Generate Captcha Image PHP

Question

I want to generate Captcha Image using PHP imagettftext. And following is my code. It gives an empty image. I want to resolve this issue.

I have tested the code but was unable to find why the image is not bieng showed although my random text is being passed to the function of captcha image generation.

<?php

    function generateRandomString($length = 10) {
        $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        $randomString = '';
        for ($i = 0; $i < $length; $i++) {
            $randomString .= $characters[rand(0, strlen($characters) - 1)];
        }
        return $randomString;
    }

    function generateCaptchaImage($text = 'good'){
        echo $text;
        echo 'OK';
        // Set the content-type
        header('Content-Type: image/png');

        $width = 200;
        $height = 30;
        $font = 'ThisisKeSha.ttf';

        // Create the image
        $im = imagecreatetruecolor($width, $height);

        //ADD NOISE - DRAW background squares
        $square_count = 6;
        for ($i = 0; $i < 10; $i++) {
          $cx = (int)rand(0, $width/2);
          $cy = (int)rand(0, $height);
          $h  = $cy + (int)rand(0, $height/5);
          $w  = $cx + (int)rand($width/3, $width);
          imagefilledrectangle($im, $cx, $cy, $w, $h, $white);
        }

        //ADD NOISE - DRAW ELLIPSES
        $ellipse_count = 5;
        for ($i = 0; $i < $ellipse_count; $i++) {
          $cx = (int)rand(-1*($width/2), $width + ($width/2));
          $cy = (int)rand(-1*($height/2), $height + ($height/2));
          $h  = (int)rand($height/2, 2*$height);
          $w  = (int)rand($width/2, 2*$width);
          imageellipse($im, $cx, $cy, $w, $h, $grey);
        }

        // Add the text
        imagettftext($im, 20, 0, 10, 20, $black, $font, $text);

        imagepng($im);

    }

    $randomString = generateRandomString();
    generateCaptchaImage($randomString);

    ?>

Answer 1

It's a easy way to create captacha in PHP, You can try this,

<?php
@session_start();
header("Content-type: image/png");
$_SESSION["captcha"] = substr(md5(time()),0,5);
$im = imagecreate(110, 30);
$white = imagecolorallocate($im, 244, 255, 255);
$red = imagecolorallocate($im, 255, 255, 255);
$black = imagecolorallocate($im, 0, 0, 0);
$size = $_SESSION["captcha"];
$text = "$size";
$font = 'comic.TTF';
imagettftext($im, 20, 0, 25, 20, $red, $font, $text);
imagettftext($im, 20, 0, 25, 20, $black, $font, $text);
imagepng($im);
imagedestroy($im);
?>

php session used on this. Here is more details about Captcha in PHP

Answer 2

Try this code;

<?php
    function generateRandomString($length = 10) {
        $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        $randomString = '';
        for ($i = 0; $i < $length; $i++) {
            $randomString .= $characters[rand(0, strlen($characters) - 1)];
        }
        return $randomString;
    }
    function generateCaptchaImage($text = 'good'){
        // Set the content-type
        header('Content-Type: image/png');
        $width  = 200;
        $height = 30;
        // Create the image
        $im = imagecreatetruecolor($width, $height);

        // Create some colors
        $white  = imagecolorallocate($im, 255, 255, 255);
        $grey   = imagecolorallocate($im, 128, 128, 128);
        $black  = imagecolorallocate($im, 0, 0, 0);
        imagefilledrectangle($im, 0, 0, 399, 29, $white);

        //ADD NOISE - DRAW background squares
        $square_count = 6;
        for($i = 0; $i < $square_count; $i++){
            $cx = rand(0,$width);
            $cy = (int)rand(0, $width/2);
            $h  = $cy + (int)rand(0, $height/5);
            $w  = $cx + (int)rand($width/3, $width);
            imagefilledrectangle($im, $cx, $cy, $w, $h, $white);
        }

        //ADD NOISE - DRAW ELLIPSES
        $ellipse_count = 5;
        for ($i = 0; $i < $ellipse_count; $i++) {
          $cx = (int)rand(-1*($width/2), $width + ($width/2));
          $cy = (int)rand(-1*($height/2), $height + ($height/2));
          $h  = (int)rand($height/2, 2*$height);
          $w  = (int)rand($width/2, 2*$width);
          imageellipse($im, $cx, $cy, $w, $h, $grey);
        }

        // Replace path by your own font path
        $font = 'ThisisKeSha.ttf';

        // Add some shadow to the text
        imagettftext($im, 20, 0, 11, 21, $grey, $font, $text);

        // Add the text
        imagettftext($im, 20, 0, 10, 20, $black, $font, $text);

        // Using imagepng() results in clearer text compared with imagejpeg()
        imagepng($im);
        imagedestroy($im);
    }

    $randomString = generateRandomString();
    generateCaptchaImage($randomString);
?>

You didnt generated the colors $white, $black and $grey . Also the font must be there in the same folder of this php file.

Answer 3

Nice Captcha image generator:

class captcha{
    public static function create(){

        $image = imagecreatetruecolor(160, 40);
        imagefilledrectangle($image, 0, 0, 160, 40, imagecolorallocate($image, 244, 245, 245));

        $code="";
        for($i=0;$i<6;$i++){
            $color = imagecolorallocate($image, rand(160,230), rand(160,240), rand(160,250));
            imageline($image, rand(10,140), rand(2,35), rand(10,140), rand(5,35), $color) ;
        }
        for($i=1;$i<6;$i++){
            $color = imagecolorallocate($image, rand(50,150), rand(50,140), rand(50,150));
            $char = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
            $num = $char[rand(0, strlen($char)-1)];
            $code .= $num;
            //use a proper font file like verdana.ttf and change the font name at bellow
            imagefttext($image, rand(14, 18), rand(-10,40), $i*25, rand(24,34), $color, __DIR__."/verdana.ttf", $num);
        }

        imagejpeg($image,"cap.jpg");

    }
}    

captcha::create();

echo "<img src=\"cap.jpg\">";

Answer 4

Solved from comments

• $white and $black are not defined.
• Remove echo $text; and echo 'OK';.
• Is ThisisKeSha.ttf on your server and in the same directory as this?

$white and $black were not defined.