Add corrected image generation

README.md

@@ -27,6 +27,7 @@ docker compose up -d --build
 - `POST /api/assignments` `multipart/form-data`：`username`、`title`、`images`（可多张，按上传顺序）
 - `PUT /api/assignments/{id}` `multipart/form-data`：`username`、`title`、`images`（重新上传并重新批改）
 - `GET /api/assignments/{id}?username=xxx`
+- `GET /api/assignments/{id}/corrected?username=xxx&index=0`
 - `DELETE /api/assignments/{id}?username=xxx`
 
 ## 说明

backend/Dockerfile

@@ -10,7 +10,7 @@ COPY . .
 RUN CGO_ENABLED=1 GOOS=linux go build -o /bin/homework-backend ./
 
 FROM alpine:3.20
-RUN apk add --no-cache ca-certificates
+RUN apk add --no-cache ca-certificates font-noto-cjk
 
 WORKDIR /app
 ENV DB_PATH=/data/homework.db

backend/go.mod

@@ -3,6 +3,10 @@ module homework-backend
 go 1.22
 
 require (
+	github.com/fogleman/gg v1.3.0
 	github.com/go-chi/chi/v5 v5.1.0
 	github.com/mattn/go-sqlite3 v1.14.22
+	golang.org/x/image v0.21.0
 )
+
+require github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 // indirect

backend/go.sum

@@ -1,4 +1,10 @@
+github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
+github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/go-chi/chi/v5 v5.1.0 h1:acVI1TYaD+hhedDJ3r54HyA6sExp3HfXq7QWEEY/xMw=
 github.com/go-chi/chi/v5 v5.1.0/go.mod h1:DslCQbL2OYiznFReuXYUmQ2hGd1aDpCnlMNITLSKoi8=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
+github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
 github.com/mattn/go-sqlite3 v1.14.22 h1:2gZY6PC6kBnID23Tichd1K+Z0oS6nE/XwU+Vz/5o4kU=
 github.com/mattn/go-sqlite3 v1.14.22/go.mod h1:Uh1q+B4BYcTPb+yiD3kU8Ct7aC0hY9fxUwlHK0RXw+Y=
+golang.org/x/image v0.21.0 h1:c5qV36ajHpdj4Qi0GnE0jUc/yuo33OLFaa0d+crTD5s=
+golang.org/x/image v0.21.0/go.mod h1:vUbsLavqK/W303ZroQQVKQ+Af3Yl6Uz1Ppu5J/cLz78=

backend/main.go

@@ -11,8 +11,13 @@ import (
 	"errors"
 	"fmt"
 	"html/template"
+	"image"
+	_ "image/gif"
+	"image/jpeg"
+	_ "image/png"
 	"io"
 	"log"
+	"math"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -21,9 +26,11 @@ import (
 	"strings"
 	"time"
 
+	"github.com/fogleman/gg"
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
 	_ "github.com/mattn/go-sqlite3"
+	"golang.org/x/image/font/basicfont"
 )
 
 //go:embed admin.html
@@ -47,16 +54,18 @@ type Config struct {
 }
 
 type Assignment struct {
-	ID         int64     `json:"id"`
+	ID                  int64     `json:"id"`
-	Username   string    `json:"username"`
+	Username            string    `json:"username"`
-	Title      string    `json:"title"`
+	Title               string    `json:"title"`
-	OCRText    string    `json:"ocrText"`
+	OCRText             string    `json:"ocrText"`
-	Markdown   string    `json:"markdown"`
+	Markdown            string    `json:"markdown"`
-	Feedback   string    `json:"feedback"`
+	Feedback            string    `json:"feedback"`
-	Score      int       `json:"score"`
+	Score               int       `json:"score"`
-	ImagePath  string    `json:"imagePath"`
+	ImagePath           string    `json:"imagePath"`
-	ImagePaths []string  `json:"imagePaths"`
+	ImagePaths          []string  `json:"imagePaths"`
-	CreatedAt  time.Time `json:"createdAt"`
+	CorrectedImagePath  string    `json:"correctedImagePath"`
+	CorrectedImagePaths []string  `json:"correctedImagePaths"`
+	CreatedAt           time.Time `json:"createdAt"`
 }
 
 type createAssignmentRequest struct {
@@ -66,9 +75,10 @@ type createAssignmentRequest struct {
 }
 
 type LLMResult struct {
-	Markdown string `json:"markdown"`
+	Markdown    string   `json:"markdown"`
-	Feedback string `json:"feedback"`
+	Feedback    string   `json:"feedback"`
-	Score    int    `json:"score"`
+	Score       int      `json:"score"`
+	Annotations []string `json:"annotations"`
 }
 
 type LLMImage struct {
@@ -123,9 +133,10 @@ func main() {
 		r.Get("/assignments", handleListAssignments(db))
 		r.Get("/assignments/{id}", handleGetAssignment(db))
 		r.Get("/assignments/{id}/image", handleGetAssignmentImage(db, cfg.UploadDir))
+		r.Get("/assignments/{id}/corrected", handleGetAssignmentCorrectedImage(db, cfg.UploadDir))
 		r.Post("/assignments", handleCreateAssignment(db, llmClient, cfg.UploadDir))
 		r.Put("/assignments/{id}", handleUpdateAssignment(db, llmClient, cfg.UploadDir))
-		r.Delete("/assignments/{id}", handleDeleteAssignment(db))
+		r.Delete("/assignments/{id}", handleDeleteAssignment(db, cfg.UploadDir))
 	})
 
