CAPTCHA: what changed
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| 13 | 1 | ## About | |
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| 3 | + |  According to [wikipedia](https://en.wikipedia.org/wiki/CAPTCHA), *a **CAPTCHA** (a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart") is a type of challenge–response test used in computing to determine whether or not the user is human*. | |
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| 5 | + | The component `TCaptchaLabel` allows to create a CAPTCHA to be used on any LCL form. It displays random characters which are colored and rotated and overlayed by colored lines to impede machine detection of the CAPTCHA text. | |
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| 21 | 7 | ### Author | |
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| 9 | + | Werner Pamler | |
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| 25 | 11 | ### License | |
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| 13 | + | Modified LGPL (with linking exception), like Lazarus LCL. See the file COPYING.modifiedLGPL.txt, included in the Lazarus distribution, for details about the license. | |
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| 29 | 15 | ## Description | |
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| 17 | + | `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 rotated characters and overlaid lines. | |
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| 33 | 19 | ### Methods | |
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| 21 | + | - `function`` Verify(``const`` AText: String): Boolean` - Compares whether the user-provided string `AText` matches the CAPTCHA string and returns `true` in case of an agreement, or `false` otherwise. | |
| 22 | + | - `procedure`` NewCaptcha` - Generates and displays a new CAPTCHA string | |
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| 38 | 24 | ### Properties | |
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| 26 | + | - `Text: String` - CAPTCHA string. The characters of the string are selected randomly from the `UpperCaseChars`, `LowerCaseChars`, `NumericChars` and/or `CustomChars`. | |
| 27 | + | - `NumChars: Integer` - Number of characters in the CAPTCHA, i.e. length of `Text` | |
| 28 | + | - `NumLines: Integer` - Number of lines drawn over the CAPTCHA | |
| 29 | + | - `Font1, Font2: TFont` - Two fonts to be mixed within the CAPTCHA characters randomly | |
| 30 | + | - `MaxAngle: Integer` - Maximum rotation angle (in degrees) for the characters which are rotated by a random angle between `-MaxAngle` and `+MaxAngle` | |
| 31 | + | - `Color: TColor` - 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. | |
| 32 | + | - `UpperCaseChars: String` - Contains the characters among which upper-case characters in the CAPTCHA are selected randomly. UTF8 encoding is supported as usual (and like for the following strings) | |
| 33 | + | - `LowerCaseChars: String` - Contains the characters among which lower-case characters in the CAPTCHA are selected randomly | |
| 34 | + | - `NumericChars: String` - Contains the numeric characters characters for the CAPTCHA | |
| 35 | + | - `CustomChars: String` - Contains non-alpha and non-numeric characters for the CAPTCHA | |
| 36 | + | - `Options: TCaptchaOptions` - This is a set of the following enumerated options which can be combined: | |
| 37 | + | - `coAlphaUpper` - Use upper-case characters as defined by the the `UppercaseChars` string\ | |
| 38 | + | Note: The characters which are hard to distinguish are skipped, O (upper-case o) vs 0 (zero), l (lower-case L) vs I (upper-case I) | |
| 39 | + | - `coAlphaLower` - Use lower-case characters as defined by the `LowercaseChars` string | |
| 40 | + | - `coNumeric` - Use numeric characters as defined by the `NumericChars` string | |
| 41 | + | - `coCustom` - Use special characters as defined by the `CustomChars` string | |
| 42 | + | - `coRotated` - Characters are rotated | |
| 43 | + | - `coFont1` - Font1 is used | |
| 44 | + | - `coFont2` - Font2 is used | |
| 45 | + | - `coLines` - Lines are drawn over the CAPTCHA | |
| 46 | + | - `NewCaptchaEvent: TNewCaptchaEvent` - Enumerated property which determines a short-cut how to create a new CAPTCHA string at runtime: | |
| 47 | + | - `nceNone` - Feature is deactivated; CAPTCHA can only be changed by code. | |
| 48 | + | - `nceClick` - A new CAPTCHA is created when the user clicks on the control | |
| 49 | + | - `nceDblClick` - A new CAPTCHA is created when the user double-clicks on the control. | |
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| 65 | 51 | ## Installation | |
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| 67 | 53 | ### Development version | |
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| 55 | + | The development version (aka trunk) is available at <https://sourceforge.net/p/lazarus-ccr/svn/HEAD/tree/components/captcha/>. Download the package using svn or get the zipped *snapshot* version. | |
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| 57 | + | 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"*. | |
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| 73 | 59 | ### Release version | |
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| 61 | + | The stable release version is distributed via the [[Online Package Manager|Online-Package-Manager (OPM)]]: Check the item "Captcha" in the OPM list, click "Install" and confirm the prompt to rebuild the IDE. | |
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| 77 | 63 | --- | |
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| 64 | + | *From the Free Pascal wiki, page "CAPTCHA", as it stood on 2021-10-01 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).* |