如何在使用PHP调整大小时在PNG上保持透明背景？ [英] How to keep transparent background on PNG when resizing with PHP?

问题描述

我在使用PHP调整图片大小时遇到​​问题，尤其是使用透明背景的PNG文件，而是保持透明背景，它变成黑色背景。如何解决此问题？

这是调整大小的脚本：

 <？php 
 class resize {
 
 var $ image; 
 var $ image_type; 
 
 function load（$ filename）{
 
 $ image_info = getimagesize（$ filename）; 
 $ this-> image_type = $ image_info [2]; 
 if（$ this-> image_type == IMAGETYPE_JPEG）{
 
 $ this-> image = imagecreatefromjpeg（$ filename）; 
} elseif（$ this-> image_type == IMAGETYPE_GIF）{
 
 $ this-> image = imagecreatefromgif（$ filename）; 
} elseif（$ this-> image_type == IMAGETYPE_PNG）{
 
 $ this-> image = imagecreatefrompng（$ filename）; 
} 
} 
 function save（$ filename，$ image_type = IMAGETYPE_JPEG，$ compression = 85，$ permissions = null）{
 
 if（$ image_type == IMAGETYPE_JPEG）{
 imagejpeg（$ this-> image，$ filename，$ compression）; 
} elseif（$ image_type == IMAGETYPE_GIF）{
 
 imagegif（$ this-> image，$ filename）; 
} elseif（$ image_type == IMAGETYPE_PNG）{
 
 
 
 
 imagepng（$ this-> image，$ filename）; 
} 
 if（$ permissions！= null）{
 
 chmod（$ filename，$ permissions）; 
} 
} 
函式输出（$ image_type = IMAGETYPE_JPEG）{
 
 if（$ image_type == IMAGETYPE_JPEG）{
 imagejpeg（$ this-> ;图片）; 
} elseif（$ image_type == IMAGETYPE_GIF）{
 
 imagegif（$ this-> image）; 
} elseif（$ image_type == IMAGETYPE_PNG）{
 
 imagepng（$ this-> image）; 
} 
} 
 function getWidth（）{
 
 return imagesx（$ this-> image）; 
} 
 function getHeight（）{
 
 return imagesy（$ this-> image）; 
} 
 function resizeToHeight（$ height）{
 
 $ ratio = $ height / $ this-> getHeight（）; 
 $ width = $ this-> getWidth（）* $ ratio; 
 $ this-> resize（$ width，$ height）; 
} 
 
 function resizeToWidth（$ width）{
 $ ratio = $ width / $ this-> getWidth（）; 
 $ height = $ this-> getheight（）* $ ratio; 
 $ this-> resize（$ width，$ height）; 
} 
 
 function scale（$ scale）{
 $ width = $ this-> getWidth（）* $ scale / 100; 
 $ height = $ this-> getheight（）* $ scale / 100; 
 $ this-> resize（$ width，$ height）; 
} 
 
 function resize（$ width，$ height）{
 
 $ new_image = imagecreatetruecolor（$ width，$ height）; 
 imagecopyresampled（$ new_image，$ this-> image，0，0，0，0，$ width，$ height，$ this-> getWidth（），$ this-> getHeight（））; 
 $ this-> image = $ new_image; 
} 
 
} 
？> 
  

这就是我所说的：

  $ picture_directory =images /。 $ _FILES [file] [name]; 
 
 include（'arqinc / resizing.php'）; 
 $ image = new resize（）; 
 $ image-> load（$ picture_directory）; 
 $ image-> resize（660,780）; 
 $ image-> save（$ picture_directory）; 
  

编辑：

ive将我的调整大小功能更改为：

  function resize（$ width，$ height）{
 
 $ new_image = imagecreatetruecolor（$ width，$ height）; 
 $ transparent = imagefill（$ new_image，0，0，imagecolorallocatealpha（$ new_image，255，255，255，127））; 
 imagecopyresampled（$ new_image，$ this-> image，0，0，0，0，$ width，$ height，$ this-> getWidth（），$ this-> getHeight（））; 
 $ this-> image = $ new_image; 
} 
  