 	router.Route("/backend", func(r chi.Router) {
@@ -175,6 +186,7 @@ func initDB(path string) (*sql.DB, error) {
       feedback TEXT,
       score INTEGER,
       image_path TEXT,
+      corrected_image_path TEXT,
       created_at DATETIME DEFAULT CURRENT_TIMESTAMP
     );
   `); err != nil {
@@ -183,6 +195,9 @@ func initDB(path string) (*sql.DB, error) {
 	if err := ensureColumn(db, "assignments", "image_path", "TEXT"); err != nil {
 		return nil, err
 	}
+	if err := ensureColumn(db, "assignments", "corrected_image_path", "TEXT"); err != nil {
+		return nil, err
+	}
 	return db, nil
 }
 
@@ -195,7 +210,7 @@ func handleListAssignments(db *sql.DB) http.HandlerFunc {
 		}
 
 		rows, err := db.Query(`
-      SELECT id, username, title, score, image_path, created_at
+      SELECT id, username, title, score, image_path, corrected_image_path, created_at
       FROM assignments
       WHERE username = ?
       ORDER BY created_at DESC
@@ -210,11 +225,13 @@ func handleListAssignments(db *sql.DB) http.HandlerFunc {
 		for rows.Next() {
 			var a Assignment
 			var rawImagePath string
-			if err := rows.Scan(&a.ID, &a.Username, &a.Title, &a.Score, &rawImagePath, &a.CreatedAt); err != nil {
+			var rawCorrectedPath string
+			if err := rows.Scan(&a.ID, &a.Username, &a.Title, &a.Score, &rawImagePath, &rawCorrectedPath, &a.CreatedAt); err != nil {
 				writeError(w, http.StatusInternalServerError, "failed to read assignments")
 				return
 			}
 			setImageFields(&a, rawImagePath)
+			setCorrectedImageFields(&a, rawCorrectedPath)
 			assignments = append(assignments, a)
 		}
 
@@ -238,13 +255,14 @@ func handleGetAssignment(db *sql.DB) http.HandlerFunc {
 
 		var a Assignment
 		var rawImagePath string
+		var rawCorrectedPath string
 		row := db.QueryRow(`
-      SELECT id, username, title, ocr_text, markdown, feedback, score, image_path, created_at
+      SELECT id, username, title, ocr_text, markdown, feedback, score, image_path, corrected_image_path, created_at
       FROM assignments
       WHERE id = ? AND username = ?
       LIMIT 1
     `, id, username)
-		if err := row.Scan(&a.ID, &a.Username, &a.Title, &a.OCRText, &a.Markdown, &a.Feedback, &a.Score, &rawImagePath, &a.CreatedAt); err != nil {
+		if err := row.Scan(&a.ID, &a.Username, &a.Title, &a.OCRText, &a.Markdown, &a.Feedback, &a.Score, &rawImagePath, &rawCorrectedPath, &a.CreatedAt); err != nil {
 			if errors.Is(err, sql.ErrNoRows) {
 				writeError(w, http.StatusNotFound, "assignment not found")
 				return
@@ -253,6 +271,7 @@ func handleGetAssignment(db *sql.DB) http.HandlerFunc {
 			return
 		}
 		setImageFields(&a, rawImagePath)
+		setCorrectedImageFields(&a, rawCorrectedPath)
 
 		writeJSON(w, http.StatusOK, a)
 	}
@@ -335,6 +354,83 @@ func handleGetAssignmentImage(db *sql.DB, uploadDir string) http.HandlerFunc {
 	}
 }
 
