I struggled a bit to get this working today, but eventually found a
solution. I am trying to write out JPEG images stored in the
datastore. (They are all JPEGs to begin with.)
Initially I was trying a number of things, such as dumping the JPEG
blog directly into drawImage, running the blob through the Google
Image library, wrapping the JPEG blob in a StringIO file, etc - but
either AppEngine would either completely crash, or I would get errors
like:
AttributeError: 'cStringIO.StringO' object has no attribute 'rfind'
or
IOError: Cannot open resource.
or
RuntimeError: Imaging Library not available, unable to import bitmaps
only jpegs fileName=<StringIO.StringIO instance at 0x1849d78>
The solution was to create an extension of the ImageReader class
called JpegBlobImageReader like so:
from StringIO import StringIO
from google.appengine.api import images
class JpegBlobImageReader(pdflibutils.ImageReader):
def __init__(self, blob):
self.fileName = "JPEGBLOB_%d" % id(self)
self.fp = StringIO()
self.fp.write(blob)
self._image = blob
self.jpeg_fh = self._jpeg_fh
self._data = blob
self._dataA = None
image = images.Image(blob)
self._width = image.width
self._height = image.height
self._transparent = False
You can then add an image like this:
canvas.drawImage(JpegBlobImageReader(line.item.drawing), 9*cm, height
- 10*cm, 8*cm, 8*cm)
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