use maemo camera by python

Question

I wrote a simple program for Maemo by Python to check some pixel's color every time that my function is called. But this function runs very slowly (3-5 seconds each call). Is there any faster way to do this?

import Image
import os
import sys

# sen_pos = (pixel_x, pixel_y)
def sen(sen_pos):
    os.system("gst-launch v4l2src device=/dev/video0 num-buffers=1 ! ffmpegcolorspace ! jpegenc ! filesink location=cam.jpg")
    frame = Image.open("cam.jpg")
    col = frame.getpixel((sen_pos[0], sen_pos[1]))
    avecol = sum(col) / len(col)
    if avecol > 127:
        return "white"
    elif avecol < 127:
        return "black"
    return None

Calumniate

Without being at all familiar with gstreamer, is the colorspace conversion really necessary? Also, tuning the quality parameter to jpegenc may help. – Cupcake

Answer 1

Calling an external program via os.system is likely what's taking the time.

Try using GStreamer Python Bindings instead and keeping the video object around between calls. The docs for Videomixer may help.

Grateful

Answer 2

As George says, you may be incurring overhead in a system call but I suspect the getpixel() call. PIL's getpixel() is notoriously slow. Instead load() the image and then loop through -- that should be faster.

Discontinuous