+func handleGetAssignmentCorrectedImage(db *sql.DB, uploadDir string) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		username := strings.TrimSpace(r.URL.Query().Get("username"))
+		if username == "" {
+			writeError(w, http.StatusBadRequest, "username is required")
+			return
+		}
+
+		id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
+		if err != nil {
+			writeError(w, http.StatusBadRequest, "invalid assignment id")
+			return
+		}
+
+		var imagePath sql.NullString
+		row := db.QueryRow(`
+      SELECT corrected_image_path
+      FROM assignments
+      WHERE id = ? AND username = ?
+      LIMIT 1
+    `, id, username)
+		if err := row.Scan(&imagePath); err != nil {
+			if errors.Is(err, sql.ErrNoRows) {
+				writeError(w, http.StatusNotFound, "assignment not found")
+				return
+			}
+			writeError(w, http.StatusInternalServerError, "failed to query image")
+			return
+		}
+
+		if !imagePath.Valid || strings.TrimSpace(imagePath.String) == "" {
+			writeError(w, http.StatusNotFound, "image not found")
+			return
+		}
+
+		paths := parseImagePaths(imagePath.String)
+		if len(paths) == 0 {
+			writeError(w, http.StatusNotFound, "image not found")
+			return
+		}
+
+		index := 0
+		if indexStr := r.URL.Query().Get("index"); indexStr != "" {
+			if parsed, err := strconv.Atoi(indexStr); err == nil {
+				index = parsed
+			}
+		}
+		if index < 0 || index >= len(paths) {
+			writeError(w, http.StatusNotFound, "image not found")
+			return
+		}
+
+		absImage, err := filepath.Abs(paths[index])
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "invalid image path")
+			return
+		}
+		absUpload, err := filepath.Abs(uploadDir)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, "invalid upload dir")
+			return
+		}
+		if !strings.HasPrefix(absImage, absUpload+string(os.PathSeparator)) && absImage != absUpload {
+			writeError(w, http.StatusForbidden, "invalid image path")
+			return
+		}
+
+		if _, err := os.Stat(absImage); err != nil {
+			writeError(w, http.StatusNotFound, "image not found")
+			return
+		}
+
+		w.Header().Set("Cache-Control", "private, max-age=3600")
+		http.ServeFile(w, r, absImage)
+	}
+}
+
 func handleCreateAssignment(db *sql.DB, llm *LLMClient, uploadDir string) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		contentType := r.Header.Get("Content-Type")
@@ -372,9 +468,9 @@ func handleCreateAssignment(db *sql.DB, llm *LLMClient, uploadDir string) http.H
 		}
 
 		result, err := db.Exec(`
-      INSERT INTO assignments (username, title, ocr_text, markdown, feedback, score, image_path)
+      INSERT INTO assignments (username, title, ocr_text, markdown, feedback, score, image_path, corrected_image_path)
-      VALUES (?, ?, ?, ?, ?, ?, ?)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?)
-    `, req.Username, req.Title, req.OCRText, markdown, feedback, score, "[]")
+    `, req.Username, req.Title, req.OCRText, markdown, feedback, score, "[]", "[]")
 		if err != nil {
 			writeError(w, http.StatusInternalServerError, "failed to save assignment")
 			return
@@ -382,16 +478,18 @@ func handleCreateAssignment(db *sql.DB, llm *LLMClient, uploadDir string) http.H
 
 		id, _ := result.LastInsertId()
 		assignment := Assignment{
-			ID:         id,
+			ID:                  id,
-			Username:   req.Username,
+			Username:            req.Username,
-			Title:      req.Title,
+			Title:               req.Title,
-			OCRText:    req.OCRText,
+			OCRText:             req.OCRText,
-			Markdown:   markdown,
+			Markdown:            markdown,
-			Feedback:   feedback,
+			Feedback:            feedback,
-			Score:      score,
+			Score:               score,
-			ImagePath:  "",
+			ImagePath:           "",
-			ImagePaths: []string{},
+			ImagePaths:          []string{},
-			CreatedAt:  time.Now(),
+			CorrectedImagePath:  "",
+			CorrectedImagePaths: []string{},
+			CreatedAt:           time.Now(),
 		}
 
 		writeJSON(w, http.StatusOK, assignment)
@@ -430,13 +528,14 @@ func handleUpdateAssignment(db *sql.DB, llm *LLMClient, uploadDir string) http.H
 		var existingTitle string
 		var createdAt time.Time
 		var existingImagePath sql.NullString
+		var existingCorrectedPath sql.NullString
 		row := db.QueryRow(`
-      SELECT title, created_at, image_path
+      SELECT title, created_at, image_path, corrected_image_path
       FROM assignments
       WHERE id = ? AND username = ?
       LIMIT 1
     `, id, username)
-		if err := row.Scan(&existingTitle, &createdAt, &existingImagePath); err != nil {
+		if err := row.Scan(&existingTitle, &createdAt, &existingImagePath, &existingCorrectedPath); err != nil {
 			if errors.Is(err, sql.ErrNoRows) {
 				writeError(w, http.StatusNotFound, "assignment not found")
 				return
@@ -506,19 +605,31 @@ func handleUpdateAssignment(db *sql.DB, llm *LLMClient, uploadDir string) http.H
 			})
 		}
 
-		markdown, feedback, score, err := llm.FormatAndGradeFromImages(r.Context(), title, images)
+		llmResult, err := llm.FormatAndGradeFromImagesResult(r.Context(), title, images)
 		if err != nil {
 			writeError(w, http.StatusBadGateway, fmt.Sprintf("llm failed: %v", err))
 			return
 		}
 
+		markdown := llmResult.Markdown
+		feedback := llmResult.Feedback
+		score := llmResult.Score
+
+		annotations := buildAnnotations(llmResult, markdown, feedback, score)
+		correctedPaths, err := generateCorrectedImages(uploadDir, imagePaths, title, annotations)
+		if err != nil {
+			log.Printf("corrected image failed: %v", err)
+			correctedPaths = []string{}
+		}
+
 		imagePathsJSON, _ := json.Marshal(imagePaths)
+		correctedPathsJSON, _ := json.Marshal(correctedPaths)
 
