我正在使用AVFoundation构建一个应用程序。
在- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
方法中,在调用[assetWriterInput appendSampleBuffer:sampleBuffer]
之前。
我使用像素缓冲区处理样本缓冲区中的像素(使用像素缓冲区应用效果)。
但客户还想将文本(时间戳和帧计数器)添加到帧中,但我还没有找到一种方法来实现这一点。
我尝试将样本缓冲区转换为图像,在图像上应用文本,然后将图像转换回样本缓冲区,但是接下来...(未完待续)
CMSampleBufferDataIsReady(sampleBuffer)
失败。
这是我的UIImage类别方法:
+ (UIImage *) imageFromSampleBuffer:(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 newContext = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
CGImageRef newImage = CGBitmapContextCreateImage(newContext);
CGContextRelease(newContext);
CGColorSpaceRelease(colorSpace);
UIImage *newUIImage = [UIImage imageWithCGImage:newImage];
CFRelease(newImage);
return newUIImage;
}
并且
- (CMSampleBufferRef) cmSampleBuffer
{
CGImageRef image = self.CGImage;
NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
[NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
nil];
CVPixelBufferRef pxbuffer = NULL;
CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault,
self.size.width,
self.size.height,
kCVPixelFormatType_32ARGB,
(__bridge CFDictionaryRef) options,
&pxbuffer);
NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);
CVPixelBufferLockBaseAddress(pxbuffer, 0);
void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
NSParameterAssert(pxdata != NULL);
CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pxdata, self.size.width,
self.size.height, 8, 4*self.size.width, rgbColorSpace,
kCGImageAlphaNoneSkipFirst);
NSParameterAssert(context);
CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image),
CGImageGetHeight(image)), image);
CGColorSpaceRelease(rgbColorSpace);
CGContextRelease(context);
CVPixelBufferUnlockBaseAddress(pxbuffer, 0);
CMVideoFormatDescriptionRef videoInfo = NULL;
CMSampleBufferRef sampleBuffer = NULL;
CMSampleBufferCreateForImageBuffer(kCFAllocatorDefault,
pxbuffer, true, NULL, NULL, videoInfo, NULL, &sampleBuffer);
return sampleBuffer;
}
有什么想法吗?
编辑:
我已经按照Tony的回答修改了我的代码。(谢谢!) 这段代码可以工作:
CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress( pixelBuffer, 0 );
EAGLContext *eaglContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
CIContext *ciContext = [CIContext contextWithEAGLContext:eaglContext options:@{kCIContextWorkingColorSpace : [NSNull null]} ];
UIFont *font = [UIFont fontWithName:@"Helvetica" size:40];
NSDictionary *attributes = @{NSFontAttributeName: font,
NSForegroundColorAttributeName: [UIColor lightTextColor]};
UIImage *img = [UIImage imageFromText:@"01 - 13/02/2014 15:18:21:654" withAttributes:attributes];
CIImage *filteredImage = [[CIImage alloc] initWithCGImage:img.CGImage];
[ciContext render:filteredImage toCVPixelBuffer:pixelBuffer bounds:[filteredImage extent] colorSpace:CGColorSpaceCreateDeviceRGB()];
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);