//继承ScreenShotBase的构造函数，将img设置为背景
public CroppedForm(Image img, CameraCaptureForm form)
: base(img)
{
this.camera = form;
InitializeComponent();
}
//继承ScreenShotBase的构造函数，将img设置为背景
public CroppedForm(Image img, CameraCaptureForm form) : base(img)
{
this.camera = form;
InitializeComponent();
}