.NET生成水印更好的方法实例代码_ASP.NET教程

前言

众所周知为了保护知识产权，防止资源被盗用，水印在博客、网店等场景中非常常见。

本文首先演示了基于System.Drawing.Image做正常操作。然后基于Direct2D/WIC/DirectWrite，演示了一种全新、不同的“骚”操作。

方法1-System.Drawing给图片加水印

System.Drawing.Image原生属于GDI的一部分，是Windows Only，但随着NuGet包System.Drawing.Common的发布，现在System.Drawing.Image已经支持linux：

1	`Install-Package System.Drawing.Common -Version 4.5.1`

以下代码演示了如何从给图片加水印：

									// 加水印

									var watermarkedStream = new MemoryStream();

									using (var img = Image.FromStream(File.OpenRead(@"D:\_\WatermarkDemo.png")))

									{

									 using (var graphic = Graphics.FromImage(img))

									 {

									  var font = new Font("微软雅黑", 30, FontStyle.Bold, GraphicsUnit.Pixel);

									  var color = Color.FromArgb(128, 255, 255, 255);

									  var brush = new SolidBrush(color);

									  var point = new Point(img.Width - 130, img.Height - 50);

									  graphic.DrawString("水印在此", font, brush, point);

									  img.Save(watermarkedStream, ImageFormat.Png);

									 }

									}

效果如图（没有黄色剪头）：

.NET生成水印更好的方法实例代码

附：Edi.Wang做了一个NuGet包，可以轻松地配置水印参数：

NuGet：https://github.com/EdiWang/Edi.ImageWatermark

文章：https://edi.wang/post/2018/10/12/add-watermark-to-uploaded-image-aspnet-core

方法2-Direct2D/WIC给图片加水印

Direct2D源于Windows 8/IE 10，安装IE 10之后，Windows 7也能用。Direct2D基于Direct3D，很显然，是Windows Only的。

Direct2D是Windows下一代的2D渲染库，随着Direct2D一起发布的，还有Windows Imaging Component（简称WIC）和DirectWrite。

相关说明和文档链接：

技术	说明	链接
Direct2D	基于硬件加速的2D图形渲染	Go
WIC	高性能图片编码、解码	Go
DirectWrite	基于硬件加速的文字渲染	Go

如果您打开链接看了一眼，就不难看出，这些技术都是基于COM的，但我们使用.NET，不是吗？

好在我们有SharpDX

SharpDX对这些DirectX技术做了封装，在这个Demo中，我们需要安装SharpDX.Direct2D1和SharpDX.Mathematics两个包：

1 2	`Install-Package SharpDX.Direct2D1 -Version 4.2.0` `Install-Package SharpDX.Mathematics -Version 4.2.0`

以下代码演示了如何使用SharpDX.Direct2D1给图片加水印：

									using D2D = SharpDX.Direct2D1;

									using DWrite = SharpDX.DirectWrite;

									using SharpDX;

									using SharpDX.IO;

									using WIC = SharpDX.WIC;

									MemoryStream AddWatermark(Stream fileName, string watermarkText)

									{

									  using (var wic = new WIC.ImagingFactory2())

									  using (var d2d = new D2D.Factory())

									  using (var image = CreateWicImage(wic, fileName))

									  using (var wicBitmap = new WIC.Bitmap(wic, image.Size.Width, image.Size.Height, WIC.PixelFormat.Format32bppPBGRA, WIC.BitmapCreateCacheOption.CacheOnDemand))

									  using (var target = new D2D.WicRenderTarget(d2d, wicBitmap, new D2D.RenderTargetProperties()))

									  using (var bmpPicture = D2D.Bitmap.FromWicBitmap(target, image))

									  using (var dwriteFactory = new SharpDX.DirectWrite.Factory())

									  using (var brush = new D2D.SolidColorBrush(target, new Color(0xff, 0xff, 0xff, 0x7f)))

									  {

									    target.BeginDraw();

									    {

									      target.DrawBitmap(bmpPicture, new RectangleF(0, 0, target.Size.Width, target.Size.Height), 1.0f, D2D.BitmapInterpolationMode.Linear);

									      target.DrawRectangle(new RectangleF(0, 0, target.Size.Width, target.Size.Height), brush);

									      var textFormat = new DWrite.TextFormat(dwriteFactory, "微软雅黑", DWrite.FontWeight.Bold, DWrite.FontStyle.Normal, 30.0f);

									      target.DrawText(watermarkText, textFormat, new RectangleF(target.Size.Width - 130, target.Size.Height - 50, int.MaxValue, int.MaxValue), brush);

									    }

									    target.EndDraw();

									    var ms = new MemoryStream();

									    SaveD2DBitmap(wic, wicBitmap, ms);

									    return ms;

									  }

									}

									void SaveD2DBitmap(WIC.ImagingFactory wicFactory, WIC.Bitmap wicBitmap, Stream outputStream)

									{

									  using (var encoder = new WIC.BitmapEncoder(wicFactory, WIC.ContainerFormatGuids.Png))

									  {

									    encoder.Initialize(outputStream);

									    using (var frame = new WIC.BitmapFrameEncode(encoder))

									    {

									      frame.Initialize();

									      frame.SetSize(wicBitmap.Size.Width, wicBitmap.Size.Height);

									      var pixelFormat = wicBitmap.PixelFormat;

									      frame.SetPixelFormat(ref pixelFormat);

									      frame.WriteSource(wicBitmap);

									      frame.Commit();

									      encoder.Commit();

									    }

									  }

									}

									WIC.FormatConverter CreateWicImage(WIC.ImagingFactory wicFactory, Stream stream)

									{

									  using (var decoder = new WIC.PngBitmapDecoder(wicFactory))

									  {

									    var decodeStream = new WIC.WICStream(wicFactory, stream);

									    decoder.Initialize(decodeStream, WIC.DecodeOptions.CacheOnLoad);

									    using (var decodeFrame = decoder.GetFrame(0))

									    {

									      var converter = new WIC.FormatConverter(wicFactory);

									      converter.Initialize(decodeFrame, WIC.PixelFormat.Format32bppPBGRA);

									      return converter;

									    }

									  }

									}