support add media thumb attachment

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

@@ -0,0 +1,42 @@
+package com.imyeyu.api.util;
+
+import org.bytedeco.javacv.FFmpegFrameGrabber;
+import org.bytedeco.javacv.Frame;
+import org.bytedeco.javacv.Java2DFrameConverter;
+
+import javax.imageio.ImageIO;
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+
+/**
+ *
+ *
+ * @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;
+    }
+}