Fastest Way To Loop Through Every Pixel

[Paul McGuire]

"Chaos" <psnim2000 at gmail.com> wrote in message
news:1154280523.162997.298400 at i42g2000cwa.googlegroups.com...
>
> Paul McGuire wrote:
> > "Paul McGuire" <ptmcg at austin.rr._bogus_.com> wrote in message
> > news:Grhyg.21879$Cn6.17684 at tornado.texas.rr.com...
> > > "Chaos" <psnim2000 at gmail.com> wrote in message
> > > news:1154055002.495073.171650 at i3g2000cwc.googlegroups.com...
> > > >
> > > >
> > > > myCol = (0.3 * image.GetRed(thisX, thisY)) + (0.59 *
> > > > image.GetGreen(thisX, thisY)) + (0.11 * image.GetBlue(thisX, thisY))
> > > > if myCol < darkestCol:
> > > >    darkestCol = myCol
> > > >    possX = thisX
> > > >    possY = thisY
> > > >
> > >
> > > Psyco may be of some help to you, especially if you extract out your
myCol
> > > expression into its own function, something like:
> > >
> > > def darkness(img,x,y):
> > >     return  (0.3 * img.GetRed(x,y)) + (0.59 * img.GetGreen(x,y)) +
(0.11 *
> > > img.GetBlue(x,y))
> > >
> > <snip>
> >
> > Even better than my other suggestions might be to write this function,
and
> > then wrap it in a memoizing decorator
> >
(http://wiki.python.org/moin/PythonDecoratorLibrary#head-11870a08b0fa59a8622
> > 201abfac735ea47ffade5) - surely there must be some repeated colors in
your
> > image.
> >
> > -- Paul
>
> Its not only finding the darkest color, but also finding the X position
> and Y Position of the darkest color.
>

Sorry, you are correct.  To take advantage of memoizing, the darkness method
would have to work with the r, g, and b values, not the x's and y's.

-- Paul


import psyco
psyco.full()

IMAGE_WIDTH = 200
IMAGE_HEIGHT = 200
imgColRange = range(IMAGE_WIDTH)
imgRowRange = range(IMAGE_HEIGHT)

@memoize    # copy memoize from
http://wiki.python.org/moin/PythonDecoratorLibrary, or similar
def darkness(r,g,b):
    return 0.3*r + 0.59*g + 0.11*b

def getDarkestPixel(image):
    getR = image.GetRed
    getG = image.GetGreen
    getB = image.GetBlue

    darkest = darkness( getR(0,0), getG(0,0), getB(0,0) )
    # or with PIL, could do
    # darkest = darkness( *getpixel(0,0) )
    dkX = 0
    dkY = 0
    for r in imgRowRange:
        for c in imgColRange:
            dk = darkness( getRed(r,c), getGrn(r,c), getBlu(r,c) )
            if dk < darkest:
                darkest = dk
                dkX = c
                dkY = r
    return dkX, dkY