Add metadata header to thumbnail contact sheets

Implemented metadata header rendering on contact sheets showing:
- Filename and file size
- Video resolution and duration

Uses FFmpeg pad and drawtext filters to create an 80px header area
with white text on black background.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

internal/thumbnail/generator.go

@@ -299,15 +299,19 @@ func (g *Generator) generateContactSheet(ctx context.Context, config Config, dur
 	// Build tile filter
 	tileFilter := fmt.Sprintf("scale=%d:%d,tile=%dx%d", thumbWidth, thumbHeight, config.Columns, config.Rows)
 
-	// Add timestamp overlay if requested
-	if config.ShowTimestamp {
-		// This is complex for contact sheets, skip for now
+	// Build video filter
+	var vfilter string
+	if config.ShowMetadata {
+		// Add metadata header to contact sheet
+		vfilter = g.buildMetadataFilter(config, duration, thumbWidth, thumbHeight, selectFilter, tileFilter)
+	} else {
+		vfilter = fmt.Sprintf("%s,%s", selectFilter, tileFilter)
 	}
 
 	// Build FFmpeg command
 	args := []string{
 		"-i", config.VideoPath,
-		"-vf", fmt.Sprintf("%s,%s", selectFilter, tileFilter),
+		"-vf", vfilter,
 		"-frames:v", "1",
 		"-y",
 	}
@@ -326,6 +330,57 @@ func (g *Generator) generateContactSheet(ctx context.Context, config Config, dur
 	return outputPath, nil
 }
 
+// buildMetadataFilter creates a filter that adds metadata header to contact sheet
+func (g *Generator) buildMetadataFilter(config Config, duration float64, thumbWidth, thumbHeight int, selectFilter, tileFilter string) string {
+	// Get file info
+	fileInfo, _ := os.Stat(config.VideoPath)
+	fileSize := fileInfo.Size()
+	fileSizeMB := float64(fileSize) / (1024 * 1024)
+
+	// Get video info (we already have duration, just need dimensions)
+	_, videoWidth, videoHeight, _ := g.getVideoInfo(context.Background(), config.VideoPath)
+
+	// Format duration as HH:MM:SS
+	hours := int(duration) / 3600
+	minutes := (int(duration) % 3600) / 60
+	seconds := int(duration) % 60
+	durationStr := fmt.Sprintf("%02d\\:%02d\\:%02d", hours, minutes, seconds)
+
+	// Get just the filename without path
+	filename := filepath.Base(config.VideoPath)
+
+	// Calculate sheet dimensions
+	sheetWidth := thumbWidth * config.Columns
+	sheetHeight := thumbHeight * config.Rows
+	headerHeight := 80
+
+	// Build metadata text lines
+	// Line 1: Filename and file size
+	line1 := fmt.Sprintf("%s (%.1f MB)", filename, fileSizeMB)
+	// Line 2: Resolution, FPS, Duration
+	line2 := fmt.Sprintf("%dx%d | Duration\\: %s", videoWidth, videoHeight, durationStr)
+
+	// Create filter that:
+	// 1. Generates contact sheet from selected frames
+	// 2. Creates a blank header area
+	// 3. Draws metadata text on header
+	// 4. Stacks header on top of contact sheet
+	filter := fmt.Sprintf(
+		"%s,%s,pad=%d:%d:0:%d:black,"+
+		"drawtext=text='%s':fontcolor=white:fontsize=14:x=10:y=10,"+
+		"drawtext=text='%s':fontcolor=white:fontsize=12:x=10:y=35",
+		selectFilter,
+		tileFilter,
+		sheetWidth,
+		sheetHeight+headerHeight,
+		headerHeight,
+		line1,
+		line2,
+	)
+
+	return filter
+}
+
 // calculateTimestamps generates timestamps for thumbnail extraction
 func (g *Generator) calculateTimestamps(config Config, duration float64) []float64 {
 	var timestamps []float64

main.go

@@ -1709,6 +1709,30 @@ func (s *appState) handleModuleDrop(moduleID string, items []fyne.URI) {
 		return
 	}
 
+	// If thumb module, load video into thumb slot
+	if moduleID == "thumb" {
+		path := videoPaths[0]
+		go func() {
+			src, err := probeVideo(path)
+			if err != nil {
+				logging.Debug(logging.CatModule, "failed to load video for thumb: %v", err)
+				fyne.CurrentApp().Driver().DoFromGoroutine(func() {
+					dialog.ShowError(fmt.Errorf("failed to load video: %w", err), s.window)
+				}, false)
+				return
+			}
+
+			// Update state and show module (with small delay to allow flash animation)
+			time.Sleep(350 * time.Millisecond)
+			fyne.CurrentApp().Driver().DoFromGoroutine(func() {
+				s.thumbFile = src
+				s.showModule(moduleID)
+				logging.Debug(logging.CatModule, "loaded video for thumb module")
+			}, false)
+		}()
+		return
+	}
+
 	// Single file or non-convert module: load first video and show module
 	path := videoPaths[0]
 	logging.Debug(logging.CatModule, "drop on module %s path=%s - starting load", moduleID, path)
@@ -6773,6 +6797,47 @@ func (s *appState) handleDrop(pos fyne.Position, items []fyne.URI) {
 		return
 	}
 
+	// If in thumb module, handle single video file
+	if s.active == "thumb" {
+		// Collect video files from dropped items
+		var videoPaths []string
+		for _, uri := range items {
+			if uri.Scheme() != "file" {
+				continue
+			}
+			path := uri.Path()
+			if s.isVideoFile(path) {
+				videoPaths = append(videoPaths, path)
+			}
+		}
+
+		if len(videoPaths) == 0 {
+			logging.Debug(logging.CatUI, "no valid video files in dropped items")
+			dialog.ShowInformation("Thumbnail Generation", "No video files found in dropped items.", s.window)
+			return
+		}
+
+		// Load first video
+		go func() {
+			src, err := probeVideo(videoPaths[0])
+			if err != nil {
+				logging.Debug(logging.CatModule, "failed to load video for thumb: %v", err)
+				fyne.CurrentApp().Driver().DoFromGoroutine(func() {
+					dialog.ShowError(fmt.Errorf("failed to load video: %w", err), s.window)
+				}, false)
+				return
+			}
+
+			fyne.CurrentApp().Driver().DoFromGoroutine(func() {
+				s.thumbFile = src
+				s.showThumbView()
+				logging.Debug(logging.CatModule, "loaded video into thumb module")
+			}, false)
+		}()
+
+		return
+	}
+
 	// If in merge module, handle multiple video files
 	if s.active == "merge" {
 		// Collect all video files from the dropped items