溃哦！

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。