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用代码拍照。我将如何为前置摄像头执行此操作？
【问题讨论】：
如何使用 AVFoundation 前置摄像头捕捉图像：
开发注意事项：
ViewController.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
#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
将它连接到带有 UIImageView 的 UIViewController 用于快照，它会工作的！快照以 2.0 秒的间隔以编程方式拍摄，无需任何用户输入。注释掉选中的行以移除预览层和快照反馈。
还有任何问题/cmets，请告诉我！
【讨论】：
将以上代码转换为 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
}
}
【讨论】：
您可能需要使用AVFoundation 来捕获视频流/图像而不显示它。与UIImagePickerController 不同，它不能“开箱即用”。以 Apple 的 AVCam 为例，了解一下。
【讨论】：
如果有人在 2017 年仍在寻找解决方案，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
}
}
另外，我找到了一种从 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
}
【讨论】：
在 UIImagePickerController 类的文档中有一个名为 takePicture 的方法。它说：
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。
【讨论】：