PHP uses GD library to draw pictures and generate verification code pictures_PHP tutorial

PHP uses the GD library to draw pictures and generate verification code images

First of all, make sure that the GD extension function is turned on in the php.ini settings. The test is as follows

print_r(gd_info());

If the following content is printed out, it means that the GD function is turned on:

Array
(
    [GD Version] => bundled (2.0.34 compatible)
    [FreeType Support] => 1
    [FreeType Linkage] => with freetype
    [T1Lib Support] => 1
    [GIF Read Support] => 1
    [GIF Create Support] => 1
    [JPG Support] => 1
    [PNG Support] => 1
    [WBMP Support] => 1
    [XPM Support] => 
    [XBM Support] => 1
    [JIS-mapped Japanese Font Support] => 
)

The general steps for GD drawing are as follows:

1. Create a canvas resource

2. Create a color brush

3. Drawing

4. Save the picture or export the picture

5. Destroy memory canvas resources

The test code is as follows:

<!--?php
header(Content-type: image/jpeg);

$width = 400;   //宽，高
$height = 400;  

$image = imagecreate($width, $height); //第一步：创建空白图像

$white = imagecolorallocate($image, 0, 0, 0);  //第一次对 imagecolorallocate() 的调用会给基于调色板的图像填充背景色，即用 imagecreate() 建立的图像。 

$green = imagecolorallocate($image, 0, 255, 0); //第二步：为图像分配颜色

imageline($image, 0, 20, 400, 20, $green);  //第三步：画线
imagerectangle($image,100,40,300,100,$green);  //画矩形
imagearc($image, 200, 150, 90, 90, 0, 360, $green); //画圆
imagestring($image, 14, 100, 240, PHP is NiuBi HongHong!, $green); //写字符串

$str=abcdefghjklmnpqrstuvwxyz23456789;
$randstr = substr(str_shuffle($str), 0,4);
imagestring($image, 14, 100, 260, $randstr, $green); //验证码

imagettftext($image, 14, 0, 100, 300, $green, &#39;./MSJHBD.TTF&#39;, 中文vsEnglish);  //中文验证

// imagejpeg($image,&#39;./test.jpg&#39;);   //在当前路径下保存图片为test.jpg
imagejpeg($image);  //第四步：不加文件名，直接输出到网页     

imagedestroy($image);   //第五步：销毁，回收资源
?-->

The test pictures are as follows:

Note: The GD library is powerful and can draw various reports (such as bar charts, pie charts, etc.), thumbnails, watermarked images and stock trend charts

<!--?php
header(Content-type: image/png);

$width = 300;   //原图宽，高
$height = 210;  

$thumb_width = (int)$width/2;
$thumb_height = (int)$height/2;


$dst = imagecreate($thumb_width,$thumb_height); //创建缩略图画布

$gray = imagecolorallocate($dst, 100, 100, 100);


$src = imagecreatefrompng(&#39;./me.png&#39;); //读取原图

//把原图copy到缩略图画布上
imagecopyresampled($dst, $src, 0, 0, 0, 0, $thumb_width, $thumb_height, $width, $height); 

imagepng($dst,&#39;./me_thumb.png&#39;);

imagedestroy($dst);
imagedestroy($src);
?-->

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