二維碼掃描：ZBar,ZXing的使用

原文鏈接：http://blog.csdn.net/whjblog/article/details/15809859

iOS二維碼掃描開源庫主要有Zbar和ZXing，在完成項目的過程中都用過，開始時用了Zbar，但其相對於ZXing掃描識別效率太低，無法達到項目要求，所以改用ZXing。兩個開源庫都可以識別二維碼，但ZBar還支持條形碼，ZXing識別條形碼還需要改一些地方。

一、ZBar的使用

1.下載ZBar SDK，將ZBarSDK拖動到Xcode項目

下載地址：https://github.com/bmorton/ZBarSDK

2.添加framework框架

      * AVFoundation.framework (weak)
      * CoreMedia.framework (weak)
      * CoreVideo.framework (weak)
      * QuartzCore.framework

3.掃描代碼

引入頭文件 #import  "ZBarSDK.h" ,實現ZBarReaderDelegate協議

ZBarReaderViewController *reader = [ZBarReaderViewController new];
   reader.readerDelegate = self;
   reader.supportedOrientationsMask = ZBarOrientationMaskAll;

   ZBarImageScanner *scanner = reader.scanner;

   [scanner setSymbology: ZBAR_I25
                  config: ZBAR_CFG_ENABLE
                      to: 0];

   [self presentModalViewController:reader animated:YES];
   [reader release];

掃描結果回調

- (void) imagePickerController: (UIImagePickerController*) reader didFinishPickingMediaWithInfo: (NSDictionary*) info
{
    id<NSFastEnumeration> results = [info objectForKey: ZBarReaderControllerResults];
    ZBarSymbol *symbol = nil;
    for(symbol in results)
        break;

    text =  symbol.data ;
}

還可以在ZBarReaderViewController自定義掃描界面和掃描區域（scanCrop）。

二、ZXing的使用

1.下載ZXIng，下載地址： https://github.com/zxing/zxing   .由於支持各種語言，整個工程比較大，IOS 只需保留cpp和iphone這2個文件夾，整個目錄結構不變，cpp文件夾只保留cpp/core/src/zxing下面的內容，其餘都可以全部刪除。然後把刪減好的zxing目錄移動到我們的iOS項目的目錄下(也可以右擊選擇Add files to ‘project’)，並在 zxing/iphone/ZXingWidget/目錄下把ZXingWidget.xcodeproj拖動到我們的項目工程中。

2.選擇 target ——>Build Phases   在 Link Binary with Libraries裏 添加libZXingWidget.a，在Target Dependencies添加ZXingWidget。在target ——>Build Settings ——>Headers Search Path 添加兩個路徑： 


./zxing/iphone/ZXingWidget/Classes

./zxing/cpp/core/src

第一個設成recursive ，第二個設成non-recursive

添加一下frameworks 支持

• AVFoundation
• AudioToolbox
• CoreVideo
• CoreMedia
• libiconv
• AddressBook
• AddressBookUI

3.掃描代碼

（1）直接引用

頭文件：
#import <ZXingWidgetController.h>

#import <QRCodeReader.h>

掃描調用代碼：

ZXingWidgetController *widController = [[ZXingWidgetController alloc] initWithDelegate:self showCancel:YES OneDMode:NO];
   NSMutableSet *readers = [[NSMutableSet alloc] init];
   QRCodeReader *qrcodeReader = [[QRCodeReader alloc] init];
   [readers addObject:qrcodeReader];
   widController.readers = readers;
   [self presentViewController:widController animated:YES completion:^{}];

掃描結果回調：

@protocol ZXingDelegate
- (void)zxingController:(ZXingWidgetController*)controller didScanResult:(NSString *)result;
- (void)zxingControllerDidCancel:(ZXingWidgetController*)controller;
@end

