Interesting request. I'd say you need to research two things first.
Read through the RFC that covers how the file upload control works
(
http://www.ietf.org/rfc/rfc1867.txt), and maybe the w3c mention of it
(
http://www.w3.org/TR/html4/interact/forms.html). After that consider
setting up a test upload form and receiving script on your server,
sniff your connection using ethereal or similar, and do an upload. This
should give you a solid understanding of what exactly the server
expects.
Now I'll take a theoretical stab at a solution. AFAIK there is now way
in javascript to access that actual image raster data, just properties
of the img element such as src. What I think might work is this:
1. When the user selects the image they want, get the url of it in JS
via the src property.
2. Dispatch a request using AJAX to the server for that image. This is
where it starts to get tricky since the server will respond with raw
image data (JPG/PNG/GIF) and the corresponding MIME type, and as such
the browser will probably not populate either the responseText or
responseXML. However you may be able to access the image data via
responseBody property - I'm not sure.
The other alternative here is to have the server serve images
indirectly through a script (that reads and dumps the image data). The
server script could search for a certain header, which your AJAX
request would have to set, and when it sees that header, dump the image
data as a base64 encoded string and use text/plain as the MIME type.
When your xmlhttp object gets a response, it will have the base64
encoded image in the responseText property, which you can then post to
the server as a normal form (that is, without the
enctype="multip art/form-data").
3. The server receiving the posted image data will need to know that
its receiving base64 image data, so you'd need to set some headers in
your AJAX post. The server would then know to decode the string back to
it's original binary format - the image.
Let me know how you progress with this - if I ever get a break i may
have to take a crack at it.
SammyBar wrote:
Hi all,
I wonder is it possible to upload the content of an <imgfield to a server.
The content of the <imgwas downloaded from a web site different from the
one it should be uploaded. The image file should not be saved locally before
uploading. It should not be visible any <input type=file on the form.
How can it be done?
I'm working on a project where client javascript requests an image server to
generate dynamic images. The client selects the image it wants and uploads
this to another server which stores the image. I know it is very simple to
upload a file to a server by using <input type=file but it is not the
case. The image I need to uploaded is stored on a <img field and is not
saved to local file system.
Any hint is welcomed
Thanks in advance
Sammy
