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How can I convert an RGB image into grayscale in Python?
...a luma value, but it means you can do it all in matplotlib.
Background:
http://matplotlib.sourceforge.net/api/colors_api.html
http://en.wikipedia.org/wiki/HSL_and_HSV
Alternatively, you could use PIL or the builtin colorsys.rgb_to_yiq() to convert to a colorspace with a true luma value. You co...
Efficiency of purely functional programming
...eUploader: {
brandingHtml: "Powered by \u003ca href=\"https://imgur.com/\"\u003e\u003csvg class=\"svg-icon\" width=\"50\" height=\"18\" viewBox=\"0 0 50 18\" fill=\"none\" xmlns=\"http://www.w3.org/2000/svg\"\u003e\u003cpath d=\"M46.1709 9.17788C46.1709 8.26454 46.2665 7.94324 4...
diff to output only the file names
... tars with wget and extract them into the directories old/ and new/:
wget http://download.dokuwiki.org/src/dokuwiki/dokuwiki-2014-09-29d.tgz
wget http://download.dokuwiki.org/src/dokuwiki/dokuwiki-2014-09-29.tgz
mkdir old && tar xzf dokuwiki-2014-09-29.tgz -C old --strip-components=1
mkdir ...
Getting error: Peer authentication failed for user “postgres”, when trying to get pgsql working with
...ermission to connect to.
Here is what I do on Debian to setup postgres:
http://www.postgresql.org/download/linux/debian/ (Wheezy 7.x)
as root …
root@www0:~# echo "deb http://apt.postgresql.org/pub/repos/apt/ wheezy-pgdg main" >> /etc/apt/sources.list
root@www0:~# wget --quiet ...
What are the applications of binary trees?
...multimap, set, and multiset.
Example code for an AVL tree can be found at http://ideone.com/MheW8
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CSS: 100% font size - 100% of what?
...6px), which may not have been intended.
This can help in the explanation:
http://www.w3.org/TR/2011/REC-CSS2-20110607/syndata.html#value-def-percentage
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Neo4j - Cypher vs Gremlin query language
...code and perform various tasks from the server, without having to take the HTTP hit from the REST interface. Among others, Gremlin will let you modify data.
However, when all I want is to query data, I go with Cypher as it is more readable and easier to maintain. Gremlin is the fallback when a limi...
Get first key in a (possibly) associative array?
... seconds
array_keys to get first key: 10.059751987457 seconds
reset+key http://3v4l.org/b4DrN/perf#tabs
foreach http://3v4l.org/gRoGD/perf#tabs
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Why does changing 0.1f to 0 slow down performance by 10x?
... -msse -mfpmath=sse
(corresponding credits to Carl Hetherington [1])
[1] http://carlh.net/plugins/denormals.php
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内存优化总结:ptmalloc、tcmalloc和jemalloc - 操作系统(内核) - 清泛网 - ...
...malloc一块内存，作为整个连接生命周期内的内存池。 当HTTP请求到达的时候，又会malloc一块当前请求阶段的内存池, 因此对malloc的分配速度有一定的依赖关系。(而apache的内存池是有父子关系的，请求阶段的内存池会和连接阶段的...