how to convert canvas to image to upload to flask?

Question

Alright so I'm trying to upload a resized canvas image as a file to Flask.

First I tried to use the canvas.toDataURL() to convert it to a base64(?) string then tried to upload that as an image using formdata with AJAX, no luck.

Then I tried converting the base64 to a blob using this function:

    function toblob(stuff) {
    var g, type, bi, ab, ua, b, i;
    g = stuff.split(',');
    if (g[0].split('png')[1])
        type = 'png';
    else if (g[0].split('jpeg')[1])
        type = 'jpeg';
    else
        return false;
    bi = atob(g[1]);
    ab = new ArrayBuffer(bi.length);
    ua = new Uint8Array(ab);
    for (i = 0; i < bi.length; i++) {
        ua[i] = bi.charCodeAt(i);
    }
    b = new Blob([ua], {
        type: "image/" + type
    });
    return b;
}

not image...

here's the ajax form I used:

s = new FormData();
s.append('image', toblob(d)); \\I believe I refer to this with request.files['image']?
var g = $.ajax({
    url: 'url', 
    type: 'POST',
    processData : false,
    contentType : false, 
    data: s
}) //POSTDATA

Heres what I have so far serverside:

@app.route('/requests/<req>', methods=['POST'])
def requests(req=None): 
        if req == 'upload' and request.method == 'POST' and request.files['file']:
    file = request.files['image'] \\referring to formdata() key
    if file and allowed_file(file.filename):
        n = secure_filename(file.filename)
        file.save(os.path.join(app.config['UPLOAD_FOLDER'],n))
        return redirect(url_for('index', p=n))

ALL THAT ASIDE AND MORE IMPORTANTLY

I feel pretty confident that the javascript is doing a good job of sending the data as many other stackoverflow questions use the same method for PHP servers and the server is indeed recieving the data.

My problem is that I don't know how to convert this data into a physical file to store into a directory?

I've tried using the upload tutorial but the data isn't a file so that doesn't work.
I found one tutorial on how to upload blobs (I think?) but it doesn't work because it uses "files" which isn't defined.

Is there any way I can convert this data into physical image file through flask or js?

THANKYOU!

Posting a blob via ajax https://stackoverflow.com/a/19032688/1783439 — nu everest, May 22 '17 at 15:39

score 6 · Accepted Answer · edited Jun 20 '20 at 09:12

Found a work-around! instead of using Flask's file.save(), I used werkzeug's FileStorage() Which (as far as I know) a raw version of the file.save() I used it by specifying the filename and stream(which is a blob FYI) like so:

FileStorage(stream=request.files['image']).save(os.path.join(app.config['AUTHOR_FOLDER'],'testpic.jpg')))

Plopped it down into the script, dodged around the error 400s and barely scrapped together a working function! haha.

It works but I have no idea how secure it is or how stable it is, just going to go with it for now. If any one has any experience please help me out. Thanks!

Life is awesome!

how to convert canvas to image to upload to flask?

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