還需要把引入的.m文件改爲.mm。

（2）自定義掃描

我的項目要求中需要自定義掃描界面和掃描區域，還要加入C語言混編，所以就用了這種方法。

頭文件：

#import <AssetsLibrary/AssetsLibrary.h>
#import <QRCodeReader.h>
#import <TwoDDecoderResult.h>
#import <Decoder.h>

初始化AVCapture

- (void)initCapture
{
  AVCaptureDevice* inputDevice =
    [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
  AVCaptureDeviceInput *captureInput =
    [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:nil];
  AVCaptureVideoDataOutput *captureOutput = [[AVCaptureVideoDataOutput alloc] init];
  captureOutput.alwaysDiscardsLateVideoFrames = YES;
  [captureOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];
  NSString* key = (NSString*)kCVPixelBufferPixelFormatTypeKey;
  NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
  NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
  [captureOutput setVideoSettings:videoSettings];
  self.captureSession = [[[AVCaptureSession alloc] init] autorelease];

  NSString* preset = 0;
  if (NSClassFromString(@"NSOrderedSet") && // Proxy for "is this iOS 5" ...
      [UIScreen mainScreen].scale > 1 &&
      isIPad() &&
      [inputDevice
        supportsAVCaptureSessionPreset:AVCaptureSessionPresetiFrame960x540]) {
    preset = AVCaptureSessionPresetiFrame960x540;
  }
  if (!preset) {
    preset = AVCaptureSessionPresetMedium;
  }
  self.captureSession.sessionPreset = preset;

  [self.captureSession addInput:captureInput];
  [self.captureSession addOutput:captureOutput];

  [captureOutput release];

  if (!self.prevLayer) {
    self.prevLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
  }
  self.prevLayer.frame = self.view.bounds;
  self.prevLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
  [self.view.layer addSublayer: self.prevLayer];
  [self.captureSession startRunning];
}

 得到AVCapture回調函數

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    if (!isScanning||delegate==nil) {
        return;
    }
    if (sampleBuffer)
    {
        //將sampleBuffer轉化爲UIImage
        UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
        //用Decoder來解析識別圖像
        [self decodeImage:image];
    }
}

- (void)decodeImage:(UIImage *)image
{
    NSMutableSet *qrReader = [[NSMutableSet alloc] init];
    QRCodeReader *qrcoderReader = [[QRCodeReader alloc] init];
    [qrReader addObject:qrcoderReader];
    [qrcoderReader release];

    Decoder *decoder = [[Decoder alloc] init];
    decoder.delegate = self;
    decoder.readers = qrReader;
    [decoder decodeImage:image];
    [decoder release];
    [qrReader release];
}

Decoder回調獲得識別結果

@optional
- (void)decoder:(Decoder *)decoder willDecodeImage:(UIImage *)image usingSubset:(UIImage *)subset;
- (void)decoder:(Decoder *)decoder didDecodeImage:(UIImage *)image usingSubset:(UIImage *)subset withResult:(TwoDDecoderResult *)result;
- (void)decoder:(Decoder *)decoder failedToDecodeImage:(UIImage *)image usingSubset:(UIImage *)subset reason:(NSString *)reason;
- (void)decoder:(Decoder *)decoder foundPossibleResultPoint:(CGPoint)point;

注意掃描的畫面不會跟着設備旋轉，當橫豎轉換是需要改變畫面

CGFloat angle = 0.0f;
    switch (barOrientation)
    {
        case UIInterfaceOrientationPortrait:
            angle = 0.0f;
            break;
        case UIInterfaceOrientationPortraitUpsideDown:
            angle = M_PI;
            break;
        case UIInterfaceOrientationLandscapeLeft:
            angle = M_PI / 2;
            break;
        case UIInterfaceOrientationLandscapeRight:
            angle = -M_PI / 2;
            break;
        default:
            break;
    }
    CATransform3D transform =  CATransform3DMakeRotation(angle, 0, 0, 1.0);
    self.captureVideoPreviewLayer.transform =transform;
    self.captureVideoPreviewLayer.frame = layerframe;