Move RawFrame to wpiutil and add function to generate RawFrames of AprilTags

[r4stered]

Per discussion on the FRC discord, users should be able to easily generate an OpenCV Mat of the two AprilTag families used in FRC. I tested it on my PC and it generated the images properly in Java and C++.

I am unfamiliar with how people usually use OpenCV Mats in Java, but I think you would have to call .release() on the mat returned from the methods.

Not sure the best way to add a test for this...

[PeterJohnson]

What’s the actual use case for this? Simulation? I’d also like to split getting a raw bitmap apart from the OpenCV Mat bits.

[r4stered]

What’s the actual use case for this? Simulation? I’d also like to split getting a raw bitmap apart from the OpenCV Mat bits.

The primary use case is simulation. Being able to access the AprilTags as OpenCV mats allows someone to easily draw them to a screen for visualization. In photonvision the new simulation feature generates a simulated camera feed with apriltags included to feed into the detection algorithm.

As for splitting up the bitmap and cv mat stuff, do you mean instead of returning a cv::Mat, you could return a java BufferedImage or even just a byte[]?

[PeterJohnson]

Right; because BufferedImage is AWT we probably wouldn’t use it directly, but we should have a similar class to use across WPILib (cscore has https://github.com/wpilibsuite/allwpilib/blob/main/cscore/src/main/java/edu/wpi/first/cscore/raw/RawFrame.java which could be refactored to wpiutil so it can be used more broadly). And then we could provide a lightweight library to translate that to OpenCV. The ultimate goal here is to remove the direct opencv dependency from WPILib.

[r4stered]

@PeterJohnson Any suggestions or blockers for this PR?