CAPTCHA Gallery

Securimage produces a wide range of image styles through its configuration options. The same core library generates dramatically different-looking CAPTCHAs depending on the settings you use — colors, fonts, distortion level, background images, and the number of confounding lines drawn over the characters.

The gallery below illustrates some of the key configuration dimensions:

Configuration Examples

Default Style

Out of the box, Securimage renders coloured characters on a white background with moderate distortion and a few arc lines. The default settings work on all servers with GD installed.

High Contrast (Black on White)

<?php
// securimage_show.php
$img->image_bg_color = new Securimage_Color('#ffffff');
$img->text_color     = new Securimage_Color('#000000');
$img->line_color     = new Securimage_Color('#666666');
$img->perturbation   = 0.6;

Dark Background

<?php
$img->image_bg_color = new Securimage_Color('#1a1a2e');
$img->text_color     = new Securimage_Color('#e0e0e0');
$img->line_color     = new Securimage_Color('#4a4a6a');
$img->perturbation   = 0.75;
$img->num_lines      = 8;

Minimal (Low Friction for Accessibility)

<?php
$img->image_bg_color = new Securimage_Color('#fafafa');
$img->text_color     = new Securimage_Color('#333333');
$img->perturbation   = 0.4;   // less distortion
$img->num_lines      = 2;     // fewer lines
$img->code_length    = 4;     // shorter code
$img->charset        = 'ABCDEFGHKLMNPRSTUVWXYZ'; // no ambiguous chars

Numbers Only (Easier to Type)

<?php
$img->charset      = '23456789'; // no 0 or 1 (ambiguous)
$img->code_length  = 6;
$img->perturbation = 0.8;

Randomized Properties (Harder for Bots)

<?php
$img->code_length  = rand(4, 7);
$img->num_lines    = rand(4, 12);
$img->perturbation = (rand(60, 90) / 100); // 0.6 to 0.9

Generate Your Own

The best way to see what a configuration looks like is to try it. Download Securimage from GitHub, modify securimage_show.php, and load it directly in your browser.

See the full customisation guide for a complete list of all configurable properties.

Considering a Different Approach?

Image CAPTCHAs like Securimage add friction to your forms. If you're looking for something invisible or more modern, see our CAPTCHA alternatives guide — covering Cloudflare Turnstile, hCaptcha, honeypot techniques, and more.