php等比缩放图片处理

php图片处理时有时需要对图片进行二次处理，比如把图片裁剪到指定范围

案例：

    /**
     * 等比缩放图片处理
     * @param $sourceImage 原图片
     * @param int $height 裁剪高度
     * @param int $width 裁剪宽度
     * @param string $dir 新图片目录
     * @return bool|string
     * @throws Exception
     */
    public static function dealImageSize($sourceImage, $height=300, $width=300, $dir = "MapSearch/"){
        if(empty($sourceImage)){
            throw new Exception('缺少必要参数', 400);
        }
        $source_path = $sourceImage;
        $source_info = getimagesize($source_path);
        $source_width = $source_info[0];
        $source_height = $source_info[1];
        $source_mime = $source_info['mime'];
        $source_ratio = $source_height / $source_width;
        $target_ratio = $height / $width;
        // 源图过高
        if ($source_ratio > $target_ratio)
        {
            $cropped_width = $source_width;
            $cropped_height = $source_width * $target_ratio;
            $source_x = 0;
            $source_y = ($source_height - $cropped_height) / 2;
        }
        // 源图过宽
        elseif ($source_ratio < $target_ratio)
        {
            $cropped_width = $source_height / $target_ratio;
            $cropped_height = $source_height;
            $source_x = ($source_width - $cropped_width) / 2;
            $source_y = 0;
        }
        // 源图适中
        else
        {
            $cropped_width = $source_width;
            $cropped_height = $source_height;
            $source_x = 0;
            $source_y = 0;
        }
　　　　　//获取图片类型 并载入一个新的画像
        [$source_image,$source_type] = self::switchType($source_mime,$source_path);
        $target_image = imagecreatetruecolor($width, $height);
        $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);
        $tmpDir = EASYSWOOLE_ROOT . '/runtime/'.$dir;
        if (!file_exists($tmpDir)) {
            mkdir($tmpDir, 0777, true);//检查是否有该文件夹，如果没有就创建，并给予最高权限
        }
        // 裁剪
        imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
        // 缩放
        imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $width, $height, $cropped_width, $cropped_height);
        $file_name = $tmpDir.rand(0000,9999).".".$source_type;
        imagepng($target_image,$file_name);
        imagedestroy($target_image);
        return $file_name;
    }


    /**
　　　* 获取图片类型
     * @param $source_mime
     * @param $source_path
     * @return array|bool
     */
    public static function switchType($source_mime,$source_path){
        switch ($source_mime)
        {
            case 'image/gif':
                $source_image = imagecreatefromgif($source_path);
                $source_type = "gif";
                break;
            case 'image/jpeg':
                $source_image = imagecreatefromjpeg($source_path);
                $source_type = "jpg";
                break;
            case 'image/png':
                $source_type = "png";
                $source_image = imagecreatefrompng($source_path);
                break;
            default:
                return false;
                break;
        }
        return [$source_image,$source_type];
    }

以上就是今天的全部内容！