将Mat（OpenCV）数据类型写入Java或Android中的csv文件

我喜欢将Mat类型的数据从OpenCV推到一个csv文件中。我可以从Mat转换为字节数组，然后写入文本文件，但是我从没有得到完整的图像。始终获得图像的一部分。有什么事吗

printtoTextFile(Mat d, File file_g){
   Size size = d.size();
   byte[] a = new byte[(int) (d.width * d.height)];
   d.get(0, 0, a);//I get byte array here for the whole image
   FileOutputStream fos_g = null;
    OutputStreamWriter ow = null;
    BufferedWriter fwriter = null;
    try {
        fos_g = new FileOutputStream(file_g);
        ow = new OutputStreamWriter(fos_g);
        fwriter = new BufferedWriter(ow);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
   for (x = 0; x < size.height; x++){
            for (y = 0; y < size.width; y++){
                fwriter.write(String.valueOf(a[(int) (x * size.width + y)]));
                ow.flush();
                fwriter.write(","); 
                ow.flush();
            }
            fwriter.write("\n");
            ow.flush();
            //fos_g.flush();
        }
        fos_g.flush();
        try {
            fos_g.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}