limitCroppingRectangle

bool limitCroppingRectangle(cv::Rect& rect, const int& im_width, const int& im_height) {
    bool changed = false;
    if (rect.x<0)                         {rect.width  += rect.x;          rect.x = 0;  changed = true;}
    if (rect.x + rect.width > im_width)   {rect.width  = im_width - rect.x;             changed = true;}
    if (rect.y<0)                         {rect.height += rect.y;          rect.y = 0;  changed = true;}
    if (rect.y + rect.height > im_height) {rect.height = im_height - rect.y;            changed = true;}
    return changed;
}