C# 图片格式（JPG，BMP，PNG，GIF）等转换为ICO图标

using System;
using System.Drawing;
using System.Windows.Forms;
using System.IO;

namespace ICOTest
{
public partial class Form1 : Form
{
string FileName = "C:\\";
public Form1()
{
InitializeComponent();
}

//核心代码
private void button1_Click(object sender, EventArgs e)
{
Size size = new Size(32, 32);
//获得原始图片文件
using (Bitmap bm = new Bitmap(FileName))
{
//从现有图像缩小，为了得到合适的ICO文件
using (Bitmap iconBm = new Bitmap(bm, size))
{
//如果是windows调用，直接下面一行代码就可以了
//此代码不能在web程序中调用，会有安全异常抛出
using (Icon icon = Icon.FromHandle(iconBm.GetHicon()))
{
string Name_ = "C:\\ICO\\" + DateTime.Now.Ticks.ToString() + ".ico";
using (Stream stream = new System.IO.FileStream(Name_, System.IO.FileMode.Create))
{

icon.Save(stream);
MessageBox.Show("转换成功。路径是：" + Name_);
}
}
}
}
}

private void button2_Click(object sender, EventArgs e)
{
openFileDialog1.Filter = "JPG|*.jpg|BMP|*.bmp|PNG|*.png|GIF|*.gif";
DialogResult D = openFileDialog1.ShowDialog();
if (D == DialogResult.OK)
{
FileName = this.openFileDialog1.FileName.Trim();
this.textBox1.Text = FileName;
}
}
}
}

图像界面效果如下：