fix: focus scale adjust subject guide

app/api/canvas/local-edit/route.ts

@@ -791,8 +791,18 @@ function getScaleAdjustVisualGuidePlacement(params: {
     sourceTop + 1,
     height
   );
-  const sourceWidth = Math.max(1, Math.round(sourceRight - sourceLeft));
-  const sourceHeight = Math.max(1, Math.round(sourceBottom - sourceTop));
+  const sourceFootprintBox = {
+    left: Math.round(sourceLeft),
+    top: Math.round(sourceTop),
+    width: Math.max(1, Math.round(sourceRight - sourceLeft)),
+    height: Math.max(1, Math.round(sourceBottom - sourceTop)),
+  };
+  const sourceBox = getScaleAdjustFocusedSourceBox({
+    region,
+    sourceBox: sourceFootprintBox,
+  });
+  const sourceWidth = sourceBox.width;
+  const sourceHeight = sourceBox.height;
   const widthScale = target.width / Math.max(1, sourceWidth);
   const heightScale = target.height / Math.max(1, sourceHeight);
   const uniformScale = Math.max(
@@ -831,16 +841,64 @@ function getScaleAdjustVisualGuidePlacement(params: {
     placedTop: Math.max(0, Math.round(placedTop)),
     placedWidth: Math.max(1, Math.round(placedWidth)),
     sourceBox: {
-      left: Math.round(sourceLeft),
-      top: Math.round(sourceTop),
+      left: sourceBox.left,
+      top: sourceBox.top,
       width: sourceWidth,
       height: sourceHeight,
     },
+    sourceFootprintBox,
     targetBox: target,
     uniformScale,
   };
 }
 
+function getScaleAdjustFocusDirection(region: NormalizedLocalEditRegion) {
+  const text = normalizeScaleAdjustModelText(region.prompt);
+  const compact = text.replace(/[^a-z0-9\u4e00-\u9fa5]+/g, "");
+  if (text.includes("left") || compact.includes("左")) return "left";
+  if (text.includes("right") || compact.includes("右")) return "right";
+  if (text.includes("top") || compact.includes("上")) return "top";
+  if (text.includes("bottom") || compact.includes("下")) return "bottom";
+  return "";
+}
+
+function getScaleAdjustFocusedSourceBox(params: {
+  region: NormalizedLocalEditRegion;
+  sourceBox: { left: number; top: number; width: number; height: number };
+}) {
+  const { region, sourceBox } = params;
+  const direction = getScaleAdjustFocusDirection(region);
+  if (!direction) return sourceBox;
+
+  const minWidth = Math.max(1, Math.round(sourceBox.width * 0.42));
+  const minHeight = Math.max(1, Math.round(sourceBox.height * 0.42));
+  let left = sourceBox.left;
+  let top = sourceBox.top;
+  let width = sourceBox.width;
+  let height = sourceBox.height;
+
+  if (direction === "left") {
+    width = Math.max(minWidth, Math.round(sourceBox.width * 0.68));
+  } else if (direction === "right") {
+    const nextWidth = Math.max(minWidth, Math.round(sourceBox.width * 0.68));
+    left = sourceBox.left + sourceBox.width - nextWidth;
+    width = nextWidth;
+  } else if (direction === "top") {
+    height = Math.max(minHeight, Math.round(sourceBox.height * 0.72));
+  } else if (direction === "bottom") {
+    const nextHeight = Math.max(minHeight, Math.round(sourceBox.height * 0.72));
+    top = sourceBox.top + sourceBox.height - nextHeight;
+    height = nextHeight;
+  }
+
+  return {
+    left,
+    top,
+    width,
+    height,
+  };
+}
+
 function buildScaleAdjustPatchMaskSvg(params: { height: number; width: number }) {
   const { height, width } = params;
   const blur = Math.max(2, Math.min(14, Math.round(Math.min(width, height) * 0.035)));
@@ -966,7 +1024,7 @@ async function buildScaleAdjustVisualLayoutGuideBuffer(params: {
       scalePercent,
       width: sourceWidth,
     });
-    sourceFootprintBoxes.push(placement.sourceBox);
+    sourceFootprintBoxes.push(placement.sourceFootprintBox);
     placements.push(placement);
 
     const resizedCropBuffer = await sharp(sourceBuffer, { failOn: "none" })
@@ -1989,6 +2047,7 @@ export async function POST(request: NextRequest) {
               : undefined,
           sourceImageUrl,
           regions: regions.map((region) => region.rect),
+          regionPrompts: regions.map((region) => region.prompt),
           ...(typeof scalePercent === "number"
             ? { scalePercent: scalePercent as ScaleAdjustPercent }
             : {}),

lib/canvas/generate-image.ts

@@ -56,6 +56,7 @@ export interface CanvasScaleAdjustVerificationConfig {
   allowOutsideChangedWhenChangedInside?: boolean;
   protectedRegions?: CanvasLocalEditCompositeRegion[];
   rejectFailedCandidates?: boolean;
+  regionPrompts?: string[];
   sourceImageUrl: string;
   regions: CanvasLocalEditCompositeRegion[];
   targetRegions?: CanvasLocalEditCompositeRegion[];
@@ -1405,6 +1406,63 @@ function getRawPixelIndex(width: number, x: number, y: number) {
   return (y * width + x) * 3;
 }
 
