Converting webcam program to process one image - c++

Question

I am currently trying to modify a program that takes in a webcam stream as input. The problem is, when I try to alter the program to use a single image, it doesn't display the output that I am expecting e.g. with video stream (code below)
#include "opencv2/opencv.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/videoio.hpp"
#include <opencv2/highgui.hpp>
#include <opencv2/video.hpp>
#include "BackgroundRemover.h"
#include "SkinDetector.h"
#include "FaceDetector.h"
#include "FingerCount.h"
using namespace cv;
using namespace std;
int main(int, char**) {
VideoCapture videoCapture(0);
videoCapture.set(CV_CAP_PROP_SETTINGS, 1);
if (!videoCapture.isOpened()) {
cout << "Can't find camera!" << endl;
return -1;
}
Mat frame, frameOut, handMask, foreground, fingerCountDebug;
BackgroundRemover backgroundRemover;
SkinDetector skinDetector;
FaceDetector faceDetector;
FingerCount fingerCount;
for (int i = 0; i < 2; i++)
{
videoCapture >> frame;
frameOut = frame.clone();
skinDetector.drawSkinColorSampler(frameOut);
foreground = backgroundRemover.getForeground(frame);
faceDetector.removeFaces(frame, foreground);
handMask = skinDetector.getSkinMask(foreground);
fingerCountDebug = fingerCount.findFingersCount(handMask, frameOut);
imshow("output", frameOut);
imshow("foreground", foreground);
imshow("handMask", handMask);
imshow("handDetection", fingerCountDebug);
if (i == 0)
{
backgroundRemover.calibrate(frame);
skinDetector.calibrate(frame);
}
}
waitKey(0);
}
The output shows a detection. Whereas, if I modify the code so that frame doesn't read from the video stream, the output shows nothing at all. Can anybody help to fix this? EDIT: Due to confusion from some members of the community, the modified code is below that reads in a single image:
#include "opencv2/opencv.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/imgproc.hpp"
#include "opencv2/videoio.hpp"
#include <opencv2/highgui.hpp>
#include <opencv2/video.hpp>
#include "BackgroundRemover.h"
#include "SkinDetector.h"
#include "FaceDetector.h"
#include "FingerCount.h"
using namespace cv;
using namespace std;
int main(int, char**) {
string imageName("C:/Users/whoever/Desktop/hand_test.jpg"); // by default
Mat image;
image = imread(imageName.c_str(), IMREAD_COLOR); // Read the file
Mat frame, frameOut, handMask, foreground, fingerCountDebug;
BackgroundRemover backgroundRemover;
SkinDetector skinDetector;
FaceDetector faceDetector;
FingerCount fingerCount;
for (int i = 0; i < 2; i++)
{
frame = image;
frameOut = frame.clone();
skinDetector.drawSkinColorSampler(frameOut);
foreground = backgroundRemover.getForeground(frame);
faceDetector.removeFaces(frame, foreground);
handMask = skinDetector.getSkinMask(foreground);
fingerCountDebug = fingerCount.findFingersCount(handMask, frameOut);
imshow("output", frameOut);
imshow("foreground", foreground);
imshow("handMask", handMask);
imshow("handDetection", fingerCountDebug);
if (i == 0)
{
cout << "Calibrating...";
backgroundRemover.calibrate(frame);
skinDetector.calibrate(frame);
}
}
waitKey(0);
}

Answer 1

The original code processes different images captured from the camera each time it goes round the loop and outputs the differences. Since you are now using the same image every time round there are never any differences hence the output is completely blank. (Note that it will still be playing the output as a video, just a constantly blank one)
The first line in the for loop is where it grabs a new image from the camera:
videoCapture >> frame;
As you can see in your updated code you are removing this and just using the same image again:
frame = image;
Try saving 2 different images instead and have the program load in a different one each time round the loop.
Here is a fairly brute force way to do it which you could improve to load a different file each time it loops, use arrays and so on:
string imageName1("C:/Users/whoever/Desktop/hand_test_1.jpg"); // by default
string imageName2("C:/Users/whoever/Desktop/hand_test_2.jpg"); // by default
Mat image1;
Mat image2;
image1 = imread(imageName1.c_str(), IMREAD_COLOR); // Read the file
image2 = imread(imageName2.c_str(), IMREAD_COLOR); // Read the file
Mat frame, frameOut, handMask, foreground, fingerCountDebug;
BackgroundRemover backgroundRemover;
SkinDetector skinDetector;
FaceDetector faceDetector;
FingerCount fingerCount;
for (int i = 0; i < 2; i++)
{
if (i = 0) { frame = image1 } else { frame = image2 };
...