我认为您对编码参数的用法有点误解。如果您要指定编码“二进制”，那么您需要始终如一地执行此操作。但实际上你根本不需要它。您似乎混淆了 Buffer 与二进制字符串的用法。
// This tells node to load the file into a Buffer 'original_data' because you
// have not specified an encoding for the returned values. If you provided an
// encoding, then original_data would be a string with that encoding.
fs.readFile(image_origial, function(err, original_data){
// This tells node to take that buffer, and write it to the new filename.
// Again no encoding is provided, so it will assume a Buffer or utf8 string.
fs.writeFile('image_orig.jpg', original_data, function(err) {});
// This tells node to create a new buffer from the old buffer, which means
// it will iterate over original_data copying the bytes one at a time. But
// they will be identical buffers. It will ignore the 'binary' argument
// since the object you are passing isn't a string.
// Then it encodes the content of that Buffer to base64, which is fine.
var base64Image = new Buffer(original_data, 'binary').toString('base64');
// Here you decode the base64 to a buffer, which is fine, but then you
// convert the buffer into a string with encoding 'binary'. This means that
// it is a string object whose code points are bytes of the buffer.
var decodedImage = new Buffer(base64Image, 'base64').toString('binary');
// Here you try to write that String object to a file. Since the argument you
// have given is a string and you have not given an encoding argument for the
// write command, then it will assume that 'utf8' is the encoding. It will try to
// decode your binary string into a utf8 encoded buffer, and write that buffer.
// This will cause it to fail because that encoding conversion is wrong.
// Really through, 'binary' is just wrong to use. Buffers are already binary.
fs.writeFile('image_decoded.jpg', decodedImage, function(err) {});
});
下一个示例将起作用，但效率非常低，因为不需要一直更改编码，但我只是想清楚地表明它。如果你真的想要有一个特定的编码，你需要确保你是一致的。这些函数中的每一个都有一个编码参数。
fs.readFile(image_origial, 'binary', function(err, original_data){
fs.writeFile('image_orig.jpg', original_data, 'binary', function(err) {});
var base64Image = new Buffer(original_data, 'binary').toString('base64');
var decodedImage = new Buffer(base64Image, 'base64').toString('binary');
fs.writeFile('image_decoded.jpg', decodedImage, 'binary', function(err) {});
});
这是正确的做法。将所有内容都保存为 Buffer，除非您将其设为 base64。
fs.readFile(image_origial, function(err, original_data){
fs.writeFile('image_orig.jpg', original_data, function(err) {});
var base64Image = original_data.toString('base64');
var decodedImage = new Buffer(base64Image, 'base64');
fs.writeFile('image_decoded.jpg', decodedImage, function(err) {});
});