phpでキャプチャを自動生成する例

<?php
session_start(); //Set session, must be at the top
$width = 150; //Set the image width to 300 pixels
$height = 40; //set the image height to 40 pixels
$image = imagecreatetruecolor($width, $height); //set the captcha size function
$bgcolor = imagecolorallocate($image, 255, 255, 255); //captcha color RGB is (255,255,255)#ffffff
imagefill($image, 0, 0, $bgcolor); //area fill
$cap_code = "";
for($i=0;$i<4;$i++){
    $fontsize = 7; //set font size
    $fontcolor = imagecolorallocate($image, rand(0,120), rand(0,120), rand(0,120));
    //the larger the number, the lighter the color, here is the dark color 0-120
    $fontcontent = rand(0,9);
    $cap_code.=$fontcontent; //. = continuous definition of variables
    $x = ($i*150/4)+rand(5,10);
    $y = rand(5,10);
    // Set the coordinates
    imagestring($image, $fontsize, $x, $y, $fontcontent, $fontcolor);
}
$_SESSION['code'] = $cap_code; //save to session
//set interfering elements, set snowflake points
for($i=0;$i<300;$i++){
    $inputcolor = imagecolorallocate($image, rand(50,200), rand(20,200), rand(50,200));
    // set the color, 20-200 color is lighter than the number, does not interfere with reading
    imagesetpixel($image, rand(1,149), rand(1,39), $inputcolor);
    // draw a single pixel element
}
//add interfering elements, set the horizontal line (set the color of the line first, before setting the horizontal line)
for ($i=0;$i<4;$i++) {
    $linecolor = imagecolorallocate($image, rand(20,220), rand(20,220),rand(20,220));
    // Set the color of the line
    imageline($image, rand(1,149), rand(1,39), rand(1,299), rand(1,149), $linecolor);
 
}
 
//because in some browsers, the accessed content-type will be text-based (garbled), so we need to set it to the image format type
header('Content-Type:image/png');
imagepng($image); //create the png function
imagedestroy($image); //end the graphics function and eliminate $image

<?php
$iC = new idCode(5,60,30);
$iC->createPNG();

class idCode{
  private $words = array('a','b',
  'c','d','e','f','g','h','i','j','k','l',
  'm','n','o','p','q','r','s','t','u','v',
  'w','x','y','z','A','B','C','D','E','F',
  'G','H','I','J','K','L','M','N','O','P',
  'Q','R','S','T','U','V','W','X','Y','Z',
  '0','1','2','3','4','5','6','7','8','9');
  private $fonts;
  private $count;//captcha character count
  private $height;
  private $width;
  private $path = '... \myfolder\fonts';
  private $keys;

  //construct function
  public function __construct($count,$width,$height){
    $this->count = $count;
    $this->getFonts();
    $this->height = $height;
    $this->width = $width;
  }

  private function getFonts(){
    $dir = dir($this->path);

    while(false ! == ($file = $dir->read()){
        if($file ! = '.' && $file ! = '...') {
          $this->fonts[count($this->fonts)] = basename($file);
        }
    }
    $dir->close();
  }

  private function createKeys(){
    for($i = 0;$i < $this->count;$i++){
      $this->keys[$i]['char'] = $this->words[rand(0,count($this->words)-1)];
      //use font path identifier
      $this->keys[$i]['filename'] = $this->path.'\\'. $this->fonts[rand(0,count($this->fonts)-1)];
    }
  }

  public function createPNG(){
    $this->createKeys();

    //create the canvas and the color blocks
    $bg = imagecreatetruecolor($this->width + 10*2,$this->height + 3*2);//leave 10px blank on both sides,3px top and bottom
    $grey = imagecolorallocate($bg,155,155,155);
    $blue = imagecolorallocate($bg,0x00,0x00,0xff);
    //fill the background
    imagefill($bg,0,0,$grey);
    //add characters
    $pwidth = $this->width/$this->count;
    $x;$y;
    for($i = 0;$i < $this->count;$i++){
      $rotation = rand(-40,40);//deflection angle ±40°
      $fontsize = 33;
      $width_txt;
      $height_txt;

      do{
        $fontsize--;
        $bbox = imagettfbbox($fontsize,$rotation,$this->keys[$i]['filename'],$this->keys[$i]['char']);
        $width_txt = $bbox[2] - $bbox[0];//x 0 2 4 6,y1 3 5 7;lower left, lower right, upper right, upper left
        $height_txt = $bbox[7] - $bbox[1];
      }while($fontsize > 8 && ($height_txt > $this->height || $width_txt > $pwidth));

      $fontcolor = imagecolorallocate($bg,rand(0,255),rand(0,255),rand(0,255));
      $x = 8 + $pwidth*$i + $pwidth/2 - $width_txt/2;//x coordinate base position
      $y = $this->height/2 - $height_txt/2;

      imagettftext($bg,$fontsize,$rotation,$x,$y,$fontcolor,$this->keys[$i]['filename'],$this->keys[$i]['char']);
    }
    // Draw interference lines
    //add interference lines as appropriate to the font
    imageline($bg,0,15,40,10,$blue);
    //Image output header file
    header('Content-type:image/png');
    //output png image
    imagepng($bg);
    //clear cached resources
    imagedestroy($bg);
  }

  public function checkKeys($input){
    if(count($input)! =$this->count){
      return 'ERROR: incorrect length.' ;
    }else{
      for($i=0;$i < $this->count;$i++){
        //0 o O I l 1 calibration, depending on the font selected to determine if manual calibration is required
        if($input[$i] ! = $this->keys[$i]['char']){
          return 'SUCCESS.';
        }else{
          return 'ERROR: Please enter the correct verification code.' ;
        }
      }
    }
  }
}
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