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POSending images from Canvas elements using Ajax and PHP $_FILES
 

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  1. POSending images from Canvas elements using Ajax and PHP $_FILES
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    <p>I need to be able to send an image and some form fields from a client side canvas element to a PHP script, ending up in $_POST and $_FILES. When I send it like this:</p> <pre><code>&lt;script type="text/javascript"&gt; var img = canvas.toDataURL("image/png"); ... ajax.setRequestHeader('Content-Type', "multipart/form-data; boundary=" + boundary_str); var request_body = boundary + '\n' + 'Content-Disposition: form-data; name="formfield"' + '\n' + '\n' + formfield + '\n' + '\n' + boundary + '\n' + 'Content-Disposition: form-data; name="async-upload"; filename="' + "ajax_test64_2.png" + '"' + '\n' + 'Content-Type: image/png' + '\n' + '\n' + img + '\n' + boundary; ajax.send(request_body); &lt;/script&gt; </code></pre> <p>$_POST and $_FILES both come back populated, but the image data in $_FILES still needs decoding like this:</p> <pre><code>$loc = $_FILES['async-upload']['tmp_name']; $file = fopen($loc, 'rb'); $contents = fread($file, filesize($loc)); fclose($file); $filteredData=substr($contents, strpos($contents, ",")+1); $unencodedData=base64_decode($filteredData); </code></pre> <p>...in order to save it as a readable PNG. This isn't an option as I'm trying to pass the image to Wordpress's media_handle_upload() function, which requires an index to $_FILES pointing to a readable image. I also can't decode, save and alter 'tmp_name' accordingly, as it falls foul of security checks.</p> <p>So, I found this: <a href="http://www.webtoolkit.info/javascript-base64.html" rel="noreferrer">http://www.webtoolkit.info/javascript-base64.html</a> and tried to do the decode on the client side:</p> <pre><code>img_split = img.split(",",2)[1]; img_decoded = Base64.decode( img_split ); </code></pre> <p>but for some reason I still don't end up with a readable file when it gets to the PHP. So the question is: "Why?" or "What am I doing wrong?" or "Is this even possible?" :-)</p> <p>Any help very much appreciated!</p> <p>Thanks, Kane</p>
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    1. USBaronVonKaneHoffen
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    1. COI'd set a `Content-Transfer-Encoding: base64` & look at [this answer](http://stackoverflow.com/questions/934012/get-image-data-in-javascript) to lose the prefix, haven't tested it though.
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    2. CO@Wrikken Content-Transfer-Encoding, although a valid MIME header, is not a valid HTTP header. See [this appendix](http://www.w3.org/Protocols/rfc2616/rfc2616-sec19.html#sec19.4.5) of the spec.
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      1. USNathan Ostgard
    3. CO@Nathan: Ack, my mistake. Does it show I've never needed to manually build a file upload :)
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