我试图在PHP中调整透明背景的png,我在网上找到的代码示例对我不起作用.这是我正在使用的代码,建议将不胜感激!

$this->image = imagecreatefrompng($filename);

imagesavealpha($this->image, true);
$newImage = imagecreatetruecolor($width, $height);

// Make a new transparent image and turn off alpha blending to keep the alpha channel
$background = imagecolorallocatealpha($newImage, 255, 255, 255, 127);
imagecolortransparent($newImage, $background);
imagealphablending($newImage, false);
imagesavealpha($newImage, true);

imagecopyresampled($newImage, $this->image, 0, 0, 0, 0, $width, $height,  $this->getWidth(), $this->getHeight());
$this->image = $newImage;  
imagepng($this->image,$filename);

更新 "不工作"我的意思是当我调整pngs时,背景颜色会变为黑色.

我对图像缩放的讨论很感兴趣,后来发现我用来从上传的图像创建缩略图的PHP代码遇到了同样的问题.我决定尝试在底部附近发布的PHP修补程序(将伽玛值从2.2转换为1.0,调整图像大小,将伽玛值从1.0转换回2.2).这有助于解决文章中提到的问题,但是对代码的这种修改具有淘汰PNG alpha通道透明度的不幸副作用.

这是我对伽马校正的代码.

<?php
$image = imagecreatefrompng($source_file);
$resized_image = imagecreatetruecolor($new_width, $new_height);
imagealphablending($resized_image, false);
imagesavealpha($resized_image, true);
imagegammacorrect($image, 2.2, 1.0);
imagecopyresampled($resized_image, $image, 0, 0, 0, 0, $new_width, $new_height, $image_width, $image_height);
imagegammacorrect($resized_image, 1.0, 2.2);
imagepng($resized_image, $dest_file);
?>

任何人都知道如何调整图像大小,采用伽马校正技巧,同时保持原始图像的alpha通道透明度？

编辑

样本图片:

1. 原始文件 - 具有Alpha通道透明度的PNG
2. 调整了两个imagegammacorrect()函数调用的调整大小的文件
3. 调整大小的文件,同时调用imagegammacorrect()函数

在尝试更正伽玛之前,您可以看到透明度很好.(查看透明度的最简单方法是检查包裹在图像周围的段落标记,并通过FireBug或类似方法添加背景:black;到其样式属性.)

原始图像http://ender.hosting.emarketsouth.com/images/test-image.png 没有伽马校正http://ender.hosting.emarketsouth.com/images/test-image-resized-no-gamma.png 伽玛纠正 - 没有透明度http://ender.hosting.emarketsouth.com/images/test-image-resized.png

我正在使用此代码调整大小:

  <?php
// Function for resizing any jpg, gif, or png image files
function ak_img_resize($target, $newcopy, $w, $h, $ext) {
    list($w_orig, $h_orig) = getimagesize($target);
    $scale_ratio = $w_orig / $h_orig;
    if (($w / $h) > $scale_ratio) {
           $w = $h * $scale_ratio;
    } else {
           $h = $w / $scale_ratio;
    }
    $img = "";
    $ext = strtolower($ext);
    if ($ext == "gif"){ 
      $img = imagecreatefromgif($target);
    } else if($ext =="png"){ 
      $img = imagecreatefrompng($target);
    } else { 
      $img = imagecreatefromjpeg($target);
    }
    $tci = imagecreatetruecolor($w, …

我使用这个类来上传和调整图像大小.问题是图像质量不好!我需要上传图像而不会丢失质量!

class SimpleImage {

   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=75, $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 …