publish disparity from depth - Kinect

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Hi,

I want to publish disparity from the depth topic of type sensor_msgs/Image and the camera info topic of type sensor_msgs/CameraInfo, using the nodelet depth_image_proc/disparity. I want then to save it in a png file.

When I launch the nodelet depth_image_proc/disparity and the disparity_view, I got only an empty window. Here is the launch file:

<!-- Nodelet manager for this pipeline -->
<node pkg="nodelet" type="nodelet" args="manager" name="depth_image_proc_manager" output="screen"/>

<!-- Convert from depth to disparity -->
<node name="liora_disparity_from_depth_pub" pkg="nodelet" type="nodelet" args="load depth_image_proc/disparity depth_image_proc_manager --no-bond">
    <remap from="/right/camera_info"    to="$(arg topic_base)/camera_info"/> 
    <remap from="/left/image_rect"      to="$(arg topic_base)/image_depth_rect"/> 
    <remap from="/left/disparity"       to="$(arg topic_base)/disparity"/>
</node>

<node name="disparity_view" pkg="image_view" type="disparity_view">
    <remap from="image"                 to="$(arg topic_base)/disparity"/>
</node>

The depth and the camera info are good. Any idea why I don't see anything in the disparity_view? I want to save the disparity in a png file and use it with opencv in python.

Thanks!