iOS:从前置摄像头捕获图像

Question

我正在制作一个应用程序，我想在其中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。我该如何为前置摄像头执行此操作？

Answer 1

如何使用 AVFoundation 前置摄像头捕捉图像:

开发注意事项:

• 仔细检查您的应用和图片方向设置
• AVFoundation 及其相关框架是令人讨厌的庞然大物，很难理解/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-and-direct-access-to-the-camera

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

将它连接到一个 UIViewController 和一个 UIImageView 用于快照，它就会工作!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。

如有任何问题/意见，请告诉我!