.NET 6 中,使用System.Drawing操作图片,生成解决方案或打包的时候,会有警告,意思是System.Drawing仅在 'windows' 上受支持。微软官方的解释是:
System.Drawing.Common NuGet 包现在被归为 Windows 特定的库。 在为非 Windows 操作系统编译时,平台分析器会在编译时发出警告。
在非 Windows 操作系统上,除非设置了运行时配置开关,否则将引发 TypeInitializationException 异常,其中 PlatformNotSupportedException 作为内部异常
在 .NET 6 之前,使用 System.Drawing.Common 包不会产生任何编译时警告,也不会引发任何运行时异常。
从 .NET 6 开始,当为非 Windows 操作系统编译引用代码时,平台分析器会发出编译时警告。
当然,使用windows操作系统没有任何问题,Linux的话,需要单独的配置。
可以通过在runtimeconfig.json文件中将System.Drawing.EnableUnixSupport 运行时配置开关设置为来启用对 .NET 6 中的非 Windows 平台的支持:true
或者使用第三方库
ImageSharp
SkiaSharp
Microsoft.Maui.Graphics
正如标题,我使用了ImageSharp来操作图片,并给图片添加水印
//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; }
代码比较简单,首先使用SixLabors.ImageSharp.Image.LoadAsync打开图片,然后使用ImageSharp的自定义扩展方法给图片添加水印。
ApplyScalingImageWaterMark扩展方法:
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); } } }
ImageResult类:
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; } }