 		_, err = db.Exec(`
       UPDATE assignments
-      SET title = ?, ocr_text = ?, markdown = ?, feedback = ?, score = ?, image_path = ?
+      SET title = ?, ocr_text = ?, markdown = ?, feedback = ?, score = ?, image_path = ?, corrected_image_path = ?
       WHERE id = ? AND username = ?
-    `, title, "", markdown, feedback, score, string(imagePathsJSON), id, username)
+    `, title, "", markdown, feedback, score, string(imagePathsJSON), string(correctedPathsJSON), id, username)
 		if err != nil {
 			writeError(w, http.StatusInternalServerError, "failed to update assignment")
 			return
@@ -527,18 +638,23 @@ func handleUpdateAssignment(db *sql.DB, llm *LLMClient, uploadDir string) http.H
 		if existingImagePath.Valid {
 			cleanupImages(uploadDir, existingImagePath.String)
 		}
+		if existingCorrectedPath.Valid {
+			cleanupImages(uploadDir, existingCorrectedPath.String)
+		}
 
 		assignment := Assignment{
-			ID:         id,
+			ID:                  id,
-			Username:   username,
+			Username:            username,
-			Title:      title,
+			Title:               title,
-			OCRText:    "",
+			OCRText:             "",
-			Markdown:   markdown,
+			Markdown:            markdown,
-			Feedback:   feedback,
+			Feedback:            feedback,
-			Score:      score,
+			Score:               score,
-			ImagePath:  firstPath(imagePaths),
+			ImagePath:           firstPath(imagePaths),
-			ImagePaths: imagePaths,
+			ImagePaths:          imagePaths,
-			CreatedAt:  createdAt,
+			CorrectedImagePath:  firstPath(correctedPaths),
+			CorrectedImagePaths: correctedPaths,
+			CreatedAt:           createdAt,
 		}
 
 		writeJSON(w, http.StatusOK, assignment)
@@ -615,18 +731,30 @@ func handleCreateAssignmentWithImage(db *sql.DB, llm *LLMClient, uploadDir strin
 		})
 	}
 
-	markdown, feedback, score, err := llm.FormatAndGradeFromImages(r.Context(), title, images)
+	llmResult, err := llm.FormatAndGradeFromImagesResult(r.Context(), title, images)
 	if err != nil {
 		writeError(w, http.StatusBadGateway, fmt.Sprintf("llm failed: %v", err))
 		return
 	}
 
+	markdown := llmResult.Markdown
+	feedback := llmResult.Feedback
+	score := llmResult.Score
+
+	annotations := buildAnnotations(llmResult, markdown, feedback, score)
+	correctedPaths, err := generateCorrectedImages(uploadDir, imagePaths, title, annotations)
+	if err != nil {
+		log.Printf("corrected image failed: %v", err)
+		correctedPaths = []string{}
+	}
+
 	imagePathsJSON, _ := json.Marshal(imagePaths)
+	correctedPathsJSON, _ := json.Marshal(correctedPaths)
 
 	result, err := db.Exec(`
-      INSERT INTO assignments (username, title, ocr_text, markdown, feedback, score, image_path)
+      INSERT INTO assignments (username, title, ocr_text, markdown, feedback, score, image_path, corrected_image_path)
-      VALUES (?, ?, ?, ?, ?, ?, ?)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?)
-    `, username, title, "", markdown, feedback, score, string(imagePathsJSON))
+    `, username, title, "", markdown, feedback, score, string(imagePathsJSON), string(correctedPathsJSON))
 	if err != nil {
 		writeError(w, http.StatusInternalServerError, "failed to save assignment")
 		return
@@ -634,22 +762,24 @@ func handleCreateAssignmentWithImage(db *sql.DB, llm *LLMClient, uploadDir strin
 
 	id, _ := result.LastInsertId()
 	assignment := Assignment{
-		ID:         id,
+		ID:                  id,
-		Username:   username,
+		Username:            username,
-		Title:      title,
+		Title:               title,
-		OCRText:    "",
+		OCRText:             "",
-		Markdown:   markdown,
+		Markdown:            markdown,
-		Feedback:   feedback,
+		Feedback:            feedback,
-		Score:      score,
+		Score:               score,
-		ImagePath:  firstPath(imagePaths),
+		ImagePath:           firstPath(imagePaths),
-		ImagePaths: imagePaths,
+		ImagePaths:          imagePaths,
-		CreatedAt:  time.Now(),
+		CorrectedImagePath:  firstPath(correctedPaths),
+		CorrectedImagePaths: correctedPaths,
+		CreatedAt:           time.Now(),
 	}
 
 	writeJSON(w, http.StatusOK, assignment)
 }
 
-func handleDeleteAssignment(db *sql.DB) http.HandlerFunc {
+func handleDeleteAssignment(db *sql.DB, uploadDir string) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		username := strings.TrimSpace(r.URL.Query().Get("username"))
 		if username == "" {
@@ -663,6 +793,23 @@ func handleDeleteAssignment(db *sql.DB) http.HandlerFunc {
 			return
 		}
 
