feat(vision): enhance GenerateVideoPreview with format detection and frame interval

README.md

@@ -87,9 +87,15 @@ vision.Save(frame, "preview.jpg")
 // 生成图片缩略图 (WebP, 自动填充/裁剪)
 vision.GenerateImagePreview("photo.jpg", "thumb.webp", 200, 200)
 
-// 生成 4 帧动画 WebP (自动填充/裁剪, 效果动态)
+// 生成动画预览 (WebP/GIF, 默认 30s 采样一帧，自动填充/裁剪)
 vision.GenerateVideoPreview("movie.mp4", "preview.webp", 320, 180)
 
+// 生成单张预览图 (JPG/PNG, 取视频中间帧)
+vision.GenerateVideoPreview("movie.mp4", "preview.jpg", 320, 180)
+
+// 提取多张预览帧到文件夹 (输出 1.webp, 2.webp...)
+vision.GenerateVideoPreview("movie.mp4", "frames_dir", 320, 180)
+
 // 提取音频预览片段 (16kHz Ogg Opus, 最长 3 分钟)
 vision.GenerateAudioPreview("input.mp4", "preview.ogg")
 ```
@@ -119,7 +125,7 @@ vision --data "https://apigo.cc" -o qr.png --size 512
 vision in.png -o out.png --resize 800x600 --blur 1.5 --grayscale
 
 # 5. 生成视频动态预览 (WebP)
-vision video.mp4 --type video -o preview.webp --width 320 --height 180
+vision video.mp4 --type video -o preview.webp --width 320 --height 180 --step 30
 
 # 6. 生成验证码
 vision --captcha -o captcha.png --len 6

cmd/vision/main.go

@@ -39,6 +39,7 @@ var (
 	
 	// 视频
 	vtime = flag.Float64("time", 0, "提取视频帧的时间点 (秒)")
+	vstep = flag.Int("step", 30, "视频预览采样间隔 (秒，默认 30)")
 )
 
 const visionVersion = "1.0.0"
@@ -160,7 +161,7 @@ func runPreview(src string) {
 	case "image":
 		err = vision.GenerateImagePreview(src, *outFile, w, h)
 	case "video":
-		err = vision.GenerateVideoPreview(src, *outFile, w, h)
+		err = vision.GenerateVideoPreview(src, *outFile, w, h, *vstep)
 	case "audio":
 		err = vision.GenerateAudioPreview(src, *outFile)
 	default:

preview.go

@@ -38,9 +38,13 @@ func GenerateImagePreview(srcPath, outPath string, width, height int) error {
 	return Save(c, outPath)
 }
 
-// GenerateVideoPreview 生成视频预览 (动态 WebP)
+// GenerateVideoPreview 生成视频预览
-// 支持缩放并裁剪以填充指定尺寸 (Fill 模式)
+// 根据 outPath 后缀判断输出格式:
-func GenerateVideoPreview(videoPath, outPath string, width, height int) error {
+// - .webp | .gif: 生成动态动画 (默认每 30 秒采样一帧，可通过 frameInterval 调整)
+// - .jpg | .jpeg | .png: 生成单张预览图 (取视频中间帧)
+// - 其他: 将 outPath 视为文件夹，在其中生成多张静态 .webp 图像
+// frameInterval: 每隔多少秒采样一帧，默认 30。
+func GenerateVideoPreview(videoPath, outPath string, width, height int, frameInterval ...int) error {
 	v, err := NewVideo()
 	if err != nil {
 		return err
@@ -51,44 +55,71 @@ func GenerateVideoPreview(videoPath, outPath string, width, height int) error {
 		return err
 	}
 
-	// 动态计算帧数: 适合交给大模型 (VLM) 处理
+	ext := strings.ToLower(filepath.Ext(outPath))
-	// 避免过多的帧浪费 Token，每 30 秒 1 帧，最少 3 帧，最多 8 帧
+	vf := fmt.Sprintf("scale=%d:%d:force_original_aspect_ratio=increase,crop=%d:%d", width, height, width, height)
-	frameCount := int(duration / 30.0)
+
+	// 1. 单张图片模式
+	if ext == ".jpg" || ext == ".jpeg" || ext == ".png" {
+		t := duration * 0.5
+		cmd := exec.Command(v.FFmpegPath, "-ss", fmt.Sprintf("%f", t), "-i", videoPath, "-frames:v", "1", "-vf", vf, "-y", outPath)
+		return cmd.Run()
+	}
+
+	// 2. 动画或多图模式需要计算多帧
+	interval := 30
+	if len(frameInterval) > 0 && frameInterval[0] > 0 {
+		interval = frameInterval[0]
+	}
+
+	// 动态计算帧数: 避免过多的帧浪费 Token，每 interval 秒 1 帧，最少 3 帧，最多 8 帧
+	frameCount := int(duration / float64(interval))
 	if frameCount < 3 {
 		frameCount = 3
 	} else if frameCount > 8 {
 		frameCount = 8
 	}
 
-	// 在 10% 到 90% 之间均匀采样，跳过片头片尾的可能黑屏
 	times := make([]float64, frameCount)
