Fastest Way To Loop Through Every Pixel

[Nick Vatamaniuc]

Hello Chaos,

Whatever you do in "#Actions here ..." might be expressed nicely as a
ufunction for numeric. Then you might be able to convert the expression
to a numeric expression. Check out numpy/scipy.

In general, if thisHeight, thisWidth are large use xrange not range.
range() generates a list of numbers first then iterates through them.
So try that first.

Then of course if you do the whole thing many times you could just
pre-generate the indices as in:
all_indices=[]
for i in xrange(thisHeight):
  for j in xrange(thisWidth):
     all_indices.append( (i,j) )

Then each time you need to run '#Actions here...' you can just use
for (i,j) in all_indices:
    #Actions here ... blah blah

In general, if there would be a way to significantly optimize generic
for loops, they would probably be already optimized...

Nick V.


Chaos wrote:
> As my first attempt to loop through every pixel of an image, I used
>
>         for thisY in range(0, thisHeight):
>             for thisX in range(0, thisWidth):
>                   #Actions here for Pixel thisX, thisY
>
> But it takes 450-1000 milliseconds
>
> I want speeds less than 10 milliseconds
>
> I have tried using SWIG, and pypy but they all are unsuccessfull in
> compiling my files.