+		var imagePath sql.NullString
+		var correctedPath sql.NullString
+		row := db.QueryRow(`
+      SELECT image_path, corrected_image_path
+      FROM assignments
+      WHERE id = ? AND username = ?
+      LIMIT 1
+    `, id, username)
+		if err := row.Scan(&imagePath, &correctedPath); err != nil {
+			if errors.Is(err, sql.ErrNoRows) {
+				writeError(w, http.StatusNotFound, "assignment not found")
+				return
+			}
+			writeError(w, http.StatusInternalServerError, "failed to load assignment")
+			return
+		}
+
 		res, err := db.Exec(`DELETE FROM assignments WHERE id = ? AND username = ?`, id, username)
 		if err != nil {
 			writeError(w, http.StatusInternalServerError, "failed to delete assignment")
@@ -674,6 +821,13 @@ func handleDeleteAssignment(db *sql.DB) http.HandlerFunc {
 			return
 		}
 
+		if imagePath.Valid {
+			cleanupImages(uploadDir, imagePath.String)
+		}
+		if correctedPath.Valid {
+			cleanupImages(uploadDir, correctedPath.String)
+		}
+
 		writeJSON(w, http.StatusOK, map[string]any{"deleted": id})
 	}
 }
@@ -710,12 +864,12 @@ func handleAdminDashboard(db *sql.DB) http.HandlerFunc {
 	}
 }
 
-func (c *LLMClient) FormatAndGrade(ctx context.Context, title, ocrText string) (string, string, int, error) {
+func (c *LLMClient) FormatAndGradeResult(ctx context.Context, title, ocrText string) (LLMResult, error) {
 	if c.baseURL == "" || c.apiKey == "" {
-		return "", "", 0, errors.New("LLM_BASE_URL or LLM_API_KEY missing")
+		return LLMResult{}, errors.New("LLM_BASE_URL or LLM_API_KEY missing")
 	}
 
-	systemPrompt := "你是一位严谨的阅卷老师。请把 OCR 文字整理成清晰的 Markdown，保持原有题号、分点、段落与格式。然后进行详细批改：对每一道题给出参考答案、解题过程拆解、学生答案摘录、正确性判定（正确/部分正确/错误）、正确答案对比说明、考察知识点说明。最后给出整体评价与改进建议。仅输出 JSON，字段为 markdown、feedback、score(0-100整数)。不要加代码块或多余文字。"
+	systemPrompt := "你是一位严谨的阅卷老师。请把 OCR 文字整理成清晰的 Markdown，保持原有题号、分点、段落与格式。然后进行详细批改：对每一道题给出参考答案、解题过程拆解、学生答案摘录、正确性判定（正确/部分正确/错误）、正确答案对比说明、考察知识点说明。最后给出整体评价与改进建议。请额外输出 annotations 字段，数组，每条为简短批注（<=25字），用于叠加到作业图片。仅输出 JSON，字段为 markdown、feedback、score(0-100整数)、annotations。不要加代码块或多余文字。"
 	userPrompt := fmt.Sprintf("标题: %s\n\nOCR文本:\n%s", title, ocrText)
 
 	payload := map[string]any{
@@ -729,38 +883,45 @@ func (c *LLMClient) FormatAndGrade(ctx context.Context, title, ocrText string) (
 
 	content, err := c.chatCompletionWithRetry(ctx, payload)
 	if err != nil {
-		return "", "", 0, err
+		return LLMResult{}, err
 	}
 
 	result := LLMResult{}
 	if err := decodeLLMResult(content, &result); err != nil {
 		markdown, feedback, score := fallbackFromContent(content, ocrText)
-		return markdown, feedback, score, nil
+		return LLMResult{Markdown: markdown, Feedback: feedback, Score: score}, nil
 	}
 
-	markdown := strings.TrimSpace(result.Markdown)
+	result.Markdown = strings.TrimSpace(result.Markdown)
-	feedback := strings.TrimSpace(result.Feedback)
+	result.Feedback = strings.TrimSpace(result.Feedback)
-	score := result.Score
+	if result.Markdown == "" {
-	if markdown == "" {
+		result.Markdown = ocrText
-		markdown = ocrText
 	}
 
-	return markdown, feedback, score, nil
+	return result, nil
+}
+
+func (c *LLMClient) FormatAndGrade(ctx context.Context, title, ocrText string) (string, string, int, error) {
+	result, err := c.FormatAndGradeResult(ctx, title, ocrText)
+	if err != nil {
+		return "", "", 0, err
+	}
+	return result.Markdown, result.Feedback, result.Score, nil
 }
 
 func (c *LLMClient) FormatAndGradeFromImage(ctx context.Context, title, mimeType, imageBase64 string) (string, string, int, error) {
 	return c.FormatAndGradeFromImages(ctx, title, []LLMImage{{MimeType: mimeType, Base64: imageBase64}})
 }
 
-func (c *LLMClient) FormatAndGradeFromImages(ctx context.Context, title string, images []LLMImage) (string, string, int, error) {
+func (c *LLMClient) FormatAndGradeFromImagesResult(ctx context.Context, title string, images []LLMImage) (LLMResult, error) {
 	if c.baseURL == "" || c.apiKey == "" {
-		return "", "", 0, errors.New("LLM_BASE_URL or LLM_API_KEY missing")
+		return LLMResult{}, errors.New("LLM_BASE_URL or LLM_API_KEY missing")
 	}
 	if len(images) == 0 {
-		return "", "", 0, errors.New("no images provided")
+		return LLMResult{}, errors.New("no images provided")
 	}
 
