IOS5: UIView转换为视频，生成的视频已损坏

Question

我想抓取UIView，转换为图像，然后将该图像存储在视频文件(.mp4)中。我使用下一部分代码来抓取图像并将其放入像素缓冲区：

BOOL appended;
    if(input.readyForMoreMediaData==YES){
        //grab the view and convert it into image
        CGSize imgsize=self.imageSource.frame.size;
        UIGraphicsBeginImageContext(imgsize);
        [self.imageSource.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage* grabbedImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

        CVReturn cvErr = kCVReturnSuccess;
        CGImageRef image = (CGImageRef) [grabbedImage CGImage];

        NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
                                 [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
                                 nil];
        CVPixelBufferRef pxbuffer = NULL;

        CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, imgsize.width,
                                              imgsize.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, imgsize.width,
                                                     imgsize.height, 8, 4*imgsize.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);

        appended = [pxlBufAdaptor appendPixelBuffer:pxbuffer withPresentationTime:presentationTime];
        CVBufferRelease(pxbuffer );
    }

问题是，生成的视频包含损坏的图像-所有像素都偏移了。看起来内存中充满了带有偏移量的字节，而偏移量会破坏表示。

如何解决这个问题？我想要任何胶水或方向。提前谢谢。

Answer 1

这看起来很可疑：

CGContextRef context = CGBitmapContextCreate(pxdata, imgsize.width,
    imgsize.height, 8, 4*imgsize.width, rgbColorSpace, 
    kCGImageAlphaNoneSkipFirst);

您将根据图像宽度计算bytesPerRow参数，而不是询问pxbuffer的每行字节数。试试这个：

CGContextRef context = CGBitmapContextCreate(pxdata, imgsize.width,
    imgsize.height, 8, CVPixelBufferGetBytesPerRow(pxbuffer),
    rgbColorSpace, kCGImageAlphaNoneSkipFirst);

此外，使用UIGraphicsGetCurrentContext创建位图图形上下文，将层渲染到上下文中，从上下文中获取图像，销毁上下文，创建像素缓冲区，使用像素缓冲区创建位图图形上下文，并将层的图像绘制到新上下文中，似乎效率低下。为什么不用[self.imageSource.layer renderInContext:context]替换你的CGContextDrawImage调用呢