read an array of pixel values python

Question

I would like to take a screenshot with a certain range of the screen, and then I would like to check the pixel values of certain lines (eg x_axis from 400 to 800). I tried multiple ways like the imagegrab, gdi32.GetPixel and some more. It seems reading pixels values take a lot of time, so I even tried converting it into a list, something like this

im = ImageGrab.grab(box)
pixels = list(im .getdata())

Even this does not seem fast. Is there something I'm doing wrong?

mprat · Accepted Answer · 2016-12-19 19:51:44Z

1

ImageGrab returns pixels in PIL format (the Python Imaging Library: http://effbot.org/imagingbook/image.htm), and .getdata() already returns the pixels as a sequence. By wrapping it in list() again you are doing the same (expensive) operation twice. You can just do:

im = ImageGrab.grab(box)
pixels = im.getdata()

And iterate through your pixels in your favorite way.

answered Dec 19, 2016 at 19:51

mprat

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3 Comments

user3345850 Over a year ago

hey, thanks a lot.... but could you let me know if I use this for color in im.getdata(): how can I iterate in such a way that I only check every one pixel out of three

mprat Over a year ago

Do you mean you want to to process a pixel, then not process 2, then process a pixel, not process 2, etc?

mprat Over a year ago

What about this: for index, pixel in enumerate(pixels): if index % 3 == 0: # do something?

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