Question

我正在尝试查看屏幕截图中心的像素。我正在使用PngPy来阅读屏幕截图，并想快速找到像素。

import png
import itertools

r=png.Reader("myfile.png")
direct = r.asRGBA8()

bytesIter = direct[2] # returns itertools.imap object - 
                      # see https://pythonhosted.org/pypng/png.html
height = direct[1]

count=0
for row in bytesIter:
    if count >= (height/2):
        print "Half way"
        break
    count+=1

print count

无论如何都要增加迭代器而不将其读取到新对象？ 对于快速工作站上的768x1280 png（具有Alpha通道），此操作需要2秒钟。

Answer 1

您可以使用itertools中的consume recipe：

from itertools import islice
from collections import deque

def consume(iterator, n):
    "Advance the iterator n-steps ahead. If n is none, consume entirely."
    # Use functions that consume iterators at C speed.
    if n is None:
        # feed the entire iterator into a zero-length deque
        deque(iterator, maxlen=0)
    else:
        # advance to the empty slice starting at position n
        next(islice(iterator, n, n), None)

所以，在你的情况下：

consume(bytesIter, height/2)

增加itertools.imap而无需在Python中读取对象以获得性能

1 个答案: