将Buffer传递给ChildProcess Node.js [英] Pass Buffer to ChildProcess Node.js

问题描述

这里我有Node.Js，我想在子流程中进行图像处理。

Here I have on Node.Js where I want to do Image Processing in a Sub Process.

正如您将看到的那样我将文件 image.jpg 并希望在子流程中将其写回 hello.jpg ：

As you will see I take the file image.jpg and want to write it back to hello.jpg in a subprocess:

var node = require('child_process').spawn('node',['-i']);
var fs = require('fs');

node.stdout.on('data',function(data) {
  var fs = require('fs');
    var gm = require('gm').subClass({ imageMagick: true });

    gm(data)
     .resize(500, 500)
     .toBuffer("jpg", function(err, buffer) {
      if (err) {
        console.log(err);
      }else{
        fs.writeFile("hello.jpg", buffer);  
      }
   });
});


var buffer = fs.readFileSync(__dirname + "/image.jpg");
node.stdin.write(buffer);

但是当我运行此文件时出现此错误：

However when I run this file I get this error:

[错误：流产生空缓冲区]

[Error: Stream yields empty buffer]

对我来说，似乎缓冲区未正确传递给子流程？
我有什么不对？ 如何在子任务中运行图像处理。对我来说重要的是它不能从子进程中的文件中读取。因为我想再次读取一个文件，然后将缓冲区发送到几个进行图像转换的子进程。谢谢！

For me it seems like the buffer is not passed correctly to the subprocess? What do I wrong? What can I do to run Image Processing in a subtask. For me its important that Its not read from a file in the subprocess. Because I want to read one File again and then send the buffer to several subprocesses that do Image Transformations. Thanks!

推荐答案

您没有在子流程中做任何工作。它只是 node -i 而没有别的。所有的图像处理都在主进程中进行。

You are not doing any work in a subprocess. It is just node -i and nothing else. All your image processing happens in the main process.

要修复它，你可以实际运行另一个Node进程并给它一些脚本来执行，比如 worker.js ：

To fix it, you can actually run another Node process and give it some script to execute, say worker.js:

process.stdin.on('data',function(data) {
  var fs = require('fs');
    var gm = require('gm').subClass({ imageMagick: true });

    gm(data)
     .resize(500, 500)
     .toBuffer("jpg", function(err, buffer) {
      if (err) {
    console.log(err);
      }else{
    fs.writeFile("hello.jpg", buffer);
      }
   });
});

然后你将从主脚本创建一个子流程：

Then you would create a subprocess from your main script:

var node = require('child_process').spawn('node', ['worker.js']);
var fs = require('fs');

var buffer = fs.readFileSync(__dirname + "/image.jpg");
node.stdin.end(buffer);

请注意，我使用 node.stdin.end 在最后一行终止工人。

Note that I used node.stdin.end in the last line to terminate the worker.

看看集群模块。

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