PHP 实现的将图片转换为TXT

<?php
/*
2015年10月19日10:24:59
 
*/
// 打开一幅图像
 
$file_name='d:\ascii_dora.png';
$chars = "$@B%8&WM#*oahkbdpqwmZO0QLCJUYXzcvunxrjft/\|()1{}[]?-_+~<>i!lI;:,\"^`'. ";
function getimgchars($color_tran,$chars){
  $length = strlen($chars);
  $alpha=$color_tran['alpha'];
  $r=$color_tran['red'];
  $g=$color_tran['green'];
  $b=$color_tran['blue'];
  $gray = intval(0.2126 * $r + 0.7152 * $g + 0.0722 * $b);
 
  if($gray==0){
    return '.';
  }
 
  if($gray<196){
     $unit = (256.0 + 1)/$length;
    return $chars[intval($gray/$unit)];
  }
 
  return " ";
 
}
 
function color_img($color_tran,$chars){
  $length = strlen($chars);
  $alpha=$color_tran['alpha'];
 
  $r=$color_tran['red'];
  $g=$color_tran['green'];
  $b=$color_tran['blue'];
  $gray = intval(0.2126 * $r + 0.7152 * $g + 0.0722 * $b);
  $rand=rand (0, $length-1);
  $color="rgb(".$r.",".$g.",".$b.")";
  $char=$chars[$rand];
  return '<span style="color:'.$color.'" >'.$char."</span>";;
   
}
 
function resize_img($file_name,$chars,$flage=true){
  //header('Content-Type: image/jpeg');
  list($width, $height,$type) = getimagesize($file_name);
  $fun='imagecreatefrom' . image_type_to_extension($type, false);
  if($type==3){
    $flage=false;
  }
  $fun($file_name);
  $new_height =100;
  $percent=$height/$new_height;
  $new_width=$width/$percent;
  $image_p = imagecreatetruecolor($new_width, $new_height);
  $image = $fun($file_name);
  imagecopyresampled($image_p, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
  if($flage){
    return $image_p;
  }else{
    return $image;
  }
 
}
 
$im=resize_img($file_name,$chars);
 
$width=imagesx($im);
$height=imagesy($im);
 
$back_text="";
 
for($i=1;$i<=$height;$i++){
  for($j=1;$j<=$width;$j++){
    $color_index = imagecolorat($im, $j-1, $i-1);
    $color_tran = imagecolorsforindex($im, $color_index);
    $back_text.=color_img($color_tran,$chars,false);
  }
  $back_text.="<br/>";
}
  
echo "<pre>";
echo $back_text;
echo "</pre>";
//file_put_contents('1.txt',$back_text);