我正在通过套接字发送 bufferedImage,并且使用 this 中找到的示例帖子:
发件人
BufferedImage image = ....;
ImageIO.write(image, "PNG", socket.getOutputStream());
接收者
BufferedImage image = ImageIO.read(socket.getInputStream());
它有效 - 如果且仅当我在此行之后关闭发送者的输出流:
ImageIO.write(image, "PNG", socket.getOutputStream());
除了关闭outputStream之外,我还能做些什么吗?
此外,我还能做些什么来完全避免使用 ImageIO 吗?做任何事情似乎都需要很长时间。 另请注意,由于性能问题,应不惜一切代价避免以任何方式读取或写入硬盘。我需要尽可能快地进行此传输,(我正在试验并尝试创建一个类似于 VNC 的客户端,并将每个屏幕截图保存到硬盘会大大减慢一切速度)..
@乔恩斯基特
编辑3:
发件人:(请注意,我发送的是 JPG 图像,而不是 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");
接收器:(其中 input
是套接字输入流)
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() 行出现空指针异常) 我理解这个错误的意思是“图像损坏”,因为它无法初始化它。正确吗?
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() 行出现空指针异常)
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:接收器给出: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:发送方给出:java.net.SocketException: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,图像到达了,但只是部分。我将其保存到文件 (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格。这会导致图像部分损坏。这是我尝试的代码:(注意captureImg()没有错,直接保存文件就可以了)
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);
接收者:
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");
发送方仍然给出 Connection Reset by Peer: socket write 错误。 Click here for full sized image
最佳答案
一种选择是将图像写入ByteArrayOutputStream
,以便您可以确定长度,然后先将该长度写入输出流。
然后在接收端,您可以读取长度,然后将那么多字节读入字节数组,然后创建一个 ByteArrayInputStream
来包装该数组并传递该到ImageIO.read()
。
我并不完全惊讶它在输出套接字正常关闭之前不起作用 - 毕竟,一个包含有效 PNG 文件然后是其他内容的文件实际上并不是一个PNG 文件本身有效,是吗?因此,读取器需要先读取到流的末尾,然后才能完成 - 并且网络流的“结束”仅在连接关闭时出现。
编辑:这是一种将给定数量的字节读入新字节数组的方法。作为单独的“实用”方法很方便。
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 += bytesRead;
}
return data;
}
关于java - 通过java中的套接字发送屏幕截图(bufferedImage),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/14984335/