活用C#截取计算机屏幕

2022-07-15 80酷酷网 80kuku.com

今天无聊翻代码,翻出来一个以前写的C#截屏的函数...拿出来和大家共享一下.
这段代码是参照网上一段截屏的C++代码改写的.只不过把API都声明了一下而已.
声明的各API也附后.以供参照.如有问题欢迎指出.
作者：AppleDotnet

///
/// 截取部分屏幕
///
/// 左上角
/// 右下角
/// 是否全屏幕
/// 返回值Bitmap
public static Bitmap GetPartScreen(Point P1,Point P2,bool Full)
{
    IntPtr hscrdc,hmemdc;
    IntPtr hbitmap,holdbitmap;
    int nx,ny,nx2,ny2;
    nx=ny=nx2=ny2=0;
    int nwidth, nheight;
    int xscrn, yscrn;
    hscrdc = CreateDC("DISPLAY", null, null, 0);//创建DC句柄
    hmemdc = CreateCompatibleDC(hscrdc);//创建一个内存DC
    xscrn = GetDeviceCaps(hscrdc, GetDeviceCapsIndex.HORZRES);//获取屏幕宽度
    yscrn = GetDeviceCaps(hscrdc, GetDeviceCapsIndex.VERTRES);//获取屏幕高度
    if(Full)//如果是截取整个屏幕
    {
        nx = 0;
        ny = 0;
        nx2 = xscrn;
        ny2 = yscrn;
    }
    else
    {
        nx = P1.X;
        ny = P1.Y;
        nx2 =P2.X;
        ny2 =P2.Y;
        //检查数值合法性
        if(nx<0)nx = 0;
        if(ny<0)ny = 0;
        if(nx2>xscrn)nx2 = xscrn;
        if(ny2>yscrn)ny2 = yscrn;
    }
    nwidth = nx2 - nx;//截取范围的宽度
    nheight = ny2 - ny;//截取范围的高度
    hbitmap = CreateCompatibleBitmap(hscrdc, nwidth, nheight);//从内存DC复制到hbitmap句柄
    holdbitmap = SelectObject(hmemdc, hbitmap);
    BitBlt(hmemdc, 0, 0, nwidth, nheight,hscrdc, nx, ny,(UInt32)0xcc0020);
    hbitmap = SelectObject(hmemdc, holdbitmap);
    DeleteDC(hscrdc);//删除用过的对象
    DeleteDC(hmemdc);//删除用过的对象
    return Bitmap.FromHbitmap(hbitmap);//用Bitmap.FromHbitmap从hbitmap返回Bitmap
}

所用到的API声明:

[DllImport("gdi32.dll")]
public static extern IntPtr CreateDC(
string lpszDriver,        // driver name
string lpszDevice,        // device name
string lpszOutput,        // not used; should be NULL
Int64 lpInitData // optional printer data
);

[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleDC(
IntPtr hdc // handle to DC
);

[DllImport("gdi32.dll")]
public static extern int GetDeviceCaps(
IntPtr hdc,     // handle to DC
GetDeviceCapsIndex nIndex   // index of capability
);

[DllImport("gdi32.dll")]
public static extern IntPtr CreateCompatibleBitmap(
IntPtr hdc,        // handle to DC
int nWidth,     // width of bitmap, in pixels
int nHeight     // height of bitmap, in pixels
);

[DllImport("gdi32.dll")]
public static extern IntPtr SelectObject(
IntPtr hdc, // handle to DC
IntPtr hgdiobj // handle to object
);

[DllImport("gdi32.dll")]
public static extern int BitBlt(
IntPtr hdcDest, // handle to destination DC
int nXDest, // x-coord of destination upper-left corner
int nYDest, // y-coord of destination upper-left corner
int nWidth, // width of destination rectangle
int nHeight, // height of destination rectangle
IntPtr hdcSrc, // handle to source DC
int nXSrc, // x-coordinate of source upper-left corner
int nYSrc, // y-coordinate of source upper-left corner
UInt32 dwRop // raster operation code
);

[DllImport("gdi32.dll")]
public static extern int DeleteDC(
IntPtr hdc // handle to DC
);