我正在编码的Mac OS X应用程序正在使用内置的超时相机进行照片捕捉。
在MacBookAir3,2,MacBookPro8,2和MacBookPro10,2上工作正常,但在新的MacBook上它需要“黑暗”的照片。我理解这是因为自动曝光,但我很难让它工作。 AVCaptureDevice
adjustingExposure
设置为NO
,但拍摄的照片仍然完全黑暗。
代码:setupCamera
在应用启动期间调用一次
-(void) setupCamera
{
session = [[AVCaptureSession alloc] init];
session.sessionPreset = AVCaptureSessionPresetPhoto;
sessionInitialized = YES;
device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
[device lockForConfiguration:NULL];
if ([device isExposureModeSupported:AVCaptureExposureModeContinuousAutoExposure])
[device setExposureMode:AVCaptureExposureModeContinuousAutoExposure];
if ([device isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus])
[device setFocusMode:AVCaptureFocusModeContinuousAutoFocus];
if ([device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance])
[device setWhiteBalanceMode:AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance];
[device unlockForConfiguration];
NSError *error = nil;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if(error != nil) {
// ...
}
if([session canAddInput:input]) {
[session addInput:input];
} else {
// ...
}
output = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = @{ AVVideoCodecKey : AVVideoCodecJPEG };
[output setOutputSettings:outputSettings];
if([session canAddOutput:output]) {
[session addOutput:output];
} else {
// ...
}
}
...然后每次点击UI中的快照按钮都会调用shootPhoto
函数:
-(void) shootPhoto
{
[session startRunning];
if([device lockForConfiguration:NULL]) {
if ([device isExposureModeSupported:AVCaptureExposureModeContinuousAutoExposure])
[device setExposureMode:AVCaptureExposureModeContinuousAutoExposure];
if ([device isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus])
[device setFocusMode:AVCaptureFocusModeContinuousAutoFocus];
if ([device isWhiteBalanceModeSupported:AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance])
[device setWhiteBalanceMode:AVCaptureWhiteBalanceModeContinuousAutoWhiteBalance];
[device unlockForConfiguration];
}
if(device.adjustingFocus == NO && device.adjustingExposure == NO && device.adjustingWhiteBalance == NO) {
[self actuallyCapture];
} else {
[device addObserver:self forKeyPath:@"adjustingExposure" options:NSKeyValueObservingOptionNew context:MyAdjustingExposureObservationContext];
[device addObserver:self forKeyPath:@"adjustingFocus" options:NSKeyValueObservingOptionNew context:MyAdjustingFocusObservationContext];
[device addObserver:self forKeyPath:@"adjustingWhiteBalance" options:NSKeyValueObservingOptionNew context:MyAdjustingWhiteBalanceObservationContext];
}
}
-(void) actuallyCapture
{
if ([session isRunning] == NO)
return;
connection = [output connectionWithMediaType:AVMediaTypeVideo];
[output captureStillImageAsynchronouslyFromConnection:connection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
// save file etc ...
}];
}
想法是检查相机设备是否正在调整焦距,曝光或白平衡。如果不立即致电actuallyCapture
。如果正在调整 - 添加观察者并从actuallyCapture
调用observeValueForKeyPath
。
问题是addObserver
来电永远不会被调用,因为设备会返回全部adjustingX==NO
- 但是,拍摄的照片仍然很暗。
可能是什么原因?我是否正在等待白平衡和曝光调整?
我很难调试,因为我只拥有那些工作正常的设备。
答案 0 :(得分:2)
我自己设法解决了这个问题。这是我如何做到的:
为adjustingExposure
,adjustingFocus
和adjustingWhiteBalance
设置观察员:
[self.device addObserver:self forKeyPath:@"adjustingExposure" options:NSKeyValueObservingOptionNew context:MyAdjustingExposureObservationContext];
[self.device addObserver:self forKeyPath:@"adjustingFocus" options:NSKeyValueObservingOptionNew context:MyAdjustingFocusObservationContext];
[self.device addObserver:self forKeyPath:@"adjustingWhiteBalance" options:NSKeyValueObservingOptionNew context:MyAdjustingWhiteBalanceObservationContext];
要捕获照片初始化AVCaptureSession
,但设置1秒延迟计时器并在触发后实际捕获:
-(void) shootPhoto
{
dispatch_async(self.sessionQueue, ^{
if([self setupCamera]) {
self.sessionInitialized = YES;
[self.session startRunning];
self.isWaitingToCaptureImage = YES;
dispatch_async(dispatch_get_main_queue(), ^{
self.captureDelayTimer = [NSTimer scheduledTimerWithTimeInterval:1.0
target:self
selector:@selector(actuallyCapture)
userInfo:nil
repeats:NO];
});
}
});
}
在observeValueForKeyPath:ofObject:change:context
检查是否所有三项调整都已完成,如果已经完成 - 取消上面设置的计时器并拍摄照片:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if(!self.sessionInitialized || !self.isWaitingToCaptureImage) {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
return;
}
if (context != MyAdjustingExposureObservationContext && context != MyAdjustingFocusObservationContext && context != MyAdjustingWhiteBalanceObservationContext) {
[super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
return;
} else {
if (self.device.adjustingExposure || self.device.adjustingFocus || self.device.adjustingWhiteBalance) {
NSLog(@"not ready to capture yet");
return;
} else {
NSLog(@"ready to capture");
if (self.captureDelayTimer && self.captureDelayTimer.isValid) {
[self.captureDelayTimer invalidate];
self.captureDelayTimer = nil;
}
[self actuallyCaptureDispatch];
}
}
}