ios - 如何在没有用户交互的情况下从 iOS 相机捕获图像？

Question

我需要从前置摄像头捕捉静态图像并将其存储在 Documents 目录中。我在其他帖子中找到了一些代码片段，但我想分享这些代码以防其他人有类似的需求。

Answer 1

定义一个 UIImage 属性并确保您的类实现了 AVCaptureVideoDataOutputSampleBufferDelegate 协议(protocol):

@interface ViewController : UIViewController <AVCaptureVideoDataOutputSampleBufferDelegate>

@property (nonatomic, strong) UIImage *theImage;

@end

在 viewDidLoad 或其他合适的地方，添加:

    [self captureImage];

实现以下方法:

- (void)captureImage
{
    AVCaptureSession *session = [[AVCaptureSession alloc] init];
    session.sessionPreset = AVCaptureSessionPresetHigh;

    AVCaptureDevice *device = [self frontCamera];


    NSError *error = nil;
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
    if (!input) {
        // Handle the error appropriately.
        NSLog(@"no input.....");
    }
    [session addInput:input];

    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
    [session addOutput:output];
    output.videoSettings = @{ (NSString *)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_32BGRA) };

    dispatch_queue_t queue = dispatch_queue_create("MyQueue", NULL);

    [output setSampleBufferDelegate:self queue:queue];

    [session startRunning];

    [session stopRunning];
}

- (AVCaptureDevice *)frontCamera {
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if ([device position] == AVCaptureDevicePositionFront) {
        return device;
        }
    }
    return nil;
}

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


    CGImageRef cgImage = [self imageFromSampleBuffer:sampleBuffer];
    self.theImage = [UIImage imageWithCGImage: cgImage ];
    CGImageRelease( cgImage );

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsPath = [paths objectAtIndex:0];
    NSString *filePath = [documentsPath stringByAppendingPathComponent:@"image.png"];
    NSData* data = UIImagePNGRepresentation(self.theImage);
    [data writeToFile:filePath atomically:YES];
}

- (CGImageRef) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGImageRef newImage = CGBitmapContextCreateImage(newContext);
    CGContextRelease(newContext);

    CGColorSpaceRelease(colorSpace);
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    return newImage;
}