Alan Smith alanwsmith

This gist isn't mathematically rigorous so don't expect it to be as formal as something you'd find in academia.

how do you map from one range of numbers to another?

This problem arises in various math and computer science topics where your input range needs to be transformed to fit into a different range. For example, let's say you had frequency data of a song at a particular moment in time. Each sample is a value that ranges from 0 to 255. In interval notation, it would be written as [0, 255]. The square brackets denote that the endpoints are inclusive - in other words, 0 and 255 are acceptable. We want to take a sample in this range and map it to a different range. Let's say our output range is [-1, 1]. The [-1, 1] range actually pops up a lot in various fields such as graphics programming or trigonometry. For example the range for the sine and cosine functions is [-1, 1].

So we want to take the range [0, 255] and map it to the range [-1, 1]. Of course, we'd want the mapping t

Creating Timelapse Video From Photos With FFMPEG

Man, there are a lot of outdated and incomplete tutorials about creating timelapse videos from JPG images and photos. Here's a quick start guide to get going in late 2019.

Software

I'm using ffmpeg version 4.2.1 on MacOS. It is free, well supported, and scales up to practically any number of input images or output video length.

There are a dozen paid timelapse software offerings out there, but I suspect they are just polished front-ends to ffmpeg. Small timelapse videos are possible in iMovie 10.1, but adding even a modest number of images bogs it down badly. The easiest approach is to create a rough lightly compressed video with ffmpeg and then edit the result in iMovie.

	#!/bin/bash

	# This script resolves a DID, retrieves an API key, fetches a user's feed,
	# and posts a "Hello, world" message to the user's feed.

	# Resolve DID for handle
	HANDLE='felicitas.pojtinger.com'
	DID_URL="https://bsky.social/xrpc/com.atproto.identity.resolveHandle"
	export DID=$(curl -G \
	--data-urlencode "handle=$HANDLE" \

	#!/usr/bin/env bash
	# https://developers.supportbee.com/blog/setting-up-cucumber-to-run-with-Chrome-on-Linux/
	# https://gist.github.com/curtismcmullan/7be1a8c1c841a9d8db2c
	# https://stackoverflow.com/questions/10792403/how-do-i-get-chrome-working-with-selenium-using-php-webdriver
	# https://stackoverflow.com/questions/26133486/how-to-specify-binary-path-for-remote-chromedriver-in-codeception
	# https://stackoverflow.com/questions/40262682/how-to-run-selenium-3-x-with-chrome-driver-through-terminal
	# https://askubuntu.com/questions/760085/how-do-you-install-google-chrome-on-ubuntu-16-04

	# Versions
	CHROME_DRIVER_VERSION=`curl -sS https://chromedriver.storage.googleapis.com/LATEST_RELEASE`

	-- split a string
	function string:split(delimiter)
	local result = { }
	local from = 1
	local delim_from, delim_to = string.find( self, delimiter, from )
	while delim_from do
	table.insert( result, string.sub( self, from , delim_from-1 ) )
	from = delim_to + 1
	delim_from, delim_to = string.find( self, delimiter, from )
	end

	# -- mode: ruby --
	# vi: set ft=ruby :

	# Vagrantfile API/syntax version. Don't touch unless you know what you're doing!
	VAGRANTFILE_API_VERSION = "2"

	Vagrant.configure(VAGRANTFILE_API_VERSION) do \|config\|
	# All Vagrant configuration is done here. The most common configuration
	# options are documented and commented below. For a complete reference,
	# please see the online documentation at vagrantup.com.

	- Tune /etc/ssh/sshd_config

	UseDNS no # Disable DNS lookups
	GSSAPIAuthentication no # Disable negotation of slow GSSAPI

	don't forget to restart it, use a script provider to set it , or create it with veewee or snapshot it

	- Tune Vagrantfile

	vb.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]

Alan Smith alanwsmith

how do you map from one range of numbers to another?

Creating Timelapse Video From Photos With FFMPEG

Software

Resources