Hi,
you can look at this
RaspberryPi example. In particular, look for "Decimation" related parameters:
$ rosrun rtabmap_ros rtabmap --params | grep Decimation
Param: Mem/ImagePostDecimation = "1" [Image decimation (>=1) of saved data in created signatures (after features extraction). Decimation is done from the original image.]
Param: Mem/ImagePreDecimation = "1" [Image decimation (>=1) before features extraction.]
$ rosrun rtabmap_ros rgbd_odometry --params | grep Decimation
Param: Odom/ImageDecimation = "1" [Decimation of the images before registration.]
Setting decimation to 2, 640x480 -> 320x240. Setting to 4, 640x480 -> 160x120.
You can also use the
rtabmap_ros/data_throttle nodelet to decimate the images at the source.
cheers