improve small image generator, avoid zoom small image

conf/app.php

@@ -53,6 +53,7 @@ $configs = array(
     'supportedVideoExts' => array('mp4', 'mov', 'm3u8'),
     'screenshot_start' => 1000,     //视频播放页快照截取开始时间，单位：毫秒
     'screenshot_expire_seconds' => 315360000,   //视频封面图缓存3650天
+    'small_image_zoom_rate' => 2.5,   //缩略图在最小尺寸基础上的放大倍数，以确保清晰度
     'enableSmallImage' => true,     //开启图片小尺寸缩略图，设置 false 则关闭
 
     /*

themes/beauty/controller/SiteController.php

@@ -270,7 +270,7 @@ Class SiteController extends Controller {
 
             if (empty($cachedData)) {
                 //从缓存数据中获取目录的realpath
-                $cachedData = Common::getCacheFromFile($cacheId);
+                $cachedData = Common::getCacheFromFile($cacheId, $expireSeconds);
                 if (!empty($cachedData)) {
                     $realpath = $cachedData[$cateId]['realpath'];
                     $scanner = new DirScanner();
@@ -374,15 +374,23 @@ Class SiteController extends Controller {
             list($naturalWidth, $naturalHeight, $imgTypeIndex, $style) = getimagesize($img_filepath);
             $imgType = image_type_to_extension($imgTypeIndex);
 
+            //小图片则保持原图尺寸
+            if ($naturalWidth <= $max_width || $naturalHeight <= $max_height) {
+                return false;
+            }
+
             //生成同比例缩略图尺寸
+            $zoomRate = FSC::$app['config']['small_image_zoom_rate'];        //缩略图在最小尺寸基础上放大比例，为确保清晰度
             $width = $min_width;
             $height = $min_height;
             $aspect = $naturalHeight / $naturalWidth;
             if ($naturalWidth <= $naturalHeight) {
-                $width = $width * 2.5 <= $max_width ? (int)($width * 2.5) : $max_width;
+                if ($width * $zoomRate >= $naturalWidth) {return false;}        //避免把小图片放大
+                $width = $width * $zoomRate <= $max_width ? (int)($width * $zoomRate) : $max_width;
                 $height = (int)($width * $aspect);
             }else {
-                $height = $height * 2.5 <= $max_height ? (int)($height * 2.5) : $max_height;
+                if ($height * $zoomRate >= $naturalHeight) {return false;}      //避免把小图片放大
+                $height = $height * $zoomRate <= $max_height ? (int)($height * $zoomRate) : $max_height;
                 $width = (int)($height / $aspect);
             }