5

我想在特定情况下捕获图像，例如按下按钮时；但我不想显示任何视频预览屏幕。我想 captureStillImageAsynchronouslyFromConnection 是我需要在这种情况下使用的。目前，如果我显示视频预览，我可以捕获图像。但是，如果我删除代码以显示预览，应用程序将崩溃并显示以下输出：

2012-04-07 11:25:54.898 imCapWOPreview [748:707] *** 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“***-[AVCaptureStillImageOutput captureStillImageAsynchronouslyFromConnection:completionHandler:] - 已通过非活动/无效连接。 ' *** First throw call stack: (0x336ee8bf 0x301e21e5 0x3697c35d 0x34187 0x33648435 0x310949eb 0x310949a7 0x31094985 0x310946f5 0x3109502d 0x3109350f 0x31092f01 0x310794ed 0x31078d2d 0x37db7df3 0x336c2553 0x336c24f5 0x336c1343 0x336444dd 0x336443a5 0x37db6fcd 0x310a7743 0x33887 0x3382c) terminate called throwing an exception(lldb)

所以这是我的实现：

BIDViewController.h：

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>

@interface BIDViewController : UIViewController
{
    AVCaptureStillImageOutput *stillImageOutput;
}
@property (strong, nonatomic) IBOutlet UIView *videoPreview;
- (IBAction)doCap:(id)sender;

@end

BIDViewController.m 中的相关人员：

#import "BIDViewController.h"

@interface BIDViewController ()

@end

@implementation BIDViewController
@synthesize capturedIm;
@synthesize videoPreview;

- (void)viewDidLoad
{
[super viewDidLoad];
[self setupAVCapture];
}

- (BOOL)setupAVCapture
{
NSError *error = nil;

AVCaptureSession *session = [AVCaptureSession new];
[session setSessionPreset:AVCaptureSessionPresetHigh];

/*
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
captureVideoPreviewLayer.frame = self.videoPreview.bounds;
[self.videoPreview.layer addSublayer:captureVideoPreviewLayer];    
 */

// Select a video device, make an input
AVCaptureDevice *backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error];
if (error)
    return NO;
if ([session canAddInput:input])
    [session addInput:input];

// Make a still image output
stillImageOutput = [AVCaptureStillImageOutput new];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[stillImageOutput setOutputSettings:outputSettings];    
if ([session canAddOutput:stillImageOutput])
    [session addOutput:stillImageOutput];

[session startRunning];

return YES;
}

- (IBAction)doCap:(id)sender {
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in stillImageOutput.connections)
{
    for (AVCaptureInputPort *port in [connection inputPorts])
    {
        if ([[port mediaType] isEqual:AVMediaTypeVideo] )
        {
            videoConnection = connection;
            break;
        }
    }
    if (videoConnection) { break; }
}

[stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection 
  completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *__strong error) {
      // Do something with the captured image
  }];

}

使用上面的代码，如果调用了doCap，那么就会发生崩溃。另一方面，如果我在 setupAVCapture 函数中删除以下注释

/*
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
captureVideoPreviewLayer.frame = self.videoPreview.bounds;
[self.videoPreview.layer addSublayer:captureVideoPreviewLayer];    
 */

然后它可以正常工作。

总之，我的问题是，如何在受控实例中捕获图像而不显示预览？

4

3 回答 3

8

我使用以下代码从前置摄像头（如果可用）或使用后置摄像头进行捕获。在我的 iPhone 4S 上运行良好。

-(void)viewDidLoad{

    AVCaptureSession *session = [[AVCaptureSession alloc] init];
    session.sessionPreset = AVCaptureSessionPresetMedium;

    AVCaptureDevice *device = [self frontFacingCameraIfAvailable];

    NSError *error = nil;
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
    if (!input) {
        // Handle the error appropriately.
        NSLog(@"ERROR: trying to open camera: %@", error);
    }
    [session addInput:input];

//stillImageOutput is a global variable in .h file: "AVCaptureStillImageOutput *stillImageOutput;"
    stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
    [stillImageOutput setOutputSettings:outputSettings];

    [session addOutput:stillImageOutput];

