c# wpf 利用截屏键实现截屏功能

    最近做一个wpf程序需要截图功能，查找资料费了一些曲折，跟大家分享一下。

    先是找到了这样一份代码：

    static class ScreenCut

    {

        public static System.Drawing.Bitmap GetScreenSnapshot()

        {

            System.Drawing.Rectangle rc = System.Windows.Forms.SystemInformation.VirtualScreen;

            System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(rc.Width, rc.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

            using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))

            {

                g.CopyFromScreen(rc.X, rc.Y, 0, 0, rc.Size, System.Drawing.CopyPixelOperation.SourceCopy);

            }

            return bitmap;

        }

        public static BitmapSource ToBitmapSource(this System.Drawing.Bitmap bmp)

        {

            BitmapSource returnSource;

            try

            {

                returnSource = System.Windows.Interop.Imaging.CreateBitmapSourceFromHBitmap(bmp.GetHbitmap(), IntPtr.Zero, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions());

            }

            catch

            {

                returnSource = null;

            }

            return returnSource;

        }

 

        public static BitmapSource CopyFromScreenSnapshot(BitmapSource screenSnapshot, Rect region)

        {

            var sourceRect = new System.Drawing.Rectangle((int)region.Left, (int)region.Top, (int)region.Width, (int)region.Height);

            var destRect = new System.Drawing.Rectangle(0, 0, sourceRect.Width, sourceRect.Height);

 

            if (screenSnapshot != null)

            {

                var bitmap = new System.Drawing.Bitmap(sourceRect.Width, sourceRect.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb);

                using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap))

                {

                    g.DrawImage(bitmap, destRect, sourceRect.Left, sourceRect.Top, sourceRect.Width, sourceRect.Height, System.Drawing.GraphicsUnit.Pixel);

                }

 

                return bitmap.ToBitmapSource();

            }

 

            return null;

        }

}

 

调用时包装一下，下面的函数截下屏幕指定区域并保存：

    System.Drawing.Image takePicture(Rect wnd, String saveLocation, String pictureName)

{    

        BitmapSource bitmapScr = ScreenCut.CopyFromScreenSnapshot(ScreenCut.ToBitmapSource(ScreenCut.GetScreenSnapshot()),wnd);

        PngBitmapEncoder encoder = new PngBitmapEncoder();

        encoder.Frames.Add(BitmapFrame.Create(bitmapScr));

        FileStream fileStream = new FileStream(saveLocation + "\\" + pictureName ".png", FileMode.Create, FileAccess.Write);

        encoder.Save(fileStream);

        fileStream.Close();

}

 

但实际效果保存下来的图是空的，经验证前两个函数没有问题。于是我查资料找到了另一种切割BitmapSource的方法，将第三个函数改成这样：

BitmapSource CopyFromScreenSnapshot(BitmapSource screenSnapshot, Rect region)

{

        Int32Rect window = new Int32Rect(region.X, region.Y, region.Width, region.Height);

        BitmapSource bitmapScr = ScreenCut.ToBitmapSource(ScreenCut.GetScreenSnapshot());

        //计算Stride

        int stride = bitmapScr.Format.BitsPerPixel * window.Width / 8;

        //声明字节数组

        byte[] data = new byte[window.Height * stride];

        //调用CopyPixels

        bitmapScr.CopyPixels(window, data, stride, 0);

        PngBitmapEncoder encoder = new PngBitmapEncoder();

    return BitmapSource.Create(window.Width, window.Height, 0, 0, PixelFormats.Bgr32, null, data, stride);

}

 

这样总算能截到屏了。不过后来发现在某些主题下有些程序的窗口在截下的图中是透明的。这个方法还是不够完美。

我想到了利用键盘的截屏键截图再进行剪切的方法。分为三步：1、模拟按下截屏键 2、从剪贴板获取图片 3、截取和保存图片。

对于第一点，利用SendMessage函数发送WM_KEY事件没有用，不过我找到了另一个模拟键盘输入的方法：

using System.Runtime.InteropServices;

    [DllImport("user32.dll")]

    static extern void keybd_event

    (

        byte bVk,// 虚拟键值

        byte bScan,// 硬件扫描码    

        uint dwFlags,// 动作标识    

        IntPtr dwExtraInfo// 与键盘动作关联的辅加信息    

);

 

上面这个函数对本程序发送按钮事件，模拟截屏键的话像下面这样写，wpf需要在项目添加引用System.Windows.Forms

const int VK_SNAPSHOT = 0x2C;

    public void PrintScreen()

    {

        keybd_event((byte)VK_SNAPSHOT, 0, 0x0, IntPtr.Zero);//down  

        System.Windows.Forms.Application.DoEvents();//强制窗口响应按钮事件

        keybd_event((byte)VK_SNAPSHOT, 0, 0x2, IntPtr.Zero);//up  

        System.Windows.Forms.Application.DoEvents();

}

 

接下来从剪贴板获取图片，wpf需要在项目添加引用System.Windows.Forms  System.Drawing

    if (System.Windows.Forms.Clipboard.ContainsImage())

    {

       System.Drawing.Image image = System.Windows.Forms.Clipboard.GetImage();

}

 

然后剪切。

    System.Drawing.Image cutPicture(System.Drawing.Image image, Int32Rect window)

    {

        PrintScreen();

        if (window.X + window.Width > image.Width)

            window.Width = image.Width - window.X;

        if (window.Y + window.Height > image.Height)

            window.Height = image.Height - window.Y;

        if (image == null)

        {

            //新建一个bmp图片

            System.Drawing.Image bitmap = new System.Drawing.Bitmap(window.Width, window.Height);

            //新建一个画板

            System.Drawing.Graphics graphic = System.Drawing.Graphics.FromImage(bitmap);

            //设置高质量查值法

            graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

            //设置高质量，低速度呈现平滑程度

            graphic.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

            //清空画布并以透明背景色填充

            graphic.Clear(System.Drawing.Color.Transparent);

            //在指定位置并且按指定大小绘制原图片的指定部分

            graphic.DrawImage(image, new System.Drawing.Rectangle(0, 0, window.Width, window.Height), new System.Drawing.Rectangle(window.X, window.Y, window.Width, window.Height), System.Drawing.GraphicsUnit.Pixel);

            return bitmap;

        }

        else

        {

            return null;

        }

}

 

最后包装一下

    System.Drawing.Image cutScreen(Int32Rect window)

    {

        PrintScreen();

        Thread.Sleep(1000);

        if (System.Windows.Forms.Clipboard.ContainsImage())

        {

            System.Drawing.Image image = cutPicture(System.Windows.Forms.Clipboard.GetImage(), Int32Rect window);

            return image;

        }

        else

        {

            Console.WriteLine("clipboard doesn't contain picture");

            return null;

        }

}

System.Drawing.Image类有实例函数Save，保存很简单，就不细说了。

资料来源：

http://www.cnblogs.com/zhouyinhui/archive/2010/08/20/1804762.html

https://www.mgenware.com/blog/?p=285

http://blog.csdn.net/testcs_dn/article/details/39762017