但现在它保持背景白色，不透明。

编辑2：

解决了这个调整大小功能的问题， p>

http://mediumexposure.com/smart-image-resizing-while-preserving-transparency-php-and-gd-library/

感谢
Tahir Yasin 链接它：D

解决方案

我发现另一篇有相同问题的帖子，根据后面的代码可以用来保存透明度。

  imagealphablending（$ targetImage，false）; 
 imagesavealpha（$ targetImage，true）; 
  

参考：

请投票，如果它有助于你。 ：）

I'm having a issue when resizing pictures with PHP, especially with PNG files with transparent backgrounds, instead keeping the transparent background, it turns into a black background. How can I fix this?

This is the script for resizing:

<?php         
class resize{

   var $image;
   var $image_type;

   function load($filename) {

      $image_info = getimagesize($filename);
      $this->image_type = $image_info[2];
      if( $this->image_type == IMAGETYPE_JPEG ) {

         $this->image = imagecreatefromjpeg($filename);
      } elseif( $this->image_type == IMAGETYPE_GIF ) {

         $this->image = imagecreatefromgif($filename);
      } elseif( $this->image_type == IMAGETYPE_PNG ) {

         $this->image = imagecreatefrompng($filename);
      }
   }
   function save($filename, $image_type=IMAGETYPE_JPEG, $compression=85, $permissions=null) {

      if( $image_type == IMAGETYPE_JPEG ) {
         imagejpeg($this->image,$filename,$compression);
      } elseif( $image_type == IMAGETYPE_GIF ) {

         imagegif($this->image,$filename);
      } elseif( $image_type == IMAGETYPE_PNG ) {




         imagepng($this->image,$filename);
      }
      if( $permissions != null) {

         chmod($filename,$permissions);
      }
   }
   function output($image_type=IMAGETYPE_JPEG) {

      if( $image_type == IMAGETYPE_JPEG ) {
         imagejpeg($this->image);
      } elseif( $image_type == IMAGETYPE_GIF ) {

         imagegif($this->image);
      } elseif( $image_type == IMAGETYPE_PNG ) {

         imagepng($this->image);
      }
   }
   function getWidth() {

      return imagesx($this->image);
   }
   function getHeight() {

      return imagesy($this->image);
   }
   function resizeToHeight($height) {

      $ratio = $height / $this->getHeight();
      $width = $this->getWidth() * $ratio;
      $this->resize($width,$height);
   }

   function resizeToWidth($width) {
      $ratio = $width / $this->getWidth();
      $height = $this->getheight() * $ratio;
      $this->resize($width,$height);
   }

   function scale($scale) {
      $width = $this->getWidth() * $scale/100;
      $height = $this->getheight() * $scale/100;
      $this->resize($width,$height);
   }

   function resize($width,$height) {

      $new_image = imagecreatetruecolor($width, $height);   
      imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
      $this->image = $new_image;
   }      

}
?>

And this is how I call it:

$picture_directory="images/" . $_FILES["file"]["name"];

    include('arqinc/resizing.php');
    $image = new resize();
    $image->load($picture_directory);
    $image->resize(660,780);
    $image->save($picture_directory);

EDIT:

ive changed my resize function to this:

function resize($width,$height) {

      $new_image = imagecreatetruecolor($width, $height);
      $transparent=imagefill($new_image, 0, 0, imagecolorallocatealpha($new_image, 255, 255, 255, 127));
      imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
      $this->image = $new_image;
   }  

But now it keeps the background white, not transparent.

EDIT 2:

Solved, this resize function is broken, this one works flawlessly:

http://mediumexposure.com/smart-image-resizing-while-preserving-transparency-php-and-gd-library/

Thanks to Tahir Yasin for linking it :D

解决方案

I found another post with same question, according to that post following code can be used to preserve transparancy.

imagealphablending( $targetImage, false );
imagesavealpha( $targetImage, true );

Reference: Can PNG image transparency be preserved when using PHP's GDlib imagecopyresampled?

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