PHP script to render a single transparent pixel (PNG or GIF)

Question

I have to create a PHP that will return an image stream of one transparent dot (PNG or GIF)

Could you point me to an easy to use solution?

Answer 1

In PHP 5.4 and higher it is possible to use hex2bin, which is roughly two times faster than base64_decode (tested with the blank GIF file below). The code to output images would be:

Transparent 1x1 PNG:

header('Content-Type: image/png');
die(hex2bin('89504e470d0a1a0a0000000d494844520000000100000001010300000025db56ca00000003504c5445000000a77a3dda0000000174524e530040e6d8660000000a4944415408d76360000000020001e221bc330000000049454e44ae426082'));

Transparent 1x1 GIF:

header('Content-Type: image/gif');
die(hex2bin('47494638396101000100900000ff000000000021f90405100000002c00000000010001000002020401003b'));

You can easily convert base64 encoded data into hexadecimal:

echo bin2hex(base64_decode($data));

Or a file:

echo bin2hex(base64_decode(file_get_contents($filename)));

However, using the native PHP escape method suggested by @Lukas Liesis is the fastest, about 12.5 times faster than base64_decode, according to my benchmark. And it would work with virtually any version of PHP. Here are the code snippets:

Transparent 1x1 PNG:

header('Content-Type: image/png');
die("\x89\x50\x4e\x47\x0d\x0a\x1a\x0a\x00\x00\x00\x0d\x49\x48\x44\x52\x00\x00\x00\x01\x00\x00\x00\x01\x01\x03\x00\x00\x00\x25\xdb\x56\xca\x00\x00\x00\x03\x50\x4c\x54\x45\x00\x00\x00\xa7\x7a\x3d\xda\x00\x00\x00\x01\x74\x52\x4e\x53\x00\x40\xe6\xd8\x66\x00\x00\x00\x0a\x49\x44\x41\x54\x08\xd7\x63\x60\x00\x00\x00\x02\x00\x01\xe2\x21\xbc\x33\x00\x00\x00\x00\x49\x45\x4e\x44\xae\x42\x60\x82");

Transparent 1x1 GIF:

header('Content-Type: image/gif');
die("\x47\x49\x46\x38\x39\x61\x01\x00\x01\x00\x90\x00\x00\xff\x00\x00\x00\x00\x00\x21\xf9\x04\x05\x10\x00\x00\x00\x2c\x00\x00\x00\x00\x01\x00\x01\x00\x00\x02\x02\x04\x01\x00\x3b");

Creating such a string is easy with regular expressions (as it's done once, it doesn't have to work fast):

echo preg_replace('/../','\\x\0',bin2hex($data));

Or from a file:

echo preg_replace('/../','\\x\0',bin2hex(file_get_contents($filename)));