update png

README.md

@@ -119,7 +119,7 @@ $DOWNLOAD_DIR/
 ```
 
 [查看蛋白质3D结构](https://www.pdbus.org/3d-view)
-<div style="position: relative; display: inline-block;">
+<div style="display: flex; justify-content: center; align-items: center;">
   <img src="./docs/result_pdb.png" alt="Image">
   <div style="position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%); background: rgba(0, 0, 0, 0.5); color: #fff; padding: 10px;">
     红色为真实结构，蓝色为预测结构