这篇文章将为大家详细讲解有关使用.NET怎么生成水印，文章内容质量较高，因此小编分享给大家做个参考，希望大家阅读完这篇文章后对相关知识有一定的了解。
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：
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）：
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：
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;
}
}
}调用方式：
File.WriteAllBytes(@"D:\_\Demo2.png", AddWatermark(File.OpenRead(@"D:\_\WatermarkDemo.png"), "水印在此").ToArray());
效果也是一切正常：
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