原文:Taking WPF “Screenshots”

I was recently working on a Surface project at Microsoft (that will be shown at BETT  ) and one of the requirements was to provide an external “administration console”.  As part of that console I wanted to show an “screenshot” of the current game running on the Surface unit; after playing around for a while it turned out it was pretty straightforward.

We did consider sending over the RAW XAML from the Surface to the Console, but that would potentially have issues when resources weren’t available, so the approach that was taken was to create a JPG screenshot and send it over as a byte array via WCF.

Rendering to a BitmapFrame

The key to this approach is RenderTargetBitmap which allows us to render any WPF Visual to a BitmapFrame as follows:

RenderTargetBitmap renderTarget = new RenderTargetBitmap(, , , , PixelFormats.Pbgra32);
renderTarget.Render(myVisual);
BitmapFrame bitmapFrame = BitmapFrame.Create(renderTarget);

Then from there we can use JpegBitmapEncoder to create a JPG from that BitmapFrame:

JpegBitmapEncoder jpgEncoder = new JpegBitmapEncoder();
jpgEncoder.Frames.Add(bitmapFrame);

Then we can output that JPG to a stream of our choice using the Save() method.

Problems

While this works for many cases, and indeed worked perfectly for the Surface application, we do encounter problems when the source we are rendering has Transforms applied or when it’s not positioned at 0,0.  When this occurs the screenshots we take will have the content shifted“out of frame” resulting in black borders, or content missing altogether.  The following screenshot demonstrates the problem:

Workaround

To work around the problem we can use a VisualBrush to “draw” our source element onto a new Visual, and render that with our RenderTargetBitmap:

DrawingVisual drawingVisual = new DrawingVisual();
DrawingContext drawingContext = drawingVisual.RenderOpen();
using (drawingContext)
{
drawingContext.DrawRectangle(sourceBrush, null, new Rect(new Point(, ), new Point(, )));
}
renderTarget.Render(drawingVisual);

It’s not ideal, but I’ve yet to find a better workaround for it.

Putting it all Together

To make it more useful, we can wrap the whole lot up into a Extension Method.  Rather than extending Visual, I’ve chosen to use UIElement so I have access to the RenderSize to calculate the required size of the output bitmap.  I’ve also included parameters to scale the resulting bitmap and to set the JPG quality level:

///
/// Gets a JPG "screenshot" of the current UIElement
///
/// UIElement to screenshot
/// Scale to render the screenshot
/// JPG Quality
/// Byte array of JPG data public static byte[] GetJpgImage(this UIElement source, double scale, int quality)
{
double actualHeight = source.RenderSize.Height;
double actualWidth = source.RenderSize.Width; double renderHeight = actualHeight * scale;
double renderWidth = actualWidth * scale; RenderTargetBitmap renderTarget = new RenderTargetBitmap((int) renderWidth, (int) renderHeight, , , PixelFormats.Pbgra32); VisualBrush sourceBrush = new VisualBrush(source); DrawingVisual drawingVisual = new DrawingVisual(); DrawingContext drawingContext = drawingVisual.RenderOpen(); using (drawingContext)
{
drawingContext.PushTransform(new ScaleTransform(scale, scale)); drawingContext.DrawRectangle(sourceBrush, null, new Rect(new Point(, ), new Point(actualWidth, actualHeight)));
} renderTarget.Render(drawingVisual); JpegBitmapEncoder jpgEncoder = new JpegBitmapEncoder(); jpgEncoder.QualityLevel = quality; jpgEncoder.Frames.Add(BitmapFrame.Create(renderTarget)); Byte[] _imageArray; using (MemoryStream outputStream = new MemoryStream()) { jpgEncoder.Save(outputStream); _imageArray = outputStream.ToArray(); } return _imageArray;
}

WPF 对控件进行截图且不丢失范围(转载)的更多相关文章

  1. wpf 对控件进行截图,获取快照

    有时候我们项目,在执行某个操作后,会生成一些数据结果,如报表一类的东西,我们需要对结果进行保存,甚至是生成word文档. 那么首先获取到控件快照就最基本的条件. 生成快照的静态方法类 using Sy ...

  2. WPF常用控件应用demo

    WPF常用控件应用demo 一.Demo 1.Demo截图如下: 2.demo实现过程 总体布局:因放大缩小窗体,控件很根据空间是否足够改变布局,故用WrapPanel布局. <ScrollVi ...

