C#实现：图片转ICON图标，可放缩图像

var bt = new Bitmap(@"C:\Users\xxx\Pictures\LOGO.png");
bt = bt.Resize(new Size(100, 50)); //扩展方法放缩图像
var icon = Icon.FromHandle(bt.GetHicon());
using (Stream stream = new System.IO.FileStream(@"C:\Users\xxx\Pictures\LOGO.ico", FileMode.Create)) {
    icon.Save(stream);
}

public static class myclass {
    public static Bitmap Resize(this Bitmap ori, Size newsize) {
        var newbt = new Bitmap(newsize.Width, newsize.Height);
        var graphics = System.Drawing.Graphics.FromImage(newbt);
        graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
        graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
        graphics.DrawImage(ori, 0, 0, newsize.Width, newsize.Height);
        return newbt;
    }
}