图片按比例缩放

按比例缩小

Rectangle resize(Size s, Size to) {
    if (s.Width == to.Width && s.Height == to.Height) {
        return new Rectangle(0, 0, s.Width, s.Height);
    } else if (s.Width < to.Width && s.Height < to.Height) {
        return new Rectangle((to.Width - s.Width) / 2, (to.Height - s.Height) / 2, s.Width, s.Height);
    } else if (s.Width < to.Width && s.Height >= to.Height) {
        var re = (float)s.Width / s.Height;
        var toWidth = re * to.Height;
        return new Rectangle((int)((toWidth - s.Width) / 2), 0, (int)toWidth, to.Height);
    } else if (s.Width >= to.Width && s.Height < to.Height) {
        var re = (float)s.Height / s.Width;
        var toHeight = re * to.Width;
        return new Rectangle(0, (int)((to.Height - toHeight) / 2), to.Width, (int)toHeight);
    } else if (s.Width >= s.Height) {
        var toWidth = to.Width;
        var re = (float)s.Height / s.Width;
        var toHeight = re * to.Width;
        return new Rectangle((to.Width - toWidth) / 2, (int)((to.Height - toHeight) / 2), toWidth, (int)toHeight);
    } else {
        var toHeight = to.Height;
        var re = (float)s.Width / s.Height;
        var toWidth = re * to.Height;
        return new Rectangle((int)((to.Width - toWidth) / 2), (int)((to.Height - toHeight) / 2), (int)toWidth, (int)toHeight);
    }
}