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:
有什么区别?
System.Drawing 只花了 14 行, Direct2D 却需要整整 60 行! 复杂程度惊人! 为什么要舍简单求复杂呢?
因为 System.Drawing 没有硬件加速, 而且生成的图片也没有反走样 (Anti-aliasing), 这导致使用 System.Drawing 相比之下较慢, 而且生成图片的效果稍差:
很明显可以看出, Direct2D 生成的图片更平滑.
来源: https://www.cnblogs.com/sdflysha/p/better-way-to-generate-watermark.html