PHP based on the GD library image processing method summary _php skills

This article describes the PHP based on the GD library image processing methods. Share to everyone for your reference, specific as follows:

GD Image Processing Technology

Extension=php_gd2.dll

Create Canvas

Canvas, a resource-type data, an operational image resource

Create canvas (New)

Imagecreate (width,height)//Create a palette based canvas

Imagecreatetruecolor (width,height)//Create a true Color canvas

Create a canvas based on a picture (open)

Imagecreatefromjpeg (URL)
Imagecreatefrompng (URL)
Imagecreatefromgif (URL)

Manipulating canvas

Assign color: If you want to use a color on the canvas, you should first assign the color to the canvas.

(color identification) = Imagecolorallocate (img,r,g,b)

Fill Canvas

Imagefill (img,x,y, color identification)

Output canvas

1. Output to picture file

2. Direct output, you need to tell the browser output for picture information (header ("content-type:image/png;") ）

Imagepng (Img[,url])
imagejpeg ()
imagegif ()

Destroying Canvas Resources

Imagedestroy (IMG)

<?php
Header (' content-type:image/png ');
$img = Imagecreate (300,300);
$color = Imagecolorallocate ($img, 223,22,44);
Imagefill ($img, 3,3, $color);
Imagepng ($img);
Imagedestroy ();
? >

The Operation effect chart is as follows:

Verification Code Implementation

<?php
  Header (' content-type:image/png ');
  $code = ' 123456789abcdefghijklmnpqrstuvwxvz ';
  $length = strlen ($code);
  $print = ';
  For ($i =0 $i <4; $i + +) {
    $print. = $code [Mt_rand (0, $length-1)];
  }  echo $print;
  $img = Imagecreatefrompng ('./str.png ');
  $color = Mt_rand (0,1) ==1?imagecolorallocate ($img, 0,0,0): Imagecolorallocate ($img, 255,255,255);
  Picture size
  $img _width = Imagesx ($img);
  $img _height = Imagesy ($img);
  Font size
  $font = 5;
  $font _width = Imagefontwidth ($font);
  $font _height = Imagefontheight ($font);
  $fin _w = ($img _width-$font _width*4)/2;
  $fin _h = ($img _height-$font _height)/2;
  Imagestring ($img, $font, $fin _w, $fin _h, $print, $color);
  Imagepng ($img);
  Imagedestroy ($img);
? >
<image src= "gd_string.php" onclick= "this.src= ' gd_string.php?ra= ' +math.random ()" ></image>

The Operation effect chart is as follows:

<?php
session_start ();
$im =imagecreatetruecolor (80,30);
$str = "";
For ($i =0 $i <4; $i + +) {
  $str. =dechex (rand (0,15));
$_session[' code ']= $str;
$white =imagecolorallocate ($im, 255,255,255);
Imagestring ($im, rand (2,5), Rand (0,70), Rand (0,10), $str, $white);
Imagettftext ($im, Rand (0,5), Rand (0,180), Rand (0,100), Rand (0,10), $white, "Simhei.ttf", $str);
For ($i =0 $i <20; $i + +) {
$color =imagecolorallocate ($im, Rand (0,255), Rand (0,255), Rand (0,255));
Imageline ($im, Rand (0,90), Rand (0,20), Rand (0,100), Rand (0,100), $color);
Header ("Content-type:image/png");
Imagepng ($im);
Imagedestroy ($im);
? >

Note: no extra output before and after picture output

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