Author Archives: Marco Barnig

WebDAV

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Last Update : July 1, 2012

WebDAV (Web-based Distributed Authoring and Versioning) is a set of methods based on HTTP that facilitates collaboration between users in editing and managing documents and files stored on servers. WebDAV was defined in RFC 4918 by a working group of the Internet Engineering Task Force (IETF).

The WebDAV protocol makes the Web a readable and writable medium. It provides a framework for users to create, change and move documents on a server.

Resources about WebDAV are available at the webdav.org website.

YUI compressor for Javascript and CSS

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The YUI Compressor is a JavaScript compressor which, in addition to removing comments and white-spaces, obfuscates local variables using the smallest possible variable name.

The YUI Compressor is also able to safely compress CSS files. The decision on which compressor is being used is made on the file extension (js or css).

The YUI Compressor is written in Java and relies on Rhino to tokenize the source JavaScript file. It starts by analyzing the source JavaScript file to understand how it is structured. It then prints out the token stream, omitting as many white space characters as possible, and replacing all local symbols by a letter symbol wherever such a substitution is appropriate . The CSS compression algorithm uses a set of finely tuned regular expressions to compress the source CSS file. The YUI Compressor is open-source.

Several GUI’s are available :

Online versions are available at the website of Zileex Media, of  Rodolphe Stoclin and of gpbmike.

WordPress plugin & theme development

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WordPress Codex provides a huge documentation for programmers who want to develop plugins or themes for the WordPress Blog program.

WordPress Plugin: A WordPress Plugin is a set of one or more functions, written in the PHP scripting language, that adds a specific set of features or services to the WordPress weblog, which can be seamlessly integrated with the weblog using access points and methods provided by the WordPress API.

Resources :

WordPress Theme : A WordPress Theme is a collection of files that work together to produce a graphical interface with an underlying unifying design for a weblog. These files are called template files. A Theme modifies the way the site is displayed, without modifying the underlying software. Themes may include customized template files, image files, style sheets, custom pages, as well as any necessary code files and scripts.

Resources :

WordPress Templates : Template files are the building blocks of your WordPress site. They fit together like the pieces of a puzzle to generate the web pages on your site. Some templates are used on all the web pages, while others are used only under specific conditions.

Resources :

Color Gamut

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CIExy1931

In color reproduction, the color gamut is a complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a certain output device. The term gamut was adopted from the field of music, where it means the set of pitches of which musical melodies are composed.

Generally, the color gamut is specified in the hue–saturation plane, as many systems can produce colors over a wide intensity range within their color gamut; in addition, for subtractive color systems, such as printing, the range of intensity available in the system is for the most part meaningless outside the context of its illumination. When certain colors cannot be displayed within a particular color model, those colors are said to be out of gamut.

While processing a digital image, the most convenient color model used is the RGB model. Printing the image requires transforming the image from the original RGB color space to the printer’s CMYK color space. During this process, the colors from the RGB which are out of gamut must be  converted to values within the CMYK space gamut (gamut mapping).

There are several reasonable strategies for performing gamut mappings, these are called rendering intents. Four particular strategies were defined by the International Color Consortium (ICC), with the following names : Absolute Colormetric, Relative Colormetric, Perceptual, Saturation.

Gamuts are commonly represented as areas in the CIE 1931 chromaticity diagram. The accessible gamut depends on the brightness; a full gamut must therefore be represented in 3D space. Systems that use additive color processes usually have a color gamut which is roughly a convex polygon in the hue-saturation plane.

A list of representative color systems ordered from large to small color gamut is shown hereafter :

  • Laser video projector
  • Photographic film
  • CRT Monitor
  • LCD Monitor
  • Television
  • Painting
  • Printing

An interactive Flash demo explaining color gamut mapping is available at the website of the Stanford University. Gamutvision, an gamut viewer, is available from Imatest LCC (Norman Koren).

Different color spaces have been defined for digital image processing : RGB, LAB, CMYK. The sRGB IEC-61966-2.1 color space was conceived as a multipurpose color space standard for consumer digital devices (s stands for standard in sRGB). Other RGB color spaces are Apple RGB, ColorMatch RGB, ProPhoto RGB, Adobe RGB (1988) and PhotGamutRGB. A comparison between sRGB and Adobe RGB is shown at the website of Cambridge in Colour.

