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:
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Install-Package System.Drawing.Common -Version 4.5.1
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以下代码演示了如何从给图片加水印:
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// 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);
}
}
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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:
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Install-Package SharpDX.Direct2D1 -Version 4.2.0
Install-Package SharpDX.Mathematics -Version 4.2.0
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以下代码演示了如何使用SharpDX.Direct2D1给图片加水印:
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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;
}
}
}
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调用方式:
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File.WriteAllBytes( @"D:\_\Demo2.png" , AddWatermark(File.OpenRead( @"D:\_\WatermarkDemo.png" ), "水印在此" ).ToArray());
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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。
总结
以上就是这篇文章的全部内容了,希望本文的内容对大家的学习或者工作具有一定的参考学习价值,谢谢大家对服务器之家的支持。
原文链接:https://www.cnblogs.com/sdflysha/p/better-way-to-generate-watermark.html