Quickly getting the color of some pixels on the screen in Python on Windows 7

Question

I need to get the color of some pixels on the screen or from the active window, and I need to do so quickly. I've tried using win32gui and ctypes/windll, but they're much too slow. Each of these programs gets the color of 100 pixels:

import win32gui
import time
time.clock()
for y in range(0, 100, 10):
    for x in range(0, 100, 10):
        color = win32gui.GetPixel(win32gui.GetDC(win32gui.GetActiveWindow()), x , y)
print(time.clock())

and

from ctypes import windll
import time
time.clock()
hdc = windll.user32.GetDC(0)
for y in range(0, 100, 10):
    for x in range(0, 100, 10):
        color = windll.gdi32.GetPixel(hdc, x, y)
print(time.clock())

Each of these takes about 1.75 seconds. I need a program like this to take less than 0.1 seconds. What's making it so slow?

I'm working with Python 3.x and Windows 7. If your solution requires I use Python 2.x, please link me to an article showing how to have Python 3.x and 2.x both installed. I looked, but couldn't figure out how to do this.

Thanks!

Answer 1

I had this same exact problem, and solved it (in Java, in C#). The main idea behind the solution is GetPixel from screen is slow, and you can't fix that. But as you need some pixels, you can get a bunch of them all at once.

The time that it took to get 64 pixels was 98 times faster.

Answer 2

Thanks to Margus' direction, I focused on getting the image before extracting the pixel information. Here's a workable solution using the Python Imaging Library (PIL), which requires Python 2.x.

import ImageGrab
import time
time.clock()
image = ImageGrab.grab()
for y in range(0, 100, 10):
    for x in range(0, 100, 10):
        color = image.getpixel((x, y))
print(time.clock())

I don't think it gets any simpler than that. This takes (on average) 0.1 seconds, which is a little slower than I'd like but fast enough.

As for having Python 3.x and 2.x both installed, I separated that into a new question. I'm still having some trouble with it, but it's generally working.

Answer 3

This is better than using getpixel all the time and works faster.

import ImageGrab

px=ImageGrab.grab().load()
for y in range(0,100,10):
    for x in range(0,100,10):
        color=px[x,y]

Reference: Image.load

Answer 4

Disabling Windows Desktop Composition speeds pixel up reading A LOT.

Computer -> Properties -> Advanced system settings -> Performance -> desktop composition [ ] (warning this disables Windows's transparency effects)

Python 2.7 (Should be same for 3.x)

win32gui.GetPixel()     #1.75s => 20ms
windll.gdi32.GetPixel() #1.75s => 3ms (fastest)
image.getpixel()        # 0.1s => 50ms
px[]                    # 0.1s => 50ms

AutoIt for comparison

$timer = TimerInit()

For $x = 0 To 100 Step 10
    For $y = 0 To 100 Step 10
        PixelGetColor($x,$y) ;slow => 1ms
    Next
Next

ConsoleWrite("Time: " & TimerDiff($timer)/1000 & @CRLF)