php的GD库能否按百分比压缩图片?

用php的GD库压缩图片时，可以填入具体的宽和高进行压缩。那么，能否按百分比压缩呢，比如压缩为原图的90%，80%….等?

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用php的GD库压缩图片时，可以填入具体的宽和高进行压缩。那么，能否按百分比压缩呢，比如压缩为原图的90%，80%….等?

可以啊，中午刚给朋友搞了个压缩的，

<code>    <?php    /*+-----------------------------------------------------------------------+*/    /*+ jpg,gif,png图片等比例压缩                                             +*/    /*+-----------------------------------------------------------------------+*/    class RarImag{     /**      * 得到等比例缩放的长宽      */     function getNewSize($maxWidth, $maxHeight, $srcWidth, $srcHeight) {      if($srcWidth > $maxWidth) {       $maxWidth = $maxWidth;       if($srcHeight > $maxHeight) {        $maxHeight = ($srcHeight/$srcHeight) * $maxWidth;       } else {         $maxHeight = $srcHeight;       }       return array('width' => $maxWidth,'height' => $maxHeight);      }          if($srcHeight > $maxHeight) {       $maxHeight = $maxHeight;       if($srcWidth > $maxWidth) {         $maxWidth = ($srcWidth/$srcHeight) * $maxHeight;       } else {         $maxWidth = $srcWidth;       }       return array('width' => $srcWidth,'height' => $maxHeight);      }          return array('width' => $srcWidth,'height' => $srcHeight);    }     /**      * 等比例生成缩略图      *      * @param  String  $srcFile  原始文件路径      * @param  String  $dstFile  目标文件路径      * @param  Integer  $maxWidth  生成的目标文件的最大宽度      * @param  Integer  $maxHeight  生成的目标文件的最大高度      * @return  Boolean  生成成功则返回true，否则返回false      */     function makeThumb($srcFile, $dstFile, $maxWidth, $maxHeight) {      if ($size = getimagesize($srcFile)) {       $srcWidth = $size[0];       $srcHeight = $size[1];       $mime = $size['mime'];       switch ($mime) {        case 'image/jpeg';         $isJpeg = true;         break;        case 'image/gif';         $isGif = true;         break;        case 'image/png';         $isPng = true;         break;        default:         return false;         break;       }       //header("Content-type:$mime");       $arr = $this->getNewSize($maxWidth, $maxHeight, $srcWidth, $srcHeight);       $thumbWidth = $arr['width'];       $thumbHeight = $arr['height'];       if (isset($isJpeg) && $isJpeg) {        $dstThumbPic = imagecreatetruecolor($thumbWidth, $thumbHeight);        $srcPic = imagecreatefromjpeg($srcFile);        imagecopyresampled($dstThumbPic, $srcPic, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $srcWidth, $srcHeight);        imagejpeg($dstThumbPic, $dstFile, 100);        imagedestroy($dstThumbPic);        imagedestroy($srcPic);        return true;       } elseif (isset($isGif) && $isGif) {        $dstThumbPic = imagecreatetruecolor($thumbWidth, $thumbHeight);        //创建透明画布        imagealphablending($dstThumbPic, true);        imagesavealpha($dstThumbPic, true);        $trans_colour = imagecolorallocatealpha($dstThumbPic, 0, 0, 0, 127);        imagefill($dstThumbPic, 0, 0, $trans_colour);        $srcPic = imagecreatefromgif($srcFile);        imagecopyresampled($dstThumbPic, $srcPic, 0, 0, 0, 0, $thumbWidth, $thumbHeight, $srcWidth, $srcHeight);        imagegif($dstThumbPic, $dstFile);        imagedestroy($dstThumbPic);        imagedestroy($srcPic);        return true;       } elseif (isset($isPng) && $isPng) {        $dstThumbPic = imagecreatetruecolor($thumbWidth, $thumbHeight);        //创建透明画布        imagealphablending($dstThumbPic, true);        imagesavealpha($dstThumbPic, true);        $trans_colour = imagecolorallocatealpha($dstThumbPic, 0, 0, 0, 127);        imagefill($dstThumbPic, 0, 0, $trans_colour);        $srcPic = imagecreatefrompng($srcFile);        imagecopyresampled($dstThumbPic, $srcPic, 0, 0, 0, 0, $thumbWi<mark>6来源gaodaimacom搞#^代%!码网</mark><strong>搞gaodaima代码</strong>dth, $thumbHeight, $srcWidth, $srcHeight);        imagepng($dstThumbPic, $dstFile);        imagedestroy($dstThumbPic);        imagedestroy($srcPic);        return true;       } else {        return false;       }      } else {       return false;      }     }    }    ?></code>

imagejpeg() 有一个参数可以设定压缩比例
http://php.net/manual/zh/function.imagejpeg.php

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