我有一个条形码扫描仪，我使用 IOS7 中的一些新的AVCapture API 编写。一切都很好，但是在我从捕获输出中获取满足数据后，我很想抓取图像。下面的方法是我在 SKU 等上进行查找的委托，并且也想抓取图像。这种方法可以做到吗？
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection
{
...
}
【问题讨论】：
标签： ios ios7 avcapturesession
要具体回答您的问题，不，没有办法从 AVCaptureMetadataOutput 实例中保存图像。
但是，正如codingVoldemort 的优秀示例所示，您可以创建一个AVCaptureStillImageOutput 实例并将其添加到您的AVCaptureSession 输出中。一旦您的应用检测到一些元数据，您就可以立即触发对该 CaptureStillImageOutput 实例的捕获。
这里有一个更明确的解决方案，使用codingVoldemort的初始代码作为基础：
首先，无论您在何处建立AVCaptureSession，都向其中添加AVCaptureStillImageOutput：
_session = [[AVCaptureSession alloc] init];
_output = [[AVCaptureMetadataOutput alloc] init];
[_output setMetadataObjectsDelegate:self queue:dispatch_get_main_queue()];
[_session addOutput:_output];
_stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
[_session addOutput:_stillImageOutput];
现在，在- captureOutput: didOutputMetadataObjects 中，您可以在触发该方法时捕获静止图像：
AVCaptureConnection *stillImageConnection = [_stillImageOutput connectionWithMediaType:AVMediaTypeVideo];
[stillImageConnection setVideoOrientation:AVCaptureVideoOrientationPortrait];
[stillImageConnection setVideoScaleAndCropFactor:1.0f];
[_stillImageOutput setOutputSettings:[NSDictionary dictionaryWithObject:AVVideoCodecJPEG
forKey:AVVideoCodecKey]];
_stillImageOutput.outputSettings = @{AVVideoCodecKey: AVVideoCodecJPEG, AVVideoQualityKey:@1};
[stillImageOutput captureStillImageAsynchronouslyFromConnection:stillImageConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
if (error) {
NSLog(@"error: %@", error);
}
else {
NSData *jpegData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image =[UIImage imageWithData:jpegData];
//Grabbing the image here
dispatch_async(dispatch_get_main_queue(), ^(void) {
//Update UI if necessary.
});
}
}
];
【讨论】：
试试这个方法：
-(void)captureZoomedImage:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
// Find out the current orientation and tell the still image output.
AVCaptureConnection *stillImageConnection = [stillImageOutput connectionWithMediaType:AVMediaTypeVideo];
UIDeviceOrientation curDeviceOrientation = [[UIDevice currentDevice] orientation];
AVCaptureVideoOrientation avcaptureOrientation = [self avOrientationForDeviceOrientation:curDeviceOrientation];
[stillImageConnection setVideoOrientation:avcaptureOrientation];
[stillImageConnection setVideoScaleAndCropFactor:1.0f];
[stillImageOutput setOutputSettings:[NSDictionary dictionaryWithObject:AVVideoCodecJPEG
forKey:AVVideoCodecKey]];
stillImageOutput.outputSettings = @{AVVideoCodecKey: AVVideoCodecJPEG, AVVideoQualityKey:@1};
[stillImageOutput captureStillImageAsynchronouslyFromConnection:stillImageConnection
completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
if (error) {
[self displayErrorOnMainQueue:error withMessage:@"Take picture failed"];
}
else {
NSData *jpegData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
UIImage *image =[UIImage imageWithData:jpegData];
//Grabbing the image here
dispatch_async(dispatch_get_main_queue(), ^(void) {
//Update UI if necessary.
});
}
}
];
}
【讨论】：
AVCaptureVideoDataOutputSampleBufferDelegate 协议的委托方法。您可以在这里阅读所有相关信息：developer.apple.com/librarY/mac/documentation/AVFoundation/…
我想将 Tim 的回答翻译成 Swift =) 这是第一节：
let session = AVCaptureSession()
var metadataOutput = AVCaptureMetadataOutput()
var stillCameraOutput = AVCaptureStillImageOutput()
let sessionQueue = dispatch_async(dispatch_get_main_queue(), nil)
metadataOutput.setMetadataObjectsDelegate(self, queue: sessionQueue)
if session.canAddOutput(metadataOutput) {
session.addOutput(metadataOutput)
}
session.addOutput(stillCameraOutput)
这是第二个：
var image = UIImage()
let stillImageConnection = stillCameraOutput.connectionWithMediaType(AVMediaTypeVideo)
stillImageConnection.videoOrientation = .Portrait
stillImageConnection.videoScaleAndCropFactor = 1.0
stillCameraOutput.captureStillImageAsynchronouslyFromConnection(stillImageConnection, completionHandler: { (imageDataSampleBuffer, error) in
if (error != nil) {
print("There are some error in capturing image")
} else {
let jpegData = AVCaptureStillImageOutput.jpegStillImageNSDataRepresentation(imageDataSampleBuffer)
image = UIImage(data: jpegData)!
}
})
【讨论】：