-	systemPrompt := "你是一位严谨的阅卷老师。请根据作业图片识别内容，整理为清晰的 Markdown，保持题号、分点、段落与格式。然后进行详细批改：对每一道题给出参考答案、解题过程拆解、学生答案摘录、正确性判定（正确/部分正确/错误）、正确答案对比说明、考察知识点说明。最后给出整体评价与改进建议。若题目或答案无法识别，请明确标注“无法辨识”。仅输出 JSON，字段为 markdown、feedback、score(0-100整数)。不要加代码块或多余文字。"
+	systemPrompt := "你是一位严谨的阅卷老师。请根据作业图片识别内容，整理为清晰的 Markdown，保持题号、分点、段落与格式。然后进行详细批改：对每一道题给出参考答案、解题过程拆解、学生答案摘录、正确性判定（正确/部分正确/错误）、正确答案对比说明、考察知识点说明。最后给出整体评价与改进建议。若题目或答案无法识别，请明确标注“无法辨识”。请额外输出 annotations 字段，数组，每条为简短批注（<=25字），用于叠加到作业图片。仅输出 JSON，字段为 markdown、feedback、score(0-100整数)、annotations。不要加代码块或多余文字。"
 	userText := fmt.Sprintf("标题: %s\n以下图片按上传顺序依次为第1页、第2页……请综合批改。", title)
 
 	contentParts := make([]map[string]any, 0, len(images)+1)
@@ -785,23 +946,30 @@ func (c *LLMClient) FormatAndGradeFromImages(ctx context.Context, title string,
 
 	content, err := c.chatCompletionWithRetry(ctx, payload)
 	if err != nil {
-		return "", "", 0, err
+		return LLMResult{}, err
 	}
 
 	result := LLMResult{}
 	if err := decodeLLMResult(content, &result); err != nil {
 		markdown, feedback, score := fallbackFromContent(content, "未识别到有效内容。")
-		return markdown, feedback, score, nil
+		return LLMResult{Markdown: markdown, Feedback: feedback, Score: score}, nil
 	}
 
-	markdown := strings.TrimSpace(result.Markdown)
+	result.Markdown = strings.TrimSpace(result.Markdown)
-	feedback := strings.TrimSpace(result.Feedback)
+	result.Feedback = strings.TrimSpace(result.Feedback)
-	score := result.Score
+	if result.Markdown == "" {
-	if markdown == "" {
+		result.Markdown = "未识别到有效内容。"
-		markdown = "未识别到有效内容。"
 	}
 
-	return markdown, feedback, score, nil
+	return result, nil
+}
+
+func (c *LLMClient) FormatAndGradeFromImages(ctx context.Context, title string, images []LLMImage) (string, string, int, error) {
+	result, err := c.FormatAndGradeFromImagesResult(ctx, title, images)
+	if err != nil {
+		return "", "", 0, err
+	}
+	return result.Markdown, result.Feedback, result.Score, nil
 }
 
 func (c *LLMClient) chatCompletionWithRetry(ctx context.Context, payload map[string]any) (string, error) {
@@ -924,6 +1092,87 @@ func fallbackFromContent(content, defaultMarkdown string) (string, string, int)
 	return markdown, "", score
 }
 
+func buildAnnotations(result LLMResult, markdown, feedback string, score int) []string {
+	annotations := normalizeAnnotations(result.Annotations)
+	if len(annotations) == 0 {
+		annotations = deriveAnnotations(feedback)
+	}
+	if len(annotations) == 0 {
+		annotations = deriveAnnotations(markdown)
+	}
+	if len(annotations) == 0 {
+		annotations = []string{"已完成批改，请查看详细结果。"}
+	}
+	if score > 0 && !hasScoreAnnotation(annotations) {
+		annotations = append([]string{fmt.Sprintf("评分：%d", score)}, annotations...)
+	}
+	if len(annotations) > 8 {
+		annotations = append(annotations[:8], "更多细节请查看批改结果")
+	}
+	return annotations
+}
+
+func normalizeAnnotations(raw []string) []string {
+	if len(raw) == 0 {
+		return nil
+	}
+	normalized := make([]string, 0, len(raw))
+	for _, item := range raw {
+		clean := strings.TrimSpace(item)
+		if clean == "" {
+			continue
+		}
+		normalized = append(normalized, clean)
+	}
+	return normalized
+}
+
+func hasScoreAnnotation(lines []string) bool {
+	for _, line := range lines {
+		if strings.Contains(line, "评分") || strings.Contains(strings.ToLower(line), "score") {
+			return true
+		}
+	}
+	return false
+}
+
+func deriveAnnotations(text string) []string {
+	text = strings.TrimSpace(text)
+	if text == "" {
+		return nil
+	}
+	parts := splitSentences(text)
+	lines := make([]string, 0, len(parts))
+	for _, part := range parts {
+		clean := strings.TrimSpace(part)
+		if clean == "" {
+			continue
+		}
+		lines = append(lines, clean)
+	}
+	return lines
+}
+
+func splitSentences(text string) []string {
+	var parts []string
+	var buf strings.Builder
+	for _, r := range []rune(text) {
+		if r == '\r' {
+			continue
+		}
+		buf.WriteRune(r)
+		switch r {
+		case '\n', '。', '；', ';', '!', '！', '?', '？':
+			parts = append(parts, buf.String())
+			buf.Reset()
+		}
+	}
+	if buf.Len() > 0 {
+		parts = append(parts, buf.String())
+	}
+	return parts
+}
+
 func ensureColumn(db *sql.DB, table, column, columnType string) error {
 	rows, err := db.Query(fmt.Sprintf("PRAGMA table_info(%s);", table))
 	if err != nil {
@@ -955,6 +1204,9 @@ func parseImagePaths(raw string) []string {
 	if raw == "" {
 		return nil
 	}
+	if raw == "null" {
+		return nil
+	}
 	if strings.HasPrefix(raw, "[") {
 		var paths []string
 		if json.Unmarshal([]byte(raw), &paths) == nil {
@@ -970,6 +1222,12 @@ func setImageFields(a *Assignment, raw string) {
 	a.ImagePath = firstPath(paths)
 }
 
