phpBB API Documentation
Class

captcha

class captcha

Main non-gd captcha class

Properties

$filtered_pngs
$width
$height

Methods

captcha()

Define filtered pngs on init
execute($code, $seed)

Create the image containing $code with a seed of $seed
randomise($scanline, $width)

This is designed to randomise the pixels of the image data within certain limits so as to keep it readable.
png_chunk($length, $type, $data)

This creates a chunk of the given type, with the given data of the given length adding the relevant crc
create_png($raw_image, $width, $height)

Creates greyscale 8bit png - The PNG spec can be found at http://www.libpng.org/pub/png/spec/PNG-Contents.html we use png because it's a fully recognised open standard and supported by practically all modern browsers and OSs
define_filtered_pngs()

png image data Each 'data' element is base64_encoded uncompressed IDAT

Details

at line 33
public captcha()

Define filtered pngs on init

at line 42
public execute($code, $seed)

Create the image containing $code with a seed of $seed

Parameters

$code
$seed

at line 117
public randomise($scanline, $width)

This is designed to randomise the pixels of the image data within certain limits so as to keep it readable.

It also varies the image width a little

Parameters

$scanline
$width

at line 147
public png_chunk($length, $type, $data)

This creates a chunk of the given type, with the given data of the given length adding the relevant crc

Parameters

$length
$type
$data

at line 160
public create_png($raw_image, $width, $height)

Creates greyscale 8bit png - The PNG spec can be found at http://www.libpng.org/pub/png/spec/PNG-Contents.html we use png because it's a fully recognised open standard and supported by practically all modern browsers and OSs

Parameters

$raw_image
$width
$height

at line 241
public define_filtered_pngs()

png image data Each 'data' element is base64_encoded uncompressed IDAT