我最近关注了本教程，但问题是当我保存 PNG 时它具有纯黑色背景？.. 我对 php 相当陌生.. 如何用透明背景保存它？
这是php类：
# include("classes/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= $newHeight;
}
else
// *** Image to be resized is a square
{
if ($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);
}
}
?>
我知道很多代码..但我不知道哪些部分是至关重要的..抱歉...
非常感谢任何帮助。