问题描述
我在OS X 10.8.2在Python建立一个自动化的机器人比赛的进程,并在研究的Python GUI自动化的过程中我发现autopy。鼠标操作API是伟大的,但它似乎屏幕捕获方法依赖于德precated OpenGL的方法...
I'm in the process of building an automated game bot in Python on OS X 10.8.2 and in the process of researching Python GUI automation I discovered autopy. The mouse manipulation API is great, but it seems that the screen capture methods rely on deprecated OpenGL methods...
有没有获得在OS X中一个像素的颜色值的任何有效的方法?我现在能想到的唯一的办法就是使用使用os.system(抓屏foo.png)
但过程似乎有不必要的开销,因为我会很轮询快。
Are there any efficient ways of getting the color value of a pixel in OS X? The only way I can think of now is to use os.system("screencapture foo.png")
but the process seems to have unneeded overhead as I'll be polling very quickly.
推荐答案
一个小的改进,但使用TIFF COM pression的选项抓屏
是有点快
A small improvement, but using the TIFF compression option for screencapture
is a bit quicker:
$ time screencapture -t png /tmp/test.png
real 0m0.235s
user 0m0.191s
sys 0m0.016s
$ time screencapture -t tiff /tmp/test.tiff
real 0m0.079s
user 0m0.028s
sys 0m0.026s
这确实有大量的开销,就像你说的(子进程的创建,写/从磁盘读取,COM pressing / DECOM pressing)。
This does have a lot of overhead, as you say (the subprocess creation, writing/reading from disc, compressing/decompressing).
相反,你可以使用PyObjC使用 CGWindowListCreateImage
来捕获屏幕。我发现它花了约70ms的(〜14fps)捕捉1680×1050像素的屏幕,并在内存中访问的值
Instead, you could use PyObjC to capture the screen using CGWindowListCreateImage
. I found it took about 70ms (~14fps) to capture a 1680x1050 pixel screen, and have the values accessible in memory
一些随机的注意事项:
- 导入
Quartz.CoreGraphics
模块是最慢的部分,约1秒钟。同样是用于导入大多数PyObjC模块也是如此。不太可能的事情在这种情况下,但对于短暂的过程,你可能会更好写在ObjC工具 - 指定一个较小的区域是有点快,但不是巨大(〜为100x100px块为40ms,70ms的〜为1680×1050)。大部分的时间似乎在刚刚
CGDataProviderCopyData code>呼叫花 - 我不知道是否有直接访问数据的方式,因为我们不需要修改
- 的
ScreenPixel.pixel
的功能是pretty快,但访问大量的像素依然很慢(因为0.01ms * 1650 * 1050
是17秒左右) - 如果你需要访问大量的像素,可能会比较快,以struct.unpack_from
他们都一气呵成。 LI>
- Importing the
Quartz.CoreGraphics
module is the slowest part, about 1 second. Same is true for importing most of the PyObjC modules. Unlikely to matter in this case, but for short-lived processes you might be better writing the tool in ObjC - Specifying a smaller region is a bit quicker, but not hugely (~40ms for a 100x100px block, ~70ms for 1680x1050). Most of the time seems to be spent in just the
CGDataProviderCopyData
call - I wonder if there's a way to access the data directly, since we dont need to modify it? - The
ScreenPixel.pixel
function is pretty quick, but accessing large numbers of pixels is still slow (since0.01ms * 1650*1050
is about 17 seconds) - if you need to access lots of pixels, probably quicker tostruct.unpack_from
them all in one go.
这里的code:
import time
import struct
import Quartz.CoreGraphics as CG
class ScreenPixel(object):
"""Captures the screen using CoreGraphics, and provides access to
the pixel values.
"""
def capture(self, region = None):
"""region should be a CGRect, something like:
>>> import Quartz.CoreGraphics as CG
>>> region = CG.CGRectMake(0, 0, 100, 100)
>>> sp = ScreenPixel()
>>> sp.capture(region=region)
The default region is CG.CGRectInfinite (captures the full screen)
"""
if region is None:
region = CG.CGRectInfinite
else:
# TODO: Odd widths cause the image to warp. This is likely
# caused by offset calculation in ScreenPixel.pixel, and
# could could modified to allow odd-widths
if region.size.width % 2 > 0:
emsg = "Capture region width should be even (was %s)" % (
region.size.width)
raise ValueError(emsg)
# Create screenshot as CGImage
image = CG.CGWindowListCreateImage(
region,
CG.kCGWindowListOptionOnScreenOnly,
CG.kCGNullWindowID,
CG.kCGWindowImageDefault)
# Intermediate step, get pixel data as CGDataProvider
prov = CG.CGImageGetDataProvider(image)
# Copy data out of CGDataProvider, becomes string of bytes
self._data = CG.CGDataProviderCopyData(prov)
# Get width/height of image
self.width = CG.CGImageGetWidth(image)
self.height = CG.CGImageGetHeight(image)
def pixel(self, x, y):
"""Get pixel value at given (x,y) screen coordinates
Must call capture first.
"""
# Pixel data is unsigned char (8bit unsigned integer),
# and there are for (blue,green,red,alpha)
data_format = "BBBB"
# Calculate offset, based on
# http://www.markj.net/iphone-uiimage-pixel-color/
offset = 4 * ((self.width*int(round(y))) + int(round(x)))
# Unpack data from string into Python'y integers
b, g, r, a = struct.unpack_from(data_format, self._data, offset=offset)
# Return BGRA as RGBA
return (r, g, b, a)
if __name__ == '__main__':
# Timer helper-function
import contextlib
@contextlib.contextmanager
def timer(msg):
start = time.time()
yield
end = time.time()
print "%s: %.02fms" % (msg, (end-start)*1000)
# Example usage
sp = ScreenPixel()
with timer("Capture"):
# Take screenshot (takes about 70ms for me)
sp.capture()
with timer("Query"):
# Get pixel value (takes about 0.01ms)
print sp.width, sp.height
print sp.pixel(0, 0)
# To verify screen-cap code is correct, save all pixels to PNG,
# using http://the.taoofmac.com/space/projects/PNGCanvas
from pngcanvas import PNGCanvas
c = PNGCanvas(sp.width, sp.height)
for x in range(sp.width):
for y in range(sp.height):
c.point(x, y, color = sp.pixel(x, y))
with open("test.png", "wb") as f:
f.write(c.dump())
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