GDI+（1.图像预览及转换）

1.缩略图（放大/缩小图片）

2.图片复制、剪切

Graphics g2 = pictureBox1.CreateGraphics();
SolidBrush brush = new SolidBrush(Color.White);
g2.FillRectangle(brush, rect);

3.图像缩放及文件格式转换

MyBitmap.Save(fileName + ".jpg", System.Drawing.Imaging.ImageFormat.Gif);
MyBitmap.Save(fileName + ".png", System.Drawing.Imaging.ImageFormat.Jpeg);
MyBitmap.Save(fileName + ".gif", System.Drawing.Imaging.ImageFormat.Png);
MyBitmap.Save(fileName + ".tif", System.Drawing.Imaging.ImageFormat.Tiff);
MyBitmap.Save(fileName + ".wmf", System.Drawing.Imaging.ImageFormat.Wmf);