How to save an HTML5 Canvas as an image on a server?

Question

I\'m working on a generative art project where I would like to allow users to save the resulting images from an algorithm. The general idea is:

• Create an image

Answer 1

I think you should tranfer image in base64 to image with blob, because when you use base64 image, it take a lot of log lines or a lot of line will send to server. With blob, it only the file. You can use this code bellow:

dataURLtoBlob = (dataURL) ->
  # Decode the dataURL
  binary = atob(dataURL.split(',')[1])
  # Create 8-bit unsigned array
  array = []
  i = 0
  while i < binary.length
    array.push binary.charCodeAt(i)
    i++
  # Return our Blob object
  new Blob([ new Uint8Array(array) ], type: 'image/png')

And canvas code here:

canvas = document.getElementById('canvas')
file = dataURLtoBlob(canvas.toDataURL())

After that you can use ajax with Form:

  fd = new FormData
  # Append our Canvas image file to the form data
  fd.append 'image', file
  $.ajax
    type: 'POST'
    url: '/url-to-save'
    data: fd
    processData: false
    contentType: false

---

This code using CoffeeScript syntax.

if you want to use javascript, please paste the code to http://js2.coffee

Answer 2

Send canvas image to PHP:

var photo = canvas.toDataURL('image/jpeg');                
$.ajax({
  method: 'POST',
  url: 'photo_upload.php',
  data: {
    photo: photo
  }
});

Here's PHP script:
photo_upload.php

<?php

    $data = $_POST['photo'];
    list($type, $data) = explode(';', $data);
    list(, $data)      = explode(',', $data);
    $data = base64_decode($data);

    mkdir($_SERVER['DOCUMENT_ROOT'] . "/photos");

    file_put_contents($_SERVER['DOCUMENT_ROOT'] . "/photos/".time().'.png', $data);
    die;
?>