我想在特定情况下捕获图像，例如按下按钮时;但我不想显示任何视频预览屏幕。我想captureStillImageAsynchronouslyFromConnection是我需要用于此场景的东西。目前，如果我显示视频预览，我可以捕获图像。但是，如果我删除代码以显示预览，则应用程序会崩溃，并显示以下输出：
2012-04-07 11：25：54.898 imCapWOPreview [748：707] ***终止应用 由于未捕获的异常'NSInvalidArgumentException'，原因：'*** - [AVCaptureStillImageOutput captureStillImageAsynchronouslyFromConnection：completionHandler：] - 无效/无效连接已通过。' ***首先抛出调用堆栈：（0x336ee8bf 0x301e21e5 0x3697c35d 0x34187 0x33648435 0x310949eb 0x310949a7 0x31094985 0x310946f5 0x3109502d 0x3109350f 0x31092f01 0x310794ed 0x31078d2d 0x37db7df3 0x336c2553 0x336c24f5 0x336c1343 0x336444dd 0x336443a5 0x37db6fcd 0x310a7743 0x33887 0x3382c）终止调用抛出异常（lldb）
所以这是我的实施：
BIDViewController.h：
#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>
@interface BIDViewController : UIViewController
{
AVCaptureStillImageOutput *stillImageOutput;
}
@property (strong, nonatomic) IBOutlet UIView *videoPreview;
- (IBAction)doCap:(id)sender;
@end
BIDViewController.m中的相关人员：
#import "BIDViewController.h"
@interface BIDViewController ()
@end
@implementation BIDViewController
@synthesize capturedIm;
@synthesize videoPreview;
- (void)viewDidLoad
{
[super viewDidLoad];
[self setupAVCapture];
}
- (BOOL)setupAVCapture
{
NSError *error = nil;
AVCaptureSession *session = [AVCaptureSession new];
[session setSessionPreset:AVCaptureSessionPresetHigh];
/*
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
captureVideoPreviewLayer.frame = self.videoPreview.bounds;
[self.videoPreview.layer addSublayer:captureVideoPreviewLayer];
*/
// Select a video device, make an input
AVCaptureDevice *backCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:backCamera error:&error];
if (error)
return NO;
if ([session canAddInput:input])
[session addInput:input];
// Make a still image output
stillImageOutput = [AVCaptureStillImageOutput new];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[stillImageOutput setOutputSettings:outputSettings];
if ([session canAddOutput:stillImageOutput])
[session addOutput:stillImageOutput];
[session startRunning];
return YES;
}
- (IBAction)doCap:(id)sender {
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in stillImageOutput.connections)
{
for (AVCaptureInputPort *port in [connection inputPorts])
{
if ([[port mediaType] isEqual:AVMediaTypeVideo] )
{
videoConnection = connection;
break;
}
}
if (videoConnection) { break; }
}
[stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *__strong error) {
// Do something with the captured image
}];
}
使用上面的代码，如果调用了doCap，则会发生崩溃。另一方面，如果我在setupAVCapture函数中删除以下注释
/*
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
captureVideoPreviewLayer.frame = self.videoPreview.bounds;
[self.videoPreview.layer addSublayer:captureVideoPreviewLayer];
*/
然后它没有任何问题。
总之，我的问题是，如何在不显示预览的情况下在受控实例中捕获图像？
答案 0 :(得分：8)
我使用以下代码从前置摄像头（如果可用）或使用后置摄像头进行捕获。适用于我的iPhone 4S。
-(void)viewDidLoad{
AVCaptureSession *session = [[AVCaptureSession alloc] init];
session.sessionPreset = AVCaptureSessionPresetMedium;
AVCaptureDevice *device = [self frontFacingCameraIfAvailable];
NSError *error = nil;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (!input) {
// Handle the error appropriately.
