Black Hat transform

This transform extract finer details from the image as well. This is the difference between the morphological closing of an image and the image itself. This gives us the objects in the image that are smaller than the structuring element and darker than its surroundings:

Let's look at the function to perform a Black Hat transform:

Mat performBlackHat(Mat inputImage, int morphologyElement, int morphologySize)
{
    Mat outputImage;
    int morphologyType;

    if(morphologyElement == 0)
        morphologyType = MORPH_RECT;
    else if(morphologyElement == 1)
        morphologyType = MORPH_CROSS;
    else if(morphologyElement == 2)
        morphologyType = MORPH_ELLIPSE;

    // Create the structuring element for erosion
    Mat element = getStructuringElement(morphologyType, Size(2*morphologySize + 1, 2*morphologySize + 1), Point(morphologySize, morphologySize));

    // Apply black hat operation to the image using the structuring element
    outputImage = performClosing(inputImage, morphologyElement, morphologySize) - inputImage;

    // Return the output image
    return outputImage;
}