通过JQuery AJAX上传图像

Question

I looked around and just couldn't find what I'm looking for without additional plugins/libraries . I want to upload an image and process it serverside via JQuery AJAX, but I can't figure out how to pass and process it. Any help is much appreciated!

Answer 1

Though Diodeus is correct, it isn't quite that difficult. Just maddening.

HTML5 does expose what is called the FileReader API, which is still relatively new and unsupported on legacy browsers, but which will make your job easier. I have a small app which accepts images on the client side and, using the FileReader API, converts them to base-64 for uploading to the server.

The following is the function I call upon a user's uploading an image. App.FileReader is an instantiation of the HTML5 FileReader, which is declared simply like:

App.FileReader = window.FileReader ? new FileReader : null;

Upon upload, I read the image as a dataURL using the FileReader, and push the data into an unused tag. The FileReader itself retains the read data, which is why it is a good idea to only instantiate one FileReader at a time.

    if (input.files && input.files[0]) {

        if (App.FileReader) {

            App.FileReader.onload = function (e) {
                $('#createMomentImagePreview').attr('src', e.target.result);
            }

            App.FileReader.readAsDataURL(input.files[0]);

            $this.uploadedImage = true
        }

        else {
            $('#createMomentImagePreview').attr('src', 'http://d33w6ffaa49e6z.cloudfront.net/media/ImageLoaded.png');

            $this.uploadedImage = true
        }
    }

This is the AJAX call for uploading to the server, where data represents the read file, or "App.FileReader.result":

    $.ajax({
        url: '/image',
        type: 'POST',
        data: {
            image: App.FileReader.result
        }
    }).done(function(data){

        callback(data);

    }).fail(function() {
        console.log("Image upload failed!")
        alert("Sorry, there was an error uploading your image to the database.")
    })

Server-side (and I'm using Node with Express, so this might not apply), I can convert the base64 string to a Buffer (Blob) and send that up to S3 using Knox's putBuffer. This is waaaaaay simpler than actually authenticating with S3 AND trying to get it to play nice with your binary data.

if (req.body.image.match(/^data:image\/png;base64,/)) {
    var image = new Buffer(req.body.image.replace(/^data:image\/png;base64,/,""), "base64");
}

else if (req.body.image.match(/^data:image\/jpeg;base64,/)) {
    var image = new Buffer(req.body.image.replace(/^data:image\/jpeg;base64,/,""), "base64");
}

awsClient.putBuffer(image, '/' + imagePath + '.jpg', headers, function(err, stream) {

          if (err) {
            console.log(err);
            return false
          }

          res.send(200, imagePath + '.jpg')

          image = null;

        });

In either case, once you have the base64 data on your server you've made significant progress. You could use ImageMagick to handle processing as well. For what it's worth, I hope this helps you out in some way!