-	if frameCount == 1 {
+	for i := 0; i < frameCount; i++ {
-		times[0] = duration * 0.5
+		times[i] = duration * (0.10 + 0.80*(float64(i)/float64(frameCount-1)))
-	} else {
-		for i := 0; i < frameCount; i++ {
-			times[i] = duration * (0.10 + 0.80*(float64(i)/float64(frameCount-1)))
-		}
 	}
 
-	tmpDir, _ := os.MkdirTemp("", "frames")
+	// 2a. 动画模式 (.webp, .gif)
-	defer os.RemoveAll(tmpDir)
+	if ext == ".webp" || ext == ".gif" {
+		tmpDir, _ := os.MkdirTemp("", "frames")
+		defer os.RemoveAll(tmpDir)
 
-	// 使用 ffmpeg 的 scale 和 crop 滤镜实现 Fill 效果
+		for i, t := range times {
-	vf := fmt.Sprintf("scale=%d:%d:force_original_aspect_ratio=increase,crop=%d:%d", width, height, width, height)
+			framePath := filepath.Join(tmpDir, fmt.Sprintf("frame_%02d.png", i))
+			cmd := exec.Command(v.FFmpegPath, "-ss", fmt.Sprintf("%f", t), "-i", videoPath, "-frames:v", "1", "-vf", vf, "-y", framePath)
+			if err := cmd.Run(); err != nil {
+				return err
+			}
+		}
 
+		var cmd *exec.Cmd
+		if ext == ".webp" {
+			cmd = exec.Command(v.FFmpegPath, "-framerate", "1", "-i", filepath.Join(tmpDir, "frame_%02d.png"),
+				"-c:v", "libwebp", "-lossless", "0", "-quality", "70", "-loop", "0", "-y", outPath)
+		} else {
+			cmd = exec.Command(v.FFmpegPath, "-framerate", "1", "-i", filepath.Join(tmpDir, "frame_%02d.png"), "-y", outPath)
+		}
+		return cmd.Run()
+	}
+
+	// 2b. 文件夹多图模式
+	if err := os.MkdirAll(outPath, 0755); err != nil {
+		return err
+	}
 	for i, t := range times {
-		framePath := filepath.Join(tmpDir, fmt.Sprintf("frame_%02d.png", i))
+		framePath := filepath.Join(outPath, fmt.Sprintf("%d.webp", i+1))
-		// 使用 -ss 快速 seek，性能极高
+		cmd := exec.Command(v.FFmpegPath, "-ss", fmt.Sprintf("%f", t), "-i", videoPath, "-frames:v", "1", "-vf", vf, "-c:v", "libwebp", "-quality", "80", "-y", framePath)
-		cmd := exec.Command(v.FFmpegPath, "-ss", fmt.Sprintf("%f", t), "-i", videoPath, "-frames:v", "1", "-vf", vf, "-y", framePath)
 		if err := cmd.Run(); err != nil {
 			return err
 		}
 	}
 
-	// 生成 WebP 动画，每秒 1 帧 (1000ms 间隔，让大模型能看清每一帧)
+	return nil
-	cmd := exec.Command(v.FFmpegPath, "-framerate", "1", "-i", filepath.Join(tmpDir, "frame_%02d.png"), 
-		"-c:v", "libwebp", "-lossless", "0", "-quality", "70", "-loop", "0", "-y", outPath)
-	return cmd.Run()
 }
 
 // GenerateAudioPreview 提取 3 分钟内的音频用于预览或语音转写

preview_test.go

@@ -76,6 +76,32 @@ func TestPreviewer(t *testing.T) {
 		}
 	})
 
+	t.Run("GenerateVideoPreview_SingleImage", func(t *testing.T) {
+		jpgPath := filepath.Join(tmpDir, "preview.jpg")
+		err := GenerateVideoPreview(videoPath, jpgPath, 160, 120)
+		if err != nil {
+			t.Errorf("GenerateVideoPreview (jpg) failed: %v", err)
+		}
+		if _, err := os.Stat(jpgPath); os.IsNotExist(err) {
+			t.Error("JPG output not created")
+		}
+	})
+
+	t.Run("GenerateVideoPreview_Directory", func(t *testing.T) {
+		dirPath := filepath.Join(tmpDir, "frames_dir")
+		err := GenerateVideoPreview(videoPath, dirPath, 160, 120)
+		if err != nil {
+			t.Errorf("GenerateVideoPreview (dir) failed: %v", err)
+		}
+		files, err := os.ReadDir(dirPath)
+		if err != nil {
+			t.Fatalf("ReadDir failed: %v", err)
+		}
+		if len(files) == 0 {
+			t.Error("No frames generated in directory")
+		}
+	})
+
 	t.Run("GenerateAudioPreview", func(t *testing.T) {
 		err := GenerateAudioPreview(videoPath, oggPath)
 		if err != nil {