C#实现类似qq的屏幕截图程序

下面是“C#实现类似qq的屏幕截图程序”的完整攻略：

1.概述

通常实现屏幕截图的方式是利用系统API，将当前屏幕截图保存至剪切板中，进而另行操作。需要说明的是，虽然C#中提供了WinForm等快速开发工具，但利用系统API会是更加底层、高效的方法。

2.实现步骤

2.1.注册快捷键

用户在截图的时候经常需要使用快捷键配合，所以先来一段注册程序快捷键的代码。

[DllImport( "user32.dll" )]
public static extern bool RegisterHotKey( IntPtr hWnd, int id, uint fsModifiers, uint vk );

[DllImport( "user32.dll" )]
public static extern bool UnregisterHotKey( IntPtr hWnd, int id );

public const int WM_HOTKEY = 0x0312;

protected override void WndProc( ref Message m )
{
    switch ( m.Msg )
    {
        case WM_HOTKEY:
            // 处理快捷键事件
            break;
    }
    base.WndProc( ref m );
}

2.2.屏幕截图

利用user32.dll中提供的BitBlt函数可以不绘制窗口快速截屏，代码如下：

public static Bitmap PrintWindow()
{
    var screenWidth = Screen.PrimaryScreen.Bounds.Width;
    var screenHeight = Screen.PrimaryScreen.Bounds.Height;
    var screenDC = GetDC( IntPtr.Zero );
    var memoryDC = CreateCompatibleDC( screenDC );
    var bitmap = new Bitmap( screenWidth, screenHeight );
    var bitmapHandle = bitmap.GetHbitmap();

    SelectObject( memoryDC, bitmapHandle );
    BitBlt( memoryDC, 0, 0, screenWidth, screenHeight, screenDC, 0, 0, CopyPixelOperation.SourceCopy | CopyPixelOperation.CaptureBlt );

    bitmap.ReleaseHbitmap();
    DeleteDC( memoryDC );
    ReleaseDC( IntPtr.Zero, screenDC );

    return bitmap;
}

2.3.用户选择截图区域

用户在截图的时候只需要选择需要截图的区域即可，所以需要在用户选择时绘制一个矩形。代码如下：

private Rectangle _rectSelect;
private bool _isSelecting;

protected override void OnMouseDown( MouseEventArgs e )
{
    if ( e.Button == MouseButtons.Left )
    {
        _isSelecting = true;
        _rectSelect = new Rectangle( e.Location, new Size( 0, 0 ) );
    }
    base.OnMouseDown( e );
}

protected override void OnMouseMove( MouseEventArgs e )
{
    if ( _isSelecting )
    {
        _rectSelect.Width = e.X - _rectSelect.Location.X;
        _rectSelect.Height = e.Y - _rectSelect.Location.Y;
        Invalidate();
    }
    base.OnMouseMove( e );
}

protected override void OnMouseUp( MouseEventArgs e )
{
    if ( e.Button == MouseButtons.Left )
    {
        _isSelecting = false;
        OnEndSelect( _rectSelect );
        _rectSelect = new Rectangle( 0, 0, 0, 0 );
    }
    base.OnMouseUp( e );
}

protected override void OnPaint( PaintEventArgs e )
{
    // 绘制矩形
    if ( !_rectSelect.IsEmpty )
    {
        ControlPaint.DrawFocusRectangle( e.Graphics, _rectSelect, Color.White, Color.Black );
    }
    base.OnPaint( e );
}

2.4.裁剪图像

选定截图区域后，需要将屏幕截图图像按照选定区域裁剪，获取其部分图像。将截图矩形转换为图像坐标后，通过GDI+中的Graphics类的DrawImage方法，轻松地完成图像裁剪过程，具体代码如下：

public static Bitmap CutImage( Bitmap bmp, Rectangle rect )
{
    if ( bmp == null ) throw new ArgumentNullException( nameof( bmp ) );

    var bitmap = new Bitmap( rect.Width, rect.Height, bmp.PixelFormat );

    using ( var g = Graphics.FromImage( bitmap ) )
    {
        g.DrawImage( bmp, 0, 0, rect, GraphicsUnit.Pixel );
    }

    return bitmap;
}

2.5.将图像保存至剪切板中

将裁剪好的部分图像保存至剪切板中，能够方便地进行后续的操作，如粘贴到其他应用程序中。具体实现如下：

public static void CopyImageToClipboard( Bitmap bmp )
{
    if ( bmp != null ) Clipboard.SetImage( bmp );
}

至此，一款简单的屏幕截图工具就大功告成啦！

3.示例说明

3.1.基础示例

下方代码和截图展示了一种最基本的屏幕截图工具的实现，仅捕捉全屏画面并将其复制到剪贴板。

public class ScreenShotForm : Form
{
    private ScreenShotForm()
    {
        RegisterHotKey( Handle, 1001, 0, (uint) Keys.F9 );
    }

    protected override void WndProc( ref Message m )
    {
        switch ( m.Msg )
        {
            case WM_HOTKEY:
                PrintWindow();
                break;
        }
        base.WndProc( ref m );
    }
}

3.2.高级示例

高级示例演示了如何实现截图选择。在这个示例中，我们创建了一个继承自Form的截图菜单，实现了用户选择截取的矩形区域，并保存截取的图像至剪切板。

public class ScreenShotMenu : Form
{
    private Rectangle _rectSelect;
    private bool _isSelecting;

    public new void Show()
    {
        RegisterHotKey( Handle, 1001, 0, (uint) Keys.F9 );

        var bmp = (Bitmap) Clipboard.GetImage();
        Size = new Size( bmp.Width, bmp.Height );
        BackgroundImage = bmp;

        base.Show();
    }

    private void OnEndSelect( Rectangle rect )
    {
        if ( !_isSelecting ) return;

        _isSelecting = false;
        var bmp = (Bitmap) Clipboard.GetImage();

        var rectScreen = new Rectangle( 0, 0, bmp.Width, bmp.Height );
        var rectUser = new Rectangle( rect.X - rectScreen.X, rect.Y - rectScreen.Y, rect.Width, rect.Height );
        var bmpCut = CutImage( bmp, rectUser );

        Clipboard.SetImage( bmpCut );
    }

    protected override void OnMouseDown( MouseEventArgs e )
    {
        if ( e.Button == MouseButtons.Left )
        {
            _isSelecting = true;
            _rectSelect = new Rectangle( e.Location, new Size( 0, 0 ) );
        }
        base.OnMouseDown( e );
    }

    protected override void OnMouseMove( MouseEventArgs e )
    {
        if ( _isSelecting )
        {
            _rectSelect.Width = e.X - _rectSelect.Location.X;
            _rectSelect.Height = e.Y - _rectSelect.Location.Y;
            Invalidate();
        }
        base.OnMouseMove( e );
    }

    protected override void OnMouseUp( MouseEventArgs e )
    {
        if ( e.Button == MouseButtons.Left )
        {
            _isSelecting = false;
            OnEndSelect( _rectSelect );
            _rectSelect = new Rectangle( 0, 0, 0, 0 );
            Close();
        }
        base.OnMouseUp( e );
    }

    protected override void OnPaint( PaintEventArgs e )
    {
        // 绘制矩形
        if ( !_rectSelect.IsEmpty )
        {
            ControlPaint.DrawFocusRectangle( e.Graphics, _rectSelect, Color.White, Color.Black );
        }
        base.OnPaint( e );
    }
}

以上是“C#实现类似qq的屏幕截图程序”的完整攻略，希望对你有所帮助。