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：

试用了一下后，发现有这样几个问题：

1、png图片生成的缩略图是jpg格式的

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

     srcimg = $imgPath;            $this->resize_width = $width;            $this->resize_height = $height;            $this->cut = $isCut;            //图片的类型            $this->type = strtolower(substr(strrchr($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);            //生成图象            $this->newimg();            ImageDestroy ($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($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));                }                if($ratio>=$resize_ratio) {                    //高度优先                    imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);                } else {                    //宽度优先                    imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($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, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));                    }                    imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, ($this->resize_width)/$ratio, $this->width, $this->height);                } else {                    $newimg = imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);                    if($this->type=="png") {                        imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));                    }                    imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, ($this->resize_height)*$ratio, $this->resize_height, $this->width, $this->height);                }            }            if($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,0,$name_length-1);            $this->dstimg = $dstpath;        }    }?>

使用

使用时，直接调用类的构造函数即可，构造函数如下：

$resizeimage = new resizeimage($imgPath, $width, $height, $isCut, $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

$savePath：缩略图地址（可以跟原图片地址相同）

示例

效果