iOS：从前置摄像头捕获图像

iOS: Capture image from front facing camera

提问by mtmurdock

I am making an application where I would like to capture an image from the front facing camera, without presenting a capture screen of any kind. I want to take a picture completely in code without any user interaction. How would I do this for the front facing camera?

我正在制作一个应用程序，我想从前置摄像头捕获图像，而不显示任何类型的捕获屏幕。我想在没有任何用户交互的情况下完全在代码中拍照。我将如何为前置摄像头执行此操作？

回答by Ricardo RendonCepeda

How to capture an image using the AVFoundation front-facing camera:

如何使用 AVFoundation 前置摄像头捕捉图像：

Development Caveats:

开发注意事项：

• Check your app and image orientation settings carefully
• AVFoundation and its associated frameworks are nasty behemoths and very difficult to understand/implement. I've made my code as lean as possible, but please check out this excellent tutorial for a better explanation (website not available any more, link via archive.org): http://www.benjaminloulier.com/posts/ios4-and-direct-access-to-the-camera

• 仔细检查您的应用程序和图像方向设置
• AVFoundation 及其相关框架是令人讨厌的庞然大物，并且非常难以理解/实现。我已经使我的代码尽可能精简，但请查看这个优秀的教程以获得更好的解释（网站不再可用，通过 archive.org 链接）：http: //www.benjaminloulier.com/posts/ios4-并直接访问相机

ViewController.h

视图控制器.h

// Frameworks
#import <CoreVideo/CoreVideo.h>
#import <CoreMedia/CoreMedia.h>
#import <AVFoundation/AVFoundation.h>
#import <UIKit/UIKit.h>

@interface CameraViewController : UIViewController <AVCaptureVideoDataOutputSampleBufferDelegate>

// Camera
@property (weak, nonatomic) IBOutlet UIImageView* cameraImageView;
@property (strong, nonatomic) AVCaptureDevice* device;
@property (strong, nonatomic) AVCaptureSession* captureSession;
@property (strong, nonatomic) AVCaptureVideoPreviewLayer* previewLayer;
@property (strong, nonatomic) UIImage* cameraImage;

@end

ViewController.m

视图控制器.m

#import "CameraViewController.h"

@implementation CameraViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self setupCamera];
    [self setupTimer];
}

- (void)setupCamera
{    
    NSArray* devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for(AVCaptureDevice *device in devices)
    {
        if([device position] == AVCaptureDevicePositionFront)
            self.device = device;
    }

    AVCaptureDeviceInput* input = [AVCaptureDeviceInput deviceInputWithDevice:self.device error:nil];
    AVCaptureVideoDataOutput* output = [[AVCaptureVideoDataOutput alloc] init];
    output.alwaysDiscardsLateVideoFrames = YES;

    dispatch_queue_t queue;
    queue = dispatch_queue_create("cameraQueue", NULL);
    [output setSampleBufferDelegate:self queue:queue];

    NSString* key = (NSString *) kCVPixelBufferPixelFormatTypeKey;
    NSNumber* value = [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA];
    NSDictionary* videoSettings = [NSDictionary dictionaryWithObject:value forKey:key];
    [output setVideoSettings:videoSettings];

    self.captureSession = [[AVCaptureSession alloc] init];
    [self.captureSession addInput:input];
    [self.captureSession addOutput:output];
    [self.captureSession setSessionPreset:AVCaptureSessionPresetPhoto];

    self.previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
    self.previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;

    // CHECK FOR YOUR APP
    self.previewLayer.frame = CGRectMake(0, 0, self.view.frame.size.height, self.view.frame.size.width);
    self.previewLayer.orientation = AVCaptureVideoOrientationLandscapeRight;
    // CHECK FOR YOUR APP

    [self.view.layer insertSublayer:self.previewLayer atIndex:0];   // Comment-out to hide preview layer

    [self.captureSession startRunning];
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer,0);
    uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);
    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);

    self.cameraImage = [UIImage imageWithCGImage:newImage scale:1.0f orientation:UIImageOrientationDownMirrored];

    CGImageRelease(newImage);

