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PHP: Generating transparent PNG fillers

Torleif — Sun, 13 Jun 2010 13:45:38 +0000

So, I was fooling around the other day with an HTML table and wanted to make the odd rows slightly darker. Figured I could use for example an 80% transparent black PNG to do that (or could have just assigned a darker color, but where’s the fun in that?). Either way, ended up making a little something that I thought I could share just for the fun of it. I learned a few things, so maybe someone else can too

So, here’s how to make a small transparent PNG filler image on-the-fly using PHP

I called the script fill.php, and the first line looks like this:

header('Content-type: image/png');

This starts the php script and sets the content-type to image/png which means the web browser will that we are an image and not an html file which usually is the default.

Next up we get the parameters from the user:

$p = $_GET + array
(
'r' => 0,
'g' => 0,
'b' => 0,
'a' => 0,
);

Here I create an array with default values and merge it with the $_GET array so that values from the user will override the default values. This means we are sure we have all the values we need and that the user only have to specify the ones he want to.

The r, g and b values should be a number between 0 and 255 and the alpha value should be between 0 and 127. So, next up we need to make sure that that is the case so we don’t use some other bogus we might have gotten:

array_walk($p, function (&$item, $key)
{
$item = min(max(0, $item), $key == 'a' ? 127 : 255);
});

This goes through each parameter and makes sure it is a number between 0 and 255 (or 127 for the alpha).

Since we have what we need now, we can start with creating our image:

$img = @imagecreatetruecolor(15, 15)
or die('Cannot Initialize new GD image stream');

We also need to set a flag that we want to use full alpha channel information (as opposed to single-color transparency) in this image:

imagesavealpha($img, true);

We are now ready to fill our image with the color we are asked for:

$color = imagecolorallocatealpha($img,
$p['r'],
$p['g'],
$p['b'],
$p['a']);
imagefill($img, 0, 0, $color);

And finally output the result and destroy the image resource we have been working with:

imagepng($img, null, 9);
imagedestroy($img);

And that’s actually all there is to it!

The complete code looks like this:

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header('Content-type: image/png');

// Replace default parameters with user input
$p = $_GET + array
(
'r' => 0,
'g' => 0,
'b' => 0,
'a' => 0,
);

// Make sure they are within limits
// (colors: 0-255, alpha: 0-127)
array_walk($p, function (&$val, $key)
{
$val = min(max(0, $val), $key == 'a' ? 127 : 255);
});

// Create image
$img = @imagecreatetruecolor(15, 15)
or die('Cannot Initialize new GD image stream');

// Use full alpha channel information
imagesavealpha($img, true);

// Fill image
$color = imagecolorallocatealpha($img,
$p['r'],
$p['g'],
$p['b'],
$p['a']);
imagefill($img, 0, 0, $color);

// Output result
imagepng($img, null, 9);
imagedestroy($img);

If you want to check out a working demo version of this, you can test out my little testing tool I created while having fun with this at tools.geekality.net/filling-factory

Let me know what you think! And as usual, please let me know if you see something that is wrong or could be improved or anything like that

WP Latex test page

Torleif — Thu, 24 Sep 2009 16:28:41 +0000

So, as my brother noticed in my last post, I have some cool equations here. The brilliance behind it is something called LaTeX, which can be used in WordPress blogs thanks to the WP LaTeX plugin.

I am a total LaTeX newbie though, so I often struggle a bit with… getting it right. Trying it out by previewing WordPress posts is sloooow, so I decided to create myself a simple test-rig. A simple web page with a form and a button.

Let me know if you like it: tools.geekality.net/wp-latex

Helpful Unix and Mac commands

Torleif — Sat, 27 Dec 2008 16:30:35 +0000

I am for the most part a Windows user. I was kind of moving towards Linux, Ubuntu in particular, but that ship pretty much sailed when I got my hands on Windows 7. Awesome, awesome operating system. But, I still have to use some Unix and Mac systems once in a while. And then there are certain commands that I often use, but always forget since it usually goes a bit of time between times I do it. So, what follows is basically just a list of commands that I keep forgetting, but keep having to look up again.

Remove .DS_Store files

Removes all those ~~stupid~~annoying DS_Store files that Mac litters around wherever it goes. Works in the current directory and downwards.

find . -name *DS_Store -exec rm {} \;

Recursivly download a whole website

wget -T 5 -t 0 -m -np -w 5 --random-wait -E -k -p -P output/dir http://website

Show hidden files on in OS X

Swap TRUE with FALSE to hide them again. The second line kills and relaunches Finder.

defaults write com.apple.Finder AppleShowAllFiles TRUE
killall Finder && open /System/Library/CoreServices/Finder.app

Redirect std error to std out

ls -ld /home /qwerty 1>log 2>&1

Compress and decompress files

# Compress
tar czvf archive.tar.gz filedir filedir
tar cjvf archive.tar.bz2 filedir filedir

# Decompress
tar xzvf archive.tar.gz
tar xjvf archive.tar.bz2

Find open files

lsof | grep filename

SSH filesystem on Mac

First download and install sshfs for Mac OS X. Then to mount

mkdir -p ~/sshfs/server1
/Applications/sshfs/bin/mount_sshfs server1_hostname: ~/sshfs/server1

And to unmount (and uninstall the sshfs)

umount ~/sshfs/server1
sudo /Applications/sshfs/uninstall.sh