iOS之Scanning的实现

http://i.cnblogs.com/EditPosts.aspx?postid=5288517

//写在最前

/*

AVFoundation原生框架的好处就是扫描特别快效率特别高，但是可能会遇到一个问题就是不知道怎么去限制扫描范围。

二维码扫描有关优秀第三方库:---- ZXing google推出的开源项目-----ZBar SDK 里面也有详细的文档

*/

引入头文件导入流媒体需要的框架

@import AVFoundation;

//遵守协议 AVCaptureMetadataOutputObjectsDelegate

@property (nonatomic,strong)AVCaptureSession *session;

@property (nonatomic,strong)AVCaptureVideoPreviewLayer *layer;

- (void)viewDidLoad {

[super viewDidLoad];

[self startRunningSession];

[self.view bringSubviewToFront:self.v];

self.animV = [[UIView alloc]initWithFrame:CGRectMake(92, 124, 190, 2)];

self.animV.backgroundColor = [UIColor redColor];

[self.view addSubview:self.animV];

if (!_t) {

self.t = [NSTimer scheduledTimerWithTimeInterval:4.2/24 target:self selector:@selector(animateShow) userInfo:nil repeats:YES];

}

}

- (void)animateShow{

CGRect frame = self.animV.frame;

frame.origin.y += 8;

if (frame.origin.y >= 316) {

frame.origin.y = 116;

}

self.animV.frame = frame;

}

- (void)startRunningSession

// 获取 AVCaptureDevice 实例

NSError * error;

AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

[captureDevice setTorchMode:AVCaptureTorchModeOn];   //开启照明

// 初始化输入流

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:captureDevice error:&error];

if (!input) {

NSLog(@"%@", [error localizedDescription]);

}

// 创建会话

_session = [[AVCaptureSession alloc] init];

if ([_session canAddInput:input]) {

// 添加输入流

[_session addInput:input];

}

// 初始化输出流

AVCaptureMetadataOutput *captureMetadataOutput = [[AVCaptureMetadataOutput alloc] init];

if ([_session canAddOutput:captureMetadataOutput]) {

// 添加输出流

[_session addOutput:captureMetadataOutput];

}

// 创建dispatch queue.

dispatch_queue_t dispatchQueue;

dispatchQueue = dispatch_queue_create(kScanName, NULL);

[captureMetadataOutput setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];

[captureMetadataOutput setRectOfInterest:CGRectMake(100/667.0,87/375.0,200/667.0, 200/375.0)];

// 设置元数据类型 AVMetadataObjectTypeQRCode

[captureMetadataOutput setMetadataObjectTypes:@[AVMetadataObjectTypeQRCode]];

//value CGRectMake(0, 0, 1, 1). Metadata objects whose bounds do not intersect with the rectOfInterest will not be returned.

// 创建输出对象

_layer = [AVCaptureVideoPreviewLayer layerWithSession:_session];

[_layer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

[_layer setFrame:self.view.layer.frame];

[self.view.layer addSublayer:_layer];

// 开始会话

[_session startRunning];

}

#pragma  -   mark   -     AVCaptureMetadataOutputObjectsDelegate

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{

NSLog(@"-------");

if (metadataObjects && metadataObjects.count) {

AVMetadataMachineReadableCodeObject *metadataObj = [metadataObjects objectAtIndex:0];

NSString *result;

if ([[metadataObj type] isEqualToString:AVMetadataObjectTypeQRCode]) {

result = metadataObj.stringValue;

NSLog(@"result:%@",result);

} else {

NSLog(@"不是二维码");

}

[_session stopRunning];

_session = nil;

UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"QRCodeInfo"

message:result

delegate:nil

cancelButtonTitle:@"cancel"

otherButtonTitles: nil];

[alert show];

}

}

#import "cornView.h"

@import CoreGraphics;

//给扫描控制器加一个View进行遮盖处理就是上面的self.v

- (void)drawRect:(CGRect)rect {

UIBezierPath *p = [UIBezierPath bezierPathWithRect:CGRectMake(87, 56, 200, 200)];

//  NSLog(@"0000");

[[UIColor clearColor]setFill];

填充为中间没有颜色

[p fill];

填充之外的不烦

[p fillWithBlendMode:kCGBlendModeClear alpha:1];

}

//写在最后

很小的二维码,边长不到1cm，于是就修改了 sessionPreset 为 1080p 的，当时用的是ZXing, 当把图片质量改清楚时，也造成了性能的下降，基本打开扫描界面就会报memoryWarning，但是也确实解决了小二维码扫描的问题。

AVCaptureSession 可以设置 sessionPreset 属性，这个决定了视频输入每一帧图像质量的大小。

• AVCaptureSessionPreset320x240
• AVCaptureSessionPreset352x288
• AVCaptureSessionPreset640x480
• AVCaptureSessionPreset960x540
• AVCaptureSessionPreset1280x720
• AVCaptureSessionPreset1920x1080

以上列举了部分的属性值，分别代表输入图片质量大小，一般来说AVCaptureSessionPreset640x480就够使用，但是如果要保证较小的二维码图片能快速扫描，最好设置高些，如AVCaptureSessionPreset1920x1080(就是我们常说的1080p).

提升扫描速度和性能的就是设置解析的范围，在zbar和zxing中就是scanCrop, AVFoundation中设置 AVCaptureMetadataOutput 的 rectOfInterest 属性来配置解析范围。

captureOutput.rectOfInterest = CGRectMake(cropRect.origin.y/size.height,
                                         cropRect.origin.x/size.width,
                                         cropRect.size.height/size.height,
                                         cropRect.size.width/size.width);
rectOfInterest是基于图像的大小裁剪的。

》》》此博文源于各路汇总。