PHP调整图像大小并保存为透明PNG
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【中文标题】PHP调整图像大小并保存为透明PNG【英文标题】：PHP Resize image and save as transparent PNG 【发布时间】：2016-02-04 07:25:23 【问题描述】：我做错了什么？它适用于 jpg 和 gif，但不适用于 transparent png 文件。检查了其他一些问题，但不明白，因为我对 php 不是很好。如果有人能解决这个问题，我将不胜感激！
<?php
# ========================================================================#
# Requires : Requires PHP5, GD library.
# Usage Example:
# include("resize_class.php");
# $resizeObj = new resize('images/cars/large/input.jpg');
# $resizeObj -> resizeImage(150, 100, 0);
# $resizeObj -> saveImage('images/cars/large/output.jpg', 100);
# ========================================================================#
class resize
// *** Class variables
private $image;
private $width;
private $height;
private $imageResized;
function __construct($fileName)
// *** Open up the file
$this->image = $this->openImage($fileName);
// *** Get width and height
$this->width = imagesx($this->image);
$this->height = imagesy($this->image);
## --------------------------------------------------------
private function openImage($file)
// *** Get extension
$extension = strtolower(strrchr($file, '.'));
switch($extension)
case '.jpg':
case '.jpeg':
$img = @imagecreatefromjpeg($file);
break;
case '.gif':
$img = @imagecreatefromgif($file);
break;
case '.png':
$img = @imagecreatefrompng($file);
break;
default:
$img = false;
break;
return $img;
## --------------------------------------------------------
public function resizeImage($newWidth, $newHeight, $option="auto")
// *** Get optimal width and height - based on $option
$optionArray = $this->getDimensions($newWidth, $newHeight, $option);
$optimalWidth = $optionArray['optimalWidth'];
$optimalHeight = $optionArray['optimalHeight'];
// *** Resample - create image canvas of x, y size
$this->imageResized = imagecreatetruecolor($optimalWidth, $optimalHeight);
imagecopyresampled($this->imageResized, $this->image, 0, 0, 0, 0, $optimalWidth, $optimalHeight, $this->width, $this->height);
// *** if option is 'crop', then crop too
if ($option == 'crop')
$this->crop($optimalWidth, $optimalHeight, $newWidth, $newHeight);
## --------------------------------------------------------
private function getDimensions($newWidth, $newHeight, $option)
switch ($option)
case 'exact':
$optimalWidth = $newWidth;
$optimalHeight= $newHeight;
break;
case 'portrait':
$optimalWidth = $this->getSizeByFixedHeight($newHeight);
$optimalHeight= $newHeight;
break;
case 'landscape':
$optimalWidth = $newWidth;
$optimalHeight= $this->getSizeByFixedWidth($newWidth);
break;
case 'auto':
$optionArray = $this->getSizeByAuto($newWidth, $newHeight);
$optimalWidth = $optionArray['optimalWidth'];
$optimalHeight = $optionArray['optimalHeight'];
break;
case 'crop':
$optionArray = $this->getOptimalCrop($newWidth, $newHeight);
$optimalWidth = $optionArray['optimalWidth'];
$optimalHeight = $optionArray['optimalHeight'];
break;
return array('optimalWidth' => $optimalWidth, 'optimalHeight' => $optimalHeight);
## --------------------------------------------------------
private function getSizeByFixedHeight($newHeight)
$ratio = $this->width / $this->height;
$newWidth = $newHeight * $ratio;
return $newWidth;
private function getSizeByFixedWidth($newWidth)
$ratio = $this->height / $this->width;
$newHeight = $newWidth * $ratio;
return $newHeight;
private function getSizeByAuto($newWidth, $newHeight)
if ($this->height < $this->width)
// *** Image to be resized is wider (landscape)
$optimalWidth = $newWidth;
$optimalHeight= $this->getSizeByFixedWidth($newWidth);
elseif ($this->height > $this->width)
// *** Image to be resized is taller (portrait)
$optimalWidth = $this->getSizeByFixedHeight($newHeight);
$optimalHeight= $newHeight;
else
// *** Image to be resizerd is a square
if ($newHeight < $newWidth)
$optimalWidth = $newWidth;
$optimalHeight= $this->getSizeByFixedWidth($newWidth);
else if ($newHeight > $newWidth)
$optimalWidth = $this->getSizeByFixedHeight($newHeight);
$optimalHeight= $newHeight;
else
// *** Sqaure being resized to a square
$optimalWidth = $newWidth;
$optimalHeight= $newHeight;
