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
