On PHP Extensions

While teaching PHP I mention the term “extension” quite a lot – but I have realized that this may very well be a confusing term for non-PHPers. While most PHP training courses focus on code, I believe getting to know the PHP engine and environment is almost as important as learning to use the language. Extensions are a big and important part of PHP, but they seem to be a big knowledge gap about them and Googling for articles that explain what extensions are, and how they are used and installed, hardly returns good results. So, as part of my attempt to blog about more basic PHP topics, I’ve decided to try and come up with an overview of PHP extensions.

So what are PHP extensions?

An extension in PHP is in fact a module providing some functionality to the PHP Engine. While the term makes it sound like extensions provide some kind of special functionality, in reality many of the language’s most basic functions and classes are provided in extensions. Many extensions are shipped as part of the default PHP distribution, and some are in fact compiled into PHP in such way that they cannot even be unloaded. Come to think of it, perhaps it is best to think of PHP extensions as “language modules”.

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Imagick: Maintain (fake) transparency when saving as JPEG

I haven’t blogged in a while (have been busy you know), so I’ve decided to share this small piece of knowledge I’ve obtained by experimenting. I wrote a small test app (it’s for a feature of the next version of Zend Server – maybe I’ll share it one day when the API is stable), which does some image manipulation with the ImageMagick extension.

For those of you who don’t know ImageMagick allows one to preform pretty cool stuff on images – except for the usual drawing, conversion, rotation, rescaling etc., it also exposes some API to easily preform neat effects, like drop shadow, round corners and my newest favorite (apparently only available in the very latest builds of the extension) – the Polaroid effect.

In his blog Mikko Koppanen, the author of the ImageMagick PHP extension, shows how to create drop shadows (as well as other neat things – you should check out his blog!), but in his examples Mikko will always save as PNG, which is something I dare to say most web users will not do, and prefer saving as JPEG.

Problem with many of those effects, is that they leave parts of the image as transparent. When saving the picture as JPEG (as I do, since saving as PNG produces too big files), these transparent areas appear as black.

So after some experimenting, I’ve found out that the way to work around this is to composite another opaque layer as your background layer, filled with your background color of choice (white in my case). You will of course loose the ability to place the picture on other background colors and still have a nice “transparency” look – but as long as you stick to the background color you’ve set, it will look great.

Here is a code sample producing the same thumbnail + drop shadow as in Mikko’s example, but saving it with white matte color as JPEG:


$bgColor = '#ffffff'; // End result will have a white background

/* This was taken from Mikko's example */
$im = new Imagick( 'strawberry.png' );
$im->thumbnailImage( 200, null );
$im->roundCorners( 5, 5 );

$shadow = $im->clone();
$shadow->setImageBackgroundColor( new ImagickPixel( 'black' ) );
$shadow->shadowImage( 80, 3, 5, 5 );
$shadow->compositeImage( $im, Imagick::COMPOSITE_OVER, 0, 0 );

/* My addition: clone the entire image again to create the background layer */
$bg = $shadow->clone();

/* I'm using colorFloodFiilImage with high tolerance to paint it all white - maybe there are 'cleaner' ways to do it though */
$bg->colorFloodFillImage($bgColor, 100, '#777777', 0, 0);
$bg->compositeImage($shadow, Imagick::COMPOSITE_OVER, 0, 0);

/* Display the image */
header( "Content-Type: image/jpeg" );
echo $bg;

While there’s another step in the way, and the image will only look good on white backgrounds, you can now save it as a JPEG file with good compression and acceptable file size.

Introducing Glista: Yet another to-do applet for Gtk+

Yes, there are probably a dozen out there, but none of them was just the way I wanted it to be. So I went out and started writing one: Glista.

It’s terribly simple, and I spent not more than a weekend and a couple of evenings writing it. But I have been using it successfully for over a week now and for the first time I am tracking my tasks through a desktop tool – so I’ve decided to release it.

Visit the Glista page at http://prematureoptimization.org/glista for more information.

It is written in C/Gtk+ (so it runs well on GNOME but should work on other desktops, and should also be portable to Mac / Windows). Now, I must say that I am *not* a C programmer. I suck at it in fact. But I enjoy banging my head against the C memory management wall from time to time. If you look at my code and must run to wash your eyes, tell me about it because I want to improve.

I am using the 0.1 release available on the site (and through Google Code) for some time now. I don’t plan to expand it much but there are some fixes / additions I want to add if I find the time in the next few weeks.

Try it out and tell me what you think!

BTW: I used the name “Glista” because of the common “G” prefix for Gtk+/GNOME apps, joined with “list” and an “a” just to make it cooler. A couple of days later I found it it’s actually a word – in many Slavic languages it’s the word for an earthworm, and in Russian it’s sort of the plural form for Glist which is the word for intensinal parasitic worms. Cool!