/// <summary>
/// 使用GDI+来裁剪图片
/// </summary>
/// <param name="srcImageName"></param>
/// <param name="srcRect_P_x">裁剪图片矩形起始点X</param>
/// <param name="srcRect_P_y">裁剪图片矩形起始点Y</param>
/// <param name="srcRect_width">裁剪图片矩形Width</param>
/// <param name="srcRect_height">裁剪图片矩形Height</param>
/// <returns></returns>
public Bitmap ImageResizer(string srcImageName,int srcRect_P_x,int srcRect_P_y,int srcRect_width,int srcRect_height)
{
Bitmap bitmap = new Bitmap(40, 40);//准备一张空图
Image largeImage = Image.FromFile(this.imagePath + srcImageName);//获取src图片源
Graphics grp = Graphics.FromImage(bitmap);//用指定的des图片作为画布
Rectangle srcRect = new Rectangle(srcRect_P_x, srcRect_P_y, srcRect_width, srcRect_height);//设置src图片尺寸
Rectangle desRect = new Rectangle(0, 0, bitmap.Width, bitmap.Height);//设置des图片尺寸
grp.DrawImage(largeImage, desRect, srcRect, GraphicsUnit.Pixel);//将largeImage图片中srcRect位置的图片以像素点（Pixel）的形式画到画布上，大小为desRect
return bitmap;
}