ai-chatbot/app/api/canvas/detail-subject-analyze/route.ts

import { NextResponse } from "next/server";
import sharp from "sharp";
import { auth } from "@/app/(auth)/auth";
import {
  clampNormalized,
  type DetailUiSubjectAnalysis,
} from "@/lib/detail-ui-subject-analysis";

export const runtime = "nodejs";
export const maxDuration = 30;

const ANALYZE_MAX_SIDE = 128;
const ANALYZE_FETCH_TIMEOUT_MS = 12000;

function percentile(values: number[], ratio: number) {
  if (values.length === 0) return 0;
  const sorted = [...values].sort((left, right) => left - right);
  const index = Math.max(0, Math.min(sorted.length - 1, Math.floor(sorted.length * ratio)));
  return sorted[index] || 0;
}

function buildSafeZones(params: {
  subjectBox: { x: number; y: number; width: number; height: number };
}) {
  const gap = 0.035;
  const leftWidth = Math.max(0, params.subjectBox.x - gap);
  const rightX = clampNormalized(params.subjectBox.x + params.subjectBox.width + gap);
  const rightWidth = Math.max(0, 1 - rightX);
  const topHeight = Math.max(0, params.subjectBox.y - gap);
  const bottomY = clampNormalized(params.subjectBox.y + params.subjectBox.height + gap);
  const bottomHeight = Math.max(0, 1 - bottomY);

  return {
    left:
      leftWidth > 0.16
        ? {
            x: 0,
            y: 0,
            width: leftWidth,
            height: 1,
          }
        : null,
    right:
      rightWidth > 0.16
        ? {
            x: rightX,
            y: 0,
            width: rightWidth,
            height: 1,
          }
        : null,
    top:
      topHeight > 0.16
        ? {
            x: 0,
            y: 0,
            width: 1,
            height: topHeight,
          }
        : null,
    bottom:
      bottomHeight > 0.14
        ? {
            x: 0,
            y: bottomY,
            width: 1,
            height: bottomHeight,
          }
        : null,
  };
}

function analyzeSubjectRegion(params: {
  grayscale: Uint8Array;
  width: number;
  height: number;
}): DetailUiSubjectAnalysis {
  const scores: number[] = [];
  const scoreGrid = new Float32Array(params.width * params.height);

  const pixelAt = (x: number, y: number) =>
    params.grayscale[Math.max(0, Math.min(params.grayscale.length - 1, y * params.width + x))] || 0;

  for (let y = 1; y < params.height - 1; y += 1) {
    for (let x = 1; x < params.width - 1; x += 1) {
      const gx =
        -1 * pixelAt(x - 1, y - 1) +
        1 * pixelAt(x + 1, y - 1) +
        -2 * pixelAt(x - 1, y) +
        2 * pixelAt(x + 1, y) +
        -1 * pixelAt(x - 1, y + 1) +
        1 * pixelAt(x + 1, y + 1);
      const gy =
        -1 * pixelAt(x - 1, y - 1) +
        -2 * pixelAt(x, y - 1) +
        -1 * pixelAt(x + 1, y - 1) +
        1 * pixelAt(x - 1, y + 1) +
        2 * pixelAt(x, y + 1) +
        1 * pixelAt(x + 1, y + 1);
      const edge = Math.sqrt(gx * gx + gy * gy);

      const centerBiasX = 1 - Math.abs(x / params.width - 0.5) * 1.5;
      const centerBiasY = 1 - Math.abs(y / params.height - 0.56) * 1.3;
      const centerBias = Math.max(0.15, centerBiasX * centerBiasY);
      const brightness = pixelAt(x, y) / 255;
      const contrast = Math.abs(brightness - 0.5);
      const score = edge * 0.72 + contrast * 60 + centerBias * 90;

      const index = y * params.width + x;
      scoreGrid[index] = score;
      scores.push(score);
    }
  }

  const threshold = percentile(scores, 0.84);
  let minX = params.width;
  let minY = params.height;
  let maxX = 0;
  let maxY = 0;

  for (let y = 0; y < params.height; y += 1) {
    for (let x = 0; x < params.width; x += 1) {
      const score = scoreGrid[y * params.width + x];
      if (score < threshold) continue;
      minX = Math.min(minX, x);
      minY = Math.min(minY, y);
      maxX = Math.max(maxX, x);
      maxY = Math.max(maxY, y);
    }
  }

  if (minX >= maxX || minY >= maxY) {
    minX = Math.round(params.width * 0.24);
    maxX = Math.round(params.width * 0.78);
    minY = Math.round(params.height * 0.18);
    maxY = Math.round(params.height * 0.92);
  }

  const expandX = Math.round((maxX - minX) * 0.08);
  const expandY = Math.round((maxY - minY) * 0.08);
  minX = Math.max(0, minX - expandX);
  minY = Math.max(0, minY - expandY);
  maxX = Math.min(params.width - 1, maxX + expandX);
  maxY = Math.min(params.height - 1, maxY + expandY);

  const subjectBox = {
    x: clampNormalized(minX / params.width),
    y: clampNormalized(minY / params.height),
    width: clampNormalized((maxX - minX) / params.width),
    height: clampNormalized((maxY - minY) / params.height),
    confidence: 0.72,
  };

  return {
    subjectBox,
    safeZones: buildSafeZones({ subjectBox }),
    dominantHorizontal:
      subjectBox.x + subjectBox.width / 2 < 0.42
        ? "left"
        : subjectBox.x + subjectBox.width / 2 > 0.58
          ? "right"
          : "center",
    dominantVertical:
      subjectBox.y + subjectBox.height / 2 < 0.42
        ? "top"
        : subjectBox.y + subjectBox.height / 2 > 0.58
          ? "bottom"
          : "center",
  };
}

export async function POST(request: Request) {
  try {
    const session = await auth();
    if (!session?.user?.id) {
      return NextResponse.json({ success: false, error: "未登录" }, { status: 401 });
    }

    const body = (await request.json()) as { imageUrl?: string };
    const imageUrl = String(body.imageUrl || "").trim();
    if (!/^https?:\/\//i.test(imageUrl)) {
      return NextResponse.json({ success: false, error: "缺少图片地址" }, { status: 400 });
    }

    const controller = new AbortController();
    const timeout = setTimeout(() => controller.abort(), ANALYZE_FETCH_TIMEOUT_MS);
    let buffer: Buffer;
    try {
      const response = await fetch(imageUrl, {
        method: "GET",
        signal: controller.signal,
      });
      if (!response.ok) {
        throw new Error(`图片拉取失败: HTTP ${response.status}`);
      }
      buffer = Buffer.from(await response.arrayBuffer());
    } finally {
      clearTimeout(timeout);
    }

    const { data, info } = await sharp(buffer)
      .rotate()
      .resize({
        width: ANALYZE_MAX_SIDE,
        height: ANALYZE_MAX_SIDE,
        fit: "inside",
        withoutEnlargement: true,
      })
      .grayscale()
      .raw()
      .toBuffer({ resolveWithObject: true });

    const analysis = analyzeSubjectRegion({
      grayscale: data,
      width: info.width || ANALYZE_MAX_SIDE,
      height: info.height || ANALYZE_MAX_SIDE,
    });

    return NextResponse.json({
      success: true,
      data: analysis,
    });
  } catch (error) {
    console.error("[Canvas Detail Subject Analyze] Error:", error);
    return NextResponse.json(
      {
        success: false,
        error: error instanceof Error ? error.message : "主体分析失败",
      },
      { status: 500 },
    );
  }
}