function pic()
{
    //获取get传入关键词，默认一路火系统
	$kw = isset($_GET["k"]) ? $_GET["k"] : "一路火系统";
	$kw = trim($kw);
	$kw = strip_tags($kw);
	//截取最多100字符
	$dst_nr = mb_substr($kw, 0, 100, 'UTF-8');

    // ============ 新增这一行：绘图用文本转GBK，专门修复GD FreeType乱码 ============
    $drawText = iconv("UTF-8", "GBK//IGNORE", $dst_nr);
    // =========================================================================

    $cacheDir = __DIR__.'/cache';
    $cacheFile = $cacheDir.'/'.md5($dst_nr).'.jpg'; //md5仍然用原始utf8字符串，缓存key不变！
    $lockFile  = $cacheDir.'/'.md5($dst_nr).'.lock';
    //缓存已存在，直接读取磁盘静态文件返回
    if(file_exists($cacheFile)){
        read_static_file($cacheFile);
    }
    //锁文件超过120秒判定为僵尸锁，直接删除，防止进程被杀永久卡死
    if(file_exists($lockFile) && (time()-filemtime($lockFile))>120){
        @unlink($lockFile);
    }
    //创建锁文件，用于并发防竞态
    $fpLock = fopen($lockFile, 'w');
    if($fpLock === false){
        http_response_code(503);
        die('系统繁忙');
    }
    //加排他锁
    flock($fpLock, LOCK_EX);
    //拿到锁之后二次校验缓存，防止等待锁期间别的进程已经生成图片
    if(file_exists($cacheFile)){
        flock($fpLock, LOCK_UN);
        fclose($fpLock);
        @unlink($lockFile);
        read_static_file($cacheFile);
    }
    //禁用range分段请求
    if (!empty($_SERVER['HTTP_RANGE'])) {
        header("Accept-Ranges: none");
        unset($_SERVER['HTTP_RANGE']);
    }

    // ========== 改动区域：固定500*250，棕色纯色背景，不再读取image文件夹背景图 ==========
    $imgWidth  = 500;
    $imgHeight = 250;
    $dst = imagecreatetruecolor($imgWidth, $imgHeight);
    //棕色 RGB:128,74,26，可自行修改三色值调整深浅
    $bgColor = imagecolorallocate($dst,128,74,26);
    imagefill($dst,0,0,$bgColor);
    // =====================================================================================

    //字体文件路径校验
    $font = __DIR__ . '/Alibaba-PuHuiTi-Bold.ttf';
    if (!file_exists($font)) {
        http_response_code(404);
        die('字体文件缺失');
    }
    $baseFontSize = 38;    //基础字号
    $minFontSize  = 22;    //最小字号下限
    $lineGap      = 10;    //文本行间距
    $textScale    = 0.7;   //文字区域占画布比例
    //文字允许最大宽高范围
    $allowWidth  = intval($imgWidth * $textScale);
    $allowHeight = intval($imgHeight * $textScale);
    //文字白色，描边黑色半透明
    $textColor = imagecolorallocatealpha($dst,255,255,255,0);
    $strokeColor = imagecolorallocatealpha($dst,0,0,0,40);
    // 这里全部换成 $drawText，不再直接用 $dst_nr
    list($singleW) = getTextBox($baseFontSize, $drawText, $font);
    //判断是否需要自动换行
    if ($singleW <= $allowWidth) {
        $textLines = array($drawText);
    } else {
        $textLines = array();
        $tempStr = '';
        $strTotalLen = mb_strlen($dst_nr, 'UTF-8');
        //逐字符做自动换行切割（⚠️ 重点：这里循环切割依然基于原始UTF8 $dst_nr，防止切错汉字）
        for ($i = 0; $i < $strTotalLen; $i++) {
            $char = mb_substr($dst_nr, $i, 1, 'UTF-8');
            $tmpTest = iconv("UTF-8", "GBK//IGNORE", $tempStr.$char);
            list($tmpW) = getTextBox($baseFontSize, $tmpTest, $font);
            if ($tmpW > $allowWidth-5 && $tempStr !== '') {
                $textLines[] = iconv("UTF-8", "GBK//IGNORE", $tempStr);
                $tempStr = $char;
            } else {
                $tempStr .= $char;
            }
        }
        if ($tempStr !== '') $textLines[] = iconv("UTF-8", "GBK//IGNORE", $tempStr);
    }
    //字号自动降级，超出范围就缩小字号直到满足限制
    $fontsize = $baseFontSize;
    while ($fontsize >= $minFontSize) {
        $blockH = getBlockTotalHeight($textLines,$fontsize,$font,$lineGap);
        $maxLineW = 0;
        foreach ($textLines as $line) {
            list($lw) = getTextBox($fontsize,$line,$font);
            if ($lw > $maxLineW) $maxLineW = $lw;
        }
        if ($maxLineW <= $allowWidth && $blockH <= $allowHeight) break;
        $fontsize--;
    }
    //缓存每行文字宽高信息
    $lineInfo = array();
    foreach ($textLines as $lineTxt) {
        list($lw,$lh) = getTextBox($fontsize,$lineTxt,$font);
        $lineInfo[] = array('text'=>$lineTxt,'w'=>$lw,'h'=>$lh);
    }
    //计算文本块起始Y坐标，整体垂直居中
    $totalBlockH = getBlockTotalHeight($textLines,$fontsize,$font,$lineGap);
    $currentY = ($imgHeight-$totalBlockH)/2;
    foreach ($lineInfo as $info) {
        $x = ($imgWidth-$info['w'])/2; //水平居中
        $drawY = $currentY + $info['h'];
        drawStrokeText($dst,$fontsize,0,$x,$drawY,$strokeColor,$textColor,$font,$info['text']);
        $currentY += $info['h'] + $lineGap;
    }
    //新建真彩色画布，复制背景图层
    $newImg = imagecreatetruecolor($imgWidth,$imgHeight);
    imagecopy($newImg,$dst,0,0,0,0,$imgWidth,$imgHeight);
    imagedestroy($dst);
    //重点：直接写入磁盘文件，不经过PHP内存缓冲区，禁止内存图片直接输出
    $writeOk = imagejpeg($newImg, $cacheFile,90);
    imagedestroy($newImg);
    //释放文件锁，删除锁文件
    flock($fpLock, LOCK_UN);
    fclose($fpLock);
    @unlink($lockFile);
    //校验磁盘静态文件真正生成成功才输出
    if(!$writeOk || !file_exists($cacheFile)){
        http_response_code(500);
        die('图片写入磁盘失败');
    }
    //读取已经落地完成的磁盘静态jpg输出
    read_static_file($cacheFile);
}