如何在Swift中从C ++矩阵中检索值？

Question

I have a C++ function what returns a cv::Mat value

+(cv::Mat *) makeGray:(UIImage *) image {
    // Transform UIImage to cv::Mat
    cv::Mat imageMat;
    UIImageToMat(image, imageMat);

    //Transform image to grayscale
    cv::Mat grayMat;
    cv::cvtColor(imageMat, grayMat, CV_BGR2GRAY);
    return grayMat;
}

I call that function in Swift using:

let grayMat = OpenCVWrapper.makeGray(photoImageView.image)

I know Swift doesn't import cv::Mat , what's the best alternative so that I get that array in one piece?

Answer 1

This should work.. Just convert the cv::Mat to a malloc 'd byte array and return that.

+ (uint8_t *)makeGray:(UIImage *)image count:(uint32_t *)count {
    // Transform UIImage to cv::Mat
    cv::Mat imageMat;
    UIImageToMat(image, imageMat);

    //Transform image to grayscale
    cv::Mat grayMat;
    cv::cvtColor(imageMat, grayMat, CV_BGR2GRAY);

    int size = grayMat.total() * grayMat.elemSize();
    void *bytes = malloc(size);
    memcpy(bytes, grayMat.data, size);
    *count = size;
    return bytes;
}

Then on the swift side it should be an UnsafeMutablePointer<UInt8> with a count and you can free it by calling deallocate or convert it to an array of bytes.