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Motion Detection As Input

·
Inspired from the PIL version here
http://gumuz.looze.net/wordpress/index.php/archives/2005/06/06/python-webcam-fun-motion-detection/

First with typical import and Canvas, exit setup

from appuifw import *
from graphics import Image
import camera, e32
#import miso    # don't dim the light

app.body = c = Canvas()

running = 1
def quit():
    global running
    running = 0
app.exit_key_handler=quit

Then the getdata function that reads pixel data 
from image by saving/reading PNG.

def getdata(im, bpp=24):
    import struct, zlib
    im.save('D:\\pixels.png', bpp=bpp, compression='no')
    f = open('D:\\pixels.png', 'rb')
    f.seek(8 +8+13+4)
    chunk = []
    while 1:
        n = struct.unpack('>L', f.read(4))[0]
        if n==0: break  # 'IEND' chunk
        f.read(4) # 'IDAT'
        chunk.append(f.read(n))
        f.read(4)   # CRC
    f.close()
    return zlib.decompress(''.join(chunk))  # '\x00' prefix each line

Lastly, the real code follows.

last1 = '\x00' * 930    # can be anything
while running:
    im = camera.take_photo('RGB', (160,120))
    im.rectangle([(10,10),(40,40)], 0xff0000)   # red outline
    im.rectangle([(120,10),(150,40)], 0xff0000) # no code for this square
    # check hot spot whether active
    box = Image.new((30,30), 'L')  # gray scale
    box.blit(im, (10,10,40,40))
    data = getdata(box, 8)
    # check difference for motion
    pixdiff = 0
    for i in range(len(data)):
        if abs(ord(data[i])-ord(last1[i])) > 15:  # pix threshold 15/256
            pixdiff += 1
            if pixdiff > 90:    # img threshold 90/900
                im.rectangle([(10,10),(40,40)], fill=0xff0000)  # fill
                break           # motion detected
    last1 = data
    c.blit(im, (0,0), (8,12))   # show camera
    #miso.reset_inactivity_time()

When measured, it takes around 1.1 sec for each loop.
Compared this with 0.9 sec without image processing, 
out code is quite efficient.

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