Splits an [`rtabmap_msgs/msg/RGBDImage`](https://docs.ros.org/en/jazzy/p/rtabmap_msgs/msg/RGBDImage.html) back into the standard ROS image topics.
`RGBDImage` bundles color, depth and both camera infos into one message so they arrive together, which is what RTAB-Map wants. Everything else in the ROS ecosystem — RViz, `image_view`, [`depth_image_proc`](https://docs.ros.org/en/jazzy/p/depth_image_proc/) — expects separate `Image` and `CameraInfo` topics. This node unpacks the bundle for them.
It is the inverse of [rtabmap_sync](https://docs.ros.org/en/jazzy/p/rtabmap_sync/)'s `rgbd_sync`, and of its `stereo_sync` when `stereo` is set — those two are what produce an `RGBDImage` in the first place.
| `rgbd_image` | [`rtabmap_msgs/msg/RGBDImage`](https://docs.ros.org/en/jazzy/p/rtabmap_msgs/msg/RGBDImage.html) | Queue depth `queue_sub`, 5 by default. Raw or compressed images are both accepted. |
## Published Topics
The output topics are named after the **resolved** input topic, so remapping `rgbd_image` moves the outputs with it. With `rgbd_image` remapped to `/camera/rgbd_image` they are `/camera/rgbd_image/rgb/image` and so on. Setting `stereo: true` renames the two halves `left` and `right`, see [Stereo messages](#stereo-messages).
| Topic | Type | Description |
|---|---|---|
| `<rgbd_image>/rgb/image` | [`sensor_msgs/msg/Image`](https://docs.ros.org/en/jazzy/p/sensor_msgs/msg/Image.html) | The color image, decompressed if needed. |
| `<rgbd_image>/depth/image` | [`sensor_msgs/msg/Image`](https://docs.ros.org/en/jazzy/p/sensor_msgs/msg/Image.html) | The depth image, or the right image of a stereo pair. |
| `<rgbd_image>/depth/camera_info` | [`sensor_msgs/msg/CameraInfo`](https://docs.ros.org/en/jazzy/p/sensor_msgs/msg/CameraInfo.html) | For a stereo pair this is the right camera, and its `P(0,3)` carries the baseline. |
| `<rgbd_image>/rgb/image/compressed` | [`sensor_msgs/msg/CompressedImage`](https://docs.ros.org/en/jazzy/p/sensor_msgs/msg/CompressedImage.html) | The color image in [`compressed_image_transport`](https://github.com/ros-perception/image_transport_plugins)'s format, published by the node itself unless `compressed_passthrough` is false. Same for `<rgbd_image>/right/image/compressed` with `stereo: true`. See [Compressed images](#compressed-images). |
| `<rgbd_image>/depth/image/compressedDepth` | [`sensor_msgs/msg/CompressedImage`](https://docs.ros.org/en/jazzy/p/sensor_msgs/msg/CompressedImage.html) | The depth image in [`compressed_depth_image_transport`](https://github.com/ros-perception/image_transport_plugins)'s format, published by the node itself unless `compressed_depth_passthrough` is false. See [Compressed images](#compressed-images). |
| `compressed_passthrough` | `bool` | `true` | Publish the `compressed` topics (color, left and right images) from the compressed images of the input without decompressing them, in place of the `compressed` image_transport plugin. See [Compressed images](#compressed-images). |
| `compressed_depth_passthrough` | `bool` | `compressed_passthrough` | Same for the `compressedDepth` topic (depth), in place of the `compressedDepth` image_transport plugin. |
| `<color topic>.compressed.format` | `string` | `"jpeg"` | `jpeg` or `png`. With `compressed_passthrough`, used only when an image (color, left or right) has to be compressed. `<color topic>` is the color (or left) topic with `.` instead of `/`, e.g. `rgbd_image.rgb.image`. |
| `<depth topic>.compressedDepth.format` | `string` | `"png"` | `png` or `rvl` (Jazzy and later). With `compressed_depth_passthrough`, used only when the depth has to be compressed. `<depth topic>` is the depth topic with `.` instead of `/`, e.g. `rgbd_image.depth.image`. |
| `<depth topic>.compressedDepth.depth_max` | `double` | `10.0` | Same, maximum depth (m) of a 32FC1 depth image. |
| `<depth topic>.compressedDepth.depth_quantization` | `double` | `100.0` | Same, depth quantization of a 32FC1 depth image. |
The node handles **stereo**`RGBDImage` messages as well as RGB-D ones. In a stereo message the "depth" slot holds the right image, and the second camera info carries the baseline; the depth topics then carry the right camera, correctly typed as `mono8` or `bgr8` rather than mislabeled as depth.
That works, but the topic names lie. Set `stereo: true` and the outputs are named for what they hold:
Only the names change — the message contents and the order of the two halves are the same either way, so the `rgb` slot always becomes the left image. The two namings are exclusive: with `stereo: true` nothing is published on `rgb`/`depth`.
The node checks the setting against what actually arrives, going by the encoding of the second half: `16UC1`, `32FC1` and `mono16` are depth, anything else is an image. If the two disagree it logs a warning **once** and keeps forwarding — a mismatch makes the topic name misleading, not the data wrong, so it is never worth dropping a frame over.
`rgb_compressed` of an `RGBDImage` holds a JPEG or PNG image, and so does `depth_compressed` for the right image of a stereo pair. With `compressed_passthrough` (the default), the node republishes them as they are on `<rgbd_image>/rgb/image/compressed` (and `<rgbd_image>/right/image/compressed`), readable with the `compressed` transport. Their format is set from the image header, with the encoding (e.g. `"bgr8; jpeg compressed bgr8"`), which producers before 0.24 did not set. Raw images, or images whose header cannot be read, are compressed with `<color topic>.compressed.format`.
`depth_compressed` of an `RGBDImage` holds depth in `compressed_depth_image_transport`'s format, or, from rtabmap_ros before 0.24 or with `depth_compression_format: "legacy"`, in rtabmap's own format (`png`, `rvl`, `png:<max>:<q>`, `rvl:<max>:<q>`), which image_transport plugins cannot read. The node republishes both on `<rgbd_image>/depth/image/compressedDepth`, readable with the `compressedDepth` transport:
```bash
ros2 run image_transport republish compressedDepth raw --ros-args \
With `compressed_depth_passthrough` (the default), the depth is not decompressed when that can be avoided:
| Input depth | `compressedDepth` output |
|---|---|
| `compressed_depth_image_transport` format | Republished as is (RVL re-compressed as PNG before Jazzy). |
| rtabmap's legacy `png` (16UC1), `rvl`, `png:<max>:<q>`, `rvl:<max>:<q>` | Only the header is converted, the compressed payload is copied. Before Jazzy, `compressed_depth_image_transport` cannot decode RVL, so RVL payloads are re-compressed as PNG, losslessly. |
| Raw, or rtabmap's legacy `png` of 32FC1 depth (4 channels) | Compressed with the `<depth topic>.compressedDepth.*` parameters. |
The passthrough does not support the plugins' `jpeg_quality` and `png_level` parameters: to set them, set `compressed_passthrough: false` (`compressed` plugin) or `compressed_depth_passthrough: false` (`compressedDepth` plugin), and the plugin decompresses and re-compresses every frame instead. `compressed_depth_passthrough` follows `compressed_passthrough` unless set, so e.g. `compressed_passthrough: false` with `compressed_depth_passthrough: true` sets `jpeg_quality` of the color image while still passing the depth through.
