我AVCaptureSessionPhoto
用来让用户拍摄高分辨率照片。拍照时,我使用该captureOutput:didOutputSampleBuffer:fromConnection:
方法在拍摄时检索缩略图。然而,尽管我尝试在委托方法中做最少的工作,但应用程序变得有点滞后(我之所以这么说是因为它仍然可用)。此外,iPhone 往往会发热。
有什么方法可以减少 iPhone 的工作量吗?
我AVCaptureVideoDataOutput
通过执行以下操作来设置:
self.videoDataOutput = [[AVCaptureVideoDataOutput alloc] init];
self.videoDataOutput.alwaysDiscardsLateVideoFrames = YES;
// Specify the pixel format
dispatch_queue_t queue = dispatch_queue_create("com.myapp.videoDataOutput", NULL);
[self.videoDataOutput setSampleBufferDelegate:self queue:queue];
dispatch_release(queue);
self.videoDataOutput.videoSettings = [NSDictionary dictionaryWithObject: [NSNumber numberWithInt:kCVPixelFormatType_32BGRA]
forKey:(id)kCVPixelBufferPixelFormatTypeKey];
这是我的captureOutput:didOutputSampleBuffer:fromConnection
(和辅助imageRefFromSampleBuffer
方法):
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
if (videoDataOutputConnection == nil) {
videoDataOutputConnection = connection;
}
if (getThumbnail > 0) {
getThumbnail--;
CGImageRef tempThumbnail = [self imageRefFromSampleBuffer:sampleBuffer];
UIImage *image;
if (self.prevLayer.mirrored) {
image = [[UIImage alloc] initWithCGImage:tempThumbnail scale:1.0 orientation:UIImageOrientationLeftMirrored];
}
else {
image = [[UIImage alloc] initWithCGImage:tempThumbnail scale:1.0 orientation:UIImageOrientationRight];
}
[self.cameraThumbnailArray insertObject:image atIndex:0];
dispatch_async(dispatch_get_main_queue(), ^{
self.freezeCameraView.image = image;
});
CFRelease(tempThumbnail);
}
sampleBuffer = nil;
[pool release];
}
-(CGImageRef)imageRefFromSampleBuffer:(CMSampleBufferRef)sampleBuffer {
CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(imageBuffer,0);
uint8_t *baseAddress = (uint8_t *)CVPixelBufferGetBaseAddress(imageBuffer);
size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
size_t width = CVPixelBufferGetWidth(imageBuffer);
size_t height = CVPixelBufferGetHeight(imageBuffer);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGImageRef newImage = CGBitmapContextCreateImage(context);
CVPixelBufferUnlockBaseAddress(imageBuffer,0);
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
return newImage;
}