NSLog(@"ERROR: trying to open camera: %@", error);
}
[session addInput:input];
//stillImageOutput is a global variable in .h file: "AVCaptureStillImageOutput *stillImageOutput;"
stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
[stillImageOutput setOutputSettings:outputSettings];
[session addOutput:stillImageOutput];
[session startRunning];
}
-(AVCaptureDevice *)frontFacingCameraIfAvailable{
NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
AVCaptureDevice *captureDevice = nil;
for (AVCaptureDevice *device in videoDevices){
if (device.position == AVCaptureDevicePositionFront){
captureDevice = device;
break;
}
}
// couldn't find one on the front, so just get the default video device.
if (!captureDevice){
captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
}
return captureDevice;
}
-(IBAction)captureNow{
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in stillImageOutput.connections){
for (AVCaptureInputPort *port in [connection inputPorts]){
if ([[port mediaType] isEqual:AVMediaTypeVideo]){
videoConnection = connection;
break;
}
}
if (videoConnection) {
break;
}
}
NSLog(@"about to request a capture from: %@", stillImageOutput);
[stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error){
CFDictionaryRef exifAttachments = CMGetAttachment( imageSampleBuffer, kCGImagePropertyExifDictionary, NULL);
if (exifAttachments){
// Do something with the attachments if you want to.
NSLog(@"attachements: %@", exifAttachments);
}
else
NSLog(@"no attachments");
NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
UIImage *image = [[UIImage alloc] initWithData:imageData];
self.vImage.image = image;
}];
}
答案 1 :(得分：1)
好吧，我遇到了类似的问题，captureStillImageAsynchronouslyFromConnection:stillImageConnection引发了一个异常，即传递的connection无效。后来，我发现当我为会话properties而stillImageOutPut保留值时，问题就解决了。
答案 2 :(得分：1)
我是一名JavaScript开发人员。想为我的跨平台Javascript项目创建iOS本机框架
当我开始做同样的事情时，我遇到了很多问题，这些方法已被弃用，并且出现其他运行时错误。
解决所有问题后，下面是与iOS 13.5兼容的答案
该代码可帮助您在单击按钮时无需预览即可拍照。
您的.h文件
@interface NoPreviewCameraViewController : UIViewController <AVCapturePhotoCaptureDelegate> {
AVCaptureSession *captureSession;
AVCapturePhotoOutput *photoOutput;
AVCapturePhotoSettings *photoSetting;
AVCaptureConnection *captureConnection;
UIImageView *imageView;
}
@end
您的.m文件
- (void)viewDidLoad {
[super viewDidLoad];
imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height - 140)];
[self.view addSubview:imageView];
UIButton *takePicture = [UIButton buttonWithType:UIButtonTypeCustom];
[takePicture addTarget:self action:@selector(takePicture:) forControlEvents:UIControlEventTouchUpInside];
[takePicture setTitle:@"Take Picture" forState:UIControlStateNormal];
takePicture.frame = CGRectMake(40.0, self.view.frame.size.height - 140, self.view.frame.size.width - 40, 40);
[self.view addSubview:takePicture];
[self initCaptureSession];
}
- (void) initCaptureSession {
captureSession = [[AVCaptureSession alloc] init];
if([captureSession canSetSessionPreset: AVCaptureSessionPresetPhoto] ) {
[captureSession setSessionPreset:AVCaptureSessionPresetPhoto];
}
AVCaptureDeviceInput *deviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:[AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo] error:nil];
if ([captureSession canAddInput:deviceInput]) {
[captureSession addInput:deviceInput];
}
photoOutput = [[AVCapturePhotoOutput alloc] init];
if ([captureSession canAddOutput:photoOutput]) {
[captureSession addOutput:photoOutput];
}
[captureSession startRunning];
}
-(void) setNewPhotoSetting {
photoSetting = [AVCapturePhotoSettings photoSettingsWithFormat:@{AVVideoCodecKey : AVVideoCodecTypeJPEG}];
[photoOutput setPhotoSettingsForSceneMonitoring:photoSetting];
}
- (IBAction)takePicture:(id)sender {
captureConnection = nil;
[self setNewPhotoSetting];
for (AVCaptureConnection *connection in photoOutput.connections) {
for (AVCaptureInputPort *port in [connection inputPorts]) {
if ([[port mediaType] isEqual: AVMediaTypeVideo]) {
captureConnection = connection;
NSLog(@"Value of connection = %@", connection);
NSLog(@"Value of captureConnection = %@", captureConnection);
break;
}
}
if (captureConnection) {
break;
}
}
[photoOutput capturePhotoWithSettings:photoSetting delegate:self];
}