我正在研究更多的小型项目,这些项目稍后将包含在一个新项目中。它基本上是一个测试单元。
我正在做的是创建一个AVCaptureSession
然后创建一个方法OutputSampleBufferDelegate
。在该方法中,我将sampleBuffer
into a UIImage
并保存UIImage
。当我在 iPhone 4 上运行该应用程序时,它每秒只能保存 2-3 张图像。必须有一种更有效的方法来保存图像。
有人可以帮我加快速度吗?
Thanks!
很多代码都来自这里 http://developer.apple.com/library/ios/#qa/qa1702/_index.html
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
UIImage *resultUIImage = [self imageFromSampleBuffer:sampleBuffer];
NSData *imageData = [NSData dataWithData:UIImagePNGRepresentation(resultUIImage)];
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [paths objectAtIndex:0];
CMTime frameTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer);
NSString *filename = [NSString stringWithFormat:@"%f.png", CMTimeGetSeconds(frameTime)];
NSString *finalPath = [path stringByAppendingString:filename];
[imageData writeToFile:finalPath atomically:YES];
}
// 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;
}
使用此代码,我可以将图像保存时间缩短至 0.1 秒。
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
{
double frameTime = CFAbsoluteTimeGetCurrent();
UIImage *resultUIImage = [self imageFromSampleBuffer:sampleBuffer];
// takes freaking forever to do.
double pre = CFAbsoluteTimeGetCurrent();
NSData *imageData = UIImageJPEGRepresentation(resultUIImage, 0.9);
NSLog(@"It took to write the file:%f",CFAbsoluteTimeGetCurrent()-pre);
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory
,NSUserDomainMask
, YES);
NSString *path = [paths objectAtIndex:0];
NSString *filename = [NSString stringWithFormat:@"%f.png", frameTime];
NSString *finalPath = [path stringByAppendingString:filename];
[imageData writeToFile:finalPath atomically:YES];
}
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