  3. WPF开源控件扩展库 - MaterialDesignExtensions

    Material Design Extensions 在WPF开源控件库 Material Design in XAML Toolkit(本站介绍:链接)的基础上进行了控件扩展和特性新增.本开源项目中 ...

  4. C# WPF开源控件库:MahApps.Metro

    其实站长很久之前就知道这个开源WPF控件库了,只是一直欣赏不了这种风格,但也star了该项目.每次浏览该仓库时,发现star越来越多,也看到很多网友对它的褒奖,所以今天就向大家推荐这款WPF控件库. ...

  5. WPF Popup 控件导致被遮挡内容不刷新的原因

    WPF Popup 控件导致被遮挡内容不刷新的原因 周银辉 今天在写一个WPF控件时用到了Popup控件,很郁闷的情况是:当popup关闭时,原来被popup挡住的界面部分不刷新,非要手动刷新一下(比 ...

  6. 创建 WPF 工具箱控件

    创建 WPF 工具箱控件 WPF (Windows Presentation Framework) 工具箱控件模板允许您创建 WPF 控件,会自动添加到 工具箱 安装扩展的安装. 本主题演示如何使用模 ...

  7. wpf打印控件 实现分页打印控件功能

    因为 要实现打印 wpf  listbox控件  数据特别多 要打印在 几张纸上    找了几天 都没有找到相关的例子 现在 解决了 在这里和大家分享一下 public void print(Fram ...

  8. WPF 分页控件 WPF 多线程 BackgroundWorker

    WPF 分页控件 WPF 多线程 BackgroundWorker 大家好,好久没有发表一篇像样的博客了,最近的开发实在头疼,很多东西无从下口,需求没完没了,更要命的是公司的开发从来不走正规流程啊, ...

  9. WPF Image控件中的ImageSource与Bitmap的互相转换

    原文:WPF Image控件中的ImageSource与Bitmap的互相转换  1.从bitmap转换成ImageSource [DllImport("gdi32.dll", ...

随机推荐

  1. LwIP Application Developers Manual5---高层协议之DHCP,AUTOIP,SNMP,PPP

    1.前言 本文主要讲述高层协议,包括DHCP 2.DHCP 2.1 从应用的角度看DHCP 你必须确保在编译和链接时使能DHCP,可通过在文件lwipopts.h里面定义LWIP_DHCP选项,该选项 ...

  2. Nest + typeorm

    1\     Nest (https://nestjs.com/)  is a framework for building efficient, scalable Node.js web appli ...

  3. 纪念一下我对Kalman的无限崇拜之情

    今天用Kalman来求线性预测模型的系数,和LMS一对比,天啦噜,我感叹了半小时... 和LMS需要选合适的步长,样本序列需要足够长,迭代次数需要足够多,相比,卡尔曼真是帅呆了!不需要步长!不需要蒙特 ...

  4. Python3学习笔记32-xlwt模块

    xlwt模块是用来写入excel的第三方模块,需要下载安装后才能使用. 设置字体样式 import xlwt #初始化一个excel excel = xlwt.Workbook(encoding='u ...

  5. 后台拼接json字符串,传到前台时注意特殊符号处理

    1.后台拼接常用的形式:     sb.AppendFormat("\"字段名\":\"{0}\"", i + 1); 这个要注意字符串截断 ...

  6. VS 2008的64位编译环境的安装和使用

    1. 安装64位编译环境 最近准备编译64位版本的程序.因为之前已经安装了VS 2008,开始以为只是使用VS 2008的安装文件添加功能即可,后来发现没这么简单.直接双击VS 2008的安装文件来安 ...

  7. boost 随机数发生器

    Random     随机数 在很多应用中都需要使用随机数.本库力求提供一个高效的,通用的随机数库.boost库有多种随机数生成方式.先熟悉一下各种随机数生成器的概念. 数字生成器(Number Ge ...

  8. $Django Rest Framework-序列化组件

    1 序列化组件 e=serializers.SerializerMethodField()   # 方法名:叫get_字段名, 参数,返回字典  def get_e(self,obj): #obj为b ...

  9. php password_hash

    2018-1-6 17:22:13 星期六 php 自带的密码生成方法, 如果生成密码最好使用这个, 这个是"单程"的, 没有解密函数 $a = '123456'; $b = pa ...

  10. UML建模图

    UML 2.0规范 迅速成为建立软件系统可视化.规范.文档的标准.统一建模语言(UML) 也被用于非软件系统的建模,并在很多领域,诸如金融,军事,工程方面应用广泛. UML 2 定义了13种基本的图, ...