image - 在这个node.js图像模块中，我应该使用哪个？ (读取流还是从路径？)

Question

什么是“流”？我应该使用下面哪一个最快？有没有办法从内存中打开它，就像缓冲区一样？

// can provide either a file path or a ReadableStream
// (from a local file or incoming network request)
var readStream = fs.createReadStream('/path/to/my/img.jpg');
gm(readStream, 'img.jpg')
.write('/path/to/reformat.png', function (err) {
  if (!err) console.log('done');
});

// can also stream output to a ReadableStream
// (can be piped to a local file or remote server)
gm('/path/to/my/img.jpg')
.resize('200', '200')
.stream(function (err, stdout, stderr) {
  var writeStream = fs.createWriteStream('/path/to/my/resized.jpg');
  stdout.pipe(writeStream);
});

// pass a format or filename to stream() and
// gm will provide image data in that format
gm('/path/to/my/img.jpg')
.stream('png', function (err, stdout, stderr) {
  var writeStream = fs.createWriteStream('/path/to/my/reformated.png');
  stdout.pipe(writeStream);
});

// combine the two for true streaming image processing
var readStream = fs.createReadStream('/path/to/my/img.jpg');
gm(readStream, 'img.jpg')
.resize('200', '200')
.stream(function (err, stdout, stderr) {
  var writeStream = fs.createWriteStream('/path/to/my/resized.jpg');
  stdout.pipe(writeStream);
});

// when working with input streams and any 'identify'
// operation (size, format, etc), you must pass "{bufferStream: true}" if
// you also need to convert (write() or stream()) the image afterwards
// NOTE: this temporarily buffers the image stream in Node memory
var readStream = fs.createReadStream('/path/to/my/img.jpg');
gm(readStream, 'img.jpg')
.size({bufferStream: true}, function(err, size) {
  this.resize(size.width / 2, size.height / 2)
  this.write('/path/to/resized.jpg', function (err) {
    if (!err) console.log('done');
  });
});

Answer 1

流一次从文件中读取一个数据 block 。它对于读取大文件很有用，而无需将整个内容存储在内存中。

如果您已经打开了一个流并且尚未开始发出数据，请传递该流。否则给它一个路径，它将必须打开一个新流。