getblobimagedims.py

# for GAE - tries get the image size... not too efficient...
# could throw lots of different exceptions, including DeadlineExceededError
class ImageBlobHelper(object):
    @staticmethod
    def TryGetWidthHeight(blobinfo, read_increments = 32768):
        total_read = 0
        blob_key = blobinfo.key();
        data = ''
        while total_read < blobinfo.size:
            data_read = blobstore.fetch_data(blob_key, total_read, total_read+read_increments)
            total_read += len(data_read)
            data += data_read 
            try:
                imgtemp = images.Image(image_data=data)
                res = (imgtemp.width, imgtemp.height)
                return res
            except images.BadImageError, images.NotImageError:
                pass
        
        raise images.BadImageError("Unable to get width and height")