remove-background

Overview

This example shows you how to remove the background of an image using depth camera with range filter.

Expect Output

Prerequisite

• OpenCV Viewer
• Align Depth & Color
• Range Filter

Tutorial

Modify from range-filter, we add two variables to determinate the desired distance. Then add two keyboard shortcut to set these values.

double thresholdValueUp = 530;
double thresholdValueDown = 385;
char input;

input = cv::waitKey(1);
if (input == 'p')
{
    if (thresholdValueUp + 5 <= 2000)
        thresholdValueUp += 5;
    else
        thresholdValueUp = 2000;

    std::cout << "Threshold Value (Up):" << thresholdValueUp << " (Down):" << thresholdValueDown << std::endl;
}
else if (input == 'o')
{
    if (thresholdValueUp - 5 >= 0 && thresholdValueUp - 5 >= thresholdValueDown)
        thresholdValueUp -= 5;

    std::cout << "Threshold Value (Up):" << thresholdValueUp << " (Down):" << thresholdValueDown << std::endl;
}
else if (input == 'x')
{
    if (thresholdValueDown + 5 <= 2000 && thresholdValueDown + 5 <= thresholdValueUp)
        thresholdValueDown += 5;

    std::cout << "Threshold Value (Up):" << thresholdValueUp << " (Down):" << thresholdValueDown << std::endl;
}
else if (input == 'z')
{
    if (thresholdValueDown - 5 >= 0)
        thresholdValueDown -= 5;
    else
        thresholdValueDown = 0;

    std::cout << "Threshold Value (Up):" << thresholdValueUp << " (Down):" << thresholdValueDown << std::endl;
}

Using these two values to create range filter mask image like we did before.

cv::threshold(thres, thres, thresholdValueDown, 1024, cv::THRESH_TOZERO);
cv::threshold(thres, thres, thresholdValueUp, 1024, cv::THRESH_TOZERO_INV);
cv::threshold(thres, thres, 1, 1024, cv::THRESH_BINARY);

Then we use OpenCV bitwise_and operation on the color image and the mask. We also need to convert the mask to CV_8UC1 because that the format needed by bitwise_and. Finally we will get the result image that remove the background.

thres.convertTo(thres, CV_8UC1, 255.0 / 1024.0);
cv::Mat res;
cv::bitwise_and(colorMat, colorMat, res, thres);

Full code

remove-background.cpp