php如何產生持透明png的圖片縮圖

註：此功能依賴GD2圖形庫

最近要用php產生縮圖，在網上找了一下，發現了這篇文章：PHP產生圖片縮圖

試用了一下後，發現有這樣幾個問題：

1、png圖片產生的縮圖是jpg格式的

2、png圖片產生的縮圖沒有了透明（半透明）效果（填充了黑色背景）

3、代碼文法比較老

因此，在這個版本的基礎上簡單修改最佳化了一下。

PHP產生縮圖類

php /* * desc: Resize Image(png, jpg, gif)     * author: 十年後的盧哥哥(http://www.cnblogs.com/lurenjiashuo/)     * date: 2014.11.13     * base from: http://www.oschina.net/code/snippet_5189_2491 */class ResizeImage { //圖片類型private$type; //實際寬度private$width; //實際高度private$height; //改變後的寬度private$resize_width; //改變後的高度private$resize_height; //是否裁圖private$cut; //源圖象private$srcimg; //靶心圖表象地址private$dstimg; //臨時建立的圖象private$im; function __construct($imgPath, $width, $height, $isCut, $savePath) { $this->srcimg = $imgPath; $this->resize_width = $width; $this->resize_height = $height; $this->cut = $isCut; //圖片的類型$this->type = strtolower(substr(strrchr($this->srcimg,"."),1)); //初始化圖象$this->initi_img(); //靶心圖表象地址$this -> dst_img($savePath); //--$this->width = imagesx($this->im); $this->height = imagesy($this->im); //產生圖象$this->newimg();            ImageDestroy ($this->im);        } privatefunction newimg() { //改變後的圖象的比例$resize_ratio = ($this->resize_width)/($this->resize_height); //實際圖象的比例$ratio = ($this->width)/($this->height); if($this->cut) { //裁圖$newimg = imagecreatetruecolor($this->resize_width,$this->resize_height); if($this->type=="png") {                    imagefill($newimg, 0, 0, imagecolorallocatealpha($newimg, 0, 0, 0, 127));                } if($ratio>=$resize_ratio) { //高度優先 imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width,$this->resize_height, (($this->height)*$resize_ratio), $this->height);                } else { //寬度優先 imagecopyresampled($newimg, $this->im, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width)/$resize_ratio));                }            } else { //不裁圖if($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,$this->dstimg);            }        } //初始化圖象privatefunction initi_img() { if($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);            }        } //圖象目標地址privatefunction 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

使用時，直接調用類的建構函式即可，建構函式如下：

$resizeimage = new resizeimage($imgPath, $width, $height, $isCut, $savePath);

參數

$imgPath：原圖片地址

$width：縮圖寬

$height：縮圖高

$isCut：是否裁剪，bool值

$savePath：縮圖地址（可以跟原圖片地址相同）

樣本

php include "ResizeImage.php"; //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", 320, 240, false, "img/test_320_240.png"); ?>

效果

以上就介紹了php如何產生持透明png的圖片縮圖，包括了php產生縮圖方面的內容，希望對PHP教程有興趣的朋友有所協助。

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