简单二维码的读取

二维码的读取
1.需要导入AVFoundation框架
2.步骤：
// 1). 初始化捕捉设备：AVCaptureDevice；
// 2)准备捕捉输入流：AVCaptureDeviceInput；
// 3)设置元数据输出：AVCaptureMetadataOutput
// （设置输出代理：setMetadataObjectsDelegate,设置扫描的范围：rectOfInterest）；
// 4)显示捕捉会话层：AVCaptureSession
// （输入流添加到会话层，输出流添加到会话层，必须设置元数据的输出类型：metadataObjectTypes）；
// 5)捕捉对象预览图层：（将预览图层插入到当前视图的layer层上 ： insertSublayer: atIndex: ；
// 6)启动拍摄会话：startRunning

3.code:步骤：

1).实例化拍摄设备

AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];    

2).准备输入设备

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:nil];

3).设置元输出数据

//3).1实例化拍摄元输出数据
AVCaptureMetadataOutput *dataOutput = [[AVCaptureMetadataOutput alloc]init];

//3).2设置元代理
[dataOutput setMetadataObjectsDelegate:self   queue:dispatch_get_main_queue()];

4).设置扫描范围为扫描框内,注意,设置范围的x,y轴是于iOS的x,y轴相反的

CGRect rect = KScreenBounds;    
// containerView是扫描框控件
CGRect containerRect = _containerView.frame;
// dataOutput.rectOfInterest =  CGRectMake(0, 0, 1, 1);  
dataOutput.rectOfInterest = CGRectMake(containerRect.origin.y / rect.size.height ,  containerRect.origin.x / rect.size.width, containerRect.size.height / rect.size.height, containerRect.size.width /  rect.size.width);

5).添加拍摄会话层

AVCaptureSession *session = [[AVCaptureSession alloc]init]; 
//5).1 输入添加到会话层 AVCaptureDeviceInput extend  AVCaptureInput
[session addInput:input];

//5).2 输出也添加到会话层 AVCaptureMetadataOutput extend  AVCaptureOutput
[session addOutput:dataOutput];

// 5).3 设置输出数据类型，需要将元数据输出添加到会话后，才能指定元数据类型，否则会报错
[dataOutput setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];
self.session = session;

6).捕捉对象预览图层

AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
previewLayer.frame = self.view.bounds;
self.previewLayer = previewLayer;
//6).1 将预览图层插入到当前视图的layer层上
[self.view.layer insertSublayer:previewLayer atIndex:0];
//启动拍摄会话
[session startRunning];

4.AVCaptureMetadataOutputObjectsDelegate输出的结果
//调用代理方法：会不停的调用

 // 1. 如果扫描完成，停止会话
  [self.session stopRunning];

 // 2. 删除预览图层
 //  [self.previewLayer removeFromSuperlayer];

NSLog(@"%@", metadataObjects);
// 3. 设置界面显示扫描结果

if (metadataObjects.count > 0) {
    AVMetadataMachineReadableCodeObject *obj = metadataObjects[0];
    // 提示：如果需要对url或者名片等信息进行扫描，可以在此进行扩展！
    NSLog(@"%@", obj.stringValue);
    content = obj.stringValue;
 }

5.选择相册中有效的二维码：通过代理（UIImagePickerControllerDelegate）方法获得UImage

UIImage *imge = [info valueForKey:UIImagePickerControllerEditedImage];
NSLog(@"%@",imge);
//取出选中的图片
UIImage *pickImage = info[UIImagePickerControllerOriginalImage];
NSData *imageData = UIImagePNGRepresentation(pickImage);
CIImage *ciImage = [CIImage imageWithData:imageData];

//创建探测器
CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeQRCode context:nil options:@{CIDetectorAccuracy: CIDetectorAccuracyLow}];
NSArray *feature = [detector featuresInImage:ciImage];
if (feature.count == 0) {
    content = @"http://www.jianshu.com/users/319658cc7821/latest_articles/";
}
//取出探测到的数据
for (CIQRCodeFeature *result in feature) {
    content = result.messageString;
}
//进行处理(音效、页面跳转,返回等)
//    [self playBeep];
     [_pickerCtr dismissViewControllerAnimated:YES completion:nil];