    [session startRunning];
}

-(AVCaptureDevice *)frontFacingCameraIfAvailable{

    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    AVCaptureDevice *captureDevice = nil;

    for (AVCaptureDevice *device in videoDevices){

        if (device.position == AVCaptureDevicePositionFront){

            captureDevice = device;
            break;
        }
    }

    //  couldn't find one on the front, so just get the default video device.
    if (!captureDevice){

        captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    }

    return captureDevice;
}

-(IBAction)captureNow{

    AVCaptureConnection *videoConnection = nil;
    for (AVCaptureConnection *connection in stillImageOutput.connections){
        for (AVCaptureInputPort *port in [connection inputPorts]){

            if ([[port mediaType] isEqual:AVMediaTypeVideo]){

                videoConnection = connection;
                break;
            }
        }
        if (videoConnection) { 
           break; 
        }
    }

    NSLog(@"about to request a capture from: %@", stillImageOutput);
    [stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error){

         CFDictionaryRef exifAttachments = CMGetAttachment( imageSampleBuffer, kCGImagePropertyExifDictionary, NULL);
         if (exifAttachments){

            // Do something with the attachments if you want to. 
            NSLog(@"attachements: %@", exifAttachments);
        }
        else
            NSLog(@"no attachments");

        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
        UIImage *image = [[UIImage alloc] initWithData:imageData];

        self.vImage.image = image;
    }];
}
于 2012-04-15T06:46:08.947 回答
1

好吧，我遇到了一个类似的问题，即captureStillImageAsynchronouslyFromConnection:stillImageConnection引发了一个异常，即通过connection无效。后来，我发现当我properties参加会议并stillImageOutPut保留价值观时，问题得到了解决。

于 2013-12-29T12:24:07.123 回答
1

我是一名 JavaScript 开发人员。想为我的跨平台 Javascript 项目创建一个 iOS 原生框架

当我开始这样做时，我遇到了许多不推荐使用的方法和其他运行时错误的问题。

解决所有问题后，以下是符合 iOS 13.5 的答案

该代码可帮助您在没有预览的情况下单击按钮拍照。

你的 .h 文件

@interface NoPreviewCameraViewController : UIViewController <AVCapturePhotoCaptureDelegate> {
    AVCaptureSession *captureSession;
    AVCapturePhotoOutput *photoOutput;
    AVCapturePhotoSettings *photoSetting;
    AVCaptureConnection *captureConnection;
    UIImageView *imageView;
}
@end

你的 .m 文件


- (void)viewDidLoad {
    [super viewDidLoad];
    imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height - 140)];
    [self.view addSubview:imageView];
    UIButton *takePicture = [UIButton buttonWithType:UIButtonTypeCustom];
    [takePicture addTarget:self action:@selector(takePicture:) forControlEvents:UIControlEventTouchUpInside];
    [takePicture setTitle:@"Take Picture" forState:UIControlStateNormal];
    takePicture.frame = CGRectMake(40.0, self.view.frame.size.height - 140,  self.view.frame.size.width - 40, 40);
    [self.view addSubview:takePicture];
    [self initCaptureSession];
}

- (void) initCaptureSession {
    captureSession = [[AVCaptureSession alloc] init];
    if([captureSession canSetSessionPreset: AVCaptureSessionPresetPhoto] ) {
        [captureSession setSessionPreset:AVCaptureSessionPresetPhoto];
    }
    AVCaptureDeviceInput *deviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] error:nil];
    if ([captureSession canAddInput:deviceInput]) {
        [captureSession addInput:deviceInput];
    }
    photoOutput = [[AVCapturePhotoOutput alloc] init];
    if ([captureSession canAddOutput:photoOutput]) {
        [captureSession addOutput:photoOutput];
    }
    [captureSession startRunning];
}

-(void) setNewPhotoSetting {
    photoSetting = [AVCapturePhotoSettings photoSettingsWithFormat:@{AVVideoCodecKey : AVVideoCodecTypeJPEG}];
    [photoOutput setPhotoSettingsForSceneMonitoring:photoSetting];
}

- (IBAction)takePicture:(id)sender {
    captureConnection = nil;
    [self setNewPhotoSetting];
    for (AVCaptureConnection *connection in photoOutput.connections) {
        for (AVCaptureInputPort *port in [connection inputPorts]) {
            if ([[port mediaType] isEqual: AVMediaTypeVideo]) {
                captureConnection = connection;
                
                NSLog(@"Value of connection = %@", connection);
                NSLog(@"Value of captureConnection = %@", captureConnection);
                
                break;
            }
        }
        if (captureConnection) {
            break;
        }
    }
    [photoOutput capturePhotoWithSettings:photoSetting delegate:self];
}
于 2020-07-17T05:54:32.050 回答