diff --git a/lib/canvas/generate-image.ts b/lib/canvas/generate-image.ts
index 1002ef17c..3443b2e8d 100644
--- a/lib/canvas/generate-image.ts
+++ b/lib/canvas/generate-image.ts
@@ -2804,7 +2804,7 @@ async function applyScaleAdjustPatchCompositeToImages(params: {
       })
       .png({ compressionLevel: 6 })
       .toBuffer();
-    const patchMask =
+    const diffPatchMask =
       composite.maskMode === "diff"
         ? await buildLocalEditDiffCompositeMask({
             composite: {
@@ -2823,15 +2823,22 @@ async function applyScaleAdjustPatchCompositeToImages(params: {
             sourceBuffer: sourcePatchBuffer,
             width: workspaceBox.width,
           })
-        : staticPatchMask;
+        : null;
+    const patchMask = diffPatchMask || staticPatchMask;
     if (!patchMask) {
       throw new Error("比例调整局部结果合成失败：无法生成合成蒙版");
     }
-    const patchOverlayBuffer = await sharp(resizedGeneratedBuffer, { failOn: "none" })
-      .ensureAlpha()
-      .composite([{ input: patchMask, blend: "dest-in" }])
-      .png({ compressionLevel: 6 })
-      .toBuffer();
+    const patchOverlayBuffer = diffPatchMask
+      ? await sharp(resizedGeneratedBuffer, { failOn: "none" })
+          .removeAlpha()
+          .joinChannel(diffPatchMask)
+          .png({ compressionLevel: 6 })
+          .toBuffer()
+      : await sharp(resizedGeneratedBuffer, { failOn: "none" })
+          .ensureAlpha()
+          .composite([{ input: patchMask, blend: "dest-in" }])
+          .png({ compressionLevel: 6 })
+          .toBuffer();
     const mergedBuffer = await sharp(sourceBuffer, { failOn: "none" })
       .ensureAlpha()
       .composite([