php生成图片验证码

起初，有一个在php.ini 看看gd库是不是开启的,
下一步，我们会考虑每一个细节的图像生成步骤。
//Send a generated image to the browser
create_image();
exit();

function create_image()
{
    //Let's generate a totally random string using md5
    $md5 = md5(rand(0,999));
    //We don't need a 32 character long string so we trim it down to 5
    $pass = substr($md5, 10, 5);

    //Set the image width and height
    $;
    $; 

    //Create the image resource
    $image = ImageCreate($width, $height); 

    //We are making three colors, white, black and gray
    $white = ImageColorAllocate($image, 255, 255, 255);
    $black = ImageColorAllocate($image, 0, 0, 0);
    $grey = ImageColorAllocate($image, 204, 204, 204);

    //Make the background black
    ImageFill($image, 0, 0, $black);

    //Add randomly generated string in white to the image
    ImageString($image, 3, 30, 3, $pass, $white);

    //Throw in some lines to make it a little bit harder for any bots to

break
    ImageRectangle($image,0,0,$width-1,$height-1,$grey);
    imageline($image, 0, $height/2, $width, $height/2, $grey);
    imageline($image, $width/2, 0, $width/2, $height, $grey);
 
    //Tell the browser what kind of file is come in
    header("Content-Type: image/jpeg");

    //Output the newly created image in jpeg format
    ImageJpeg($image);
   
    //Free up resources
    ImageDestroy($image);
}
?>

验证码调用方法

src="generate_image.php" >