DNG : Digital Negative, camera raw data format

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Last update : January 7, 2016

DNG

Digital Negative

Digital Negative (DNG) is an public archival open raw image format owned by Adobe used for digital photography. It was launched in 2004. DNG is based on the TIFF/EP standard format, and mandates significant use of metadata. Exploitation of the file format is royalty free.

Adobe provides the Digital Negative Specification, a free Adobe DNG Converter (version 6.3), which easily translates raw files from many of today’s popular cameras, an SDK (Software Development Kit) and an DNG Profile Editor.

DNG is supported by various camera providers  and photographic software developers (Adobe Photoshop, Adobe Lightroom, …). DNG is also supported by ExifTool, a platform-independent Perl library plus a command-line application for reading, writing and editing meta information in a wide variety of files, developed by Phil Harvey. ExifTool is also available as a stand-alone Windows executable and a Macintosh OS X package. The current version is 10.09 published on January 4, 2016.

Exif, IPTC, XMP

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Last update : August 25, 2013

Exif (Exchangeable image file format) is a specification for the image file format used by digital cameras and scanners. The specification uses the existing JPEG, TIFF Rev. 6.0, and RIFF WAV file formats, with the addition of specific metadata tags. It is not supported in JPEG 2000, PNG, or GIF.

Exif was created by the Japan Electronic Industries Development Association (JEIDA).

The metadata tags defined in the Exif standard cover a broad spectrum :

  • Date and time information
  • Camera settings (camera model and make, orientation, aperture, shutter speed, focal length, metering mode, ISO speed, …)
  • Thumbnails for previewing the picture
  • Geolocation
  • Descriptions
  • Copyright

The most used tool to edit Exif informations is the ExifTool by Phil Harvey. Another very useful tool is PhotoME (Photo Metadata Editor) developped by Jens Duttke which handles also embedded color (.icc) profiles.

There exist other standards to add metadata to files : IPTC (Information Interchange Model),  XMP (Extensible Metadata Platform), … Both standards allow to embed informations about authors, locations, countries, subjects etc in the image files.

IPTC was developed in the early 1990s by the International Press Telecommunications Council (IPTC) to expedite the international exchange of news among newspapers and news agencies (IPTC Photo Metadata Standards : IPTC Core and IPTC Extension). The older IPTC metadata specification (IPTC-IIM) was frozen in 1997, and the IPTC organisation has been recommending the use of the XMP-based IPTC Core specifcation since 2004.

The ExifTool (current version 9.35 released on August 17, 2013) handles also IPTC and XMP metadata. A GUI (ExiftoolGUI : current version 5.15 released on January 8, 2013) for the ExifTool has been developed by Bogdan Hrastnik.

Another great utility allowing to read and write Exif, IPTC and XMP metadata is XnView, developed by Pierre Gougelet. This program handles more than 400 graphic file formats for import and more than 50 formats for export. A new project called XnViewMP (MP stands for multi platform) supports full multicode. Version 0.61 was released on July 18, 2013.

A C++ library and a command line utility to manage image metadata, called Exiv2, is available as free software and with a commercial license, and is used in many projects.The development of Exiv2 is lead by Andreas Huggel. Version Exiv2 0.23 was released on April, 2012.

Tags and other properties of a file can de added or modified in the Windows Explorer Detail Pane or in the Properties Pane.

The following list provides some useful guides about the right use of metadata in images and in other multimedia files :

Modernizr

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last update : 18 January 2012
Modernizr is a small JavaScript library that detects the availability of native implementations for next-generation web technologies. These technologies are new features that stem from the ongoing HTML 5 and CSS 3 specifications. Many of these features are already implemented in at least one major browser. Modernizr tell you whether the current browser has this feature natively implemented or not.

  1. Modernizr tests for over 40 next-generation features, all in a matter of milliseconds;
  2. Modernizr creates a JavaScript object (named Modernizr) that contains the results of these tests as boolean properties;
  3. Modernizr adds classes to the html element that explain precisely what features are and are not natively supported. It allow you to target specific browser functionality in your stylesheet ( if-statements in your CSS ). You don’t actually need to write any Javascript to use it.

