PHP サンプルコードで画像の比例スケーリングを使用する方法

<?php 
//压缩图片 缩略图
$src= "xiezheng.jpg";
$newwid=640;
$newhei= 480;
function imgzip($src,$newwid,$newhei){
 $imgInfo = getimagesize($src);

 $imgType = image_type_to_extension($imgInfo[2], false);

 $fun = "imagecreatefrom{$imgType}";
//声明图片 打开图片 在内存中
 $image = $fun($src);
//方便配置长度宽度、高度，设置框为变量wid,高度为hei
 $wid=$imgInfo[0];
 $hei=$imgInfo[1];
//判断长度和宽度，以方便等比缩放,规格按照500, 320
 if($wid>$hei){
 $wid=$newwid;
 $hei=$newwid/($wid/$hei);
 }else {
 $wid = $newhei * ($wid / $hei);
 $hei = $newhei;
 }
//在内存中建立一张图片
 $images2 = imagecreatetruecolor($newwid, $newhei); //建立一个500*320的图片

//将原图复制到新建图片中
//imagecopyresampled($dst_image, $src_image, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h)

 imagecopyresampled($images2, $image, 0, 0, 0, 0, $wid,$hei, $imgInfo[0],$imgInfo[1]);
//销毁原始图片
 imagedestroy($image);
//直接输出图片文件

 header("Content-type: ".$imgInfo[&#39;mime&#39;]);
 imagejpeg($images2);
//保存图片 到新文件
 imagejpeg($images2, &#39;new.jpg&#39;, 100); //10代码输出图片的质量 0-100 100质量最高
//销毁
 imagedestroy($images2);
}
imgzip($src,$newwid,$newhei);
?>

/**
 * 图片缩放函数（可设置高度固定，宽度固定或者最大宽高，支持gif/jpg/png三种类型）
 * Author : Specs
 *
 * @param string $source_path 源图片
 * @param int $target_width 目标宽度
 * @param int $target_height 目标高度
 * @param string $fixed_orig 锁定宽高（可选参数 width、height或者空值）
 * @return string
 */
function myImageResize($source_path, $target_width = 200, $target_height = 200, $fixed_orig = ''){
  $source_info = getimagesize($source_path);
  $source_width = $source_info[0];
  $source_height = $source_info[1];
  $source_mime = $source_info['mime'];
  $ratio_orig = $source_width / $source_height;
  if ($fixed_orig == 'width'){
    //宽度固定
    $target_height = $target_width / $ratio_orig;
  }elseif ($fixed_orig == 'height'){
    //高度固定
    $target_width = $target_height * $ratio_orig;
  }else{
    //最大宽或最大高
    if ($target_width / $target_height > $ratio_orig){
      $target_width = $target_height * $ratio_orig;
    }else{
      $target_height = $target_width / $ratio_orig;
    }
  }
  switch ($source_mime){
    case 'image/gif':
      $source_image = imagecreatefromgif($source_path);
      break;
     
    case 'image/jpeg':
      $source_image = imagecreatefromjpeg($source_path);
      break;
     
    case 'image/png':
      $source_image = imagecreatefrompng($source_path);
      break;
     
    default:
      return false;
      break;
  }
  $target_image = imagecreatetruecolor($target_width, $target_height);
  imagecopyresampled($target_image, $source_image, 0, 0, 0, 0, $target_width, $target_height, $source_width, $source_height);
  //header('Content-type: image/jpeg');
  $imgArr = explode('.', $source_path);
  $target_path = $imgArr[0] . '_new.' . $imgArr[1];
  imagejpeg($target_image, $target_path, 100);
}

function imagecropper($source_path, $target_width, $target_height){
  $source_info = getimagesize($source_path);
  $source_width = $source_info[0];
  $source_height = $source_info[1];
  $source_mime = $source_info['mime'];
  $source_ratio = $source_height / $source_width;
  $target_ratio = $target_height / $target_width;
   
  // 源图过高
  if ($source_ratio > $target_ratio){
    $cropped_width = $source_width;
    $cropped_height = $source_width * $target_ratio;
    $source_x = 0;
    $source_y = ($source_height - $cropped_height) / 2;
  }elseif ($source_ratio < $target_ratio){ // 源图过宽
    $cropped_width = $source_height / $target_ratio;
    $cropped_height = $source_height;
    $source_x = ($source_width - $cropped_width) / 2;
    $source_y = 0;
  }else{ // 源图适中
    $cropped_width = $source_width;
    $cropped_height = $source_height;
    $source_x = 0;
    $source_y = 0;
  }
   
  switch ($source_mime){
    case &#39;image/gif&#39;:
      $source_image = imagecreatefromgif($source_path);
      break;
     
    case &#39;image/jpeg&#39;:
      $source_image = imagecreatefromjpeg($source_path);
      break;
     
    case &#39;image/png&#39;:
      $source_image = imagecreatefrompng($source_path);
      break;
     
    default:
      return false;
      break;
  }
   
  $target_image = imagecreatetruecolor($target_width, $target_height);
  $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);
   
  // 裁剪
  imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
  // 缩放
  imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);
  $dotpos = strrpos($source_path, &#39;.&#39;);
  $imgName = substr($source_path, 0, $dotpos);
  $suffix = substr($source_path, $dotpos);
  $imgNew = $imgName . &#39;_small&#39; . $suffix;
  imagejpeg($target_image, $imgNew, 100);
  imagedestroy($source_image);
  imagedestroy($target_image);
  imagedestroy($cropped_image);
}