diff --git a/application/src/main/java/run/halo/app/core/attachment/ThumbnailImgTagPostProcessor.java b/application/src/main/java/run/halo/app/core/attachment/ThumbnailImgTagPostProcessor.java
index 65293ca5b..f87537204 100644
--- a/application/src/main/java/run/halo/app/core/attachment/ThumbnailImgTagPostProcessor.java
+++ b/application/src/main/java/run/halo/app/core/attachment/ThumbnailImgTagPostProcessor.java
@@ -3,21 +3,18 @@ package run.halo.app.core.attachment;
 import static org.thymeleaf.templatemode.TemplateMode.HTML;
 
 import java.net.URI;
-import java.util.Objects;
+import java.util.Map;
 import java.util.Optional;
+import java.util.function.Predicate;
 import java.util.stream.Collectors;
 import lombok.extern.slf4j.Slf4j;
-import org.apache.commons.io.FilenameUtils;
 import org.springframework.stereotype.Component;
-import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 import org.thymeleaf.context.ITemplateContext;
 import org.thymeleaf.engine.ElementNames;
 import org.thymeleaf.model.IAttribute;
 import org.thymeleaf.model.IProcessableElementTag;
 import org.thymeleaf.processor.element.MatchingElementName;
-import org.thymeleaf.spring6.context.SpringContextUtils;
-import org.thymeleaf.spring6.context.webflux.SpringWebFluxThymeleafRequestContext;
 import reactor.core.publisher.Mono;
 import run.halo.app.infra.ExternalUrlSupplier;
 import run.halo.app.theme.dialect.ElementTagPostProcessor;
@@ -30,8 +27,12 @@ class ThumbnailImgTagPostProcessor implements ElementTagPostProcessor {
 
     private final ExternalUrlSupplier externalUrlSupplier;
 
-    public ThumbnailImgTagPostProcessor(ExternalUrlSupplier externalUrlSupplier) {
+    private final ThumbnailService thumbnailService;
+
+    public ThumbnailImgTagPostProcessor(ExternalUrlSupplier externalUrlSupplier,
+        ThumbnailService thumbnailService) {
         this.externalUrlSupplier = externalUrlSupplier;
+        this.thumbnailService = thumbnailService;
         this.matchingElementName =
             MatchingElementName.forElementName(HTML, ElementNames.forHTMLName("img"));
     }
@@ -57,63 +58,29 @@ class ThumbnailImgTagPostProcessor implements ElementTagPostProcessor {
         // get img tag
         var imageUri = srcValue.get();
 
-        if (imageUri.isAbsolute()) {
-            // check if the uri is belonged to current site
-            var requestContext = SpringContextUtils.getRequestContext(context);
-            if (!(requestContext instanceof SpringWebFluxThymeleafRequestContext wrc)) {
-                log.debug("Skip processing img tag with absolute url: {}, "
-                    + "because the request context is not webflux", imageUri);
-                return Mono.empty();
-            }
-            var externalUri = externalUrlSupplier.get();
-            if (!externalUri.isAbsolute()) {
-                externalUri = wrc.getServerWebExchange().getRequest().getURI();
-            }
-            if (!Objects.equals(externalUri.getAuthority(), imageUri.getAuthority())) {
-                log.debug("""
-                    Skip processing img tag with external absolute url: {} because \
-                    the url does not belong to the current site\
-                    """, imageUri);
-                return Mono.empty();
-            }
-        }
-
-        var path = imageUri.getPath();
-        if (!path.startsWith("/upload/")) {
-            log.debug("Skip processing img tag with non-upload path: {}", path);
-            return Mono.empty();
-        }
-
-        var fileSuffix = FilenameUtils.getExtension(imageUri.getPath());
-        if (!ThumbnailUtils.isSupportedImage(fileSuffix)) {
-            log.debug("Skip processing img tag with unsupported image suffix: {}", fileSuffix);
-            return Mono.empty();
-        }
-
-        // build thumbnails
-        var thumbnails = ThumbnailUtils.buildSrcsetMap(imageUri);
-        if (CollectionUtils.isEmpty(thumbnails)) {
-            log.debug("Skip processing img tag because the image is not supported: {}", imageUri);
-            return Mono.empty();
-        }
-
-        var modelFactory = context.getModelFactory();
-        if (!tag.hasAttribute("sizes")) {
-            tag = modelFactory.setAttribute(tag, "sizes", """
-                (max-width: 640px) 94vw, \
-                (max-width: 768px) 92vw, \
-                (max-width: 1024px) 88vw, \
-                min(800px, 85vw)\
-                """);
-        }
-        var srcset = thumbnails.keySet().stream()
-            .map(size -> {
-                var uri = thumbnails.get(size);
-                return uri + " " + size.getWidth() + "w";
+        return thumbnailService.get(imageUri)
+            .filter(Predicate.not(Map::isEmpty))
+            .map(thumbnails -> {
+                var modelFactory = context.getModelFactory();
+                var newTag = tag;
+                if (!newTag.hasAttribute("sizes")) {
+                    newTag = modelFactory.setAttribute(newTag, "sizes", """
+                        (max-width: 640px) 94vw, \
+                        (max-width: 768px) 92vw, \
+                        (max-width: 1024px) 88vw, \
+                        min(800px, 85vw)\
+                        """);
+                }
+                var srcset = thumbnails.keySet().stream()
+                    .map(size -> {
+                        var uri = thumbnails.get(size);
+                        return uri + " " + size.getWidth() + "w";
+                    })
+                    .collect(Collectors.joining(", "));
+                newTag = modelFactory.setAttribute(newTag, "srcset", srcset);
+                return newTag;
             })
-            .collect(Collectors.joining(", "));
-        tag = modelFactory.setAttribute(tag, "srcset", srcset);
-        return Mono.just(tag);
+            .defaultIfEmpty(tag);
     }
 
 }