I started with version 1.6.  and experienced a problem with Chrome 9 (beta) which was also reported by other people. The current version  2 was released on 1st June 2011.

With the help of the Modernizr library, the website haz.io gives a quick overview of a browser’s support for recent technologies in the world of HTML, CSS and Javascript.

 

How to make an iPhone web app ?

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Tetris web app for iPhone

An iPhone web application (web app) uses Web 2.0 technologies to deliver a focused solution that looks and behaves like a native iPhone application. iPhone web apps run in Safari on iPhone, the unique implementation of Safari that provides full-featured web browsing on iOS-based devices and responds to touch-based gestures.

The Apple Safari Developer / Reference Library provides guides, tutorials, code samples, FAQ’s  and best practices about the creation of web content for iOS devices. The Safari Web Content Guide, the HTML Reference, the CSS Reference and the JavaScript Guide are key documents.

A very useful tutorial about the creation of an off-line Tetris game for an iPhone has been published by Alex Kessinger on the Six Revisions Website. A tutorial about how to install a web app on iPhones has been written by jeshyr on the iTalk Magazine.

There are several tools and frameworks available to build html5/css3 web apps for iPhones or for other mobiles (cross-platforms). A list of a few ones is shown herafter :

  • iWebKit 5 : an outstanding kit with copy and paste elements designed by Christopher Plieger and Johan Van Wilsum to create iPhone web apps.
  • Appcelerator Titanium : an SDK for different application environments. The SDK provides the necessary tools, compilers and APIs for building for the target platform.
  • Sencha Touch : a free HTML5 mobile JavaScript framework that allows you to develop mobile web apps that look and feel native on iPhone and Android touchscreen devices.
  • PhoneGap : an open source development framework for building cross-platform mobile apps with support of core features in iPhone/iPod touch, iPad, Google Android, Palm, Symbian and Blackberry SDKs.
  • Corona : fast and easy development tool for iPhone, iPad and Android games and applications.
  • jQuery Mobile : Touch-Optimized Web Framework for Smartphones & Tablets.
  • iUI: iPhone User Interface Framework
  • Dashcode : part of Apples iPhone SDK

There are also tools and simulators to test created web apps :

  • Bugaboo : an App for debugging web apps on iPhone, iPad, and iPod touch devices, downloadable from the Apple App Store.
  • iPhone  simulator : web browser based simulator

You have to be aware that there are some differences between iPhone native Apps and web apps.

A native App runs code (Objective-C program) on the device and is installable through the App store (if approved by Apple). You have access to all the UI elements the iPhone uses and can do things like 3D which are impossible in the Safari browser. You need a mac to make a native App, but you can make web apps with any platform of your choice.

A web app is accessed via the Safari browser and requires no install. You are just going to a website that has a special stylesheet for the iPhone. Because a web app can also be installed on an iPhone with a custom icon, a custom startup screen, a native look-and-feel and can be used even when the phone is not connected to the Internet, the differences between Apps and web apps are becoming very small.

There are a lot of native Apps that could be run more efficient as web apps. And there are tools to convert a web app into a native App. Make your choice !

iWebKit, jQTouch and iUI

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iWebKit is a file package designed to help you create your own iPhone, iPod Touch and iPad compatible website or webapp.

iWebKit has been specially made for Apple mobile devices. Specific iphone css and html rules compatible with safari’s engine called “webkit” are used. Most browsers won’t be able to open an iWebKit site correctly, currently only chrome and safari do on a desktop PC ( http://demo.iwebkit.net).

iUI and jQTouch are frameworks that include all the css, javascript and images needed to build native looking apps.

jQTouch is a jQuery library, it’s functionality is currently comparable to  jQuery UI.

Manipulating HTTP Headers with .htaccess

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Last update : July 25, 2013

.htaccess is a very ancient configuration file that controls the Web Server running your website, and is a very powerful configuration file. htaccess is sometimes called “HyperText Access” because of its ability to control access of the WWW’s HyperText Transfer Protocol (HTTP) using Password Protection, 301 Redirects, and much much more.

The AskApache website offers a lot of tutorials, tricks and hacks for webmaster and online tools related to .htaccess.

.htaccess tips and tricks are available at the corz.org website.