    CVPixelBufferUnlockBaseAddress(imageBuffer,0);
}

- (void)setupTimer
{
    NSTimer* cameraTimer = [NSTimer scheduledTimerWithTimeInterval:2.0f target:self selector:@selector(snapshot) userInfo:nil repeats:YES];
}

- (void)snapshot
{
    NSLog(@"SNAPSHOT");
    self.cameraImageView.image = self.cameraImage;  // Comment-out to hide snapshot
}

@end

Connect this up to a UIViewController with a UIImageView for the snapshot and it'll work! Snapshots are taken programmatically at 2.0 second intervals without any user input. Comment out the selected lines to remove the preview layer and snapshot feedback.

将它连接到带有 UIImageView 的 UIViewController 用于快照，它会起作用！快照以 2.0 秒的间隔以编程方式拍摄，无需任何用户输入。注释掉所选行以删除预览层和快照反馈。

Any more questions/comments, please let me know!

如有更多问题/意见，请告诉我！

回答by Malav Soni

Convert above code to Swift 4

将上面的代码转换为 Swift 4

import UIKit
import AVFoundation

class CameraViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {

@IBOutlet weak var cameraImageView: UIImageView!

var device: AVCaptureDevice?
var captureSession: AVCaptureSession?
var previewLayer: AVCaptureVideoPreviewLayer?
var cameraImage: UIImage?

override func viewDidLoad() {
    super.viewDidLoad()

    setupCamera()
    setupTimer()
}

func setupCamera() {
    let discoverySession = AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInWideAngleCamera],
                                                            mediaType: AVMediaType.video,
                                                           position: .front)
    device = discoverySession.devices[0]

    let input: AVCaptureDeviceInput
    do {
        input = try AVCaptureDeviceInput(device: device!)
    } catch {
        return
    }

    let output = AVCaptureVideoDataOutput()
    output.alwaysDiscardsLateVideoFrames = true

    let queue = DispatchQueue(label: "cameraQueue")
    output.setSampleBufferDelegate(self, queue: queue)
    output.videoSettings = [kCVPixelBufferPixelFormatTypeKey as AnyHashable as! String: kCVPixelFormatType_32BGRA]

    captureSession = AVCaptureSession()
    captureSession?.addInput(input)
    captureSession?.addOutput(output)
    captureSession?.sessionPreset = AVCaptureSession.Preset.photo

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession!)
    previewLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
    previewLayer?.frame = CGRect(x: 0.0, y: 0.0, width: view.frame.width, height: view.frame.height)

    view.layer.insertSublayer(previewLayer!, at: 0)

        captureSession?.startRunning()
    }

    func captureOutput(_ output: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
    CVPixelBufferLockBaseAddress(imageBuffer!, CVPixelBufferLockFlags(rawValue: 0))
        let baseAddress = UnsafeMutableRawPointer(CVPixelBufferGetBaseAddress(imageBuffer!))
        let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer!)
        let width = CVPixelBufferGetWidth(imageBuffer!)
        let height = CVPixelBufferGetHeight(imageBuffer!)

        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let newContext = CGContext(data: baseAddress, width: width, height: height, bitsPerComponent: 8, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo:
        CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)

        let newImage = newContext!.makeImage()
         cameraImage = UIImage(cgImage: newImage!)

        CVPixelBufferUnlockBaseAddress(imageBuffer!, CVPixelBufferLockFlags(rawValue: 0))
    }

    func setupTimer() {
        _ = Timer.scheduledTimer(timeInterval: 2.0, target: self, selector: #selector(snapshot), userInfo: nil, repeats: true)
    }

    @objc func snapshot() {
        print("SNAPSHOT")
        cameraImageView.image = cameraImage
    }
}

回答by Kwok Pan Fung

You probably need to use AVFoundationto capture the video stream/image without displaying it. Unlike UIImagePickerController, it doesn't work 'out-of-the-box'. Look at Apple's AVCamas an example to get you started.

您可能需要使用AVFoundation捕获视频流/图像而不显示它。与 不同UIImagePickerController，它不能“开箱即用”。以 AppleAVCam为例来帮助您入门。

回答by Mihai Er?s

I converted the code above from Objc to Swift 3, if anyone still looks for a solution in 2017.

