iOS6 : How to use the conversion feature of YUV to RGB from cvPixelBufferref to CIImage

Question

从iOS6开始，Apple通过这个调用给CIImage提供了使用原生YUV的规定

initWithCVPixelBuffer:options:

在核心图像编程指南中，他们提到了这个特性

Take advantage of the support for YUV image in iOS 6.0 and later. Camera pixel buffers are natively YUV but most image processing algorithms expect RBGA data. There is a cost to converting between the two. Core Image supports reading YUB from CVPixelBuffer objects and applying the appropriate color transform.

options = @{ (id)kCVPixelBufferPixelFormatTypeKey : @(kCVPixelFormatType_420YpCvCr88iPlanarFullRange) };

但是，我无法正确使用它。我有一个原始的 YUV 数据。所以，这就是我所做的

                void *YUV[3] = {data[0], data[1], data[2]};
                size_t planeWidth[3] = {width, width/2, width/2};
                size_t planeHeight[3] = {height, height/2, height/2};
                size_t planeBytesPerRow[3] = {stride, stride/2, stride/2};
                CVPixelBufferRef pixelBuffer = NULL;
                CVReturn ret = CVPixelBufferCreateWithPlanarBytes(kCFAllocatorDefault,
                               width, 
                               height,
                               kCVPixelFormatType_420YpCbCr8PlanarFullRange, 
                               nil,
                               width*height*1.5,
                               3, 
                               YUV,
                               planeWidth,
                               planeHeight, 
                               planeBytesPerRow, 
                               nil,
                               nil, nil, &pixelBuffer); 

    NSDict *opt =  @{ (id)kCVPixelBufferPixelFormatTypeKey :
                        @(kCVPixelFormatType_420YpCbCr8PlanarFullRange) };

CIImage *image = [[CIImage alloc]   initWithCVPixelBuffer:pixelBuffer options:opt];

我的图像为零。知道我错过了什么。

编辑: 我在调用前添加了锁定和解锁基址。另外，我转储了 pixelbuffer 的数据，以确保 pixellbuffer 能够正确保存数据。看起来只有 init 调用有问题。 CIImage 对象仍然返回 nil。

 CVPixelBufferLockBaseAddress(pixelBuffer, 0);
CIImage *image = [[CIImage alloc]   initWithCVPixelBuffer:pixelBuffer options:opt];
 CVPixelBufferUnlockBaseAddress(pixelBuffer,0);

Answer 1

控制台中应该有错误消息:initWithCVPixelBuffer failed because the CVPixelBufferRef is not IOSurface backed。参见 Apple 的 Technical Q&A QA1781了解如何创建 IOSurface 支持的 CVPixelBuffer。

Calling CVPixelBufferCreateWithBytes() or CVPixelBufferCreateWithPlanarBytes() will result in CVPixelBuffers that are not IOSurface-backed...

...To do that, you must specify kCVPixelBufferIOSurfacePropertiesKey in the pixelBufferAttributes dictionary when creating the pixel buffer using CVPixelBufferCreate().

NSDictionary *pixelBufferAttributes = [NSDictionary dictionaryWithObjectsAndKeys:
    [NSDictionary dictionary], (id)kCVPixelBufferIOSurfacePropertiesKey,
    nil];
// you may add other keys as appropriate, e.g. kCVPixelBufferPixelFormatTypeKey,     kCVPixelBufferWidthKey, kCVPixelBufferHeightKey, etc.
 
CVPixelBufferRef pixelBuffer;
CVPixelBufferCreate(... (CFDictionaryRef)pixelBufferAttributes,  &pixelBuffer);

Alternatively, you can make IOSurface-backed CVPixelBuffers using CVPixelBufferPoolCreatePixelBuffer() from an existing pixel buffer pool, if the pixelBufferAttributes dictionary provided to CVPixelBufferPoolCreate() includes kCVPixelBufferIOSurfacePropertiesKey.