//指定图片路径
$src = '001.png';
//获取图片信息
$info = getimagesize($src);
//获取图片扩展名
$type = image_type_to_extension($info[2],false);
//动态的把图片导入内存中
$fun = "imagecreatefrom{$type}";
$image = $fun('001.png');
//指定字体颜色
$col = imagecolorallocatealpha($image,255,255,255,50);
//指定字体内容
$content = 'helloworld';
//给图片添加文字
imagestring($image,5,20,30,$content,$col);
//指定输入类型
header('Content-type:'.$info['mime']);
//动态的输出图片到浏览器中
$func = "image{$type}";
$func($image);
//销毁图片
imagedestroy($image);

class Image_class {
  private $image;
  private $info;

  /**
   * @param $src:图片路径
   * 加载图片到内存中
   */
  function __construct($src){
    $info = getimagesize($src);
    $type = image_type_to_extension($info[2],false);
    $this -> info =$info;
    $this->info['type'] = $type;
    $fun = "imagecreatefrom" .$type;
    $this -> image = $fun($src);
  }

  /**
   * @param $fontsize: 字体大小
   * @param $x: 字体在图片中的x位置
   * @param $y: 字体在图片中的y位置
   * @param $color: 字体的颜色是一个包含rgba的数组
   * @param $text: 想要添加的内容
   * 操作内存中的图片,给图片添加文字水印
   */
  public function fontMark($fontsize,$x,$y,$color,$text){
    $col = imagecolorallocatealpha($this->image,$color[0],$color[1],$color[2],$color[3]);
    imagestring($this->image,$fontsize,$x,$y,$text,$col);
  }
  /*
   * 输出图片到浏览器中
   */
  public function show(){
    header('content-type:' . $this -> info['mime']);
    $fun='image' . $this->info['type'];
    $fun($this->image);
  }

  /**
   * 销毁图片
   */
  function __destruct(){
    imagedestroy($this->image);
  }
}
//对类的调用
$obj = new Image_class('001.png');
$obj->fontMark(20,20,30,array(255,255,255,60),'hello');
$obj->show();

function setWater($imgSrc,$markImg,$markText,$TextColor,$markPos,$fontType,$markType)
{

  $srcInfo = @getimagesize($imgSrc);
  $srcImg_w  = $srcInfo[0];
  $srcImg_h  = $srcInfo[1];
    
  switch ($srcInfo[2]) 
  { 
    case 1: 
      $srcim =imagecreatefromgif($imgSrc); 
      break; 
    case 2: 
      $srcim =imagecreatefromjpeg($imgSrc); 
      break; 
    case 3: 
      $srcim =imagecreatefrompng($imgSrc); 
      break; 
    default: 
      die("不支持的图片文件类型"); 
      exit; 
  }
    
  if(!strcmp($markType,"img"))
  {
    if(!file_exists($markImg) || empty($markImg))
    {
      return;
    }
      
    $markImgInfo = @getimagesize($markImg);
    $markImg_w  = $markImgInfo[0];
    $markImg_h  = $markImgInfo[1];
      
    if($srcImg_w < $markImg_w || $srcImg_h < $markImg_h)
    {
      return;
    }
      
    switch ($markImgInfo[2]) 
    { 
      case 1: 
        $markim =imagecreatefromgif($markImg); 
        break; 
      case 2: 
        $markim =imagecreatefromjpeg($markImg); 
        break; 
      case 3: 
        $markim =imagecreatefrompng($markImg); 
        break; 
      default: 
        die("不支持的水印图片文件类型"); 
        exit; 
    }
      
    $logow = $markImg_w;
    $logoh = $markImg_h;
  }
    
  if(!strcmp($markType,"text"))
  {
    $fontSize = 16;
    if(!empty($markText))
    {
      if(!file_exists($fontType))
      {
        return;
      }
    }
    else {
      return;
    }
      
    $box = @imagettfbbox($fontSize, 0, $fontType,$markText);
    $logow = max($box[2], $box[4]) - min($box[0], $box[6]);
    $logoh = max($box[1], $box[3]) - min($box[5], $box[7]);
  }
    
  if($markPos == 0)
  {
    $markPos = rand(1, 9);
  }
    
  switch($markPos)
  {
    case 1:
      $x = +5;
      $y = +5;
      break;
    case 2:
      $x = ($srcImg_w - $logow) / 2;
      $y = +5;
      break;
    case 3:
      $x = $srcImg_w - $logow - 5;
      $y = +15;
      break;
    case 4:
      $x = +5;
      $y = ($srcImg_h - $logoh) / 2;
      break;
    case 5:
      $x = ($srcImg_w - $logow) / 2;
      $y = ($srcImg_h - $logoh) / 2;
      break;
    case 6:
      $x = $srcImg_w - $logow - 5;
      $y = ($srcImg_h - $logoh) / 2;
      break;
    case 7:
      $x = +5;
      $y = $srcImg_h - $logoh - 5;
      break;
    case 8:
      $x = ($srcImg_w - $logow) / 2;
      $y = $srcImg_h - $logoh - 5;
      break;
    case 9:
      $x = $srcImg_w - $logow - 5;
      $y = $srcImg_h - $logoh -5;
      break;
    default: 
      die("此位置不支持"); 
      exit;
  }
    
  $dst_img = @imagecreatetruecolor($srcImg_w, $srcImg_h);
    
  imagecopy ( $dst_img, $srcim, 0, 0, 0, 0, $srcImg_w, $srcImg_h);
    
  if(!strcmp($markType,"img"))
  {
    imagecopy($dst_img, $markim, $x, $y, 0, 0, $logow, $logoh);
    imagedestroy($markim);
  }
    
  if(!strcmp($markType,"text"))
  {
    $rgb = explode(',', $TextColor);
      
    $color = imagecolorallocate($dst_img, $rgb[0], $rgb[1], $rgb[2]);
    imagettftext($dst_img, $fontSize, 0, $x, $y, $color, $fontType,$markText);
  }
    
  switch ($srcInfo[2]) 
  { 
    case 1:
      imagegif($dst_img, $imgSrc); 
      break; 
    case 2: 
      imagejpeg($dst_img, $imgSrc); 
      break; 
    case 3: 
      imagepng($dst_img, $imgSrc); 
      break;
    default: 
      die("不支持的水印图片文件类型"); 
      exit; 
  }
    
  imagedestroy($dst_img);
  imagedestroy($srcim);
}

<"content-type:image/gif");
    imagegif($dst);
    break;
  case 2://JPG
    header("content-type:image/jpeg");
    imagejpeg($dst);
    break;
  case 3://PNG
    header("content-type:image/png");
    imagepng($dst);
    break;
  default:
    break;
  /*imagepng--以PNG格式将图像输出到浏览器或文件
  imagepng()将GD图像流(image)以png格式输出到标注输出（通常为浏览器），或者如果用filename给出了文件名则将其输出到文件*/
}
imagedestroy($dst);
?>