PHP 生成图片图片按照比例压缩，图片居中背景大小固定-蒲公英云

PHP 生成图片图片按照比例压缩，图片居中背景大小固定

PHP 7.0
需求：上传任意大小图片，按照宽高比例压缩，生成固定大小的图片，不足的地方用白边补齐

$height = $width = 400;
        $file_info = @getimagesize($filename);
        $orig_width = $file_info[0] ?? 0;
        $orig_height = $file_info[1] ?? 0;
        $file_type = $file_info['mime'] ?? '';
        // 生成等比例缩放图
        $tmp_image_width = 0;
        $tmp_image_height = 0;
        if ($orig_width / $orig_height >= $width / $height) {
            $tmp_image_width = $width;
            $tmp_image_height = round($tmp_image_width * $orig_height / $orig_width);
        } else {
            $tmp_image_height = $height;
            $tmp_image_width = round($tmp_image_height * $orig_width / $orig_height);
        }
        $tmp_image = imagecreatetruecolor($tmp_image_width, $tmp_image_height);
        $orgi_image = @imagecreatefromjpeg($filename);
        imagecopyresampled($tmp_image, $orgi_image, 0, 0, 0, 0, $tmp_image_width, $tmp_image_height, $orig_width, $orig_height);
        // 添加白色背景
        $final_image = imagecreatetruecolor($width, $height);
        $color = imagecolorallocate($final_image, 255, 255, 255);
        imagefill($final_image, 0, 0, $color);
        $x = round(($width - $tmp_image_width) / 2);
        $y = round(($height - $tmp_image_height) / 2);
        imagecopy($final_image, $tmp_image, $x, $y, 0, 0, $tmp_image_width, $tmp_image_height);
        // 输出
        $preview_img_name = 'square_img.jpg';
        imagejpeg($final_image, $preview_img_name, 100);
        imagedestroy($orgi_image);
        imagedestroy($tmp_image);
        imagedestroy($final_image);