add AttachmentVariant

src/main/java/com/imyeyu/api/util/JavaCV.java

@@ -7,36 +7,58 @@ import org.bytedeco.javacv.Java2DFrameConverter;
 import javax.imageio.ImageIO;
 import java.awt.image.BufferedImage;
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import java.io.InputStream;
 
-/**
- *
- *
- * @author 夜雨
- * @since 2025-10-23 17:05
- */
+/// JavaCV 工具类
+///
+/// @author 夜雨
+/// @since 2025-10-23 17:05
 public class JavaCV {
 
-    public static ByteArrayOutputStream captureThumbnail(InputStream stream, double targetSeconds) throws Exception {
-        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
-        try (FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(stream)) {
-            grabber.start();
-            long targetMillis = (long) (targetSeconds * 1000);
-            grabber.setTimestamp(targetMillis);
-            Frame frame;
-            while ((frame = grabber.grabImage()) != null) {
-                if (grabber.getTimestamp() >= targetMillis) {
-                    Java2DFrameConverter converter = new Java2DFrameConverter();
-                    try (converter) {
-                        BufferedImage bi = converter.getBufferedImage(frame);
-                        if (bi != null) {
-                            ImageIO.write(bi, "png", outStream);
-                            break;
-                        }
-                    }
-                }
-            }
-        }
-        return outStream;
-    }
+	/// 从视频流顺序解码并提取指定时间附近的一帧 PNG 图片
+	///
+	/// 不执行时间定位，避免为了取实时缩略图而把整个视频复制到临时文件
+	///
+	/// @param stream        视频输入流
+	/// @param targetSeconds 目标时间，单位为秒
+	/// @return PNG 图片字节流
+	/// @throws Exception 视频解析或取帧失败
+	public static ByteArrayOutputStream captureThumbnail(InputStream stream, double targetSeconds) throws Exception {
+		long targetMicros = toMicros(targetSeconds);
+		ByteArrayOutputStream firstFrame = new ByteArrayOutputStream();
+		try (FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(stream)) {
+			grabber.start();
+			try (Java2DFrameConverter converter = new Java2DFrameConverter()) {
+				Frame frame;
+				while ((frame = grabber.grabImage()) != null) {
+					BufferedImage image = converter.getBufferedImage(frame);
+					if (image == null) {
+						continue;
+					}
+					if (!(0 < firstFrame.size())) {
+						firstFrame = toPng(image);
+					}
+					if (grabber.getTimestamp() >= targetMicros) {
+						return targetMicros == 0 ? firstFrame : toPng(image);
+					}
+				}
+			}
+		}
+		// 短视频提前结束时退回首个有效帧
+		return firstFrame;
+	}
+
+	private static long toMicros(double targetSeconds) {
+		double seconds = Double.isFinite(targetSeconds) ? Math.max(0, targetSeconds) : 0;
+		return Math.round(seconds * 1_000_000D);
+	}
+
+	private static ByteArrayOutputStream toPng(BufferedImage image) throws IOException {
+		ByteArrayOutputStream output = new ByteArrayOutputStream();
+		if (ImageIO.write(image, "png", output)) {
+			return output;
+		}
+		return new ByteArrayOutputStream();
+	}
 }