+func setCorrectedImageFields(a *Assignment, raw string) {
+	paths := parseImagePaths(raw)
+	a.CorrectedImagePaths = paths
+	a.CorrectedImagePath = firstPath(paths)
+}
+
 func firstPath(paths []string) string {
 	if len(paths) == 0 {
 		return ""
@@ -1000,6 +1258,158 @@ func cleanupImages(uploadDir, raw string) {
 	}
 }
 
+func generateCorrectedImages(uploadDir string, imagePaths []string, title string, annotations []string) ([]string, error) {
+	if len(imagePaths) == 0 {
+		return nil, nil
+	}
+	annotations = normalizeAnnotations(annotations)
+	if len(annotations) == 0 {
+		annotations = []string{"已完成批改，请查看详细结果。"}
+	}
+
+	results := make([]string, 0, len(imagePaths))
+	for index, srcPath := range imagePaths {
+		filename := fmt.Sprintf("%s_%s_corrected_%d.jpg", time.Now().Format("20060102_150405"), randomToken(6), index+1)
+		dstPath := filepath.Join(uploadDir, filename)
+		if err := renderCorrectionImage(srcPath, dstPath, title, annotations); err != nil {
+			return nil, err
+		}
+		results = append(results, dstPath)
+	}
+	return results, nil
+}
+
+func renderCorrectionImage(srcPath, dstPath, title string, annotations []string) error {
+	file, err := os.Open(srcPath)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	img, _, err := image.Decode(file)
+	if err != nil {
+		return err
+	}
+
+	dc := gg.NewContextForImage(img)
+	width := float64(dc.Width())
+	height := float64(dc.Height())
+
+	fontSize := clamp(width/36.0, 18, 30)
+	if err := loadFontFace(dc, fontSize); err != nil {
+		dc.SetFontFace(basicfont.Face7x13)
+		fontSize = 14
+	}
+
+	dc.SetRGBA(1, 1, 1, 0.05)
+	dc.DrawRectangle(0, 0, width, height)
+	dc.Fill()
+
+	label := "订正"
+	if strings.TrimSpace(title) != "" {
+		label = "订正"
+	}
+	labelX := width - 24
+	labelY := 24.0
+	drawShadowText(dc, label, labelX, labelY, 1, 0)
+
+	startX := width * 0.06
+	startY := height * 0.12
+	maxWidth := width * 0.7
+	lineHeight := fontSize * 1.45
+	maxY := height * 0.9
+
+	y := startY
+	for _, note := range annotations {
+		lines := wrapText(dc, note, maxWidth)
+		for _, line := range lines {
+			if y > maxY {
+				return saveJPEG(dstPath, dc.Image())
+			}
+			drawShadowText(dc, line, startX, y, 0, 0)
+			y += lineHeight
+		}
+		y += lineHeight * 0.25
+	}
+
+	return saveJPEG(dstPath, dc.Image())
+}
+
+func loadFontFace(dc *gg.Context, size float64) error {
+	candidates := []string{
+		"/usr/share/fonts/noto/NotoSansCJK-Regular.ttc",
+		"/usr/share/fonts/noto/NotoSansCJK-Bold.ttc",
+		"/usr/share/fonts/noto/NotoSerifCJK-Regular.ttc",
+		"/usr/share/fonts/noto/NotoSerifCJK-Bold.ttc",
+		"/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf",
+	}
+	for _, path := range candidates {
+		if _, err := os.Stat(path); err != nil {
+			continue
+		}
+		if err := dc.LoadFontFace(path, size); err == nil {
+			return nil
+		}
+	}
+	return errors.New("font not found")
+}
+
+func wrapText(dc *gg.Context, text string, maxWidth float64) []string {
+	text = strings.TrimSpace(text)
+	if text == "" {
+		return nil
+	}
+
+	var lines []string
+	var current []rune
+	flush := func() {
+		if len(current) == 0 {
+			return
+		}
+		lines = append(lines, strings.TrimSpace(string(current)))
+		current = nil
+	}
+
+	for _, r := range []rune(text) {
+		if r == '\n' {
+			flush()
+			continue
+		}
+		current = append(current, r)
+		if len(current) <= 1 {
+			continue
+		}
+		if width, _ := dc.MeasureString(string(current)); width > maxWidth {
+			last := current[len(current)-1]
+			current = current[:len(current)-1]
+			flush()
+			current = []rune{last}
+		}
+	}
+	flush()
+	return lines
+}
+
+func drawShadowText(dc *gg.Context, text string, x, y, ax, ay float64) {
+	dc.SetRGBA(1, 1, 1, 0.85)
+	dc.DrawStringAnchored(text, x+1, y+1, ax, ay)
+	dc.SetRGB(0.82, 0, 0)
+	dc.DrawStringAnchored(text, x, y, ax, ay)
+}
+
+func saveJPEG(path string, img image.Image) error {
+	tmp, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer tmp.Close()
+	return jpeg.Encode(tmp, img, &jpeg.Options{Quality: 92})
+}
+
+func clamp(value, min, max float64) float64 {
+	return math.Max(min, math.Min(value, max))
+}
+
 func randomToken(length int) string {
 	const charset = "abcdefghijklmnopqrstuvwxyz0123456789"
 	buf := make([]byte, length)

