Delay after coordinate transform

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hello everyone,

I want to overlay pointcloud on image. What I have so far is this:

1. subscriber topic cloud and use tf2 do transform and publish new topic cloud_trans
2. pointcloud segmentation
3. Creating the composite LIDAR image

When I use rviz to see composite image, there is delay between pointcloud and image. And then I found there is huge delay between point in cloud and cloud_trans How can I fix it? Thanks in advance