在java中的套接字上发送屏幕截图(bufferedImage)

Question

我正在通过套接字发送bufferedImage,我正在使用此帖子中的示例:

寄件人

   BufferedImage image = ....;
   ImageIO.write(image, "PNG", socket.getOutputStream());

接收器

   BufferedImage image = ImageIO.read(socket.getInputStream());

它工作 - 如果,只有在这一行之后我关闭发送者的outputStream:

 ImageIO.write(image, "PNG", socket.getOutputStream());

除了关闭outputStream之外我还能做些什么吗？

另外,我还能做些什么来避免一共使用ImageIO吗？似乎需要很长时间才能做任何事情.另请注意,由于性能问题,应该不惜一切代价避免读取或写入硬盘.我需要尽可能快地进行这种传输,(我正在尝试并尝试创建类似于VNC的客户端并将每个屏幕截图保存到硬盘上会大大减慢一切)

@Jon Skeet

编辑3:

发件人:(请注意,我发送的JPG图像不是PNG).

                    int filesize;
                    OutputStream out = c.getClientSocket().getOutputStream();

                    ByteArrayOutputStream bScrn = new ByteArrayOutputStream();
                    ImageIO.write(screenshot, "JPG", bScrn);
                    byte[] imgByte = bScrn.toByteArray();
                    bScrn.flush();
                    bScrn.close();

                    filesize = bScrn.size();
                    out.write(new String("#FS " + filesize).getBytes()); //Send filesize
                    out.write(new String("#<IM> \n").getBytes());        //Notify start of image

                    out.write(imgByte); //Write file
                    System.out.println("Finished");                                 

收件人:( input套接字输入流在哪里)

尝试#1:

String str = input.toString();
imageBytes = str.getBytes();

InputStream in = new ByteArrayInputStream(imageBytes);
BufferedImage image = ImageIO.read(in);
in.close();

System.out.println("width=" + image.getWidth());

(失败:getWidth()行上的Nullpointer异常) 我理解这个错误意味着"损坏的图像",因为它无法初始化它.正确？

尝试#2:

byte[] imageBytes = new byte[filesize];
for (int j = 0; i < filesize; i++)
{
    imageBytes[j] = (byte) input.read();
}

InputStream in = new ByteArrayInputStream(imageBytes);
BufferedImage image = ImageIO.read(in);
in.close();

System.out.println("width=" + image.getWidth());

(失败:getWidth()行上的Nullpointer异常)

尝试#3:

if (filesize > 0)
{

    int writtenBytes = 0;
    int bufferSize = client.getReceiveBufferSize();

    imageBytes = new byte[filesize];     //Create a byte array as large as the image
    byte[] buffer = new byte[bufferSize];//Create buffer


    do {
        writtenBytes += input.read(buffer); //Fill up buffer
        System.out.println(writtenBytes + "/" + filesize); //Show progress

        //Copy buffer to the byte array which will contain the full image
        System.arraycopy(buffer, 0, imageBytes, writtenBytes, client.getReceiveBufferSize());
        writtenBytes+=bufferSize;

    } while ((writtenBytes + bufferSize) < filesize);

    // Read the remaining bytes
    System.arraycopy(buffer, 0, imageBytes, writtenBytes-1, filesize-writtenBytes);
    writtenBytes += filesize-writtenBytes;
    System.out.println("Finished reading! Total read: " + writtenBytes + "/" + filesize);

}

InputStream in = new ByteArrayInputStream(imageBytes);
BufferedImage image = ImageIO.read(in);
in.close();

(失败:接收者给出:空指针异常)

尝试4:

   int readBytes = 0;
   imageBytes = new byte[filesize];     //Create a byte array as large as the image



    while (readBytes < filesize)
    {
        readBytes += input.read(imageBytes);
    }

    InputStream in = new ByteArrayInputStream(imageBytes);
    BufferedImage image = ImageIO.read(in);
    in.close();

    System.out.println("width=" + image.getWidth());

(失败:发送者给出:java.net.SocketException:通过对等方重置连接:套接字写入错误)

尝试#5:

使用Jon skeet的代码片段,图像到达,但只是部分.我将它保存到文件(1.jpg)中以查看发生了什么,它实际上发送了80%的图像,而文件的其余部分则填充了空白区域.这导致部分损坏的图像.这是我试过的代码:(请注意,captureImg()没有错,保存文件直接工作)

发件人:

    Socket s = new Socket("127.0.0.1", 1290);
    OutputStream out = s.getOutputStream();

    ByteArrayOutputStream bScrn = new ByteArrayOutputStream();
    ImageIO.write(captureImg(), "JPG", bScrn);
    byte imgBytes[] = bScrn.toByteArray();
    bScrn.close();

    out.write((Integer.toString(imgBytes.length)).getBytes());
    out.write(imgBytes,0,imgBytes.length);

Reciever:

    InputStream in = clientSocket.getInputStream();
    long startTime = System.currentTimeMillis();

    byte[] b = new byte[30];
    int len = in.read(b);

    int filesize = Integer.parseInt(new String(b).substring(0, len));

    if (filesize > 0)
    {
        byte[] imgBytes = readExactly(in, filesize);
        FileOutputStream f = new FileOutputStream("C:\\Users\\Dan\\Desktop\\Pic\\1.jpg");
        f.write(imgBytes);
        f.close();

        System.out.println("done");

发送方仍然通过对等方重置连接:套接字写入错误. 点击此处查看完整尺寸的图片

Answer 1

一种选择是将图像写入a,ByteArrayOutputStream以便您可以确定长度,然后首先将该长度写入输出流.

然后在接收端,可以读取的长度,则读取多个字节到字节数组,然后创建一个ByteArrayInputStream包阵列,并通过该对ImageIO.read().

在输出套接字正常关闭之前它不起作用我并不感到惊讶 - 毕竟,包含有效PNG文件然后其他东西的文件本身并不是一个有效的PNG文件,是吗？因此,读者需要在流完成之前读取到流的末尾 - 并且只有在连接关闭时才会出现网络流的"结束".

编辑:这是一种将给定字节数读入新字节数组的方法.作为一个单独的"实用"方法是很方便的.

public static byte[] readExactly(InputStream input, int size) throws IOException
{
    byte[] data = new byte[size];
    int index = 0;
    while (index < size)
    {
        int bytesRead = input.read(data, index, size - index);
        if (bytesRead < 0)
        {
            throw new IOException("Insufficient data in stream");
        }
        index += size;
    }
    return data;
}