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Visual CAPTCHA component for Lazarus
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Description
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The component TCaptchaLabel descends from TGraphicControl and contains its own
drawing routine. Just place it on the form and use it. It displays a random
string with slanted characters and overlaid lines.
The method Verify() checks whether a user-provided string matches the
captcha string and returns true.
There are several properties to define its behaviour:
* NumChars: Number of characters in the captcha
* NumLines: Number of lines drawn over the captcha
* Font1, Font2: two fonts to be mixed within the captcha randomly
* MaxAngle: maximum rotation angle for the characters which are rotated by a
random angle between -MaxAngle and +MaxAngle
* Color: the background color of the area of the control covered by the captcha.
Character and line colors are selected such that a minimum brightness difference
to the background color is achieved.
* Options: This is a set of the following options which can be combined:
* coAlphaUpper: Use uppercase characters as defined by the the UppercaseChars string
* coAlphaLower: Use lowercase characters as defined by the LowercaseChars string
* coNumeric: Use numeric characters as defined by the NumericChars string
(the characters which are hard to distinguish are skipped,
zero vs uppercase O, lowercase L vs upper case I)
* coCustom: Use special characters as defined by the CustomChars string
* coRotated: Characters are rotated
* coFont1: Font1 is used
* coFont2: Font2 is used
* coLines: Lines are drawn over the captcha
* NewCaptchaEvent: Enumerated property for how to quickly select of a new captcha
string at runtime:
* nceNone: deactivated; captcha can only be changed by code.
* nceClick: a new captcha is created when the user clicks on the control
* nceDblClick: a new captcha is created when the user double-clicks on the control.
Installation
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* Load the package file captcha_pkg.lpk into the Lazarus Package Editor and
click "Use" > "Install" to rebuild the Lazarus IDE. When Lazarus restarts you
find the new component in the palette "Misc".
License
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LGPL with linking exception, like the Lazarus LCL.
See the file COPYING.modifiedLGPL.txt, included in the Lazarus distribution,
for details about the license.
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