DEPRECATION WARNING

This documentation is not using the current rendering mechanism and is probably outdated. The extension maintainer should switch to the new system. Details on how to use the rendering mechanism can be found here.

Administration

To install the extension just install it as usual using the Extension Manager. While you are installing the extension you have some options by which you can configure the captcha image to be generated.

Setting: Basic

  • Use TTF [basic.useTTF] When set all letters will get rendered using "imagettftext".

Warning

The support for non-TTF rendering has been dropped. Always keep this checkbox active.

  • Image width [basic.imgWidth] The width of the captcha image in pixels
  • Image height [basic.imgHeight] The height of the captcha image in pixels
  • Captcha chars [basic.captchaChars] The number of characters of which the captcha shall consist.

Setting: Characters

  • No numbers [characters.noNumbers] Setting this option will remove any number character (0-9) from the list of characters (a-zA-z0-9) from which the captcha is generated.
  • No lowercase characters [characters.noLower] Setting this option will remove any lowercase characters (a-z) from the list of characters (a-zA-z0-9) from which the captcha is generated.
  • No uppercase characters [characters.noUpper] Setting this option will remove any uppercase characters (a-z) from the list of characters (a-zA-z0-9) from which the captcha is generated.
  • Exclude chars [characters.excludeChars] The characters listed in this field will not get used for rendering the captcha. By default this field already contains a preset which consists of characters that can easily get taken for each other and upper/lower case characters which look quite the same.

Setting: Rendering

  • Y Offset [rendering.ypos] The numer of pixels which the first character is away from the top left corner in vertical direction. Incrementing this value moves the rendered captcha "down".
  • Letter spacing [rendering.letterSpacing] This value determines the space in pixels between each cpatcha character.
  • Angle [rendering.angle] The angle in degree which each letter is rotated maximally clock-, or counterclock-wise. The actual angle for each character will get determined randomly for each single letter.
  • X Difference [rendering.diffx] The limit in pixels by which each letter is shifted to the left/right maximally. By default this value is "0" as those values can sum up and result in quite different width of the generated captcha which in turn has to get taken account for when setting the image width.
  • Y Difference [rendering.diffy] The limit in pixels by which each letter is shifted up/down maximally. The actual amount of pixels will get determined randomly for each letter.
  • X Offset [rendering.xpos] The numer of pixels which the first character is away from the top left corner in horizontal direction. Incrementing this value moves the rendered captcha "right".

Setting: Background

  • Noises [background.noises] Determines the number of "obfuscating" ellipses that will get drawn on the background.
  • Background color [background.backcolor] The background color of the captcha in a format like used in CSS (#12ab34, #ff0000 for red, etc.)
  • Obfuscation color [background.obfusccolor] The color of the obfuscating ellipses.

Setting: Font

  • Text color [font.textcolor] The color of the captcha letters.
  • Font size [font.fontSize] The font size in pixels.
  • Font file [font.fontFile] A path to the TTF file which shall be used to render the captcha characters. By default the captcha extension comes shipped with a "Vera.ttf" font which is an open source variant of "Verdana".
  • Bold text [basic.bold] When set the text in the generated captcha image will be somewhat more bold and easier to read. But keep in mind, that the sense of a captcha is to make the text unrecognizable for computer spam programs.