frontend/app/page.tsx

@@ -14,6 +14,8 @@ type AssignmentSummary = {
   score: number;
   imagePath?: string;
   imagePaths?: string[];
+  correctedImagePath?: string;
+  correctedImagePaths?: string[];
   createdAt: string;
 };
 
@@ -23,6 +25,8 @@ type AssignmentDetail = AssignmentSummary & {
   feedback: string;
   imagePath?: string;
   imagePaths?: string[];
+  correctedImagePath?: string;
+  correctedImagePaths?: string[];
 };
 
 type ImageItem = {
@@ -394,9 +398,15 @@ export default function HomePage() {
   const imageUrlFor = (id: number, index = 0) =>
     `${apiBase}/assignments/${id}/image?username=${encodeURIComponent(savedUser)}&index=${index}`;
 
+  const correctedImageUrlFor = (id: number, index = 0) =>
+    `${apiBase}/assignments/${id}/corrected?username=${encodeURIComponent(savedUser)}&index=${index}`;
+
   const imageCountFor = (item: AssignmentSummary) =>
     item.imagePaths?.length ?? (item.imagePath ? 1 : 0);
 
+  const correctedImageCountFor = (item: AssignmentSummary) =>
+    item.correctedImagePaths?.length ?? (item.correctedImagePath ? 1 : 0);
+
   const selectedImagePaths =
     selected?.imagePaths && selected.imagePaths.length > 0
       ? selected.imagePaths
@@ -404,6 +414,13 @@ export default function HomePage() {
       ? [selected.imagePath]
       : [];
 
+  const selectedCorrectedPaths =
+    selected?.correctedImagePaths && selected.correctedImagePaths.length > 0
+      ? selected.correctedImagePaths
+      : selected?.correctedImagePath
+      ? [selected.correctedImagePath]
+      : [];
+
   return (
     <main>
       <div className="page">
@@ -574,6 +591,19 @@ export default function HomePage() {
                         保存图片{imageCountFor(item) > 1 ? ` (${imageCountFor(item)}张)` : ""}
                       </a>
                     )}
+                    {correctedImageCountFor(item) > 0 && (
+                      <a
+                        className="button secondary"
+                        href={correctedImageUrlFor(item.id, 0)}
+                        download={`assignment-${item.id}-corrected-1.jpg`}
+                        onClick={(event) => event.stopPropagation()}
+                      >
+                        保存订正图
+                        {correctedImageCountFor(item) > 1
+                          ? ` (${correctedImageCountFor(item)}张)`
+                          : ""}
+                      </a>
+                    )}
                     <button
                       className="button secondary"
                       onClick={(event) => {
@@ -636,6 +666,31 @@ export default function HomePage() {
                   </div>
                 </div>
               )}
+              {selectedCorrectedPaths.length > 0 && (
+                <div style={{ display: "grid", gap: 12 }}>
+                  <div className="assignment-meta">
+                    <span>订正效果图（共 {selectedCorrectedPaths.length} 张）</span>
+                  </div>
+                  <div className="image-grid">
+                    {selectedCorrectedPaths.map((_, index) => (
+                      <div key={`${selected.id}-corrected-${index}`} className="image-card">
+                        <img
+                          className="preview"
+                          src={correctedImageUrlFor(selected.id, index)}
+                          alt={`订正图 ${index + 1}`}
+                        />
+                        <a
+                          className="button secondary"
+                          href={correctedImageUrlFor(selected.id, index)}
+                          download={`assignment-${selected.id}-corrected-${index + 1}.jpg`}
+                        >
+                          保存订正第 {index + 1} 张
+                        </a>
+                      </div>
+                    ))}
+                  </div>
+                </div>
+              )}
               <div className="markdown">
                 <ReactMarkdown>{selected.markdown}</ReactMarkdown>
               </div>