注：此功能依赖GD2图形库
最近要用PHP生成缩略图，在网上找了一下，发现了这篇文章：PHP生成图片缩略图
试用了一下后，发现有这样几个问题：
2、png图片生成的缩略图没有了透明（半透明）效果（填充了黑色背景）
3、代码语法比较老
因此，在这个版本的基础上简单修改优化了一下。
PHP生成缩略图类
PHP;">
function __construct($imgPath,$width,$height,$isCut,$savePath) {
$this->srcimg = $imgPath;
$this->resize_width = $width;
$this->resize_height = $height;
$this->cut = $isCut;
//<a href="https://www.jb51.cc/tag/tupian/" target="_blank" class="keywords">图片</a>的类型
$this->type = strtolower(substr(strrchr($this->srcimg,"."),1));
//初始化图象
$this->initi_img();
//目标图象地址
$this -> dst_img($savePath);
//--
$this->width = imagesx($this->im);
$this->height = imagesy($this->im);
//<a href="https://www.jb51.cc/tag/shengcheng/" target="_blank" class="keywords">生成</a>图象
$this->newimg();
ImageDestroy ($this->im);
}
private function newimg() {
//改变后的图象的比例
$resize_ratio = ($this->resize_width)/($this->resize_height);
//实际图象的比例
$ratio = ($this->width)/($this->height);
if($this->cut) {
//裁图
$newimg = imagecreatetruecolor($this->resize_width,$this->resize_height);
if($this->type=="png") {
imagefill($newimg,imagecolorallocatealpha($newimg,127));
}
if($ratio>=$resize_ratio) {
//高度优先
imagecopyresampled($newimg,$this->im,$this->resize_width,$this->resize_height,(($this->height)*$resize_ratio),$this->height);
} else {
//宽度优先
imagecopyresampled($newimg,$this->width,(($this->width)/$resize_ratio));
}
} else {
//不裁图
if($ratio>=$resize_ratio) {
$newimg = imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);
if($this->type=="png") {
imagefill($newimg,127));
}
imagecopyresampled($newimg,($this->resize_width)/$ratio,$this->height);
} else {
$newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);
if($this->type=="png") {
imagefill($newimg,($this->resize_height)*$ratio,$this->height);
}
}
if($this->type=="png") {
imagesavealpha($newimg,true);
imagepng ($newimg,$this->dstimg);
} else {
imagejpeg ($newimg,$this->dstimg);
}
}
//初始化图象
private function initi_img() {
if($this->type=="jpg") {
$this->im = imagecreatefromjpeg($this->srcimg);
}
if($this->type=="gif") {
$this->im = imagecreatefromgif($this->srcimg);
}
if($this->type=="png") {
$this->im = imagecreatefrompng($this->srcimg);
}
}
//图象目标地址
private function dst_img($dstpath) {
$full_length = strlen($this->srcimg);
$type_length = strlen($this->type);
$name_length = $full_length-$type_length;
$name = substr($this->srcimg,$name_length-1);
$this->dstimg = $dstpath;
}
}
?>
使用
$resizeimage = new resizeimage($imgPath,$savePath);
参数
$imgPath：原图片地址$width：缩略图宽
$height：缩略图高
$isCut：是否裁剪，bool值
示例
PHP;">
//jpg
$jpgResize = new ResizeImage("img/test_1920_1200.jpg",320,240,false,"img/test_320_240.jpg");
$jpgResize = new ResizeImage("img/test_1920_1200.jpg",320,240,false,"img/test_320_240.jpg");
//png
$pngResize = new ResizeImage("img/test_1024_746.png","img/test_320_240.png");
?>
效果
