图像操作时：sun.awt.image.ToolkitImage cannot be cast to java.awt.image.BufferedImage解

图像操作时：sun.awt.image.ToolkitImage cannot be cast to java.awt.image.BufferedImage
图像操作时：想要将一个JFrame的Panel中createImage产生的Image图像转化为BufferedImage图像，
使用ImageProducer ip=new MemoryImageSource(iw,ih,pixels,0,iw);
tmp=createImage(ip);
BufferedImage im=（BufferedImage）tmp;
方法强制转换时产生错误
提示：sun.awt.image.ToolkitImage cannot be cast to java.awt.image.BufferedImage

[解决办法]