Developing a Captcha Application with an Image Generator Class with PHP 5 - Developing a basic noisy image generation system
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As I stated in the section that you just read, the best way to demonstrate how the two previously defined classes can be put to work together to implement a simple noisy image system is by developing an example where you can see how they function in tandem.
So first I will list the complete source code corresponding to the two classes. Here it is:
// define 'ImageGenerator' class
class ImageGenerator{
private $width=400;
private $height=300;
private $bgColor='0,0,0';
private $textColor='255,255,255';
private $inputString='Default Input String';
private $bgImage=NULL;
private $img;
// initialize input arguments
public function __construct($inputString='Default Input String'){
if(strlen($inputString>255)){
throw new Exception('Invalid length for input string.');
}
$this->inputString=$inputString;
}
public function setImageWidth($width=400){
if(!is_int($width)&&$width>800){
throw new Exception('Invalid width for image stream.');
}
$this->width=$width;
}
public function setImageHeight($height=300){
if(!is_int($width)&&$height>600){
throw new Exception('Invalid height for image stream.');
}
}
public function setImageBgColor($bgColor='0,0,0'){
if(!preg_match("/^d{1,3},d{1,3},d{1,3}$/",$bgColor)){
throw new Exception('Invalid format for background color.');
}
$this->bgColor=$bgColor;
}
public function setImageTextColor($textColor='255,255,255'){
if(!preg_match("/^d{1,3},d{1,3},d{1,3}$/",$textColor)){
throw new Exception('Invalid format for text color.');
}
$this->textColor=$textColor;
}
public function setBgImage($bgImage='default.gif'){
if(!file_exists($bgImage)){
throw new Exception('Invalid background image.');
}
$this->bgImage=$bgImage;
}
public function setImageFont($font){
if(!file_exists($font)){
throw new Exception('Invalid image font.');
}
$this->font=$font;
}
// create image stream
public function displayImageStream(){
$this->img=$this->bgImage!=NULL?imagecreatefromgif($this-
>bgImage):imagecreate($this->width,$this->height);
$bgColor=explode(',',$this->bgColor);
$textColor=explode(',',$this->textColor);
// allocate background color on image stream
imagecolorallocate($this->img,$bgColor[0],$bgColor[1],$bgColor
[2]);
// allocate text color on image stream
$textColor=imagecolorallocate($this->img,$textColor[0],$textColor
[1],$textColor[2]);
// load font
if(!imagestring($this->img,5,$this->width/2-strlen($this-
>inputString)*5,$this->height/2-5,$this->inputString,$textColor)){
throw new Exception('Error creating image text');
}
header("Content-type: image/gif");
// display image
imagegif($this->img);
// free up memory
imagedestroy($this->img);
}
}
class RandomGenerator{
private $length;
private $chars="ABCDEFGHIJKLMNPQRSTUVWXYZ123456789";
public function __construct($length=4){
if(!is_int($length)||$length<1){
throw new Exception('Invalid length for random string.');
}
$this->length=$length;
}
public function getRandomValue(){
$rndstr='';
$maxvalue=strlen($this->chars)-1;
for($i=0;$i<$this->length;$i++){
$rndstr.=substr($this->chars,rand(0,$maxvalue),1);
}
return $rndstr;
}
}
Now, take a look at the following code sample, which shows how to embed dynamically several four-digit random strings into a predefined image stream:
try{
// create new instance of 'RandomGenerator' class
$rnd=new RandomGenerator();
// create new instance of 'ImageGenerator' class
$imgGen=new ImageGenerator($rnd->getRandomValue());
// display image stream on the browser
$imgGen->displayImageStream();
}
catch(Exception $e){
echo $e->getMessage();
exit();
}
There you have it! By using the pair of PHP 5 classes that I built previously, it was feasible to develop a fully-functional noisy image application, which can be easily incorporated into any existing web site to prevent (at least partially) automated submissions of its web forms.
Final thoughts
Unfortunately, this series has come to and end. Hopefully the whole learning experience has been positive, since you learned how to utilize the functionality provided by some of the most important functions packaged with the GD extension to build an image generator class. As you have seen, such a class can be really handy for creating, among other useful things, a simple and efficient noisy image system.
See you in the next PHP development tutorial!
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