I'm working on an Appengine application in Java that allows users to
upload images drawn through an HTML5 canvas library called PaintWeb
(http://code.google.com/p/paintweb/).
Currently I have a servlet that receives the XMLHttpRequest POST from
the paintweb javascript library as a formencoded image.
1. Paintweb.js library sends XMLHttpRequest POST
send = 'dataURL=' + encodeURIComponent(ev.dataURL),
headers = {'Content-Type': 'application/x-www-form-
urlencoded'};
2. A custom servlet decodes the form encoded image data as a blob and
stores that in the Datastore with an associated Drawing entity
3 Custom servlet serves the Blob's in the datastore as
ContentType("image/png")
I'm curious if I can use the new BlobstoreService and ImageService
features to upload my HTML5 canvas images and serve them as pure Blobs
(as shown in this tutorial
http://ikaisays.com/2010/09/08/gwt-blobstore-the-new-high-performance-image-serving-api-and-cute-dogs-on-office-chairs/)
According to the documentation (http://code.google.com/appengine/docs/
java/blobstore/overview.html#Uploading_a_Blob) it seems like the major
stopping point is that I need to POST a form with:
<input type="file" name="myFile">
Which I don't think is possible from Paintweb.
Possibly a work around would be if there was some way on the server
side to store a blob in the Blobstorage (instead of the datastore) so
that you could reap the benefits of not using your CPU quota to serve
images.
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