Windows + Qt and how to capture webcam feed without OpenCV

Question

I'm fighting with this problem from a long time. I can't get OpenCV to work, and I have follow a lot of tutorials about it and how to use in Qt, so I get tired and I want to avoid the use of OpenCV for this.

Now, my requirement or question... I need to show a webcam feed (real time video, without audio) in a Qt GUI application with only one button: "Take Snapshot" which, obviusly, take a picture from the current feed and store it.

That's all.

Is there anyway to get this done without using OpenCV ?

System specification:

• Qt 4.8

• Windows XP 32 bits

• USB 2.0.1.3M UVC WebCam (the one I'm using now, it should support other models too)

Hope anybody can help me with this because I'm getting crazy.

Thanks in advance!

Answer 1

Ok, I finally did it, so I will post here my solution so we have something clear about this.

I used a library called 'ESCAPI': http://sol.gfxile.net/escapi/index.html

This provide a extremely easy way to capture frames from the device. With this raw data, I just create a QImage which later show in a QLabel.

I created a simple object to handle this.

#include <QDebug>
#include "camera.h"

Camera::Camera(int width, int height, QObject *parent) :
    QObject(parent),
    width_(width),
    height_(height)
{
    capture_.mWidth = width;
    capture_.mHeight = height;
    capture_.mTargetBuf = new int[width * height];

    int devices = setupESCAPI();
    if (devices == 0)
    {
        qDebug() << "[Camera] ESCAPI initialization failure or no devices found";
    }
}

Camera::~Camera()
{
    deinitCapture(0);
}

int Camera::initialize()
{
    if (initCapture(0, &capture_) == 0)
    {
        qDebug() << "[Camera] Capture failed - device may already be in use";
        return -2;
    }
    return 0;
}

void Camera::deinitialize()
{
    deinitCapture(0);
}

int Camera::capture()
{
    doCapture(0);
    while(isCaptureDone(0) == 0);

    image_ = QImage(width_, height_, QImage::Format_ARGB32);
    for(int y(0); y < height_; ++y)
    {
        for(int x(0); x < width_; ++x)
        {
            int index(y * width_ + x);
            image_.setPixel(x, y, capture_.mTargetBuf[index]);
         }
    }
    return 1;
}

And the header file:

#ifndef CAMERA_H
#define CAMERA_H

#include <QObject>
#include <QImage>
#include "escapi.h"

class Camera : public QObject
{
    Q_OBJECT

public:
    explicit Camera(int width, int height, QObject *parent = 0);
    ~Camera();
    int initialize();
    void deinitialize();
    int capture();
    const QImage& getImage() const { return image_; }
    const int* getImageRaw() const { return capture_.mTargetBuf; }

private:
    int width_;
    int height_;
    struct SimpleCapParams capture_;
    QImage image_;
};

#endif // CAMERA_H

It's so simple, but just for example purposes. The use should be something like:

Camera cam(320, 240);
cam.initialize();
cam.capture();
QImage img(cam.getImage());
ui->label->setPixmap(QPixmap::fromImage(img));

Of course, you can use a QTimer and update the frame in QLabel and you will have video there...

Hope it help! and thanks Nicholas for your help!