.NET中生成水印更好的方法
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
:
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。
作者:周杰
出处:https://www.cnblogs.com/sdflysha
本文采用
知识共享署名-非商业性使用-相同方式共享 2.5 中国大陆许可协议
进行许可,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出原文连接。
原文地址:https://www.cnblogs.com/sdflysha/p/better-way-to-generate-watermark.html