Get Binary Representation of PIL Image Without Saving

Question

I am writing an application that uses images intensively. It is composed of two parts. The client part is written in Python. It does some preprocessing on images and sends them over TCP to a Node.js server. After preprocessing, the Image object looks like this:

window = img.crop((x,y,width+x,height+y))
window = window.resize((48,48),Image.ANTIALIAS)

To send that over socket, I have to have it in binary format. What I am doing now is:

window.save("window.jpg")
infile = open("window.jpg","rb")
encodedWindow = base64.b64encode(infile.read())
#Then send encodedWindow 

This is a huge overhead, though, since I am saving the image to the hard disk first, then loading it again to obtain the binary format. This is causing my application to be extremely slow. I read the documentation of PIL Image, but found nothing useful there.

Answer 1

According to the documentation, (at effbot.org):

"You can use a file object instead of a filename. In this case, you must always specify the format. The file object must implement the seek, tell, and write methods, and be opened in binary mode."

This means you can pass a StringIO object. Write to it and get the size without ever hitting the disk.

Like this:

s = StringIO.StringIO()
window.save(s, "jpg")
encodedWindow = base64.b64encode(s.getvalue())