.NET6使用ImageSharp实现给图片添加水印

//ImageFile为图片物理路径，如下方的注释
        public async Task<ImageResult> WaterMark(string ImageFile)
        {
            ImageResult result = new ImageResult();
            //var ImageFile = "D:\www\wwwroot\upload\5176caebc1404caa8b0b350181ae28ab.jpg";
            var WaterMark = "D:\\www\\wwwroot\\watermark.png";
            string FileName = Guid.NewGuid().ToString("N") + ".jpg";
            string SavePath = "D:\\www\\wwwrootupload\\" + FileName;
            string imgurl = "/upload/"+FileName;
            //为了与System.Drawing.Common有所区别，引用使用全路径
            using (var image = await SixLabors.ImageSharp.Image.LoadAsync(ImageFile))
            {
                using (var clone = image.Clone(ctx => ctx.ApplyScalingImageWaterMark("center")))
                {
                    await clone.SaveAsync(SavePath);
                }
                result.width = image.Width;
                result.height = image.Height;

                result.url = imgurl;
                result.format = ".jpg";
                result.state = true;
            }
            return result;
        }

public static class ImageSharpExtention
{
    public static IImageProcessingContext ApplyScalingImageWaterMark(this IImageProcessingContext processingContext, string waterPosition = "center",string waterPath)
    {
         using (var mark_image = SixLabors.ImageSharp.Image.Load(waterPath))
            {
                int markWidth = mark_image.Width;
                int markHeight = mark_image.Height;

                var imgSize = processingContext.GetCurrentSize();

                if (markWidth >= imgSize.Width || markHeight >= imgSize.Height) //对水印图片进行缩放
                {
                    if (imgSize.Width > imgSize.Height)//横的长方形
                    {
                        markWidth = imgSize.Width / 2; //宽缩放一半
                        markHeight = (markWidth * imgSize.Height) / imgSize.Width;
                    }
                    else
                    {
                        markHeight = imgSize.Height / 2;
                        markWidth = (markHeight * imgSize.Width) / imgSize.Height;
                    }
                    mark_image.Mutate(mk => mk.Resize(markWidth, markHeight));
                }
                //水印图片完成成立，开始根据位置添加水印
                var position = waterPosition;
                if (string.IsNullOrEmpty(position))
                {
                    position = "center";
                }
                position = position.ToLower();
                if (string.IsNullOrEmpty(position))
                {
                    position = "center";
                }
                SixLabors.ImageSharp.Point point = new SixLabors.ImageSharp.Point();
                //左上
                if (position.Contains("lefttop"))
                {
                    point.X = 10;
                    point.Y = 10;
                }
                //上中
                if (position.Contains("topcenter"))
                {
                    point.X = (imgSize.Width - mark_image.Width) / 2;
                    point.Y = 10;
                }
                //右上
                if (position.Contains("righttop"))
                {
                    point.X = (imgSize.Width - mark_image.Width) - 10;
                    point.Y = 10;
                }
                //右中
                if (position.Contains("rightcenter"))
                {
                    point.X = (imgSize.Width - mark_image.Width) - 10;
                    point.Y = (imgSize.Height - mark_image.Height) / 2;
                }
                //右下
                if (position.Contains("rightbottom"))
                {
                    point.X = (imgSize.Width - mark_image.Width) - 10;
                    point.Y = (imgSize.Height - mark_image.Height) - 10;
                }
                //下中
                if (position.Contains("bottomcenter"))
                {
                    point.X = (imgSize.Width - mark_image.Width) / 2;
                    point.Y = (imgSize.Height - mark_image.Height) - 10;
                }
                //左下
                if (position.Contains("leftbottom"))
                {
                    point.X = 10;
                    point.Y = (imgSize.Height - mark_image.Height) - 10;
                }
                //左中
                if (position.Contains("leftcenter"))
                {
                    point.X = 10;
                    point.Y = (imgSize.Height - mark_image.Height) / 2;
                }
                if (position.Contains("center"))
                {
                    point.X = (imgSize.Width - mark_image.Width) / 2;
                    point.Y = (imgSize.Height - mark_image.Height) / 2;
                }
                float opacity=(float)0.8;//设置不透明度，0-1之间
                
                //添加水印
                return processingContext.DrawImage(mark_image,point,opacity);

            }
    }
}

public class ImageResult
    {
        /// <summary>
        /// 文件名
        /// </summary>
        public string id { get; set; }

        /// <summary>
        /// 文件大小
        /// </summary>
        public string size { get; set; }

        /// <summary>
        /// 文件路径
        /// </summary>
        public string url { get; set; }

        /// <summary>
        /// 文件格式
        /// </summary>
        public string format { get; set; }

        /// <summary>
        /// 上传状态
        /// </summary>
        public bool state { get; set; }

        /// <summary>
		/// 上传消息
		/// </summary>
		public string msg { get; set; }

        /// <summary>
        /// 图片宽
        /// </summary>
        public int width { get; set; }

        /// <summary>
        /// 图片高
        /// </summary>
        public int height { get; set; }
    }