20c03-1.php

来自「介绍PHP5的给类型函数应用」· PHP 代码 · 共 69 行

<?php
// Generate a CAPTCHA graphic.

// Start off by defining a new image, define our dimensions
$w = 300;
$h = 50;
$gfx = imagecreatetruecolor($w, $h);

// Turn on antialiasing so that curvy things look better.
imageantialias($gfx, true);

// Declare white as our background color:
$white = imagecolorallocate($gfx, 255, 255, 255);
imagefilledrectangle($gfx, 0, 0, $w-1, $h-1, $white);

// Generate a 6-8 character string of only uppercase characters:
$str = '';
foreach (range(0, rand(5,7)) as $r) {
	$str .= chr(rand(65,90));
}

// Now, divide the width by the length to find approximate positions
// for each character to appear:
$pos = $w / strlen($str);

// Now we can loop through printing out these characters
foreach(range(0, strlen($str) - 1) as $s) {
	// Randomly generate a grayscale color, but only 'dark' ones
	$shade = rand(0, 100);
	
	// Declare this color:
	$tmpgray = imagecolorallocate($gfx, $shade, $shade, $shade);
	
	// Now, we can draw this one character, messing with it as much as
	// possible while we do so:
	imagettftext($gfx,     // The graphics object to draw on
		rand($h/3, $h/2),  // Font Size, between 1/3 and 1/2 full height
		rand(-60, 60),     // Slant angle, highly variable
		$s*$pos+($pos*.4), // X, stabilized at equal places
		rand($h*.5,$h*.7), // Y, Variable between half or a bit lower.
		$tmpgray,          // The color to do it with - gray
		'arial',           // The font to use.
		$str{$s});         // Just print this character
}

// Now crosshatch the entire background with various shades of gray lines
// Loop from negative height to width to ensure we draw over everything
foreach(range(-$h, $w, 5) as $x) {
	// Randomly generate a shade of gray, but not the darkest ones.
	$shade = rand(50,254);
	$tmpgray = imagecolorallocate($gfx, $shade, $shade, $shade);
	
	// Now draw two lines from here, One diagonally down, one diagonally up
	// at slightly random angles
	imageline($gfx, $x, 0, $x+$h+rand(0,25), $h-1, $tmpgray);
	imageline($gfx, $x, $h-1, $x+$h+rand(0,25), 0, $tmpgray);
}

// We are now done with our manipulations.  Before we output this, set
// the actual string as part of a session variable:
session_start();
$_SESSION['captcha'] = $str;

// Let the browser know that we are going to output this as a PNG
header('Content-type: image/png');

// And then output our new image:
imagepng($gfx);
?>