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Set transparent background using ImageMagick and commandline prompt

Suppose you have any image (PNG or JPG). This image has a white background and I need to make this background transparent. ...
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Regular expression for letters, numbers and - _

...iteral . References regular-expressions.info/Anchors, Character Classes and Repetition In PHP Here's a snippet to show how you can use this pattern: <?php $arr = array( 'screen123.css', 'screen-new-file.css', 'screen_new.js', 'screen new file.css' ); foreach ($arr as $s) { if...
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Pandas: drop a level from a multi-level column index?

... If the index you are trying to drop is on the left (row) side and not the top (column) side, you can change "columns" to "index" and use the same method: >>> df.index = df.index.droplevel(1) – Idodo Nov 28 '18 at 12:13 ...
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Define a lambda expression that raises an Exception

...ption without defining a named function. All you need is a strong stomach (and 2.x for the given code): type(lambda:0)(type((lambda:0).func_code)( 1,1,1,67,'|\0\0\202\1\0',(),(),('x',),'','',1,''),{} )(Exception()) And a python3 strong stomach solution: type(lambda: 0)(type((lambda: 0).__code_...
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How to remove leading zeros from alphanumeric text?

... "]"); } See also regular-expressions.info repetitions, lookarounds, and anchors String.replaceFirst(String regex) share | improve this answer | follow ...
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Swift equivalent for MIN and MAX macros

In C / Objective-C it is possible to find the minimum and maximum value between two numbers using MIN and MAX macros. Swift doesn't support macros and it seems that there are no equivalents in the language / base library. Should one go with a custom solution, maybe based on generics like this one ?...
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Efficiently test if a port is open on Linux?

...mp;6 I'm using 6 as the file descriptor because 0,1,2 are stdin, stdout, and stderr. 5 is sometimes used by Bash for child processes, so 3,4,6,7,8, and 9 should be safe. As per the comment below, to test for listening on a local server in a script: exec 6<>/dev/tcp/127.0.0.1/445 || echo "N...
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Does ARC support dispatch queues?

... The short answer: YES, ARC retains and releases dispatch queues. And now for the long answer… If your deployment target is lower than iOS 6.0 or Mac OS X 10.8 You need to use dispatch_retain and dispatch_release on your queue. ARC does not manage ...
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Why use softmax as opposed to standard normalization?

... There is one nice attribute of Softmax as compared with standard normalisation. It react to low stimulation (think blurry image) of your neural net with rather uniform distribution and to high stimulation (ie. large numbers, think crisp image) with probabilities close to 0 and 1. ...
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Can I specify multiple users for myself in .gitconfig?

... You can manually edit those config files with git config --edit and git config --global --edit. And in case you missed Abizern’s comment, a repository’s config file is at <repo-root>/.git/config. – Rory O'Kane Apr 25 '12 at 20:01 ...