焦点(自动对焦)在相机中不起作用(AVFoundation AVCaptureSession) [英] Focus (Autofocus) not working in camera (AVFoundation AVCaptureSession)
问题描述
我正在使用标准 AVFoundation 类来捕获视频并显示预览 (http://developer.apple.com/library/ios/#qa/qa1702/_index.html)
I am using standard AVFoundation classes to capture video and show preview (http://developer.apple.com/library/ios/#qa/qa1702/_index.html)
这是我的代码:
- (void)setupCaptureSession {
NSError *error = nil;
[self setCaptureSession: [[AVCaptureSession alloc] init]];
self.captureSession.sessionPreset = AVCaptureSessionPresetMedium;
device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
if ([device isFocusModeSupported:AVCaptureFocusModeContinuousAutoFocus] && [device lockForConfiguration:&error]) {
[device setFocusMode:AVCaptureFocusModeContinuousAutoFocus];
[device unlockForConfiguration];
}
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
error:&error];
if (!input) {
// TODO: Obsługa błędu, gdy nie uda się utworzyć wejścia
}
[[self captureSession] addInput:input];
AVCaptureVideoDataOutput *output = [[[AVCaptureVideoDataOutput alloc] init] autorelease];
[[self captureSession] addOutput:output];
dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
[output setSampleBufferDelegate:self queue:queue];
dispatch_release(queue);
output.videoSettings =
[NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:kCVPixelFormatType_32BGRA]
forKey:(id)kCVPixelBufferPixelFormatTypeKey];
output.minFrameDuration = CMTimeMake(1, 15);
[[self captureSession] startRunning];
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [AVCaptureVideoPreviewLayer layerWithSession:self.captureSession];
captureVideoPreviewLayer.frame = previewLayer.bounds;
[previewLayer.layer insertSublayer:captureVideoPreviewLayer atIndex:0];
[previewLayer setHidden:NO];
mutex = YES;
}
// Delegate routine that is called when a sample buffer was written
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection {
if (mutex && ![device isAdjustingFocus] && ![device isAdjustingExposure] && ![device isAdjustingWhiteBalance]) {
// something
}
}
// Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer {
// Get a CMSampleBuffer's Core Video image buffer for the media data
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
// Lock the base address of the pixel buffer
CVPixelBufferLockBaseAddress(imageBuffer, 0);
// Get the number of bytes per row for the pixel buffer
void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);
// Get the number of bytes per row for the pixel buffer
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
// Get the pixel buffer width and height
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
// Create a device-dependent RGB color space
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
// Create a bitmap graphics context with the sample buffer data
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
// Create a Quartz image from the pixel data in the bitmap graphics context
CGImageRef quartzImage = CGBitmapContextCreateImage(context);
// Unlock the pixel buffer
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
// Free up the context and color space
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
// Create an image object from the Quartz image
UIImage *image = [UIImage imageWithCGImage:quartzImage];
// Release the Quartz image
CGImageRelease(quartzImage);
return (image);
}
一切正常,但有时会出现一些问题:
Everything is working OK but sometimes it have some issues:
- Camera Focus 无法正常工作 - 随机出现,有时有效,有时无效.我在不同的设备上尝试过 iPhone 4 和 3GS.我试图谷歌它,但没有结果.人们只提到损坏的设备,但我检查了 3 部 iPhone 4 和 1 部 iPhone 3GS.问题无处不在.
- 相机加载时间过长.我正在使用 ScannerKit API,出于同样的原因,它也在使用相机,它的加载速度比我的实现快大约两倍.
任何想法可能是什么问题?第一个问题肯定更重要.
Any ideas what can be a problem? The first issue is definitely more important.
推荐答案
老问题,但无论如何可能会节省几个小时的挫败感.在调用 setFocusMode
之前设置兴趣点很重要,否则您的相机会将焦点设置到上一个焦点.将 setFocusMode
视为 COMMIT.同样适用于 setExposureMode
.
Old question but anyway may save somebody hours of frustration. It's important to set the point of interest before calling setFocusMode
, otherwise your camera will set focus to the previous focus point. Think of setFocusMode
as COMMIT. Same applies to setExposureMode
.
Apple 的 AVCam 示例完全错误且损坏.
AVCam sample by Apple is totally wrong and broken.
这篇关于焦点(自动对焦)在相机中不起作用(AVFoundation AVCaptureSession)的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!