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Web Wiz CATCHA Image Customisation

The Web Wiz CAPTCHA security image can be customised to both match the colours of your own site and also configure the distortion type and noise levels.

The guidelines bellow describe how you can customise Web Wiz CAPTCHA security image.

  1. Open in notepad the file named 'CAPTCHA_configuration.asp' found in the 'CAPTCHA' directory. Within this file you will find a number of configuration options for Web Wiz CAPTCHA. Further instructions on this page describe how to alter the settings in this file which effect the CAPTCHA image.

  2. All colours used need to be in Hexadecimal, if you do a search of Google for 'Hexadecimal Colours' you will find charts giving you the hexadecimal colour codes.
  3. Locate within the file 'CAPTCHA_configuration.asp' the following section that contains the CAPTCHA image configuration settings:-

    '****                  CAPTCHA Image Settings                      ****

  4. Background, Border, and Character Colours

    The first configuration options are for the CAPTCHA image background colour, border colour, and character colour, which can changed using hexadecimal colour codes by updating the sections shown in bold below.

    'Background Colour
    strCanvasColour = "FFFFFF"

    'Border Colour
    strBorderColour = "999999"

    'Character Colour
    strCharacterColour = "006600"

  5. Random Character Line Placement

    Random line placement is were characters are placed in random above and below the horizontal centre line of the image. This is good way to avoid character detection by automated software. This can be disabled by changing True shown below in bold to False.

    'Random Character Line Placement
    blnRandomLinePlacement = True


  6. Random Character Skewing

    Random character skewing is were characters are randomly skewed, it's a bit like having random characters in italic. This is good way to avoid character detection by automated software by making it harder for automated programs to read the character. This can be disabled by changing True shown below in bold to False.

    'Random Character Skewing
    blnSkewing = True

  7. Noise Settings

    The next two points cover noise. The only part where humans still outperform computers is segmentation. By placing noise into the image it creates background clutter which OCR and automated computer programs find hard distinguish between. Often OCR software will use colour filters to try and remove noise, to prevent this it is good to set noise colours as the same colours as the character and/or background colours.

  8. Pixelation Noise

    Pixelation Noise are were random pixels are changed to a different colour creating noise on the image. Web Wiz CAPTCHA allows you to set two colours and two noise levels for pixelation. Changing the numbers shown below in bold will determine the level of noise, the hexadecimal colours shown in bold set the colours for the two pixelation sets.

    'Pixelation Noise #1
    intNoiseLevel1 = 8
    strNoiseColour1 = "FFFFFF"

    'Pixelation Noise #2
    intNoiseLevel2 = 3
    strNoiseColour2 = "006600"

  9. Noise Lines

    Noise Lines is were random lines at varying angles are drawn across the image. Web Wiz CAPTCHA allows you to set two sets of noise lines in different colours. You can set the number of noise lines that will be applied by changing the numbers shown below in bold, the colours are set using hexadecimal colours codes shown in bold.

    'Noise Lines #1
    intNoiseLines1 = 5
    strNoiseLinesColour1 = "006600"

    'Noise Lines #2
    intNoiseLines2 = 3
    strNoiseLinesColour2 = "FFFFFF"

  10. Once you have finished customising the CAPTCHA image save the 'CAPTCHA_configuration.asp' and test to make sure that your settings are correct. It's important to find a good balance between making the CAPTCHA image so difficult to read that your visitors have a hard time reading it and so easy that it offers no protection against automated programs.

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