return array('optimalWidth' => $optimalWidth, 'optimalHeight' => $optimalHeight);
## --------------------------------------------------------
private function getOptimalCrop($newWidth, $newHeight)
$heightRatio = $this->height / $newHeight;
$widthRatio = $this->width / $newWidth;
if ($heightRatio < $widthRatio)
$optimalRatio = $heightRatio;
else
$optimalRatio = $widthRatio;
$optimalHeight = $this->height / $optimalRatio;
$optimalWidth = $this->width / $optimalRatio;
return array('optimalWidth' => $optimalWidth, 'optimalHeight' => $optimalHeight);
## --------------------------------------------------------
private function crop($optimalWidth, $optimalHeight, $newWidth, $newHeight)
// *** Find center - this will be used for the crop
$cropStartX = ( $optimalWidth / 2) - ( $newWidth /2 );
$cropStartY = ( $optimalHeight/ 2) - ( $newHeight/2 );
$crop = $this->imageResized;
//imagedestroy($this->imageResized);
// *** Now crop from center to exact requested size
$this->imageResized = imagecreatetruecolor($newWidth , $newHeight);
imagecopyresampled($this->imageResized, $crop , 0, 0, $cropStartX, $cropStartY, $newWidth, $newHeight , $newWidth, $newHeight);
## --------------------------------------------------------
public function saveImage($savePath, $imageQuality="100")
// *** Get extension
$extension = strrchr($savePath, '.');
$extension = strtolower($extension);
switch($extension)
case '.jpg':
case '.jpeg':
if (imagetypes() & IMG_JPG)
imagejpeg($this->imageResized, $savePath, $imageQuality);
break;
case '.gif':
if (imagetypes() & IMG_GIF)
imagegif($this->imageResized, $savePath);
break;
case '.png':
// *** Scale quality from 0-100 to 0-9
$scaleQuality = round(($imageQuality/100) * 9);
// *** Invert quality setting as 0 is best, not 9
$invertScaleQuality = 9 - $scaleQuality;
if (imagetypes() & IMG_PNG)
imagepng($this->imageResized, $savePath, $invertScaleQuality);
break;
// ... etc
default:
// *** No extension - No save.
break;
imagedestroy($this->imageResized);
## --------------------------------------------------------
?>
【问题讨论】：
欢迎来到 ***，请查看如何编写 MCEV 问题并相应地修改您的问题。 【参考方案1】：看看这个函数：
function resizePng($im, $dst_width, $dst_height)
$width = imagesx($im);
$height = imagesy($im);
$newImg = imagecreatetruecolor($dst_width, $dst_height);
imagealphablending($newImg, false);
imagesavealpha($newImg, true);
$transparent = imagecolorallocatealpha($newImg, 255, 255, 255, 127);
imagefilledrectangle($newImg, 0, 0, $width, $height, $transparent);
imagecopyresampled($newImg, $im, 0, 0, 0, 0, $dst_width, $dst_height, $width, $height);
return $newImg;
在这篇文章中：How do I resize pngs with transparency in PHP?
也许可以帮到你！运气！
【讨论】：
添加了它，但它仍然不起作用。 imagealphablending($this->image, false); imagesavealpha($this->image, true); $transparent = imagecolorallocatealpha($this->image, 255, 255, 255, 127); imagefilledrectangle($this->image, 0, 0, $width, $height, $transparent); $this->imageResized = imagecreatetruecolor($optimalWidth, $optimalHeight); imagecopyresampled($this->imageResized, $this->image, 0, 0, 0, 0, $optimalWidth, $optimalHeight, $this->width, $this->height);【参考方案2】：替换resizeImages函数
public function resizeImage($newWidth, $newHeight, $option="auto")
// *** Get optimal width and height - based on $option
$optionArray = $this->getDimensions($newWidth, $newHeight, $option);
$optimalWidth = $optionArray['optimalWidth'];
$optimalHeight = $optionArray['optimalHeight'];
// *** Resample - create image canvas of x, y size
$this->imageResized = imagecreatetruecolor($optimalWidth, $optimalHeight);
// *** Support transparent png
if(imagetypes() & IMG_PNG)
imagealphablending($this->imageResized, false);
imagesavealpha($this->imageResized,true);
$transparent = imagecolorallocatealpha($this->imageResized, 255, 255, 255, 127);
imagefilledrectangle($this->imageResized, 0, 0, $optimalWidth, $optimalHeight, $transparent);
imagecopyresampled($this->imageResized, $this->image, 0, 0, 0, 0, $optimalWidth, $optimalHeight, $this->width, $this->height);
// *** if option is 'crop', then crop too
if ($option == 'crop')
$this->crop($optimalWidth, $optimalHeight, $newWidth, $newHeight);
【讨论】：
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