From 8ecece64e13df89ad7ad8514b2d57a3028319e28 Mon Sep 17 00:00:00 2001
From: 134 <a134@134deMacBook-Pro.local>
Date: Fri, 3 Jul 2026 20:20:54 +0800
Subject: [PATCH] fix: filter cutout matte artifacts

---
 app/api/canvas/local-edit/route.ts | 57 ++++++++++++++++++++----------
 1 file changed, 38 insertions(+), 19 deletions(-)

diff --git a/app/api/canvas/local-edit/route.ts b/app/api/canvas/local-edit/route.ts
index 0a0059076..5ad3bb8aa 100644
--- a/app/api/canvas/local-edit/route.ts
+++ b/app/api/canvas/local-edit/route.ts
@@ -111,8 +111,7 @@ const SCALE_ADJUST_STRUCTURE_LOCK_MIN_MASK_RATIO = 0.006;
 const SCALE_ADJUST_STRUCTURE_LOCK_COMPONENT_MIN_RATIO = 0.00018;
 const SCALE_ADJUST_RMBG_MIN_ALPHA_RATIO = 0.012;
 const SCALE_ADJUST_RMBG_MAX_SOLID_ALPHA_RATIO = 0.92;
-const SCALE_ADJUST_RMBG_ALPHA_CLEAN_THRESHOLD = 96;
-const SCALE_ADJUST_RMBG_ALPHA_MEDIAN_SIZE = 5;
+const SCALE_ADJUST_RMBG_ALPHA_CLEAN_THRESHOLD = 42;
 const MIN_REGION_EDGE_PX = 24;
 const SCALE_ADJUST_OPERATION = "scale-adjust";
 type LocalEditOperation = "local-edit" | typeof SCALE_ADJUST_OPERATION;
@@ -1712,36 +1711,48 @@ function getScaleAdjustAlphaBoundingBox(params: {
 
 async function cleanScaleAdjustAlphaChannel(params: {
   height: number;
+  referenceRawRgb?: Buffer | null;
   rawRgba: Buffer;
   threshold?: number;
   width: number;
 }) {
   const {
     height,
+    referenceRawRgb = null,
     rawRgba,
     threshold = SCALE_ADJUST_RMBG_ALPHA_CLEAN_THRESHOLD,
     width,
   } = params;
   const pixelCount = Math.floor(rawRgba.length / 4);
-  const initialAlpha = Buffer.alloc(pixelCount);
-  for (let index = 0; index < pixelCount; index += 1) {
-    const sourceAlpha = rawRgba[index * 4 + 3] || 0;
-    initialAlpha[index] = sourceAlpha >= threshold ? 255 : 0;
-  }
-
-  const alphaData = await sharp(initialAlpha, {
-    raw: { channels: 1, height, width },
-  })
-    .median(SCALE_ADJUST_RMBG_ALPHA_MEDIAN_SIZE)
-    .threshold(128)
-    .raw()
-    .toBuffer();
   const cleanedRaw = Buffer.from(rawRgba);
   const cleanedAlpha = Buffer.alloc(pixelCount);
+  const range = Math.max(1, 255 - threshold);
+  const hasReference =
+    referenceRawRgb && referenceRawRgb.length >= pixelCount * 3;
 
   for (let index = 0; index < pixelCount; index += 1) {
+    const colorIndex = index * 4;
     const alphaIndex = index * 4 + 3;
-    const nextAlpha = alphaData[index] >= 128 ? 255 : 0;
+    const sourceAlpha = rawRgba[alphaIndex] || 0;
+    let matteArtifact = false;
+    if (hasReference && sourceAlpha >= threshold) {
+      const r = rawRgba[colorIndex] || 0;
+      const g = rawRgba[colorIndex + 1] || 0;
+      const b = rawRgba[colorIndex + 2] || 0;
+      const luma = getScaleAdjustPixelLuma(r, g, b);
+      const channelSpread = Math.max(r, g, b) - Math.min(r, g, b);
+      const refIndex = index * 3;
+      const refLuma = getScaleAdjustPixelLuma(
+        referenceRawRgb?.[refIndex] || 0,
+        referenceRawRgb?.[refIndex + 1] || 0,
+        referenceRawRgb?.[refIndex + 2] || 0
+      );
+      matteArtifact = luma <= 18 && channelSpread <= 18 && refLuma >= 42;
+    }
+    const nextAlpha =
+      sourceAlpha < threshold || matteArtifact
+        ? 0
+        : Math.max(0, Math.min(255, Math.round(((sourceAlpha - threshold) / range) * 255)));
     cleanedRaw[alphaIndex] = nextAlpha;
     cleanedAlpha[index] = nextAlpha;
   }
@@ -1818,6 +1829,16 @@ async function buildScaleAdjustRmbgStructureLockedComposite(params: {
     const cutoutWidth = Math.round(Number(cutoutMetadata.width || 0));
     const cutoutHeight = Math.round(Number(cutoutMetadata.height || 0));
     if (cutoutWidth <= 0 || cutoutHeight <= 0) return null;
+    const sameSizeCutout =
+      Math.abs(cutoutWidth - placement.sourceBox.width) <= 2 &&
+      Math.abs(cutoutHeight - placement.sourceBox.height) <= 2;
+    const sourceCropRaw = sameSizeCutout
+      ? await sharp(sourceCropBuffer, { failOn: "none" })
+          .removeAlpha()
+          .toColorspace("srgb")
+          .raw()
+          .toBuffer()
+      : null;
 
     const cutoutRaw = await sharp(normalizedCutout, { failOn: "none" })
       .ensureAlpha()
@@ -1825,6 +1846,7 @@ async function buildScaleAdjustRmbgStructureLockedComposite(params: {
       .toBuffer();
     const { cleanedAlpha, cleanedRaw } = await cleanScaleAdjustAlphaChannel({
       height: cutoutHeight,
+      referenceRawRgb: sourceCropRaw,
       rawRgba: cutoutRaw,
       width: cutoutWidth,
     });
@@ -1851,9 +1873,6 @@ async function buildScaleAdjustRmbgStructureLockedComposite(params: {
       return null;
     }
 
-    const sameSizeCutout =
-      Math.abs(cutoutWidth - placement.sourceBox.width) <= 2 &&
-      Math.abs(cutoutHeight - placement.sourceBox.height) <= 2;
     const fullAlphaMask = cleanedAlpha;
     const sourceMaskBuffer = sameSizeCutout
       ? fullAlphaMask