Serving images from a Raspberry Pi camera over HTTP

Question

I have a Pi with a camera module that I control with Python.

I created a web server with web.py that allows me to make HTTP requests to the PI to retrieve an image. There are two optional parameters to specify the width and height of the image. The code looks like this (imports omitted):

urls = (
    '/capture', 'Capture'
)

# start with default values for resolution
width = 1024
height = 768

if __name__ == "__main__":

    app = web.application(urls, globals())
    app.run()

class Capture:
    def GET(self):
        input = web.input(w="0", h="0")                 # reading user input of resolution values for 

        input.w = int(input.w)                          # to integer
        input.h = int(input.h)

        if input.w == 0:
            input.w = width                             # no width given, use saved one
        else:
            input.w = max(0,min(2592, input.w))         # clamp to range of valid values

        if input.h == 0:
            input.h = height                            # no height given, use saved one
        else:
            input.h = max(0,min(1944, input.h))         # clamp to range of valid values

        camera = picamera.PiCamera()                    # camera
        camera.resolution = (input.w, input.h)
        camera.capture('picture.jpg')                   # capture image to file
        camera.close()

        web.header('Content-Type', 'image/jpg')
        return open('picture.jpg',"rb").read()          # read image from file and respond

I understand that the code handling the width and height is not very elegant and could be shorter.

To get an image, I can enter http://<PI IP address>/capture in a browser. The problem is that it takes quite a while (1311ms): waiting 1264ms and receiving 47ms.

The results are obviously the same on different browsers because this is a server-side issue.

How can I get the image more quickly?

I think saving to an image file first and reopening that to get the return value is redundant (and possibly slow), but I don't know how to make the capture() function return the value directly (so that I could return it to the client directly). I do not necessarily need jpeg format.