解決C#全屏幕截圖的實現方法

2020-01-24 03:17:22

字體：大中小

來源：轉載

供稿：網友

今天一位同事想寫一個全屏幕截圖的代碼。當然要實現的第一步是能夠獲取整個屏幕的位圖，記得Win32 API的CreateDC, BitBlt等函數可以使用。于是上網查了下，果然屏幕截圖用這些函數。但winform已經可以把API都忘記了，所以得尋找一個無Win32 API的實現方式。綜合了網上的實現，以及自己的一些設計，實現思路如下：
1. 開始截圖時，創建一個與屏幕大小一樣的位圖，然后用Graphics.CopyFromScreen()把屏幕位圖拷貝到該位圖上。這是很關鍵的一步，這樣所有的操作就都可以在該位圖上進行了，而無實際屏幕無關了。

復制代碼代碼如下:

Code
int width = Screen.PrimaryScreen.Bounds.Width;
int height = Screen.PrimaryScreen.Bounds.Height;
Bitmap bmp = new Bitmap(width, height);
using (Graphics g = Graphics.FromImage(bmp)) {
    g.CopyFromScreen(0, 0, 0, 0, new Size(width, height));
}

2. 接下來為了方便在這之上進行截圖，有一個很重要的設計實現方式：用全屏幕窗體代替現有真實屏幕，這樣就可以把截圖過程的所有操作都在那個窗體上實現（該窗體設置成無邊框，高寬等于屏幕大小即可），另外為了顯示掩蔽效果（只能正常顯示選擇的部分屏幕內容，而其實部分用一個如半透明層覆蓋），就添加一層半透明位置位圖。具體代碼如下：

復制代碼代碼如下:

Code
public partial class FullScreenForm : Form {
    private Rectangle rectSelected = Rectangle.Empty;
    private bool isClipping = false;
    private Bitmap screen;
    private Bitmap coverLayer = null;
    private Color coverColor;
    private Brush rectBrush = null;
    private Bitmap resultBmp = null;
    public FullScreenForm(Bitmap screen) {
        InitializeComponent();
        int width = Screen.PrimaryScreen.Bounds.Width;
        int height = Screen.PrimaryScreen.Bounds.Height;
        coverLayer = new Bitmap(width, height);
        coverColor = Color.FromArgb(50, 200, 0, 0);
        rectBrush = new SolidBrush(coverColor);
        using (Graphics g = Graphics.FromImage(coverLayer)) {
            g.Clear(coverColor);
        }
        this.Bounds = new Rectangle(0, 0, width, height);
        this.screen = screen;
        this.DoubleBuffered = true;
    }
    protected override void OnMouseDown(MouseEventArgs e) {
        if (e.Button == MouseButtons.Left) {
            isClipping = true;
            rectSelected.Location = e.Location;
        }
        else if (e.Button == MouseButtons.Right) {
            this.DialogResult = DialogResult.OK;
        }
    }
    protected override void OnMouseMove(MouseEventArgs e) {
        if (e.Button == MouseButtons.Left && isClipping) {
            rectSelected.Width = e.X - rectSelected.X;
            rectSelected.Height = e.Y - rectSelected.Y;

            this.Invalidate();
        }
    }
    protected override void OnMouseUp(MouseEventArgs e) {
        if (e.Button == MouseButtons.Left && isClipping) {
            rectSelected.Width = e.X - rectSelected.X;
            rectSelected.Height = e.Y - rectSelected.Y;
            this.Invalidate();
            resultBmp = new Bitmap(rectSelected.Width, rectSelected.Height);
            using (Graphics g = Graphics.FromImage(resultBmp)) {
                g.DrawImage(screen,new Rectangle(0, 0, rectSelected.Width, rectSelected.Height), rectSelected, GraphicsUnit.Pixel);
            }
            this.DialogResult = DialogResult.OK;
        }
    }
    protected override void OnPaint(PaintEventArgs e) {
        Graphics g = e.Graphics;
        g.DrawImage(screen, 0, 0);
        g.DrawImage(coverLayer, 0, 0);
        PaintRectangle();
    }
    protected override void OnPaintBackground(PaintEventArgs e) {

    }
    protected override void OnKeyDown(KeyEventArgs e) {
        if (e.KeyCode == Keys.Escape) {
            this.DialogResult = DialogResult.Cancel;
        }
    }
    private void PaintRectangle() {
        using (Graphics g = Graphics.FromImage(coverLayer)) {
            g.Clear(coverColor);
            GraphicsPath path = new GraphicsPath();
            path.AddRectangle(this.Bounds);
            path.AddRectangle(rectSelected);
            g.FillPath(rectBrush, path);
            g.DrawRectangle(Pens.Blue, rectSelected);
        }
    }
    public Bitmap ResultBitmap {
        get { return resultBmp; }
    }
}