C# 计算图片最大缩放宽高的函数

/// <summary>
        /// 计算同比缩放的值
        /// </summary>
        /// <param name="oW">原宽</param>
        /// <param name="oH">原高</param>
        /// <param name="w">目标宽</param>
        /// <param name="h">目标高</param>
        /// <param name="mode">HW(指定高宽缩放（可能变形）),W(指定宽，高按比例),H(指定高，宽按比例),MaxHW(最大宽高比例缩放，比如原100*50->50*30，则结果是50*25)</param>
        /// <returns></returns>
        public static WidthHeight TBScale(double oW,double oH,double w,double h,string mode= "W")
        {
            WidthHeight wh = new WidthHeight();
            double ow = wh.width = oW;
            double oh = wh.height = oH;

            switch (mode)
            {
                case "HW":  //指定高宽缩放（可能变形）  
                    wh.width = (int)w;
                    wh.height = (int)h;
                    break;
                case "W":   //指定宽，高按比例                    
                    wh.height = oH * w / oW;
                    break;
                case "H":   //指定高，宽按比例
                    wh.width = oW * h / oH;
                    break;
                case "Cut": //指定高宽裁减（不变形）                
                    if ((double)oW / (double)oH > (double)wh.width / (double)wh.height)
                    {
                        oh = oH;
                        ow = oH * wh.width / wh.height;
                    }
                    else
                    {
                        ow = oW;
                        oh = oW * h / wh.width;
                    }
                    break;
                case "MaxHW"://最大宽高比例缩放，比如原100*50->50*30，则结果是50*25
                    var rmaxhw_d1w = oW * 1.0 / w;
                    var rmaxhw_d2h = oH * 1.0 / h;
                    if (rmaxhw_d1w > rmaxhw_d2h)
                    {
                        if (rmaxhw_d1w <= 1)
                        {
                            wh.width = oW; h = oH;
                            goto case "HW";
                        }
                        wh.width = w;
                        goto case "W";
                    }
                    if (rmaxhw_d2h <= 1)
                    {
                        wh.width = oW; h = oH;
                        goto case "HW";
                    }
                    wh.height = h;
                    goto case "H";
                default:
                    break;
            }
            wh.width = (int)wh.width;
            wh.height = (int)wh.height;
            return wh;
        }
    }

　　

/// <summary>
    /// 宽高类
    /// </summary>
    public class WidthHeight
    {
        /// <summary>
        /// 宽
        /// </summary>
        public double width { get; set; }
        /// <summary>
        /// 高
        /// </summary>
        public double height { get; set; }
    }