Objective-C在没有相机界面的情况下拍摄照片的简单方法.只需从相机获取图片并保存到文件

Question

我没有找到一种没有相机界面拍照的简单方法.我只需要从相机中获取一张照片并将其保存到文件中.

Answer 1

我用这段代码用前置摄像头拍照.并非所有代码都是我的,但我没有找到原始来源的链接.此代码还会产生快门声.图像质量不是很好(它很暗)所以代码需要一两个调整.

-(void) takePhoto 
{
    AVCaptureDevice *frontalCamera;

    NSArray *allCameras = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];

    for ( int i = 0; i < allCameras.count; i++ )
    {
        AVCaptureDevice *camera = [allCameras objectAtIndex:i];

        if ( camera.position == AVCaptureDevicePositionFront )
        {
            frontalCamera = camera;
        }
    }

    if ( frontalCamera != nil )
    {
        photoSession = [[AVCaptureSession alloc] init];

        NSError *error;
        AVCaptureDeviceInput *input =
        [AVCaptureDeviceInput deviceInputWithDevice:frontalCamera error:&error];

        if ( !error && [photoSession canAddInput:input] )
        {
            [photoSession addInput:input];

            AVCaptureStillImageOutput *output = [[AVCaptureStillImageOutput alloc] init];

            [output setOutputSettings:
             [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG,AVVideoCodecKey,nil]];

            if ( [photoSession canAddOutput:output] )
            {
                [photoSession addOutput:output];

                AVCaptureConnection *videoConnection = nil;

                for (AVCaptureConnection *connection in output.connections)
                {
                    for (AVCaptureInputPort *port in [connection inputPorts])
                    {
                        if ([[port mediaType] isEqual:AVMediaTypeVideo] )
                        {
                            videoConnection = connection;
                            break;
                        }
                    }
                    if (videoConnection) { break; }
                }

                if ( videoConnection )
                {
                    [photoSession startRunning];

                    [output captureStillImageAsynchronouslyFromConnection:videoConnection
                                                        completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {

                        if (imageDataSampleBuffer != NULL)
                        {
                            NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
                            UIImage *photo = [[UIImage alloc] initWithData:imageData];
                            [self processImage:photo]; //this is a custom method
                        }
                    }];
                }
            }
        }
    }
}

photoSession是AVCaptureSession *持有这种takePhoto方法的班级的伊瓦尔.

编辑(调整):如果您将if ( videoConnection )块更改为下面的代码,您将添加1秒延迟并获得良好的图像.

if ( videoConnection )
{
    [photoSession startRunning];

    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, 1 * NSEC_PER_SEC);
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

        [output captureStillImageAsynchronouslyFromConnection:videoConnection
                                            completionHandler:^(CMSampleBufferRefimageDataSampleBuffer, NSError *error) {

            if (imageDataSampleBuffer != NULL)
            {
                NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
                UIImage *photo = [[UIImage alloc] initWithData:imageData];
                [self processImage:photo];
            }
        }];
    });
}

如果您的应用程序无法接受滞后,您可以将代码分成两部分并启动photoSessionat viewDidAppear(或类似的地方),并在需要时立即拍摄即时快照 - 通常是在一些用户交互之后.

dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, 0.25 * NSEC_PER_SEC);

也产生了良好的结果 - 所以不需要一整秒的滞后.

请注意,此代码用于拍摄带有正面相机的照片 - 如果您需要使用背面照相机,我相信您会知道如何修补它.