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RobotLocomotion / drake

Model-based design and verification for robotics.
https://drake.mit.edu
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Switch label images to unsigned (uint16_t) #11219

Open SeanCurtis-TRI opened 5 years ago

SeanCurtis-TRI commented 5 years ago

Currently, the only label image type that is defined uses signed, 16-bit integers to represent the labels. However, label values are limited to just the positive range. (Reducing the possible unique labels by half). This came up in a recent PR.

So, we can simply add the image type. However, it needs to be supported all the way through the lcm pipeline so that such images, if produced, can be reasonably consumed. Once the image exists, the RenderLabel class can be tied to that image type, and the RenderEngine class can produce it.

jwnimmer-tri commented 5 years ago

I would actually advocate for a signed 32-bit label image type as higher priority. If someone needs the last bit of label palette, chances are they need more than just one bit anyway. And 32 bits is more likely to support per-instance labels instead of per-kind labels for many use cases.

SeanCurtis-TRI commented 5 years ago

Closing as "won't do". The point that this only serves people who definitely need more than 32K labels but no more than 64K labels is probably a small user group. If and when such a use-case comes up, it can be re-opened.

jwnimmer-tri commented 3 months ago

Re-opening. We don't care about the extra 1 bit, but we do care that images are unsigned numbers! No image format can save signed numbers, so we save label images on disk as 16U monochrome, leading to user confusion when the Drake's terminology implies signed numbers.