From c79da3e1d086bb1a7910134b74ce74a1bf0cef2b Mon Sep 17 00:00:00 2001
From: 134 <a134@134deMacBook-Pro.local>
Date: Mon, 6 Jul 2026 03:41:56 +0800
Subject: [PATCH] fix: preserve single-channel scale adjust masks after blur

---
 app/api/canvas/local-edit/route.ts | 10 ++++++++++
 lib/canvas/generate-image.ts       |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/app/api/canvas/local-edit/route.ts b/app/api/canvas/local-edit/route.ts
index 78ec735f9..dec126da7 100644
--- a/app/api/canvas/local-edit/route.ts
+++ b/app/api/canvas/local-edit/route.ts
@@ -2132,7 +2132,9 @@ async function buildScaleAdjustMaskWashPatch(params: {
   const alpha = await sharp(maskBuffer, {
     raw: { channels: 1, height: box.height, width: box.width },
   })
+    .greyscale()
     .blur(Math.max(1.2, Math.min(box.width, box.height) * 0.018))
+    .greyscale()
     .raw()
     .toBuffer();
   const rgba = Buffer.alloc(box.width * box.height * 4);
@@ -2158,7 +2160,9 @@ async function buildScaleAdjustCompositeClipMaskPatch(params: {
   const alpha = await sharp(Buffer.from(maskBuffer), {
     raw: { channels: 1, height: box.height, width: box.width },
   })
+    .greyscale()
     .blur(Math.max(0.8, Math.min(box.width, box.height) * 0.006))
+    .greyscale()
     .raw()
     .toBuffer();
   const rgba = Buffer.alloc(box.width * box.height * 4);
@@ -2183,7 +2187,9 @@ async function buildScaleAdjustOverlayClipMaskPatch(imageBuffer: Buffer) {
   const alpha = await sharp(imageBuffer, { failOn: "none" })
     .ensureAlpha()
     .extractChannel(3)
+    .greyscale()
     .blur(Math.max(0.8, Math.min(width, height) * 0.006))
+    .greyscale()
     .raw()
     .toBuffer();
   const rgba = Buffer.alloc(width * height * 4);
@@ -2297,7 +2303,9 @@ async function applyScaleAdjustAlphaMaskToRgba(params: {
   const softenedAlpha = await sharp(Buffer.from(alphaMask), {
     raw: { channels: 1, height, width },
   })
+    .greyscale()
     .blur(blur)
+    .greyscale()
     .raw()
     .toBuffer();
   const output = Buffer.from(rawRgba);
@@ -3184,7 +3192,9 @@ async function buildScaleAdjustStructureLockedComposite(params: {
   const subjectAlpha = await sharp(alphaMaskForSubject, {
     raw: { channels: 1, height: bbox.height, width: bbox.width },
   })
+    .greyscale()
     .blur(Math.max(0.7, Math.min(bbox.width, bbox.height) * 0.006))
+    .greyscale()
     .png({ compressionLevel: 6 })
     .toBuffer();
   const widthFactor =
diff --git a/lib/canvas/generate-image.ts b/lib/canvas/generate-image.ts
index e56eab833..aca38923c 100644
--- a/lib/canvas/generate-image.ts
+++ b/lib/canvas/generate-image.ts
@@ -2314,7 +2314,9 @@ async function buildScaleAdjustFallbackObjectPng(params: {
   const alphaBuffer = await sharp(mask, {
     raw: { channels: 1, height: box.height, width: box.width },
   })
+    .greyscale()
     .blur(Math.max(0.7, Math.min(box.width, box.height) * 0.012))
+    .greyscale()
     .png({ compressionLevel: 6 })
     .toBuffer();