PHP实现图片压缩和等比例缩小的函数

function compressAndResizeImage($source, $maxWidth=1080, $quality=39) {
    $path = pathinfo($source);
    //创建文件夹
    $smallPath = $path['dirname'].'/small';
    if(!is_dir($smallPath)){
        mkdir($path['dirname'].'/small',0777,true);
    }

// 压缩后保存的路径
    $destination = $smallPath.'/'.$path['filename'].'.jpg';
    if(file_exists($destination)){
        return $destination;
    }
// 获取原始图片的信息
    list($origWidth, $origHeight, $type) = getimagesize($source);
// 创建原始图片资源
    if ($type == IMAGETYPE_JPEG) {
        $sourceImage = imagecreatefromjpeg($source);
    } elseif ($type == IMAGETYPE_PNG) {
        $sourceImage = imagecreatefrompng($source);
    } elseif ($type == IMAGETYPE_GIF) {
        $sourceImage = imagecreatefromgif($source);
    }else {
        $sourceImage = imagecreatefromstring($source);
    }
    if ($origWidth > $maxWidth) {
        // 计算缩放比例
        $ratio = $maxWidth / $origWidth;
        $newWidth = $maxWidth;
        $newHeight = $origHeight * $ratio;
// 创建缩放后的图片资源
        $newImage = imagecreatetruecolor($newWidth, $newHeight);
        imagecopyresampled($newImage, $sourceImage, 0, 0, 0, 0, $newWidth, $newHeight, $origWidth, $origHeight);
// 保存缩放后的图片
        imagejpeg($newImage, $destination, $quality);
        imagedestroy($newImage);
    } else{
        imagejpeg( $sourceImage, $destination, $quality);
        // 释放内存
        imagedestroy($sourceImage);
    }
    return $destination;
}