制作类似QQ截图软件

    最近在学习GDI,发现网上几篇文章在讲截图软件制作方法,学习了一点知识,在这里分享一下.  

    主要是调用WinAPI中的函数来完成主要功能.关键的函数有2个,一个是CreateDC,利用这个函数来创建一个显示器屏幕的DC(设备环境),作为源DC,再创建一个Image图像,通过这个图像的Graphics.GetHdc()方法来获取另一个DC,作为目标DC,这2个DC主要是留给第二个函数用的;第二个函数是BitBlt,这个函数将源DC上的像素扫描到目标DC中,在这里就是将显示器屏幕的像素扫描到我们创建的Image图片上.

    扫描完成之后得到的Image图像就是现在的全屏图,可以将图片保存或者拷贝待用.这就实现了全屏截图的功能.

    接下来是实现局部截图.首先将全屏截图Image通过画图画在Winform窗体上,这个可以用窗体的Paint事件来实现,当窗体改变的时候,Paint事件就会被触发.局部截图就是在已经画上了全屏图片的Winform窗体上面再画矩形,然后调用Graphics的方法DrawImage,将矩形区域的截图保存在开始创建的Image中,这样就得到了局部截图,可以将图片保存或者拷贝待用.

    功能基本上就实现了.需要注意的是,在窗体中画的矩形是可反转矩形,调用的是ControlPaint.DrawReversibleFrame()方法,这个方法需要执行2次才能画出矩形.

    主窗口代码:

    public partial class Form1 : Form
    {
        //*******************Global Varibles******************
        private Bitmap MyImage = null;
        private bool StartedCrop = false;

        Point StartPoint = new Point(0, 0);
        Rectangle SelectRect = new Rectangle();
        int DeltaX = 0;
        int DeltaY = 0;
        //****************************************************

        [DllImport("gdi32.dll", EntryPoint = "BitBlt")]
        public static extern int BitBlt(
            IntPtr hDestDC,
            int x,
            int y,
            int nWidth,
            int nHeight,
            IntPtr hSrcDC,
            int xSrc,
            int ySrc,
            System.Int32 dwRop
        );
        [DllImport("gdi32.dll", EntryPoint = "CreateDC")]
        public static extern IntPtr CreateDC(
            string lpDriverName,
            string lpDeviceName,
            string lpOutput,
            IntPtr lpInitData
        );

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.Visible = false;
            Thread.Sleep(100);
            IntPtr dc1 = CreateDC("DISPLAY", null, null, (IntPtr)null);
            Graphics g1 = Graphics.FromHdc(dc1);
            MyImage = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, g1);
            Graphics g2 = Graphics.FromImage(MyImage);
            //Visible = false;
            dc1 = g1.GetHdc();
            IntPtr dc2 = g2.GetHdc();
            BitBlt(dc2, 0, 0, Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height,
                dc1, 0, 0, 13369376);

            g1.ReleaseHdc(dc1);
            g2.ReleaseHdc(dc2);
            this.Visible = true;
            this.SetBounds(0, 0, Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height);
            this.Cursor = Cursors.Cross;
        }

        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (StartedCrop == false)
            {
                DeltaX = 0;
                DeltaY = 0;
            }
            StartedCrop = true;
            StartPoint = new Point(e.X,e.Y);
            SelectRect.Width = 0;
            SelectRect.Height = 0;
            SelectRect.X = e.X;
            SelectRect.Y = e.Y;
            Invalidate();
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            Form thisform = (Form)sender;
            if (StartedCrop)
            {
                DeltaX = e.X - StartPoint.X;
                if (DeltaX < 0)
                    DeltaX = 0;
                DeltaY = e.Y - StartPoint.Y;
                if (DeltaY < 0)
                    DeltaY = 0;
                ControlPaint.DrawReversibleFrame(thisform.RectangleToScreen(SelectRect), Color.Black, FrameStyle.Dashed);
                SelectRect.Width = e.X - SelectRect.X;
                SelectRect.Height = e.Y - SelectRect.Y;
                ControlPaint.DrawReversibleFrame(thisform.RectangleToScreen(SelectRect), Color.Black, FrameStyle.Dashed);
            }
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            if (DeltaX == 0 || DeltaY == 0)
            {
                return;
            }

            StartedCrop = false;
            SelectRect.X = e.X - StartPoint.X;
            SelectRect.Y = e.Y - StartPoint.Y;
            this.Cursor = Cursors.Cross;


            Bitmap theImage = new Bitmap(DeltaX, DeltaY);
            Graphics g = Graphics.FromImage(theImage);
            Rectangle destRect = new Rectangle(0, 0, DeltaX, DeltaY);
            g.DrawImage(MyImage, destRect, StartPoint.X, StartPoint.Y, theImage.Width, theImage.Height, GraphicsUnit.Pixel);
            MyImage = (Bitmap)theImage.Clone();
            this.SetBounds(0, 0, MyImage.Width, MyImage.Height);
            this.Visible = false;

            frmOptions optionsForm = new frmOptions();
            optionsForm.imageToSaveOrCopy = MyImage;
            optionsForm.ShowDialog();
        }

        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            if (MyImage != null)
                e.Graphics.DrawImage(MyImage, ClientRectangle, 0, 0, MyImage.Width, MyImage.Height, GraphicsUnit.Pixel);
        }

        private void Form1_Resize(object sender, EventArgs e)
        {
            Invalidate();
        }

        private void Form1_DoubleClick(object sender, EventArgs e)
        {
            Application.Exit();
        }
    }

    选项窗口代码(frmOptions)主要有2个按钮,用来保存或者拷贝截取的图片:

    public partial class frmOptions : Form
    {
        public Image imageToSaveOrCopy;

        public frmOptions()
        {
            InitializeComponent();
        }

        private void frmOptions_Load(object sender, EventArgs e)
        {

        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            if (imageToSaveOrCopy == null) {
                MessageBox.Show("You have not choose the image! Please restart this program!");
                Application.Exit();
            }

            SaveFileDialog sfd = new SaveFileDialog();
            sfd.Filter = "*.jpg|*.jpg";
            sfd.AddExtension = true;
            sfd.FileName = "1.jpg";
            if (sfd.ShowDialog() == DialogResult.OK)
            {
                imageToSaveOrCopy.Save(sfd.FileName);
            }
            Application.Exit();
        }

        private void btnCopy_Click(object sender, EventArgs e)
        {
            if (imageToSaveOrCopy == null)
            {
                MessageBox.Show("You have not choose the image! Please restart this program!");
                Application.Exit();
            }
            try
            {
                Clipboard.SetImage(imageToSaveOrCopy);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Copy to clipboard error:\r\n"+ex.Message);
            }
            Application.Exit();
        }
    }

    由于局部截图的时候需要在屏幕上面画图,而要想屏幕位置(Point)和我们主窗体的位置一一对应起来,就需要将主窗体最大化到全屏幕,为了效果好点,可以将
窗体的BorderStyle属性设置为None.这样整个工作就完成了.