[Objective-C] iOS 基本技能: 呼叫相機

超常用的iOS呼叫相機基本技能，測試完記錄一下。

使用UIImagePickerController (簡單、快速)

- (void) initCamera{

    

    NSLog(@"initCamera");

    dispatch_async(dispatch_get_main_queue(), ^{

        UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];

        

        //檢查是否支援此Source Type(相機)

        if([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {

            NSLog(@"Access Camera Device");

            

            //設定影像來源為相機

            imagePicker.sourceType =  UIImagePickerControllerSourceTypeCamera;

            imagePicker.delegate = self;

            imagePicker.allowsEditing = YES;

            

            //顯示UIImagePickerController

            [self presentViewController:imagePicker animated:YES completion:nil];

        }

        else {

            //提示使用者，目前設備不支援相機

            NSLog(@"No Camera Device");

        }

    });

    

}

//使用者按下確定時

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    //取得剛拍攝的相片(或是由相簿中所選擇的相片)

    UIImage *image=[info objectForKey:UIImagePickerControllerEditedImage];

    

    //設定ImageView的Image物件，例如：

    //yourImageView.image = image;

    

    [picker dismissViewControllerAnimated:YES completion:^{}];

}

//使用者按下取消時

- (void)imagePickerControllerDidCancel:(UIImagePickerController *)picker {

    //一般情況下沒有什麼特別要做的事情

    

    [picker dismissViewControllerAnimated:YES completion:^{}];

}

使用AV Foundation

優點就是彈性比較大，速度快

//自行定義的函式，目的用來顯示Camera所擷取到的畫面

-(void)initCameraCaptureSession {

    NSLog(@"initCameraCaptureSession");

    

    //session為AVCaptureSession型態的指標，之後將透過這個指標對Camera影像做擷取並輸出

    myCaptureSession = [[AVCaptureSession alloc] init];

    

    //設定擷取時畫面的大小，這裡提供三種等級可以選擇

    myCaptureSession.sessionPreset = AVCaptureSessionPresetMedium;

    

    //選擇Device，也就是Camera

    //建立 AVCaptureDeviceInput

    NSArray *myDevices = [AVCaptureDevice devices];

    

    for (AVCaptureDevice *device in myDevices) {

        if ([device position] == AVCaptureDevicePositionBack) {

            NSLog(@"後攝影機硬體名稱: %@", [device localizedName]);

        }

        

        if ([device position] == AVCaptureDevicePositionFront) {

            NSLog(@"前攝影機硬體名稱: %@", [device localizedName]);

        }

        

        if ([device hasMediaType:AVMediaTypeAudio]) {

            NSLog(@"麥克風硬體名稱: %@", [device localizedName]);

        }

    }

    //使用後置鏡頭當做輸入

    NSError *error = nil;

    for (AVCaptureDevice *device in myDevices) {

        if ([device position] == AVCaptureDevicePositionBack) {//指定後鏡頭

            

            AVCaptureDeviceInput *myDeviceInput = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];

            

            if (error) {

                //裝置取得失敗時的處理常式

            } else {

                NSLog(@"設定輸入端");

                

                [myCaptureSession addInput:myDeviceInput];

            }

        }

    }

    

    //影像輸出至APP上

    //建立 AVCaptureVideoPreviewLayer

    AVCaptureVideoPreviewLayer *myPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:myCaptureSession];

    [myPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];

    

    //輸出的目的地-產生一個rect的大小來輸出

    CGRect rect = CGRectMake(160, 180, 320, 240);

    [myPreviewLayer setBounds:rect];

    

    UIView *myView = [[UIView alloc]initWithFrame:rect];

    [myView.layer addSublayer:myPreviewLayer];

    

    [self.view addSubview:myView];

    

    

    //啟用攝影機

    [myCaptureSession startRunning];

    

    //取得攝影機連續影像

    myVideoDataOutput = [[AVCaptureVideoDataOutput alloc] init];

    myVideoDataOutput.videoSettings = [NSDictionary dictionaryWithObject: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey: (id)kCVPixelBufferPixelFormatTypeKey];

    

    [myVideoDataOutput setAlwaysDiscardsLateVideoFrames:YES];

    [myVideoDataOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];

    

    AVCaptureConnection *connection = [myVideoDataOutput connectionWithMediaType:AVMediaTypeVideo];

    [connection setVideoMaxFrameDuration:CMTimeMake(1, 20)];

    [connection setVideoMinFrameDuration:CMTimeMake(1, 10)];

    

    [myCaptureSession addOutput:myVideoDataOutput];

}

//丟棄延遲的影格

- (void)captureOutput:(AVCaptureOutput *)captureOutput didDropSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {

    NSLog(@"丟棄延遲的影格 didDropSampleBuffer");

}

//擷取連續影像片段

- (void)captureOutput:(AVCaptureOutput*)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection*)connection {

    NSLog(@"擷取連續影像片段 didOutputSampleBuffer");

    

    

}

旋轉與鏡射

可使用內建函式中的 AVCaptureConnection

做 setVideoOrientation: 旋轉影像，或 setVideoMirrored: 鏡射影像。

iOS 10的權限問題

在iOS10之後需要設定一下相機的存取權限不然會GG
打開info.plist檔加入新的KEY: Privacy - Camera Usage Description ，值就隨便設即可。
成功就能呼叫，就彈視窗說APP會想要取用你的相機!!

參考

http://furnacedigital.blogspot.tw/2010/12/cameraios4.html

http://furnacedigital.blogspot.tw/2012/11/avcapturevideodataoutput.html

http://furnacedigital.blogspot.tw/2012/11/avcapturestillimageoutput.html