我正在使用此代码捕获图像
#pragma mark - image capture
// Create and configure a capture session and start it running
- (void)setupCaptureSession
{
NSError *error = nil;
// Create the session
AVCaptureSession *session = [[AVCaptureSession alloc] init];
// Configure the session to produce lower resolution video frames, if your
// processing algorithm can cope. We'll specify medium quality for the
// chosen device.
session.sessionPreset = AVCaptureSessionPresetMedium;
// Find a suitable AVCaptureDevice
AVCaptureDevice *device = [AVCaptureDevice
defaultDeviceWithMediaType:AVMediaTypeVideo];
// Create a device input with the device and add it to the session.
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
error:&error];
if (!input)
{
NSLog(@"PANIC: no media input");
}
[session addInput:input];
// Create a VideoDataOutput and add it to the session
AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
[session addOutput:output];
// Configure your output.
dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
[output setSampleBufferDelegate:self queue:queue];
dispatch_release(queue);
// Specify the pixel format
output.videoSettings =
[NSDictionary dictionaryWithObject:
[NSNumber numberWithInt:kCVPixelFormatType_32BGRA]
forKey:(id)kCVPixelBufferPixelFormatTypeKey];
// If you wish to cap the frame rate to a known value, such as 15 fps, set
// minFrameDuration.
// Start the session running to start the flow of data
[session startRunning];
// Assign session to an ivar.
[self setSession:session];
}
// Delegate routine that is called when a sample buffer was written
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
{
NSLog(@"captureOutput: didOutputSampleBufferFromConnection");
// Create a UIImage from the sample buffer data
UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
//< Add your code here that uses the image >
[self.imageView setImage:image];
[self.view setNeedsDisplay];
}
// Create a UIImage from sample buffer data
- (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer
{
NSLog(@"imageFromSampleBuffer: called");
// 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);
}
-(void)setSession:(AVCaptureSession *)session
{
NSLog(@"setting session...");
self.captureSession=session;
}
捕获代码有效。但! 我需要改变一些事情: - 在我看来,来自相机的视频流。 - 从中获取图像(例如5秒)。 请帮帮我,怎么办呢?
答案 0 :(得分:18)
添加以下行
output.minFrameDuration = CMTimeMake(5, 1);
在评论下面
// If you wish to cap the frame rate to a known value, such as 15 fps, set
// minFrameDuration.
但高于
[session startRunning];
修改强>
使用以下代码预览相机输出。
AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session];
UIView *aView = self.view;
CGRect videoRect = CGRectMake(0.0, 0.0, 320.0, 150.0);
previewLayer.frame = videoRect; // Assume you want the preview layer to fill the view.
[aView.layer addSublayer:previewLayer];
编辑2: 好的..
Apple提供了一种设置minFrameDuration here
的方法现在,使用以下代码设置帧持续时间
AVCaptureConnection *conn = [output connectionWithMediaType:AVMediaTypeVideo];
if (conn.supportsVideoMinFrameDuration)
conn.videoMinFrameDuration = CMTimeMake(5,1);
if (conn.supportsVideoMaxFrameDuration)
conn.videoMaxFrameDuration = CMTimeMake(5,1);
答案 1 :(得分:15)
小心 - 来自AVCaptureOutput的回调发布在您指定的调度队列中。我看到你从这个回调中执行UI更新,这是错误的。您应该只在主队列中执行它们。 E.g。
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
{
NSLog(@"captureOutput: didOutputSampleBufferFromConnection");
// Create a UIImage from the sample buffer data
UIImage *image = [self imageFromSampleBuffer:sampleBuffer];
dispatch_async(dispatch_get_main_queue(), ^{
//< Add your code here that uses the image >
[self.imageView setImage:image];
[self.view setNeedsDisplay];
}
}
答案 2 :(得分:4)
这是一个swift版本的imageFromSampleBuffer函数:
func imageFromSampleBuffer(sampleBuffer:CMSampleBuffer!) -> UIImage {
let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
CVPixelBufferLockBaseAddress(imageBuffer, 0)
let baseAddress = CVPixelBufferGetBaseAddress(imageBuffer)
let bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer)
let width = CVPixelBufferGetWidth(imageBuffer)
let height = CVPixelBufferGetHeight(imageBuffer)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo:CGBitmapInfo = [.ByteOrder32Little, CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue)]
let context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, bitmapInfo.rawValue)
let quartzImage = CGBitmapContextCreateImage(context)
CVPixelBufferUnlockBaseAddress(imageBuffer, 0)
let image = UIImage(CGImage: quartzImage!)
return image
}
以上视频设置为我工作:
videoDataOutput = AVCaptureVideoDataOutput()
videoDataOutput?.videoSettings = [kCVPixelBufferPixelFormatTypeKey:Int(kCVPixelFormatType_32BGRA)]
videoDataOutput?.setSampleBufferDelegate(self, queue: queue)