C#开发实例-订制屏幕截图工具（七）添加放大镜功能的代码示例-木庄网络博客

本文摘自PHP中文网，作者黄舟，侵删。

由于截图时可能需要精确截取某一部分，所以需要放大镜的功能，这样截取的时候才更容易定位截图的位置。

添加PictureBox，name属性设置为“pictureBox_zoom”；

在“Form1_Load”事件处理函数中添加以下代码：

//设置放大镜的大小
            this.pictureBox_zoom.Width = this.ZoomBoxWidth;
            this.pictureBox_zoom.Height = this.ZoomBoxHeight;

在“ExitCutImage”方法中添加代码：

在“Form1_MouseUp”事件处理函数中添加代码：

在“ShowForm”方法的else条件最后添加代码：

if (this.ZoomBoxVisible)
                {
                    UpdateCutInfoLabel(UpdateUIMode.ShowZoomBox);
                    this.pictureBox_zoom.Show();
                }

在“UpdateCutInfoLabel”函数最后添加以下代码：

if (this.pictureBox_zoom.Visible || (updateUIMode & UpdateUIMode.ShowZoomBox) != UpdateUIMode.None)
            {
                Point zoomLocation = new Point(MousePosition.X + 15, MousePosition.Y + 22);
                if (zoomLocation.Y + this.pictureBox_zoom.Height > this.Height)
                {
                    if (zoomLocation.X + this.pictureBox_zoom.Width > this.Width)
                    {
                        zoomLocation = new Point(MousePosition.X - this.pictureBox_zoom.Width - 10, MousePosition.Y - this.pictureBox_zoom.Height - 10);
                    }
                    else
                    {
                        zoomLocation = new Point(MousePosition.X + 15, MousePosition.Y - this.pictureBox_zoom.Height - 15);
                    }
                }
                else
                {
                    if (zoomLocation.X + this.pictureBox_zoom.Width > this.Width)
                    {
                        zoomLocation = new Point(MousePosition.X - this.pictureBox_zoom.Width - 15, MousePosition.Y);
                    }
                }
                this.pictureBox_zoom.Location = zoomLocation;
                if (!this.pictureBox_zoom.Visible)
                {
                    this.pictureBox_zoom.Show();
                }
            }

在“Form1_KeyUp”事件处理函数中添加以下代码：

为“pictureBox_zoom”添加“Paint”事件处理程序，代码如下：

/// <summary>
/// 放大镜组件重绘事件处理程序
/// 实时显示鼠标指针位置放大后的图像
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void pictureBox_zoom_Paint(object sender, PaintEventArgs e)
{
    Bitmap bmp_lbl = new Bitmap(e.ClipRectangle.Width, e.ClipRectangle.Height);
    int srcWidth = (int)(this.ZoomBoxWidth / 10);
    int srcHeight = (int)(this.ZoomBoxHeight / 10);
 
    Bitmap bmp = new Bitmap(srcWidth, srcHeight);
    Rectangle srcRect = new Rectangle(MousePosition.X - 5, MousePosition.Y - 4, srcWidth, srcHeight);
    if (!isCuting)
    {
        srcRect = new Rectangle(MousePosition.X - 6, MousePosition.Y - 5, srcWidth, srcHeight);
    }
    Graphics g = Graphics.FromImage(bmp);
    g.DrawImage(screenImage, 0, 0, srcRect, GraphicsUnit.Pixel);
    g.Dispose();
 
    //Zoom
    int x, y;
    for (int row = 0; row < bmp.Height; row++)
    {
        for (int col = 0; col < bmp.Width; col++)
        {
            Color pc = bmp.GetPixel(col, row);
            for (int h = 0; h < 10; h++)
            {
                for (int w = 0; w < 10; w++)
                {
                    x = col * 10 + w;
                    y = row * 10 + h;
                    if (x < bmp_lbl.Width && y < bmp_lbl.Height)
                    {
                        bmp_lbl.SetPixel(x, y, pc);
                    }
                }
            }
        }
    }
 
    e.Graphics.DrawImage(bmp_lbl, 0, 0);
 
    int blockX = e.ClipRectangle.Width / 2;
    int blockY = e.ClipRectangle.Height / 2;
 
    SolidBrush brush = new SolidBrush(Color.FromArgb(10, 124, 202));
    Pen pen = new Pen(brush, 2.0F);
    e.Graphics.DrawLine(pen, new Point(0, blockY), new Point(e.ClipRectangle.Width, blockY));
    e.Graphics.DrawLine(pen, new Point(blockX, 0), new Point(blockX, e.ClipRectangle.Height));
 
    g.Dispose();
    bmp_lbl.Dispose();
}