php gd实现简单图片验证码与图片背景文字水印

1、让水印文字铺满图片：

大致效果：

代码：

<?php
function appendspreadtextmark($imagedir, $marktext)
{
    $fontfile = "simsun.ttf";
    $info = getimagesize($imagedir);
    $imwidth = $info[0];
    $imheight = $info[1];
    $type = $info[2];//1 = gif，2 = jpg，3 = png，4 = swf，5 = psd，6 = bmp，7 = tiff(intel byte order)，8 = tiff(motorola byte order)，9 = jpc，10 = jp2，11 = jpx，12 = jb2，13 = swc，14 = iff，15 = wbmp，16 = xbm
    $ext = image_type_to_extension($type, false);
    $mime = $info['mime'];
    
    $imgcrefunc = "imagecreatefrom".$ext;
    $imgres = $imgcrefunc($imagedir);
    
    $picrangelimit = $imheight > $imwidth ? $imwidth : $imheight;
    $fintsize = (int)($picrangelimit / 50);
    if ($fintsize < 5) {
        $fintsize = 5;
    }
   
    $textcolor = imagecolorallocatealpha($imgres, 0, 0, 0, 100);

    $charcount = mb_strlen($marktext, 'utf-8');
    $steplengthx = $fintsize * 4;
    $steplengthy = (int)($fintsize * $charcount * 1.2);
    $numx = (int)($imwidth / $steplengthx) + 1;
    $numy = (int)($imheight / $steplengthy) + 1;
    $pointleft = 0;
    $pointbottom = $steplengthy;
    for ($iny = 0; $iny < $numy; $iny ++) {
        $pointleft = 0;
        for ($inx = 1; $inx < $numx; $inx ++) {
            imagettftext($imgres, $fintsize, 45, $pointleft, $pointbottom, $textcolor, $fontfile, $marktext);
            $pointleft += $steplengthx;
        }
        $pointbottom += $steplengthy;
    }
    
    
    header('content-type:' . $mime);
    $imgrespfunc = 'image' . $ext;
    $imgrespfunc($imgres);
    imagedestroy($imgres);
}

$imagedir = "pic.jpg";
$marktext = "水印内容";
appendspreadtextmark($imagedir, $marktext);

 

2、简单验证码效果：

代码：

<?php
//创图像
$im = @imagecreatetruecolor(500, 150) or die("cannot initialize new gd image stream");
//分配颜色
$backgroundcolor = imagecolorallocate($im, 0, 0, 0);//第一个分配的颜色默认为背景
$textcolor = imagecolorallocate($im, 0, 0, 255);
//画像素点
for ($i=0; $i<500; $i++)
{
    imagesetpixel($im, rand(0, 500), rand(0,150), $textcolor);
}
$textstr = '$im = @imagecreatetruecolor(100, 50)';
//写字符串(原图像、字体、x坐标、y坐标、待写字符串、字符串颜色)
imagestring($im, 4, 10, 10,  $textstr, $textcolor);

$textstr = '$backgroundcolor = imagecolorallocate($im, 0, 0, 0)';
imagestring($im, 4, 10, 30,  $textstr, $textcolor);

$textstr = '$textcolor = imagecolorallocate($im, 0, 0, 255)';
imagestring($im, 4, 10, 50,  $textstr, $textcolor);  

$textstr = 'imagestring($im, 5, 10, 10,  $textstr, $textcolor)';
imagestring($im, 4, 10, 70,  $textstr, $textcolor);  



header("content-type: image/png");
imagepng($im);
imagedestroy($im);