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Securimage's configuration options control colours, fonts, distortion, backgrounds, and line count. Same library, different output.

Configuration Examples

Default Style

Out of the box: coloured characters on white, moderate distortion, a few arc lines. Needs GD and nothing else.

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

Quickest way to test: download Securimage from GitHub, edit securimage_show.php, and open it in your browser.

The full customisation guide covers every property.

Not Sold on Image CAPTCHAs?

They add friction. If you'd rather go invisible, see the CAPTCHA alternatives guide—Cloudflare Turnstile, hCaptcha, honeypot techniques, rate limiting.