问C ++ 如何完成lambda模糊调用？

// this one does not return an image
void eachPixel(const QImage &image, const std::function <void (uint)>& pixelFunc, const QRect &bounds=QRect()) {
...

    for (int y=region.y(); y<=region.bottom(); y++) {
        for (int x=region.x(); x<=region.right(); x++) {
            pixelFunc(image.pixel(x,y));
        }
    }
}

// This one returns an image
QImage eachPixel(const QImage &image, const std::function <uint (uint)>& pixelFunc, const QRect &bounds=QRect()) {
...

    QImage out(image.size(), image.format());
    for (int y=region.y(); y<=region.bottom(); y++) {
        for (int x=region.x(); x<=region.right(); x++) {
            out.setPixel(x,y, pixelFunc(image.pixel(x,y)));
        }
    }
    return out;
}

void test_pixelFunc() {
    QImage image(300,200, QImage::Format_ARGB32);
    image.fill(Qt::blue);

    QImage out = eachPixel(image, [] (uint p) -> uint { //uint specified!!
        return qRgb(qRed(p), qBlue(p), qGreen(p)); // swap green and blue channels
    }, QRect (0,0, 300, 200));
    out.save("test_pixelfunc.png");


    int accumulator=0;
    eachPixel(image, [&accumulator](uint p) -> void { // void specified!
        accumulator++;
    }, QRect (0,0, 300, 200));
    qDebug() << "accumulator" << accumulator;

};