Add ColorHandler to color points with individual RGB values

[aecins]

Adds a new PointCloudColorHandlerCustomIndividual color handler to PCLVisualizer that allows to color each point in the pointcloud with a different color. Here is an example of a visualization of a cloud where first 1/3 of points are red, second 1/3 is green and last 1/3 is blue:

[taketwo]

I'm not sure if we need an new color handler for this. Can you just change the point type to something that includes RGB field and merge the color information there?

[aecins]

You can definitely achieve the same effect by creating a new pointcloud that has RGB field and specifying the RGB values. But that requires a copy of the data. I guess it might not be too much of an issue. But I have found PointCloudColorHandlerCustomIndividual useful when I needed to quickly visualize some value computed over all of the points in the cloud and none of the default PCL color handlers did what I needed.

[taketwo]

Well in it's current form PointCloudColorHandlerCustomIndividual also requires copying of color data (line 270).

My feeling is that this handler is superfluous. I agree that there might be a use case, but arguably it is a fairly rare case, and can be covered by using an RGB-enabled point type. So I would rather be against merging this, but if there are other opinions, please post.

[aecins]

You are right about the data copy. I agree with you that this handler is not strictly speaking necessary. It would be interesting to see if anyone else has an opinion on it.

[aecins]

It seems like this feature is non-essential. Should we close this pull request?

[SergioRAgostinho]

Why not simply

capable_ = (cloud_->points.size () == rgb_values_.size ())

[SergioRAgostinho]

The use case I see for this is in case you have a colored pointcloud already but want to override its colors for visualization purposes without copying the the XYZ data. I don't really see an issue in having it as a non-essential feature, it might convenient in some situations.

Also since the PointCloudColorHandlerCustomIndividual is not precompiled, we won't be increasing the compilation time and library binary size.

[jspricke]

I agree with @taketwo that it's more consistent to create a new cloud, even in the case @SergioRAgostinho proposes.

[SergioRAgostinho]

Fair enough. Can we close this then? Sorry for the trouble @aecins :x

[aecins]

No problem, @SergioRAgostinho, this can be closed. The final decision is that this functionality is not needed so I will not implement it in PointCloudColorHandlerCustom as I suggested in #1627.

[taketwo]

Actually, I am in favor of having this functionality as a part of PointCloudColorHandlerCustom. My original concern was about having million different handlers with not exactly intuitive names (albeit logical when you know what it's doing). Now that we agreed to have a single umbrella handler for user-provided colors, I think this pull request functionality fits nicely.

[stale]

This pull request has been automatically marked as stale because it hasn't had
any activity in the past 60 days. Commenting or adding a new commit to the
pull request will revert this.

Come back whenever you have time. We look forward to your contribution.