java如何实现图片转化为数据流

/**
	 * Copy file from inputStream
	 * 
	 * @param is
	 * @param f2
	 * @throws Exception
	 */
	public static void copyFileFromInputStream( InputStream is, File f2 ) throws Exception {
		int length = 2097152;
		FileOutputStream out = new FileOutputStream( f2 );
		byte[] buffer = new byte[length];
		while (true) {
			int ins = is.read( buffer );
			if ( ins == -1 ) {
				is.close( );
				out.flush( );
				out.close( );
				break;
			}
			out.write( buffer , 0 , ins );
		}
	}

String image =   "XXX.jpg";
File imageFile= new File(System.getProperty("java.io.tmpdir"), image); //System.getProperty("java.io.tmpdir")是获取操作系统缓存的临时目录
copyFileFromInputStream(XXXX.class.getResourceAsStream("images/" + image),imageFile);
// 系统会读取XXX.class路径中images文件夹下的xxx.jpg文件，将其转换为数据流

public byte[] SetImageToByteArray（string fileName）
{ FileStream fs = new FileStream（fileName, FileMode.Open）；
int streamLength = （int）fs.Length; byte[] image = new byte[streamLength];
fs.Read（image, 0, streamLength）；
fs.Close（）；
return image; }
public byte[]
SetImageToByteArray（FileUpload FileUpload1）
{ Stream stream = FileUpload1.PostedFile.InputStream;
byte[] photo = new byte[FileUpload1.PostedFile.ContentLength];
stream.Read（photo, 0, FileUpload1.PostedFile.ContentLength）；
stream.Close（）；
return photo;
}

{ Image image; MemoryStream mymemorystream = new MemoryStream（mybyte,0, mybyte.Length）；
image = Image.FromStream（mymemorystream）；
return image;
}