+function normalizeScaleAdjustFocusText(input: unknown) {
+  return String(input || "")
+    .trim()
+    .toLowerCase()
+    .normalize("NFKC")
+    .replace(/[「」『』【】[\]()（）{}]/g, " ")
+    .replace(/[_/|:：,，.。+]+/g, " ")
+    .replace(/\s+/g, " ");
+}
+
+function getScaleAdjustFallbackFocusDirection(prompt: unknown) {
+  const text = normalizeScaleAdjustFocusText(prompt);
+  const compact = text.replace(/[^a-z0-9\u4e00-\u9fa5]+/g, "");
+  if (text.includes("left") || compact.includes("左")) return "left";
+  if (text.includes("right") || compact.includes("右")) return "right";
+  if (text.includes("top") || compact.includes("上")) return "top";
+  if (text.includes("bottom") || compact.includes("下")) return "bottom";
+  return "";
+}
+
+function getScaleAdjustFallbackFocusedSourceBox(params: {
+  prompt?: string;
+  sourceBox: ReturnType<typeof rectToPixelBox>;
+}) {
+  const { prompt, sourceBox } = params;
+  const direction = getScaleAdjustFallbackFocusDirection(prompt);
+  if (!direction) return sourceBox;
+
+  const minWidth = Math.max(1, Math.round(sourceBox.width * 0.42));
+  const minHeight = Math.max(1, Math.round(sourceBox.height * 0.42));
+  let left = sourceBox.left;
+  let top = sourceBox.top;
+  let width = sourceBox.width;
+  let height = sourceBox.height;
+
+  if (direction === "left") {
+    width = Math.max(minWidth, Math.round(sourceBox.width * 0.68));
+  } else if (direction === "right") {
+    const nextWidth = Math.max(minWidth, Math.round(sourceBox.width * 0.68));
+    left = sourceBox.left + sourceBox.width - nextWidth;
+    width = nextWidth;
+  } else if (direction === "top") {
+    height = Math.max(minHeight, Math.round(sourceBox.height * 0.72));
+  } else if (direction === "bottom") {
+    const nextHeight = Math.max(minHeight, Math.round(sourceBox.height * 0.72));
+    top = sourceBox.top + sourceBox.height - nextHeight;
+    height = nextHeight;
+  }
+
+  return {
+    left,
+    top,
+    width,
+    height,
+  };
+}
+
 function getLuma(r: number, g: number, b: number) {
   return r * 0.299 + g * 0.587 + b * 0.114;
 }
@@ -1662,13 +1720,21 @@ async function buildScaleAdjustDeterministicFallbackImages(params: {
       region: targetRegion,
       width: sourceImage.sourceWidth,
     });
+    const prompt = verification.regionPrompts?.[index] || "";
+    const focusedSourceBox = getScaleAdjustFallbackFocusedSourceBox({
+      prompt,
+      sourceBox,
+    });
     const mask = buildScaleAdjustFallbackSubjectMask({
-      box: sourceBox,
+      box: focusedSourceBox,
       raw: baseRaw,
       width: sourceImage.sourceWidth,
     });
     const maskedPixels = mask.reduce((sum, value) => sum + (value ? 1 : 0), 0);
-    if (maskedPixels < Math.max(24, sourceBox.width * sourceBox.height * 0.015)) {
+    if (
+      maskedPixels <
+      Math.max(24, focusedSourceBox.width * focusedSourceBox.height * 0.015)
+    ) {
       console.warn("[Canvas Generate Image] Scale adjust deterministic fallback skipped sparse mask:", {
         debugLabel,
         maskedPixels,
@@ -1677,19 +1743,19 @@ async function buildScaleAdjustDeterministicFallbackImages(params: {
       continue;
     }
     const background = estimateScaleAdjustFallbackBackground({
-      box: sourceBox,
+      box: focusedSourceBox,
       raw: baseRaw,
       width: sourceImage.sourceWidth,
     });
     const objectBuffer = await buildScaleAdjustFallbackObjectPng({
-      box: sourceBox,
+      box: focusedSourceBox,
       mask,
       sourceBuffer: sourceImage.sourceBuffer,
       targetBox,
     });
     baseRaw = inpaintScaleAdjustMaskedRegion({
       background,
-      box: sourceBox,
+      box: focusedSourceBox,
       mask,
       raw: baseRaw,
       width: sourceImage.sourceWidth,