如何从CVPixelBufferRef转换为openCV cv :: Mat

Question

我想对CVPixelBufferRef进行一些操作，然后拿出cv::Mat

• 收获到感兴趣的地区
• 缩放到固定维度
• 均衡直方图
• 转换为灰度 - 每像素8位（qazxsw poi）

我不确定最有效的顺序是什么，但是，我知道所有操作都可以在open：CV矩阵上使用，所以我想知道如何转换它。

CV_8UC1

Answer 1

我在一些

- (void) captureOutput:(AVCaptureOutput *)captureOutput 
         didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
         fromConnection:(AVCaptureConnection *)connection
{
     CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

     cv::Mat frame = f(pixelBuffer); // how do I implement f()?

找到了答案。为简单起见，我在这里改编它也为我做了灰度转换。

excellent GitHub source code

我在想最好的订单是：

1. 转换为灰度（因为它几乎是自动完成的）
2. 裁剪（这应该是一个快速操作，将减少要使用的像素数）
3. 缩小
4. 均衡直方图

Answer 2

我正在使用它。我的

CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
OSType format = CVPixelBufferGetPixelFormatType(pixelBuffer);

// Set the following dict on AVCaptureVideoDataOutput's videoSettings to get YUV output
// @{ kCVPixelBufferPixelFormatTypeKey : kCVPixelFormatType_420YpCbCr8BiPlanarFullRange }

NSAssert(format == kCVPixelFormatType_420YpCbCr8BiPlanarFullRange, @"Only YUV is supported");

// The first plane / channel (at index 0) is the grayscale plane
// See more infomation about the YUV format
// http://en.wikipedia.org/wiki/YUV
CVPixelBufferLockBaseAddress(pixelBuffer, 0);
void *baseaddress = CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);

CGFloat width = CVPixelBufferGetWidth(pixelBuffer);
CGFloat height = CVPixelBufferGetHeight(pixelBuffer);

cv::Mat mat(height, width, CV_8UC1, baseaddress, 0);

// Use the mat here

CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);

配置了BGR（8UC3）colorFormat。

CVImageBufferRef - > cv :: Mat

cv:Mat

cv :: Mat - > CVImageBufferRef（CVPixelBufferRef）

- (cv::Mat) matFromImageBuffer: (CVImageBufferRef) buffer {

    cv::Mat mat ;

    CVPixelBufferLockBaseAddress(buffer, 0);

    void *address = CVPixelBufferGetBaseAddress(buffer);
    int width = (int) CVPixelBufferGetWidth(buffer);
    int height = (int) CVPixelBufferGetHeight(buffer);

    mat   = cv::Mat(height, width, CV_8UC4, address, 0);
    //cv::cvtColor(mat, _mat, CV_BGRA2BGR);

    CVPixelBufferUnlockBaseAddress(buffer, 0);

    return mat;
}