如果有人在 2017 年仍然在寻找解决方案，我将上面的代码从 Objc 转换为 Swift 3。

import UIKit
import AVFoundation

class CameraViewController: UIViewController, AVCaptureVideoDataOutputSampleBufferDelegate {

@IBOutlet weak var cameraImageView: UIImageView!

var device: AVCaptureDevice?
var captureSession: AVCaptureSession?
var previewLayer: AVCaptureVideoPreviewLayer?
var cameraImage: UIImage?

override func viewDidLoad() {
    super.viewDidLoad()

    setupCamera()
    setupTimer()
}

func setupCamera() {
    let discoverySession = AVCaptureDeviceDiscoverySession(deviceTypes: [.builtInWideAngleCamera],
                                                           mediaType: AVMediaTypeVideo,
                                                           position: .front)
    device = discoverySession?.devices[0]

    let input: AVCaptureDeviceInput
    do {
        input = try AVCaptureDeviceInput(device: device)
    } catch {
        return
    }

    let output = AVCaptureVideoDataOutput()
    output.alwaysDiscardsLateVideoFrames = true

    let queue = DispatchQueue(label: "cameraQueue")
    output.setSampleBufferDelegate(self, queue: queue)
    output.videoSettings = [kCVPixelBufferPixelFormatTypeKey as AnyHashable: kCVPixelFormatType_32BGRA]

    captureSession = AVCaptureSession()
    captureSession?.addInput(input)
    captureSession?.addOutput(output)
    captureSession?.sessionPreset = AVCaptureSessionPresetPhoto

    previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
    previewLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill

    previewLayer?.frame = CGRect(x: 0.0, y: 0.0, width: view.frame.width, height: view.frame.height)

    view.layer.insertSublayer(previewLayer!, at: 0)

    captureSession?.startRunning()
}

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
    let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
    CVPixelBufferLockBaseAddress(imageBuffer!, CVPixelBufferLockFlags(rawValue: .allZeros))
    let baseAddress = UnsafeMutableRawPointer(CVPixelBufferGetBaseAddress(imageBuffer!))
    let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer!)
    let width = CVPixelBufferGetWidth(imageBuffer!)
    let height = CVPixelBufferGetHeight(imageBuffer!)

    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let newContext = CGContext(data: baseAddress, width: width, height: height, bitsPerComponent: 8, bytesPerRow: bytesPerRow, space: colorSpace, bitmapInfo:
        CGBitmapInfo.byteOrder32Little.rawValue | CGImageAlphaInfo.premultipliedFirst.rawValue)

    let newImage = newContext!.makeImage()
    cameraImage = UIImage(cgImage: newImage!)

    CVPixelBufferUnlockBaseAddress(imageBuffer!, CVPixelBufferLockFlags(rawValue: .allZeros))
}

func setupTimer() {
    _ = Timer.scheduledTimer(timeInterval: 2.0, target: self, selector: #selector(snapshot), userInfo: nil, repeats: true)
}

func snapshot() {
    print("SNAPSHOT")
    cameraImageView.image = cameraImage
}
}

Also, I found a shorter solution for getting the image from the CMSampleBuffer:

另外，我找到了从 CMSampleBuffer 获取图像的更短的解决方案：

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
    let myPixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)
    let myCIimage = CIImage(cvPixelBuffer: myPixelBuffer!)
    let videoImage = UIImage(ciImage: myCIimage)
    cameraImage = videoImage
}

回答by user3075378

There is a method called takePicture in the docs for UIImagePickerController class. It says:

UIImagePickerController 类的文档中有一个名为 takePicture 的方法。它说：

Use this method in conjunction with a custom overlay view to initiate the programmatic capture of a still image. This supports taking more than one picture without leaving the interface, but requires that you hide the default image picker controls.

将此方法与自定义叠加视图结合使用以启动静态图像的编程捕获。这支持在不离开界面的情况下拍摄多张照片，但需要您隐藏默认的图像选择器控件。